Frequently Asked Questions

Q: Radiator Bushings

How do the radiator bushings fit? It’s a standard two piece rubber bushing, one half of the bushing has a metal sleeve, the other half is just rubber. Does the metal sleeve half fit in between the frame and support? Does this bushing use a large metal ‘washer’ like the body mount bushings do?

A: You’ve got the right idea. The bushing w/the metal sleeve fits between the frame and radiator support, with the sleeve protruding upward. The other rubber piece sits on top of the support, over the sleeve. This half of the bushing has a large hole on one side, and a smaller hole on the other. Place it with the large hole fac- ing downward. Two large washers are used, one on top, and another on the underside of the frame. In addition, you should have a med- ium sized washer, a lock washer, and nut. Push the bolt in from above with one of the large washers. Use the remaining washers on the bottom.

Some repro bushings are a little large for the radiator support hole (at least it was on mine), so some triming and filing may be required. In addition, the bolt was short. The GM bushings are correctly sized, and with the correct length bolts.

Any proposed updates, changes, pictures, and/or corrections, please use our comment section below (may need to click on permalink to access comments feature). Information is subject to change and offered as is without any warranties or guarantees. Please review our Term's Of Use for more information.

Q: Fan Hits Shroud

I just bought a new Radiator and Shroud from Classic Industries for my 1969 350 TH350. The radiator is an exact fit in the car and matches the one I took out. The shroud fits nicely on the radiator but I didn’t have a shroud before so I don’t have one to match up. When I installed them I could see right away that the fan touches the Shroud at the bottom. The Shroud is 21 1/2″ and the fan is 19″ as they should be but I have 0″ clearance on the bottom and 2 1/2″ clearance on the top. Left to right is good.

Any ideas why it doesn’t match up good? Only thing I can think is that the water pump is incorrect and has the mount for the fan too low compared to original……any other ideas?

A: It may be the pulley, possibly your engine is slightly off center?

A: You Probably need new motor mounts. I had the same thing happen on my 1968. The rubber in the mounts gets squished after many years.

A: The following things come to mind:
1) Have the engine mounts ever been replaced?
2) Are the body bushings between the front sub-frame and the body original? If so, do they need to be replaced? If not, are the replacements the same height as the originals?
3) Are the body bushings between the front sub-frame and the core support original? If so, do they need to be replaced? If not, are the replacements the same height as the originals?
4) Same applies to the transmission mount.

Any or all of these could account for the motor sitting 1″ – 2″ lower than it should which would result in what you are seeing. I don’t think the water pump has anything to do with it.

Any proposed updates, changes, pictures, and/or corrections, please use our comment section below (may need to click on permalink to access comments feature). Information is subject to change and offered as is without any warranties or guarantees. Please review our Term's Of Use for more information.

Q: Fan Pulley Diameter for 1967

Whats the proper diameter of Fan Pulley for a 1967?

A: Keep in mind that there are 8 different belt and pulley configurations for a 1967 V8 car! I’m assuming you’re asking about the car noted in your tag line. The 1968 and 1969 V8 cars have only 4 possible configurations.

1967 V8 Pulley and Belt Applications (assume each config. has an alternator)

1. Standard car (no accessories)
p/n 544595 8 inch
2. Power steering only
p/n 9786819 8 inch (two groove)
3. Air conditioning only
p/n 9786909 7 1/8 inches (two grooves)
4. Air conditioning and power steering
p/n 9786909 7 1/8 inches (two grooves)
5. Air injection (A.I.R.) only
p/n 9786819 8 inch (two groove)
6. Air injection and power steering
p/n 9786819 8 inch (two groove)
7. Air injection and air conditioning
p/n 9788886 5 11/16 inch (two groove)
8. Air conditioning, power steering, and air injection
p/n 9788886 5 11/16 inch (two groove)

Any proposed updates, changes, pictures, and/or corrections, please use our comment section below (may need to click on permalink to access comments feature). Information is subject to change and offered as is without any warranties or guarantees. Please review our Term's Of Use for more information.

Q: Firebird 400 Radiator Outlet Size for 1968

I’m trying to figure out if the radiator in my 1968 Firebird 400 is original or not.

A: For starters, does your radiator have “HARRISON” embossed on the tanks ?

