Hi guys, I'm glad to have found this forum. On my very first post, unfortunately I'm needing some help. I have a 1969 Firebird with a 455 bored .030" over. It has probably 75 miles on the engine since the rebuild, where it received a new crank and forged rods and pistons. It has an Edelbrock 750 carb, Performer RPM intake, a mild cam (214/224 at .050 I believe), headers, 400 hood. I have a stock water pump, 4 core stock-type radiator, and 7-blade, 19" clutch fan. The car came with AC, which is not currently hooked up. It runs 190-210 all day around town, but as soon as you're on the highway for 10-15 minutes at cruising speed (65 mph), it creeps up to around 230F. When you shut it off, it hits 245. Start driving around again, it goes back to 230. I have several questions, concerns, issues, etc:

1) I have no idea what my compression ratio is. It's anywhere from 9.0 to 10.0 I think. I have 6X heads from a 350...could that be part of the problem (too much compression?) I only have available 87 octane in the town where I live, but I add a can of octane booster to every can. I found a compression ratio calculator online, (http://www.rbracing-rsr.com/compstaticcalc.html) but I'm not sure what the volume of the pistons should be (I have stock-type pistons with the dual valve reliefs)?

2) My overflow can/tank has a hole purposely put in the top by whomever I bought it from so they could put a bolt through to secure it down. Does this overflow tank need to be airtight? Would the radiator suck in a bunch of air if it wasn't, causing over heating?

3) Could the carb be a problem? I've recently heard that the Edelbrocks tend to overheat the fuel to the point of boiling. Anyone else use Edelbrock carbs? I should probably get a Holley.

4) Could the clutch fan not be working? How can I tell? I've been told to go with a direct-drive fan with no clutch. Any idea how much horsepower this might use? I'm think 10-15 hp maybe? I can afford that if it'll keep the engine cool.

5) The harmonic balancer may not be correct. I can't get it to line up with a timing light at all. The machine shop that did the rebuild told me they balanced the engine with the balancer on, so I'm not really too worried about it, I just can't use it to set the timing at all.

6) Could a vacuum leak cause this? It's very possible that I may have one or more leaks around the car. You can hear a hissing sound inside that sounds like it's coming from the heater controls.


It does seem to run fine, it just gets too hot! And it does ping when it gets hot, but not until then. I did find a leaky stopcock on the radiator, which I'm replacing tonight, and I'm also going to try Water Wetter with around a 25% mix of antifreeze/water (25% antifreeze/75% water). If this doesn't help, I may try a clutchless fan.

Thanks for reading all! Any suggestions please let me know! I am by no means a mechanic, I just love my car. I'll let you know if the Water Wetter helps.

Thanks,
Dan

Hi, Dan. There are two series of 6X heads. They can be identified by a number stamped in the vertical riser on the leftmost rib. Easier to find than say, so here's a pic:

http://www.wallaceracing.com/5chead.jpg

Which 6X series will make a difference.

5 and 6 are not the cause. I would suggest the clutch fan and the thermostat change. place a 160 to 180 degree thermostat. also check the timing again.

good luck.

68 400 ho 4 speed to go

Lots of things to cover...

Doesnt sound like a compression issue.

What is the timing at idle rpm(both with/without the vacuum can hooked up)and how high at what rpm?

Possible water flowing to fast at higher rpm's.
Use a thermostat?

What is the rear end gear ratio?
Do you have a tachometer?
What is the engine rpm at 65 mph?

Clutch fan engages/disengages depending on air temp.
Should be fine since it's working at idle.
Its normal to disengage at highway speeds.
Ok to have a ported over flow jug.
50/50 coolant and water is best overall for highest boiling point protection.

Only thing that stands out is the intake.
The PPM intake is to big for that carb/cam/cylinder head combo.
It's made to flow more air-n-fuel like a RAIV engine(230/240 cam/800-850 carb/big exhaust) would need.
Can be the carb is not flowing enough fuel at higher rpms along with the huge intake plenum and runners.
Try a stock or Edelbrock Performer intake.

