I have a 67 firebird that has had heating/cooling issues since I finished the build.
Cooling system: Champion cooling radiator, 2 Core, 3 Row, PN: 166-CC337 High flow water pump Stock 7 blade fan/clutch Stock fan shroud Filler panels to channel air to radiator installed 160 Degree thermostat 15 PSI rad cap
On a cooler day ~65 degrees it runs great and stays @ 160-175. Once the ambient temp reaches 70+ It runs 180-195 on the highway and quickly jumps to 200-210+ at stoplights and will reach 220 if left to idle for a few minutes. I know that 210 is fine for this engine, I just can't seem to keep it there. I do have a larger cam in the car, could this be a cause for overheating?
Most of our cars run on the hot side. You just have to get comfortable with that. 210-220 is not that bad. I’d use a 180 or 195 thermostat. The motor needs to be warm enough for normal operation. At 210 any thermostat you use will be wide open anyway.
As Bob says it's not that bad if it maxes out at 220. But if on 90+ degree days you find it going higher there is a long list of culprits. A couple of quick ones are to make sure your fan clutch is getting full engagement when at it's set point It does not matter if you just bought it as there is a lot of junk out there. Here is a video to help you get an idea of how to test it's definitely not the best so do your homework https://www.youtube.com/watch?v=cOXcrbQRDWU You should also hear a lot of roaring from the fan when revving the motor with the hood up and at full temp. Another thing to check is the depth that the fan sits into the fan shroud, to deep or not deep enough and you will have temp problems while sitting still. Unfortunately aftermarket fan clutches do not get this right. I have my original 68 unit and have compared to 3 different aftermarket units that were listed for a 68 Firebird and all 3 caused the fan to sit at different depths.
This sounds so familiar to my car. I messed around with everything, cold case radiator, flow kooler water pump, high flow 195 and 180 thermostats, more aggressive fan, and mine would still get hot idiling/sitting at stop and go lights etc. She’ll cool right back down the second I’d get moving a bit again, but as soon as I started sitting, that temp gauge would just start a climbing. My next step was going to be to throw a good electric fan on there and see what happened, but just before I ordered it, I received some real sound advice on hooking up vacuum advance on my car and making sure to have it hooked to full manifold vacuum so that it increased the timing at idle, and wow, that cheap little $10 part did the trick. I know they make adjustable vacuum advances, but I just ordered a few different standard ones from my local parts store, and found one that activated on very little vacuum at idle and it completely cured my car. I can honestly let my car set and idle on a 90+degree day. Best and cheapest upgrade I’ve ever done to my car!!
The fan sits about half way in the shroud, which I believe is the correct depth. After reading your response, I'm thinking that the clutch may not be getting full engagement because I don't really hear much fan noise when the car is at temp. I understand that 210-220 is not that bad for these cars, but the issue is keeping it at that temp. It will continue to get hotter than that while idling quickly getting up to 225 or 230.
This sounds so familiar to my car. I messed around with everything, cold case radiator, flow kooler water pump, high flow 195 and 180 thermostats, more aggressive fan, and mine would still get hot idiling/sitting at stop and go lights etc. She’ll cool right back down the second I’d get moving a bit again, but as soon as I started sitting, that temp gauge would just start a climbing. My next step was going to be to throw a good electric fan on there and see what happened, but just before I ordered it, I received some real sound advice on hooking up vacuum advance on my car and making sure to have it hooked to full manifold vacuum so that it increased the timing at idle, and wow, that cheap little $10 part did the trick. I know they make adjustable vacuum advances, but I just ordered a few different standard ones from my local parts store, and found one that activated on very little vacuum at idle and it completely cured my car. I can honestly let my car set and idle on a 90+degree day. Best and cheapest upgrade I’ve ever done to my car!!
I had read something about hooking up vacuum advance, but I'm using a MSD Pro-Billet distributor that does not have a vacuum advance mechanism in it. I don't think that initial timing would be the issue, I'm running 18 degrees initial and 36 degrees total. I had tried an electric pusher fan mounted to the front of my AC condenser, but that did not seem to help the issue either.
Yes check all the basics first like making sure all parts are functioning correctly. I have seen quite a few of those aftermarket clutch fans not getting full engagement in my time but otherwise look fine. Did you set the gap on the waterpump divider plate with your favorite BFH? I see from your response below that you have a/c an important thing to know when diagnosing a hi temp problem. I not sure if you are aware but the factory had a few tricks up there sleeves when it came to keeping our a/c birds cool. One was pulley sizes. Here is the factory manual showing the part #s and the pulley diameters are all the way to the right, make sure you have the right ones. http://www.teufert.net/partbook/67-76/1-i.pdf . Is the lower baffle in place? #3 in this diagram http://www.teufert.net/partbook/67-76/8-i.pdf Although more for cooling at speeds it does block off the holes underneath so that air only comes in mostly through the grills and the spaces below in front when sitting still and once underway does not allow the air that is ram fed through the grills to spill out below. And how about all the masticated filler pieces that seal up all the gaps around the radiator? look in the service manual under cooling system and they are listed as seals in the diagram for A/C cars https://www.firebird400ho.com/mdocuments-library/ Good luck and let us know what you find.