How about the Production Usage Code Tag ? 400 Codes…. UQ, UP

My original (UQ…RAI, 4spd) is in storage however, the “UP” tank I have is…
Upper: 1.5625″ Lower: 1.875″

Any proposed updates, changes, pictures, and/or corrections, please use our comment section below (may need to click on permalink to access comments feature). Information is subject to change and offered as is without any warranties or guarantees. Please review our Term's Of Use for more information.

Q: Heater Core Replacement (Non-A/C)

I need to replace my heater core. The service manual is not to much help. How should I go about it? How tough is it:? should I forget it and just drive when its warm?

A: It’s a tough job. Even tougher if your car has factory A/C. The core is fastened inside the air box behind the glove box. If the car doesn’t have A/C, I think you can get to all the bolts without removing the passenger side fender well. The control cables are easy to remove and replace. While you have the heater box out, it’s a good time to clean it up and freshen it up with a new coat of semi-flat black.

If your car has factory A/C, drop me a line off-list and I’ll try to help you through the details.

Any proposed updates, changes, pictures, and/or corrections, please use our comment section below (may need to click on permalink to access comments feature). Information is subject to change and offered as is without any warranties or guarantees. Please review our Term's Of Use for more information.

Q: Heater Hose Replacement with A/C

Does anyone have any suggestions on how to get the heater hoses on the heatercore on a 1969 firebird? Oh yeah, it does have air conditioning……………..

A: It’s one of the added pleasures of having an air conditioned GM car…..

Heater hose connections can be accessed from under car. Take a couple of fender skirt (inner fender) bolts loose and shove a piece of 2×4 between it so you can reach up to the hose connections. Take care not to break loose the tube that goes to heater core, otherwise you might as well pull the fender to replace heater core. If you split the old hose with a razor knife it will come off much easier.

Any proposed updates, changes, pictures, and/or corrections, please use our comment section below (may need to click on permalink to access comments feature). Information is subject to change and offered as is without any warranties or guarantees. Please review our Term's Of Use for more information.

Q: How Hot is Too Hot

One Question to all – What is hot (in your own opinion) for an engine to run? How hot – is to hot? 190?,195?, 200?,215?, 225?

A: In my opinion, 215 is when you start looking at the guage more thn the road. 225 is when I shut it down before it gets worst. 235+ and you’re in dangerous territory. 250+ things start warping and cracking.

Octane doesn’t directly affect your temps, however, if you car pings because of low octane than this can make it run hotter because you’re not running at an optimum condition so the engine has to work harder to produce the same power (and I’m sure that pre-ignition might generate more useless heat).

Get a desert cooler, a 160 thermostat, a good engine flush, a decent water pump, run a 50/50 mix (Destilled water is preferable. More water than collant is actually better for temps), run a little on the rich side, use the 400/AC car filler pannels, and everything should be ok. Almost forgot, the fan shroud itself is another important item – don’t know how many cars seem to come up short on that one.

Any proposed updates, changes, pictures, and/or corrections, please use our comment section below (may need to click on permalink to access comments feature). Information is subject to change and offered as is without any warranties or guarantees. Please review our Term's Of Use for more information.

Q: Lower Radiator Hose for 1969

I have a 1969 350ci with TH350 and NO A/C. Just bought a lower radiator hose from Ames and it didn’t fit. It was a 1.5″ I.D. hose with a flare out to 1.75″ at ONE end. It didn’t fit for two reasons. For one, it was too long and didn’t physically fit in the car. For two, both my water pump AND radiator need the 1.75″ I.D. hose.

Anyone else ever have this problem or is there something wrong with my car?

Anyone know what size hose they use on their car or where they buy them from and what the Part Number is?

A: I just bought and installed a lower radiator hose on my 1969 350ci TH350 with A/C. The hose was the same size on both ends. Without measuring it I would assume it is 1.75 inches. The hose was not very long, I would guess 15-18 inches. At any rate, I picked it up at the local NAPA auto parts store. This was about the only store in Austin that stocked the lower hose.

Any proposed updates, changes, pictures, and/or corrections, please use our comment section below (may need to click on permalink to access comments feature). Information is subject to change and offered as is without any warranties or guarantees. Please review our Term's Of Use for more information.

Q: Overheating Engine

I just recently purchased a 1967 bird with a 400 and an automatic tranny. It needs some work but for the most part is all original. The motor has 670 heads and is a YT.