Forgot, get a stock Q-jet also.

Thanks for the replies guys. Everyone seems very helpful around here! I'll check out the heads when I get home. All I know is that they're 6X and they're from a 350, so I think they're probably 93cc chambers, but I'll check for an ID# when I get home. I have tried no thermostat, 160, and 180, all work about the same. The rear end gear is a 3.55 as far as I can tell (I counted the teeth). I do have a tachometer, though I'm not sure how accurate it is. It looks like an old aftermarket one, and the needle bounces around a lot. I have a TH400 transmission with no external transmission cooler, just the one built into the radiator. The engine RPM at 65mph seems to be around 2800RPM, though it's hard to tell with the tach bouncing between 2500 and 3000. I've read a few places that more water is better (keeps the engine cooler), but maybe this is wrong? I am regretting a little bit not putting in a bigger cam when I had the engine rebuilt. I had a custom-ground RAIV-style cam that I gave to someone for helping me work on the car, but I wanted to make sure I had good vacuum for the brakes, etc. Someday I'll be getting some new aluminum heads and a bigger cam. I just spent about $3500 on the rebuild and some other parts, so not anytime soon I'm afraid. I just don't want to wreck anything by running at 230. Do forged parts offer better protection against heat warpage? I'm also thinking of putting the vinyl top back on this winter and taking care of the minor rust spots found on the roof. I got a quote for $700 to get rid of the rust on top, put the vinyl top on, and replace a few chrome pieces. Does this sound like a good price? Originally the car was silver with a black vinyl top. Right now it's a black hardtop, still having the chrome trim for the vinyl top. What do y'all think of a black car with a black vinyl top? Would that look ok? Ok, getting off-topic now, thanks for the help, any other ideas are always welcome.

I also do have a stock Q-jet. I think it may be a 650cfm but I'm not sure. I'll have to get some numbers off of it.

Stock QJets are 750 cfm except for a few early 70s 850cfms off hi performance 455s.

Plug off that vacuum leak at its source and see if it helps. If it's from the A/C, factory source for that is a hollow stud on the right rear of the carb. If not in the factory location, trace the rubber vacuum line where it comes out of the firewall near the A/C box and windshield washer hose.

Yes, a vacuum leak will cause a lean condition.
Missed that one.

obviously the car wasnt originally a 455...so was it a 400 or 350?
if it was a 400 you should have the fillers...3 sets...might be missing ,and if it was a 350 would be missing if not added by prev owner..

1) X fillers, metal plates at top in front of radiator
2) masticated fillers or rubber, on ea side of bottom of radiator
3) lower air baffle


then of cousre , check timing, and if carb runs lean it will heat up...check carb...I think besides the fillers most has been covered...
my problem was a missing fillers...also a prev owner had added a helper fan , a pusher, that slowed air flow more than helping...

first the overflow tank is not original...but shouldnt have much impact...I think.
try it wo overflow tank hooked up, and start with water/coolant level at 3" below the neck at cool temp...

Thanks for the tips. I just didn't know if the radiator would suck in too much air if the overflow wasn't sealed. I'm not sure how much suction a radiator will even cause. I've tried it without the overflow, but I think I filled it too full (almost to the top). When it got hot it spit antifreeze all over the engine bay. Does anyone have pictures of these fillers? These may be the missing link (or at least one of them). What do you think about thermal clutch fan vs. clutchless? My machine shop guy told me to go clutchless, but he's not a Pontiac guy. I don't want to be robbed of horsepower if I don't need to be. Do you think running at 230 is going to ruin anything? Do forged pistons and rods have better heat resistance than stock? I'm going to buy an infrared gun soon to at least help me confirm that my temp gauge is reading ok. I think it is though because the inside of the car gets plenty warm, but I do have headers that put off a lot of heat.

