[INchief]

If this isn't the section for this problem please let me know. I have an overhauled 287, which is the original engine from the car - 1955 4-door Chieftain. The radiator was replaced at the time of the engine OH. I recently removed the thermostat to keep coolant flow at max flow, just to help me troubleshoot. It seems kind of obvious to me what my problem is but I wanted to get the input of you guys that have more experience. I believe the radiator is too small.

I am driving an alternator, power steering (stock) and air conditioning. The water pump was replaced at overhaul. With the radiator cap off and pulling RPM above idle it seems to be flowing really well - throws coolant out of the filler neck.

I confirmed the stock temp gauge is reading correctly - when it's at the high end it is 210+.

Average day - 70-75F, the engine runs at 175-185 going down the highway, it heats up quickly pulling more power and takes a few minutes to get back to temp.

Warmer day - 80-85, the engine runs at about 190 going down the highway at 60-65.

Hot day 85+ it runs hot (190+) just driving around town, putting it on the highway isn't an option.

Is there anything to check other than the radiator that could be the issue? I think that since I'm running with no thermostat and the air temp makes a noticeable difference in the running temp, it points to the radiator. I have a fan shroud and electric fan that I have set to kick-in at 150F.

Obviously it's running too hot but I am curious what is a standard temp for a 287 to operate that you guys consider normal running the accessories that I have installed?

Thanks

[fyrffytr1]

Do you have a fan shroud?

[INchief]

yes, electric fan and shroud.

[694.1]

Factory reverse cooling? Even if the tubes are missing in the heads, it should run cool.
Presuming here you have ruled out retarded timing and a stuck heat riser...

[INchief]

Originally Posted by 694.1

Factory reverse cooling? Even if the tubes are missing in the heads, it should run cool.
Presuming here you have ruled out retarded timing and a stuck heat riser...

The gusher tubes are installed, I had to replace one and repair one.

I have not ruled out a timing issue. Would I check if the vacuum advance is working for a timing issue? I should probably check the timing anyway. The engine hits a rough spot about 40-45 MPH then smooths out. Then gets rough again around 65 MPH, then smooths out.

The heat riser on the exhaust manifold was beyond repair and I removed it, if that is the riser you are talking about.

The Pontiac manual from back on the day states the thermostat should be 150F - should this engine be running that cool? It was ready for overhaul when I bought it so the only experience I have running it is post-OH.

Thanks

[Sirrotica]

Could be 50 reasons why it overheats, but rough running needs to be addressed first.

Timing, or lean fuel mixtures will cause an engine to overheat also. My recommendation would be to get the engine running correctly first.

Not being able to run on the highway is usually an airflow through the radiator problem, or a scaled radiator insulated enough not to be able to reject heat will also cause O/H at highway speeds.

Running without a thermostat lowers the pressure in the engine generated by the waterpump, and makes steam pockets internally in the engine. You'll likely make an overheat problem worse by removing a thermostat, unless it's stuck closed. The cooling system needs the pressure in the block to eliminate the steam pockets.

Typically, unless you have a massive electric fan, you'll never move enough air through the radiator to cool a Pontiac. Pontiacs, compared to say a SBC, require a huge amount of huge airflow through the radiator to maintain their cooling. 9 times out of 10 you'll be much better off with an engine fan over an electric fan with a Pontiac engine. If you have the OEM 4 blade fan you can also try an RV style composite fan, they pull at least twice the amount of air as the OEM 4 blades do. Aftermarket flex fans should also be avoided.

Below is a link to the 6 blade composite fan, I've had great luck with them in the past cooling oval track Pontiac race cars.

https://allstarperformance.com/searc...q=nylon%20fans

Having an A/C unit also is going to make airflow through the radiator important, as the airflow is restricted. and when the A/C is operating your using already heated air to cool your radiator. Pontiac engineers also used a small waterpump pulley on A/C equipped cars from the factory to speed up the waterpump RPM for flow, and as I've already mentioned internal coolant pressure.

You mentioned a larger radiator, and from my experience adding capacity of coolant, as well as heat rejection area is never going to hurt when you've got a marginal system.

Just some quick ideas to find your problem from your statements in your post, hope something helps.

[peters23]

The original early style 4 bolt water pumps used a cast iron impeller.
Many of the replacements use a stamped steel impeller that has been shown to be inferior to the original cast iron, and may cause overheating.