It seems to over heat when sitting still. When I am driving it runs about 180 but if I sit still very long it heats up rather quick. I replaced the water pump and put a 165 thermo in it. The radiator seems to be circulating any suggestions?

A: The overheating could be several things: Poor or no coolant, Improper coolant level/mix, bad fan clutch (check hot w/ engin off. If it spins freely, it’s bad), bad fan (if it has a cheep after market flex fan these blades get weak), missing fan shroud, partially clogged radiator (have flushed), bad water pump (possibly a broken impeller. check last) . If it has A/C it could have a bunch of junk between the condenser and radiator (this happened to me on a Corvette).

Any proposed updates, changes, pictures, and/or corrections, please use our comment section below (may need to click on permalink to access comments feature). Information is subject to change and offered as is without any warranties or guarantees. Please review our Term's Of Use for more information.

Q: Overheating Engine (Part 4)

Does anyone have any suggestions for an overheating engine? I have an overheating problem with my 1968 400. When idling it’s fine. Sits right about 180-190. As soon as the car starts to move it gets hot quickly. If I stop for a light or a stop sign it immediately drops back to 180 or so. The radiator has been cored. I’ve replaced the thermostat and the fan clutch. Any other suggestions?

A: The one thing I found out was, although my radiator looked good, it was about 30% clogged. I was using a stock clutch fan and shroud. After my radiator man cleaned it out, it would idle all day long without overheating.

A: You know I was thinking the same. My 1968 400 didnt overheat during its life here in Orlando,but it was in good mechanical shape. Even with the a/c on it didnt go above 220 if idled all day.

Heres a check list.

1. water pump make sure its the proper cast iron impeller

2. thermostat 180 F is fine 160 will work too,dont leave this out

3. check timing cover and waterpump baffles these must be in good order without pinholes,if not buy the stainless replacement.

4. check static timing and advance on distributor must be right on or motor WILL overheat

5. engine condition, clogged cooling passages will ruin a motor

6. heater core still intact and flowing good

7. radiator still flows fine no bent fins and mud inbetween fins,no loose fins

8. hoses must be fresh and wire installed in lower one

9. fan pulley and fan,proper one as factory installed,no gimic ones here.

10. a/c cars (not Brads) had smaller pulleys to speed up the air /water flow

11. proper fan shroud(OHC-6 didnt use one only a finger guard)

this check list will if followed lead to a happy and cooler car. The only exception to needing auxiliary fans is large cammed ultra hi compression,ultra low gears,hi stall speed converters.A stock motor if in good condition shouldnt overheat.

A: Take a look at your lower radiator hose, squeeze it. Does it have a metal spring inside of it? If you can squeeze it flat then chances are you don’t have a spring. The lower radiator hose is the suction side and when you rev the car up with no spring in the bottom hose then alot of times it sucks the hose closed. Like when you put your finger on the end of a straw and suck on the other end it flattens in the middle and that sounds like what could be going on. Also with the car idling put your hand if front of the air breather and feel the flow of air, now have someone in the car rev it up to about 2,500 rpm and see if there is a great big boost in the amount of airflow, sometimes a new clutch doesn’t necessarily mean a good one. With the type problem you have I would say it has something to do with rpms which is generally the fan clutch or the lower radiator hose.

A: My view is that a great many overheating problems are related to wrong timing or carb set too lean. Many of us are spending big money on fancy water pumps and big radiators when we really need to sort out the basics first.

Any proposed updates, changes, pictures, and/or corrections, please use our comment section below (may need to click on permalink to access comments feature). Information is subject to change and offered as is without any warranties or guarantees. Please review our Term's Of Use for more information.

Q: Overheating Engine (Part 5)

I have tried everything suggest but I just can not find the problem to my overheating problem. I am about ready to give up and move north. Any ideas?

A: One guy on the post (forgot name) may have been close when he suggested that over heating in the first gen birds was due to the design of the cars front end. An old time radiator man I often go to said that the firebird radiators are the smallest ones Pontiac has ever put in cars and expected them to do so much ie. cool big V8s.

This guy also had an excellent tip for a mysterious overheating problem. All you overheaters may be over looking the old head gasket leak.