I did not set the gap on the new high flow water pump. I wish I knew about that before I put it in, otherwise I would've at least checked it. Part of me doubts this is the issue because the car ran hot before I installed the high flow pump but it could be a part of the problem.
The car has a vintage air AC unit installed but I rarely run it due to overheating. I was under the impression that it wouldn't have much of an affect on the cooling system when its not running because the compressor is engaged via a clutch.
The bottom baffle is in place as well as the upper baffles that tie the radiator mount to the front bumper assembly. I do not have those seals that fill in the gaps around the radiator
… I received some real sound advice on hooking up vacuum advance on my car and making sure to have it hooked to full manifold vacuum so that it increased the timing at idle, and wow, that cheap little $10 part did the trick. I know they make adjustable vacuum advances, but I just ordered a few different standard ones from my local parts store, and found one that activated on very little vacuum at idle and it completely cured my car. I can honestly let my car set and idle on a 90+degree day. Best and cheapest upgrade I’ve ever done to my car!!
Is this a thing? I’ve never heard of this before. …and I assume you mean “advances” the timing at idle…?
So, advanced timing at idle will enable your engine to run cooler?
I'm a hobbyist. Not a professional. Don't be hatin'!
I was running a complete MSD system with the Pro Billet Distributor also and sure didn’t wanna mess around removing that, but after talking to a couple guys that kept preaching to try the Vacuum Advance and literally trying everything else with no luck whatsoever, including gaping the water pump, I ended up getting desperate and removed the MSD setup and picked up a HEI, and it was by far and away the greatest thing I ever did to that car. Like I mentioned previously, I played around with a few different advance cans before settling on one and I can tell ya, I wouldn’t be afraid to go in a parade on a scorching hot day now!! If and when you run outa other options, I highly recommend trying this!! I feel like the car car even runs a bit cleaner/crisper with that HEI/Vacuum Advance Setup and looks cleaner under the hood.
Was the vacuum advance recommended only to advance timing at lower RPM? As I mentioned before I’m running 18 degrees initial timing, and the spring/bushing combo in the distributor is curved so that I reach total advance (36 degrees) at about 1800-2000 RPM. I’m not sure that adding the vacuum advance would help much in my situation.
The newer style cores flow better and a three row will flow more then an original style 4 row in a quality Radiator. That said with the flood of all the cheap but very nice looking Chinese junk on the market these days who knows,
Unfortunately the gap with the old pump could have been terrible and with the new pump is also. At this stage of the game I would not worry about it until you verify everything is working correctly As far as the a/c you are partially correct that when it's running the Condenser gets hot and prewarms the air entering the radiator. Unfortunately even when it's not running with that thing sitting in front of the radiator like a big ole billboard The restriction is like running with your hand partially blocking your mouth/nose, much harder to breath. This is part of the reason the factory made all of these modifications on a/c cars.
Sounds like you are running plenty of initial although there are many factors that determine this and unless 2 motors are built identical and in the same car and conditions every engine has it's own magic number. More spark lead or advance at idle will allow an engine up to a point to run cooler but also cause hard slow cranking of the engine especially when hot. This was part of the reason back in the day that people would use manifold instead of ported vacuum for the advance. This way the motor when cranking to start will just be at initial advance but once running and idling the Vacuum advance would kick in to whatever setpoint you installed and keep the engine cooler at idle. There is a lot of debate about running it either way and I myself feel that for a mild street cruiser ported is best for more power under light load/ throttle angle cruising and fuel mileage of course unless you have a temp problem in a modified car that cannot be solved with all the usual means. For an all out motor where wide open total horsepower is king and things like part throttle cruising response and fuel mileage mean nothing you don't need no stinken vacuum advance. Our motors can tolerate a lot of advance in lite load partial throttle conditions and the vacuum advance accomplishes this raising both power and efficiency under these conditions. It sounds like you know what your doing with the timing and I'm sure you know you can't advance initial without affecting total which is a surefire way of smoking rod bearings and motors. I just found this on Rocky Rotella's site Haven't read all the way through so hopefully it doesn't contradict and make me look like a fool https://www.pontiacv8.com/articles/2018/9/30/blrwa28r1tb0vt5c24d7ejwjskxfdq
I read through that link you posted, and they put in 12-16 degrees of vacuum advance, bringing the total (initial plus centrifugal plus vacuum) at part throttle to 45-50 degrees. Maybe this could be causing an issue as my total without vacuum is only 36 degrees.
I also checked my fan clutch, and it is fully engaging. I stuck a rolled up newspaper into the blades and they didn't stop/slow down so the clutch is good. I may pull it out and adjust the spring so that it fully engages at a lower temp.
Another thing I wanted to bring up is gaps in my fan shroud. It does not fit perfectly to the aftermarket radiator and there is a gap where the shroud overhangs and inch or two. I has notched the shroud around the inlet for the transmission cooler, but I may need to notch it a bit more to sit flat.