The coolant/water will expand(about) 2" in the radiator from cold to hot.
I use an overflow tank for 2 reasons.
Just in case of over heat, and its required at all tracks.

Not sure if you posted.
Are you use'n a fan shroud? Makes a big diff.
And make shre it's close to 50/50 into shroud opening.

If the "clutch" is good, it's better then a fixed blade over all.
A 19" flex fan will cool best at highway speeds, but you should fix the problem 1st.

The fillers work best at idle, but also help at highway speeds.

Factory thermostats are 195*.
My 1st 68 FB 400 ran 210* with a 195* stat for 5 yrs(1975-80) without any fillers, so i dont think 230* would hurt.
I do like'm at 180-190* though.

I think it was originally a 400. I looked the VIN up once and found that it was silver with a black vinyl top, had AC, and I think it was a 400. I'll have to look again. I think that very little of the mechanical stuff was left when I got it. The current engine is a 1975 455 with 6X heads (from a 1973 350 from a GTO (I think)). All I'm 100% sure of is that the old engine was a 350 (stamped on the old block). The whole saga with this car has been bittersweet (but mostly sweet). I was looking for a musclecar, preferably a 1969 Camaro, but I couldn't find anything solid that I could afford. I alsmot bought a 1996 Camaro, but at the last second I saw this in the local newspaper for $4200. The car was in California until around 1998 (so the body's fairly solid), then it came to Wisconsin, and then Dubuque, IA where I bought it. It came with a 4:11 rear gear and a bit of a tired engine. The engine only lasted about a week as I was going about 80-85 down the highway and she spun a rod bearing. I was initially pretty bummed, but then excited because I got to put in a 455 I found a block for $550 and put the whole engine together for only about $1200. It supposedly had around 340 horsepower and 460 ft-lb (dyno sim from some Pontiac website), which I thought was pretty good for the little amount of money I had in the engine. I drove it a few times a month during the nice months until around this time in 2006. I was driving her home and the oil pressure gauge dropped to 0. I pulled over right away and had it hauled home. I thought there was something seriously wrong and I didn't have the money to fix anything, so I parked it for a year. I decided to start it up last fall (2007), and the oil pressure was normal again! Maybe a loose connection in the gauge? Bummer. So I drove it a few times, but it was leaking oil, which concerned me. It turned out to be a leaking drain plug (stripped out). I got an oversized plug around May 2008 and drove it for about 5 minutes before it made an awful knocking noise. Turns out a rod bolt broke or stretched and broke the rod cap and cracked a piston. So I took the engine to the machine shop in early June this year, told him to build the bottom end to be able to withstand at least 650 hp (for when I get my nice new heads) and got it back earlier this month...I guess Pontiac rods and pistons are hard to come by these days, at least according to the guy I took it to! Anyway, needless to say I don't want the same thing to happen again. The shop guy blamed it on "peanut butter" stock Pontiac rods (meaning they suck). The engine is running about the same as it did back then, heating up to around 230 when driving down the highway, and then pinging when it gets warm. I'm not sure if that could contribute to the rod bolt/cap breaking or not, but I don't want to take any chances. I also got a nice new 7 qt Moroso oil pan during the rebuild...$230 for those suckers! Once I get this engine straightened out I only need bodywork, new carpet, air shocks, exhaust, etc...haha. I never realized how much time and money these old cars take, but it sure is worth it when you're behind the wheel! Sorry for writing a book.

Stock Pontiac rods are quite durable. The rod bolts should be replaced when the rods are resized. Blaming a broken bolt on the rod is passing the buck.

Shortage? Not really...I have over 12 sets of Pontiac rods and 3 or 4 sets of pistons.

Sounds like a fun engine, but I question the heads being off a 350 and running on 87 octane on a 455.

I haven't read yet the condition of the radiator. The symtoms of overheating on the highway are exactly what I had prior to installing a BeCool aluminum radiator in my '67. Now instead of 235 degrees on the highway it runs at 185 - 190. Very satified with the change.
Steve

Well I have chimed in on this topic with all of my attempts and findings over the last several years. However, I have something new to add.