A head gasket can develop a small leak near a water jacket. The problem may not effect the performance of the car and often is undetectable until the overheating starts. When the leak in the gasket develops between the combustion chamber and the water jacket, a small amount of compressed air is forced into the coolant while the engine is running. The results are large pockets of air forming where the water should be and turning to steam from the hot spots in the block. The results are overheating followed by blowoff over flow.

The check the old guy gave me goes like this: Disconnect the fan belts so the water pump will not turn. Disconnect the top radiator hose at the radiator and hold it up vertically while filling the radiator with water until you can see the water in the end of the hose you are holding. While everything is cold (engine, water) start the engine and watch the water in the end of the hose for small bubbles. They will appear before the hose gets to hot to hold and the indecate a bad head gasket.

This whole deal works. I used it on my 1969 and found the cracked gasket…Old radiator Bill impressed me on another occasion when I plopped down a radiator in his shop and he eyeballed it for a few seconds and proclaimed, ” that’s from a 1967 GTO!

Good luck with the heat

Any proposed updates, changes, pictures, and/or corrections, please use our comment section below (may need to click on permalink to access comments feature). Information is subject to change and offered as is without any warranties or guarantees. Please review our Term's Of Use for more information.

Q: Overheating Engine (Revisited 2)

Been playing with my 1969 with a new 455 (1000 miles) that doesn’t seem to have the correct power it should or maybe I got sold a lousy cam with the rebuild. Here’s part of what’s going on, any ideas out there?

Ran the car a little on Saturday. with an HEI and timing set at 12degress with vacuum module attached to vacuum source high on quadrajet body it will overheat at idle. Lowest idle I can achieve is 800 RPM. Running at street speeds keeps the temp down.

I have put new non-flex fan in, new radiator rot out, new water pump and thermostat at rebuild. and have had this problem since the motor was built. (shop has gone out of business, surprise!) Still runs slow, but has decent power, about equal to the 350, 2-bbl that was stock in it before. Could the cam be causing the overheating? or maybe there is something obstructing water flow internally? It still does not seem to run right.

When I started it up, it ran at high idle for over 5 minutes, choke was off, nothing would bring it down and then all of a sudden it just dropped down to 800RPM, maybe it needed to overheat to plug up some vacuum leak somewhere? Any ideas?

A: Do you have a fan shroud on it??? If not, then there is your problem since when the car is not in motion, it requires the shroud to assist the fan in sucking the cool air through the radiator.

One other thing you might try is retarding the timing. 12 degrees might be a little much.With vacuum advance, and mechanical advance, you might be actually running at well beyond 12 degrees at idle causing high heat.

A: First thing that comes to mind is the timing. If it is too retarded it will cause poor performance and overheating. I’m not sure whether the port that is “high on the quadrajet body” is ported or manifold vacuum, but if there is ANY vacuum advance at idle and you set the timing to 12 degrees, you’re timing is FAR too retarded. Disconnect the vacuum line from the carb and plug it. Just to be sure, also cap the inlet to the vacuum advance. Then set your initial timing to 12 degrees and see what happens. Might just solve both problems.

A: Did you add a full shroud? And what is the clearance between the fan blades and the shroud? Also, is the fan positioned in the rear of the shroud, inside the shroud, or is it just inside the rear of it? These factors are very important to provide good cooling suction. I ran my 1968 with no shroud, too small a fan for my shroud, and also improperly positioned and they all greatly affected the temperature of my engine at idle. I now have the original fan, with the original shroud, and with the fan spaced just inside the rear opening.

Take a look-see. If any of the ideas I mentioned are as you currently have it, try correcting it. It made a big difference with mine. Good luck.

What I mentioned about the timing is that if you have the dist too much advanced or too much retarded, that will also affect the temp. To time it, disconnect and block your vacuum source, and time the car, preferably at idle depending upon what your cam calls for, and yoru compression, I would think you should run at no more than 8 degrees but no less than 4. Remember, an increase in timing before TDC, such as going to 12 from 8, is Advancing it. Too much advance will create more heat, and if you’re really unlucky, detonation.