The fan seems to be sitting in the shroud correctly and I attached a photo of that. Would it be of any benefit to move the fan closer to the radiator? A few guys I’ve talked to have mentioned trying that.
The vacuum advance will help the car run cooler, get better gas mileage and feel more responsive/peppier at low to mid throttle angles and light load cruising Where the motor can tolerate 50 degrees or more advance. It does not come into play at idle in the stock configuration with the thermal vacuum switch until temp goes past 230. then the switch changes the vacuum source to manifold vacuum which at idle advances it to whatever the full setpoint of the canister is on top of the static timing setpoint to cool the engine down. Once it does this the switch reverts back to ported vacuum. I never understood the thinking behind buying an expensive distributor that eliminates the vacuum advance function in a street cruiser but hey to each there own. Back to your overheating at idle problem you never said what size crank and waterpump pulleys are on your engine, it's important. Here is a factory bulletin from PMD back in the day talking about overheating and those masticated seals I was talking about earlier https://firstgenfirebird.org/f-a-q/category/cooling-system/ As far as the fan depth I think it looks fine and sticking it in deeper can actually cause the air to get trapped longer in the shroud just circulating. I don't have any experience with champion radiators and I know they claim the 2 core is rated up to 400 HP but I would be suspect of that and if putting a car together using there product would have at the very least gone 3 core and knowing me most likely overkilled it with 4 which they claim is good to 800 HP. Some more things to check, is the mixture 50/50? it makes a difference. change the thermostat just because it's cheap and easy and will eliminate any questions about it opening fully. Make sure and drill a 16th of an inch hole in the flat part to eliminate the dreaded first start air pocket. On the fan clutch shut off the engine when up to full operating temp and try to turn, it should be very hard to turn. Make sure the radiator cap is holding it's full 15 pounds if you don't have the tester an auto parts store will do it for you. If you are at all suspect of the fan clutch find a fellow Pontiac guy and borrow a factory flex fan to try out it's quick and easy. Make sure the fins on the A/C condenser in front of your radiator are not mashed and layed over on both sides by someone who was heavy handed during installation, The same goes for the radiator. You can buy a fin rake to remedy this. On your timing, check to make sure the outer ring of the crank dampener has not slipped on the rubber ring causing the timing to be out even though it shows correctly with the timing light. To do this just stick a wooden dowel or something like it into the #1 spark plug hole and turn crank until you physically verify it's at tdc and check that the line on the dampener is lined up with 0. Many a mechanic has been fooled by this when not excessively out. Lastly I assume the engine timing curve and setpoints were done on an engine dyno when it was built? was the fuel mixture optimized at the same time?. If the idle circuit is to lean it will contribute to higher temps. The best thing you can do for your car is to find a good engine builder/tuner with a chassis dyno to set everything up optimally , it makes all the difference in the world. Do you know what brand and color paint was used to paint the engine?. At least on my computer screen it looks much closer to the factory color on the original engines I have torn down compared to the more blueish colors that a lot of company's sell today.
The mechanic we had help from when we restored the car recommended the MSD set up that he apparently runs in all of his cars. I built most of the car when I was 15-16 and if I could go back I would change a lot of things lol. But anyways, the crank pulley is 6.25" and the water pump pully is 8", which matches the firebirds part catalogue you had linked before.
The coolant mixture is 50/50
Changing the thermostat and having the radiator cap checked will be a project for the weekend. I'm also thinking about pulling the water pump to check the gap on the divider plate, but we'll see.
When the engine is up to operating temp, the fan is not any harder to turn than it is when the engine is cold. Is this a symptom of a bad fan clutch or improper setting of the spring?
The engine timing curve I was referring to is just the one that correlates with the spring/bushing combination currently in the distributor. I've never had the car on a dyno, but I did take it to a mechanic that specialized in old Quadra jets and had him tune it.
I didn't mean to knock your setup, For some reason I thought you bought the car the way it is built. The stock pulley sizes for a 67 V-8 with A/C and power steering, water pump pulley #18 in the chart 7 and 1/8 and crank pulley #22 in the chart 8". You would have to do the math to see if your combo matches the water pump revolutions of a stock setup at idle speed. If you spin it to slow at idle it will cause obvious problems but if you spin it to fast the coolant does not stay in the radiator long enough to do it's job in stripping the heat away, also a problem. that fan clutch sounds suspect to me and I would bolt on another non clutch type fan to test it. I know what you meant by the spark/timing curve and was assuming it was optimized on an engine dyno but recommending it and the fuel be optimized on a chassis dyno. Thanks for the info on the paint. Do you find it burns off in the usual spots like the cyl. head exhaust ports?
No worries haha, I'm kicking myself now for the way I did a couple of things but that's how you learn I guess. The water pump is a kooler master high flow pump, so maybe the coolant isn't staying in the radiator long enough. I'll see what I can find for non clutch fans. Do you have any recommendations? The paint does burn on the cylinder head exhaust ports, but I didn't know that was usual for these engines.