Last spring I installed the correct fan and at the same time added one bottle of Royal Purple's version of Water Wetter. Up until this past week I have been giving all the credit to installing the correct fan. HOWEVER, last week we pulled my motor to change the rope seal to the new BOP rear main seal. In doing so I lost my additive in the radiator.

Mind you I have been driving ALL SUMMER down here in FL and have not ran hot once since the new fan and additive. Now that I refilled the radiator and DID NOT put the additive back in, I ran warm again this past Saturday when we went to Old Town cruise.

Bottom line for me, I am now a beleiver in the radiator additives...

Well I went home last night and put a new drain stopcock on the radiator. That's where I thought (or at least hoped) the leak was coming from. I also put in some Water Wetter. I took it for a 20 minute drive and it never got above 215 until I shut it off in the driveway...when i noticed the radiator was leaking profusely...not gushing, but more than just a drip. It's coming from the driver's side towards the front of the car, from the radiator. I can see the leak, and it was coming out in a stream about the size of a pencil...not good. I guess I now have an excuse to get a Be-Cool radiator, or get mine repaired. I guess it will depend on how much they charge for repair. Eventually, I'm definitely going with the Be-Cool. I'm not sure if the 15 degree drop in temperature was from the Water Wetter or from the fact that I was just losing the coolant. Looks like no more driving for me this year. I can't afford a radiator right now

4.11 gear...AH-HA!

To much for that cam.
At highway speeds, the engine rpm is past that cam's power band, which makes the engine work harder then it should.
A 3.08-3.23 gear would be a good match.

But since your gon'a get HP heads, may want to hold off.
Need a cam around 240*-250* with a 4.11.

loosing coolant water temp would go up, so, looks like the wetter did it....fi9x the radiator ,by fixing the old or buying a new...then tset again with the wetter...

Actually it's a 3.55 gear right now...it came with a 4.11 but I swapped that out. It wasn't much fun cruising at 3500 rpm. The 3.55 seems to be all right. At 65mph it's at around 2800rpm. I'm going to see how much the radiator repair would be, otherwise just park it for the year and save up for the Be-Cool aluminum radiator.

Yeah, I didn't know if just losing a small amount might make the temp drop by dumping the heated fluid. I knew that if it ran too low on fluid it would obviously overheat and the temps would rise, but if it dumped a small amount continuously, might the temperature actually drop? I did see a couple of rubber-like flaps up near the radiator, one on each side. Those must be the "fillers" everyone is talking about. Those are the only "filler" type flaps I saw though, other than the flaps blocking the holes near the front wheels. I didn't see the "X" near the radiator.

Darnit!
Thought i had it

3.55 is still a bit for that cam, but not that bad.

If the fins bend and flake easy, just get a Be-Cool or Rodney Red radiator unless you like original appearance.

The radiator getting low can create an air pocket, acts like a blockage in the system. Temp will spike up, drop when it pushes through, spike again, etc...

Can you see the front of the radiator by looking down in front of the core support?
If so, then you dont have the "X" fillers.

Both those and the lower rubber fillers are good to have.

sounds ike you have the masticated fillers...but not the X fillers....can you see down to road below if looking in front of the radiator? if so you are missing the lower baffle, but if you cant, you have it...
the two X fillers fill the gap between the bumper are to the radiator....they would prob give you about 5F if there...400`s and ac cars had those for more air to be pushed thru the radiator...so w a 455 I`d say you need those...part no C948084 from Classic, $75...$6 for the screw set...
if you have classics catalog its on pg 343 "radiator support to bumper filler panels"
Ames has them too ,part no FP191J core support fillers $99 set

Wow, thanks so much for the heads up on the Rodney Red radiators! So much cheaper than the Be-Cool ones! At least from what I've found so far...$520 isn't bad for a new aluminum radiator with the trans cooler

What do you think of this one? Anyone ever heard of Entropy Radiators?

http://cgi.ebay.com/ebaymotors/NEW-Alumi...emZ350099130943

It sounds good and the price is right! He also has one with dual electric fans for $599.00

Try Superior Radiator. They sell on eBay. http://cgi.ebay.com/ebaymotors/67-68-69-...emZ280270334101 browse their store to find what you want, or contact them.