A: I’m going to ask a very silly (but obvious) question:

Are you running with a reasonable compression ratio for the fuel that you are using? I.E., 9-9.5:1 for 93-4 octane? The reason I ask is that it is possible that that 455 was fitted with smaller chambered heads off a 400 or 350. Any shop worth it’s salt would never have done this, but I think it happens. You should not run head chambers less than about 95 cc’s on a 455. Some 400 heads are OK, but the ones off higher compression engines will result in even higher CR on a 455. Higher compression with inadequate octane rating will result in overheating at idle and detonation under load at standard timing settings. (Not to mention broken pistons, rings, etc. Sometimes guys try to “de-tune” the ignition to get rid of the detonation, but end up losing a lot of power. (Been there, done that) Your CR must match the fuel rating or you are going to have problems. Get the head code off the center exhaust ports and make sure they are OK for a 455. Other than this, you been given some pretty good advice from others on the list…….

If I’m being too presumptuous, I appologize, but I ended up with engine damage and wished someone had told me so that I wouldn’t have to find out the hard (expensive) way.

A: I was reading the street machine articles written by Jim Hand and I came across something that jogged my memory. He warns about harmonic ballancer outer ring migration, which usually will throw your timing mark off into the retard region. This will result in heating problems and lost power. I had to replace a ballancer a few years ago because it didn’t line up with my timing pointer @ TDC. (I had just finished checking my cam timing with a degree wheel and had slipped the ballancer on @ TDC to check it). I had just never corrolated this to any previous problems. It is certainly worth looking at….. we usually take that little groove on the ballancer for granted when timing the ignition.

A: I have a ’72 455 in my 1968 and had a similar high heat problem. Apparently the crank pulley was much a much larger diameter than one that would be found on a 400. This was causing the water pump to spin faster than normal. At idle, the coolant was moving through the radiator too fast to be cooled very much. When driving, and with good air-flow through the radiator, the temp would return to normal. I put on a smaller crank pulley and the problem went away. And be aware that not all flex fans are the same. Some really suck.

A: Once again Ive been reading the FAQs and have come across a problem adressed that I encountered. The problem concerns a 1968 with a 455 and over heating.

I put a 455 in my 1967 and, of course, it ran hot. A friend did the same in his 1968 with the same results. Heres how we resolved the situation. I assume the waterpump thrustplate is not missing…Ive seen it frequently!!! First we made sure we had both the lower air baffle (below lower valence) and the two filler panels between the core support and the front bumper support. The filler panels were standard on 400s and on A/C equiped cars. The seal up the grill area and force the fan to pull air through the radiator instead of around it. This, for the most part solved the over heating at idle problem.

Both of use used 400 heads on our 455s and this contributed to the problem. After several broken pistons (we used early small chambered heads) we both switched to late model large chambered 400 heads. This, for the most part solved the problem, but we did end up installing heavy duty 4 row radiators…probably over kill, but then again summer in Florida can get things a bit warm.

Any proposed updates, changes, pictures, and/or corrections, please use our comment section below (may need to click on permalink to access comments feature). Information is subject to change and offered as is without any warranties or guarantees. Please review our Term's Of Use for more information.

Q: Overheating Problem (Revisited 3)

My Firebirdd is overheating and has low oil pressure. Is the low oil pressure causing my overheating problem.

A: I had problems with the cooling on my last 1968 after I rebuilt the engine. A few things to check

1.) Does the clutch fan actually work???? Mount a regular fan in its place to test to see if the engine now cools properly. I’ve never seen the clutch guts, but they can discontinue the correct lock-up and revolve at less than 100% of the correct idling speed. I have had this problem. It looks like the fan is working, but it is actually going much slower than it is supposed to, hense overheating.

2.) How long has your radiator been out of your car?? One of the oddities I have encountered is that when a radiator is romoved, crud (rust) that has circulated in dirty coolant will sometimes settle and clog the passages. Self flushing doesn’t seem to cure it, because it becomes hardened in the passages, just like a clogged drain in your house. It will need to be replaced, or removed and boiled by a pro radiator shop.

3.) You are running an anti-freeze/water mix aren’t you? Running 100% of either can be a problem.

4.) A recent article (either Old cars weekly / or classic auto restorer) discussed this topic in general. One of the often overlooked items is that engine blocks and head castings that sit for long periods of time without use had clogged coolant passages. Did either of yours sit without getting boiled out?

A: With regard to low oil pressure and overheating, that is a common problem. Here is the deal. Oil pressure is a measurement of resistance to flow (the flow of oil). The thinner the oil, the easier it flows. When your oil gets real hot, it flows very easy, hense the oil pressure drops. At start-up, the oil has a high viscosity (it’s thick), so there is plenty of oil pressure, but relatively low flow.

All automobile engines have a built in pressure relief valve, either in the pump or somewhere in the oiling system. In theory, you can never go above the max PSI as long as the pressure relief is working. The oil pressure will level off at high RPM because you have hit the limit of the pressure relief valve. At idle, the relief valve would only work when the oil is very thick, such as on a real cold day. It’s kind of weird that way. We often make the mistake of thinking that only oil pressure counts, but flow is just as important. That’s why most engine damage occurs at start up. There is very little or no flow for a few moments, even though the PSI jumps up instantly.

So, to answer your question. It is possible that your bearings are worn and the resistance to flow has been reduced from bearing clearances that are above the max tolerance. A pressure problem would normally show up first when the oil is hot and thin and at idle speed. It is also possible that your oil pump is worn and has reduced flow and that in turn is creating reduced pressure. When the oil is hot and therefore thin, the problems are likely to show up. But… my bet is simply that your car is running too hot. Get it to cool down and stay cool. Your oil pressure will likely rise to where it is supposed to be. Let the car idle, and watch what the oil pressure at about 195 degrees. Ideally, I would never want an older Pontiac engine to be above that temp. If the oil pressure at that temp is acceptable, then it’s just a matter of getting the engine to cool down to that level or lower. Beyond that simple diagnosis, we are talking removing the oil pan and checking the oil pump, bearings, etc. Not easy….

One last point. Are you running headers????? They aren’t causing the oil pan (and the whole engine compartment) to get hot are they? That situation will certainly cause thin oil (low PSI) and engine overheating. Headers are a real pain in a Firebird. No room to dissipate heat in the engine compartment! And…..by all means… check the other E-Mails and pay attention to the one on timing problems related to overheating. Solid advice!

A: First lets assume that the system is full of a coolant at the proper mixture and that a new and correct pressure radiator cap is in place. I also assume that the coolant was topped of after the engine ran and the thermostat opened.

What type of fan do you have?. If it is a clutch fan, is the clutch part still working? Are you using a radiator shroud? Is the fan set at a proper depth within the shroud? Are the original baffles in place on top of and underneath the core support? Do you have anything blocking the airflow in front of the radiator? Is it the proper radiator for the car(Not intended for a 6 cyl is it?). Have you had the system flushed to remove deposits/corrosion? Is the lower radiator hose collapsing when it gets hot? Do you have one with a spring in it?

If you are moving too much fluid with a higher volume pump there might not be sufficient time to absorb the heat. Retarded timing could cause it to run hot. Lean carb also. Has the engine been rebuilt recently? A tight engine may run a little hotter. Is there a possibility of air in the system casing cavitation/steam pockets? Is the thermostat working? Is the water pump impeller exactly the same size/shape as an original one? Is it possible that the water pump shaft is slipping and not turning the impeller at the intended speed?

Red-Line makes a product called water wetter that is supposed to reduce water temperature. I believe that it reduces the surface tension of the water allowing more of it to contact the metal surfaces. I think they claim about a 10 -20 degree F drop (bought mine at a auto part store). I think it helped, but can’t remember how much. It is about $7 US. (clear bottle pinkish-red fluid).

Have you tried an external oil cooler?

Has it ever run at the proper temperature? If so what have you done to it since then?

A: Back to a few basics….. What happens when the temp in your car rises???

Crap happens:

Compression maxes because the rings seal really, really tight. Try disconnecting everything (electrically from ignition circuit) and crank your engine over by hand, you’ll see the difference in resistance. Of course, you can also test this with a compression tester. Bottom line, the engine is tough to turn over.

Okay, we all know the obvious, the starter is at max stress because high temp causes high resistance in the electrical windings / armature, meaning less than ideal starting.

When the engine turns over (barely) preignition occurs and it says No go! No go!

So…. What is the answer? Don’t even think of fixing it with a starter solution. There is only one real answer…. Get the temp down…..

You can diagnose until you are ready to puke, but here are some steps I take to ensure I’m going in the right direction. From the cheapest to most expensive solution.

1.) You are running 10W40 oil. A grade of 10W30 or less will aid in the rise in engine temp.

2.) Run a blend of anti-freeze and water per the coolant mfg recommended mix

3.) Be sure to run a thermostat (don’t run without it or the coolant will not have time to cool properly).