The radiator I purchased from Jegs is an aluminum Big Block BeCool Eliminator #134-10168. The cost was just $299. It is a direct fit but needed very slight modifications to the mounting flanges. Not as fancy as the more expensive BeCool model but performs very well. I'm very satified.
Steve

Thanks again guys. I was preparing to spend at least $600 for a new radiator. $200-300 sounds much better

I'm wondering why some of these radiators are so much more expensive than others? Are you just paying for the Be Cool (etc) name? Is there anything I need to specifically look for when choosing a radiator? The wider the better and the more rows the better?

Every time a radiator is handled, from manufacturer through each distributor to final retail, a markup is made.

Superior Radiator is a manufacturer. They build them right in their shop, about 12 work stations for different materials and processes. They don't have a "sales staff" or marketing department. The person who usually answers the phone is the owner, and his station is closest to the phone hanging on the wall.

Building a brand, and selling through distributors, costs money. The consumer pays.

More rows is better on copper radiators. Aluminum rads are usually 2 row. More width is always better, until you reach the ends of the opening in the core support. Having fins behind solid steel does no good at all.

Thanks for the business lesson I work in an industry where oftentimes it is the exact opposite. We make laboratory equipment, and we sell things at "list price" here at the manufacturer, which is usually a higher price than what our distributors sell at, because we give our distributors large discounts and they can afford to pass a little savings on to the customer. The distributors pay for most of the marketing, etc, and we are basically guaranteed more sales, albeit at a lower profit margin per sale. It can go either way. It depends on how much the distributor wants to stick it to the customer and on the industry you're in. Thanks for the info on Superior Radiator. It will be hard to beat that price, and I may just be able to drive the car yet this year.

I also run a Superior alum rad. Bought it a few years back and have no issues with it. I painted the top of it semi flat black and used a stock shroud etc. and you can barely tell it's there. Good luck...

I'm in an industry where we are the distributor/reseller and sell at a significant discount to "retail" customers and give even bigger discounts to volume customers. The manufacturers foot the advertising costs, including marketing dollars for certain products featured in our own ads. Marketing doesn't cost us anything but a web site and business cards.

I just had my dad's radiator recored at Superior, they're just a few miles from me. There were probably 100 radiators, about 70% aluminum, visible in various stages of production, inspection, boxing and the shipping area when we stopped in. They called us when the radiator was done and checked and repaired the heater core when we picked it up.

Their website is one of the worst I've ever seen, but it gives the critical info. They're also not salespeople, won't tell you that you need to buy that $600 radiator, but if that's the one you want they'll be happy to build it for you.

They make an all aluminum radiator with an aluminum shroud and one or two fans. It looks like it would do an excellent job.

Was mess'n under the hood last night.
That will be a new post...
Every time i do, the open space between the radiator(Rodney Red) and the core support bothers me.
Dont have a cooling problem, but wonder how much air gets sucked in around it and not thru the support opening.
Have a trany cooler mounted directly in front on the radiator, and worried not enough air gets pulled thru it at idle.
Sure i must have tested it in the past, but gon'a do it again this weekend on "monthly engine fire up".

not exactly stock, but could you use closed cell foam/EPDM weatherstripping to fill the gap? Like maybe a decklid weatherstrip cut to fit?

On my race car I used Aluminum tape to close gaps. It's got a peel and stick backing, it's about as thick as duck tape, forms like aluminum foil but takes a bit to knock a hole in it.
Heating and air supply houses sell it. Not sure you'll find it at places like Lowes.