4.) Your timing is correct isn’t it? To much timing will making it overheat faster than you can say boilermaker. I also include correct point gap in that discussion.

5.) Your radiator isn’t even slightly plugged is it???? These are 30 year old cars. If your radiator is more than 10 years old, chances are some of the cooling rows are plugged. Have it professionally rodded out. Home mechanic cleaning materials are a joke on a radiator this old. Oh and if the radiator was removed an let to sit long enough for the sludge crud to become hardened in it, you are in for a super plug job.

6.) Your fan shroud is installed properly isn’t it??? I won’t say any more on this one.

7.) Get rid of your headers!!! Oh no… the evil of such discussion. Headers in most birds cause a problem with oil temp rise and underhood head (causing coolant temp rise). They are too close to all of the mechanicals and the starter in a bird. I have installed and removed them in several birds. That step alone can solve the problem. Consider using the HI perf manifolds for 68.

8.) If you must run headers, install an oil cooler and 4 row radiator. That will help. It may or may not solve it.

9.) Your engine isn’t worn to the point where the bearings are bad, or it has a bad oil pump, is it??? In either case, you will suffer reduced oil pressure and the problem compounds the longer the engine runs. The engine will begin to overhead from additional friction caused by reduced oil pressure. The hotter the engine, the thinner the oil gets, making flow easier and pressure worse. The only solution is to replace the problem components in your engine.

Any proposed updates, changes, pictures, and/or corrections, please use our comment section below (may need to click on permalink to access comments feature). Information is subject to change and offered as is without any warranties or guarantees. Please review our Term's Of Use for more information.

Q: Radiator Bushings

How do the radiator bushings fit? It’s a standard two piece rubber bushing, one half of the bushing has a metal sleeve, the other half is just rubber. Does the metal sleeve half fit in between the frame and support? Does this bushing use a large metal ‘washer’ like the body mount bushings do?

A: You’ve got the right idea. The bushing w/the metal sleeve fits between the frame and radiator support, with the sleeve protruding upward. The other rubber piece sits on top of the support, over the sleeve. This half of the bushing has a large hole on one side, and a smaller hole on the other. Place it with the large hole fac- ing downward. Two large washers are used, one on top, and another on the underside of the frame. In addition, you should have a med- ium sized washer, a lock washer, and nut. Push the bolt in from above with one of the large washers. Use the remaining washers on the bottom.

Some repro bushings are a little large for the radiator support hole (at least it was on mine), so some triming and filing may be required. In addition, the bolt was short. The GM bushings are correctly sized, and with the correct length bolts.

Any proposed updates, changes, pictures, and/or corrections, please use our comment section below (may need to click on permalink to access comments feature). Information is subject to change and offered as is without any warranties or guarantees. Please review our Term's Of Use for more information.

Q: RPM and Temp

I’ve got a 1968 Firebird, built 350, 3:73 rear end and a 3 speed AT. When I’m on the interstate, what is a reasonable rpm to be at (ie., what is too high). Also, I think my thermostat is blown, the engine is a 73 Pontiac, what is a good temp?

A: The higher RMP your engine runs, the greater the wear, especially for sustained periods. Not to mention the penalty in fuel economy. I’d try to keep the RPMs below 3300 or 3500 for highway cruising speeds. Depend- ing on tire size, that might be 55 or 60 MPH?

You can try a taller tire, change the rear ratio, or get an overdrivetransmission.

Regarding the temp question, I feel that 180 to 205 is within a normal range, depending on load, speed, and air temp. Even 210 is OK if climbing a steep grade on a hot day, or sitting in traffic in August. Modern cars are designed to keep pretty close to 200 for max. efficiency. A frozen thermostat in the open position will not allow the car to warm up, or be slow to warm up, and will result in premature wear in the cylinders. Heat is required for good operation, but not too much heat. Frozen shut will cause overheating pretty quick. I run a 160 or 180 degree thermostat in the summer, and a 190 in winter.

If you are relying on the factory temperature gauge to determine operat- ing temps, be warned that they were never too accurate when new, and with age, they are completely suspect. Add an aftermarket guage, even if only temporary, to determine how hot you’re engine is getting. Mech- anical guages are more accurate than electrical.

Any proposed updates, changes, pictures, and/or corrections, please use our comment section below (may need to click on permalink to access comments feature). Information is subject to change and offered as is without any warranties or guarantees. Please review our Term's Of Use for more information.

Q: Shroud Fit

Since buying the car, my wife’s 1969 bird has had a mismatch between the fan and the shroud. For some reason the fan sits too low in the shroud and rubs against the bottom. In fact, I had to clip the bottom of the shround to avoid the rubbing. The fan is 2 inches smaller in diameter than the shroud, so it should have 1 inch gap on the top and bottom, but instead it has 2 inches at top and zero on bottom.

A: Take a look at your front subframe bushings, for the radiator brace. What you are reporting sounds like these bushings are compressed and have caused the front sheet metal to droop.

A: I’ve thought of that too, but wouldn’t that cause the radiator support to drop, which would make the shroud too low? My problem is the shroud is too high.

A: Actually, it’s probably just the opposite. The fan is rubbing on the bottom so the bushings would have to be too tall.

Something simple to check is to verify that the clips holding the bottom of the shroud against the radiator and fully seated and that the shroud is sitting all the way into the clips. I have also found that the shroud will sometimes hit the lower radiator hose or the pit-cock and will keep the shroud from staying in it’s proper location.

I had a similar problem when I put my 1969 back together. I rubbed on the right side near the battery before I took it apart. After I put it all back together, using the existing bushings, I gained 1/2 of clearance. I think it was just due to a combination of moving things around.

You may also want to check that you have the correct transmission mount or that the transmission cross member isn’t bent.

Any proposed updates, changes, pictures, and/or corrections, please use our comment section below (may need to click on permalink to access comments feature). Information is subject to change and offered as is without any warranties or guarantees. Please review our Term's Of Use for more information.

Q: Sprint Radiator

What is the correct radiator for a Sprint engine? I am worried I do not have the correct one since I keep over heating plus someone mentioned my Sprint is missing “Filler Panels.”

A: Single core is correct for a 1968 Sprint, unless it had the HD cooling. Radiator should have a metal tag with the letters “ZA”. Code for the HD unit is “UF”. A 3 core from a 350 V-8 will fit right in the same location.However the finger guard may not. OHC-6s dont use a fan shroud. I think the radiator you have is clogged or in poor condition. I’ve never had an overheating problem with any OHC-6s.

A: The Filler Panels are the panels that go between the core support and the front bumper support.

They were installed in 400 cars and A/C equipped cars. The idea was to force as much air as possible through the radiator, instead of having it “leak” out around the bumper. They can be bought as repros, if you’re interested in using them.

Any proposed updates, changes, pictures, and/or corrections, please use our comment section below (may need to click on permalink to access comments feature). Information is subject to change and offered as is without any warranties or guarantees. Please review our Term's Of Use for more information.

Q: Water Pump for 1969

Were there two variations of the 1969 Water Pumps?

A: There are two pumps for a 1969 Firebird. I seen them listed as earl and late 1969 (The early pump was the short one).

3 31/32″ Hub Part#9797581 Cast number 9796351

There is also

4 15/32″ hub

You can also tell just buy looking at the water pump pulley. I’ve observed that the a/c equipped cars had the longer pump also.

Any proposed updates, changes, pictures, and/or corrections, please use our comment section below (may need to click on permalink to access comments feature). Information is subject to change and offered as is without any warranties or guarantees. Please review our Term's Of Use for more information.

Q: Sprint Radiator

What is the correct radiator for a Sprint engine? I am worried I do not have the correct one since I keep over heating plus someone mentioned my Sprint is missing “Filler Panels.”

A: Single core is correct for a 1968 Sprint, unless it had the HD cooling. Radiator should have a metal tag with the letters “ZA”. Code for the HD unit is “UF”. A 3 core from a 350 V-8 will fit right in the same location.However the finger guard may not. OHC-6s dont use a fan shroud. I think the radiator you have is clogged or in poor condition. I’ve never had an overheating problem with any OHC-6s.

A: The Filler Panels are the panels that go between the core support and the front bumper support.

They were installed in 400 cars and A/C equipped cars. The idea was to force as much air as possible through the radiator, instead of having it “leak” out around the bumper. They can be bought as repros, if you’re interested in using them.

Any proposed updates, changes, pictures, and/or corrections, please use our comment section below (may need to click on permalink to access comments feature). Information is subject to change and offered as is without any warranties or guarantees. Please review our Term's Of Use for more information.