[Goatracer1]

When that engine was new people still used Alcohol antifreeze thus the need for a low temp thermostat.

[Bill Hanlon]

Originally Posted by peters23

The original early style 4 bolt water pumps used a cast iron impeller.
Many of the replacements use a stamped steel impeller that has been shown to be inferior to the original cast iron, and may cause overheating.

I used both iron and stamped steel water pumps for many miles in my '57 GMC (Pontiac) 347 daily driver with A/C for 22 years. Both worked well.

[INchief]

Originally Posted by Sirrotica

Could be 50 reasons why it overheats, but rough running needs to be addressed first.

Timing, or lean fuel mixtures will cause an engine to overheat also. My recommendation would be to get the engine running correctly first.

Not being able to run on the highway is usually an airflow through the radiator problem, or a scaled radiator insulated enough not to be able to reject heat will also cause O/H at highway speeds.

Running without a thermostat lowers the pressure in the engine generated by the waterpump, and makes steam pockets internally in the engine. You'll likely make an overheat problem worse by removing a thermostat, unless it's stuck closed. The cooling system needs the pressure in the block to eliminate the steam pockets.

Typically, unless you have a massive electric fan, you'll never move enough air through the radiator to cool a Pontiac. Pontiacs, compared to say a SBC, require a huge amount of huge airflow through the radiator to maintain their cooling. 9 times out of 10 you'll be much better off with an engine fan over an electric fan with a Pontiac engine. If you have the OEM 4 blade fan you can also try an RV style composite fan, they pull at least twice the amount of air as the OEM 4 blades do. Aftermarket flex fans should also be avoided.

Below is a link to the 6 blade composite fan, I've had great luck with them in the past cooling oval track Pontiac race cars.

https://allstarperformance.com/searc...q=nylon%20fans

Having an A/C unit also is going to make airflow through the radiator important, as the airflow is restricted. and when the A/C is operating your using already heated air to cool your radiator. Pontiac engineers also used a small waterpump pulley on A/C equipped cars from the factory to speed up the waterpump RPM for flow, and as I've already mentioned internal coolant pressure.

You mentioned a larger radiator, and from my experience adding capacity of coolant, as well as heat rejection area is never going to hurt when you've got a marginal system.

Just some quick ideas to find your problem from your statements in your post, hope something helps.

OK, thanks for all of the input. I'm checking the timing and fuel mixture next and get thermostat back in the system. What do you mean by a "heat rejection area"?

[Sirrotica]

A larger heat rejection area is increasing the area that is exposed to air, I.E. would be a larger/thicker radiator, more surface area.

Increasing the volume of a cooling system by using a reservoir/expansion tank, will also aid in making an overtaxed system work more efficiently. Late model cars have adapted this aid to have more volume, without using a huge radiator.

At a certain point, making the radiator core thicker has very little effect on efficiency. Adding more coolant volume by adding a reservoir is fairly cheap, and not difficult.

You're probably not going to need to do any of the modifications, once you sort out the OEM cooling system, as well as engine tune. These types of modifications are more for a closed course racing application that requires a severe duty type system.

To further aid in your troubleshooting, a thermal heat gun to read different points of the cooling system would be a good tool to have.

I hope some of the suggestions will get your problem straightened out.

[INchief]

Originally Posted by Sirrotica

A larger heat rejection area is increasing the area that is exposed to air, I.E. would be a larger/thicker radiator, more surface area.

Increasing the volume of a cooling system by using a reservoir/expansion tank, will also aid in making an overtaxed system work more efficiently. Late model cars have adapted this aid to have more volume, without using a huge radiator.

At a certain point, making the radiator core thicker has very little effect on efficiency. Adding more coolant volume by adding a reservoir is fairly cheap, and not difficult.

You're probably not going to need to do any of the modifications, once you sort out the OEM cooling system, as well as engine tune. These types of modifications are more for a closed course racing application that requires a severe duty type system.

To further aid in your troubleshooting, a thermal heat gun to read different points of the cooling system would be a good tool to have.

I hope some of the suggestions will get your problem straightened out.

OK, thanks for the explanation on the heat rejection area. That makes sense and I hadn't really thought about why cars have reservoirs. I agree with getting the other issues solved before looking to increase the cooling system.

I did find some issues with timing and I'm working those out. I found the initial engine timing was off (sitting at 0 degree BTDC) and adjusted it to spec. The mechanical advance is working based on checking the timing through 2400 RPM.

I also found my vacuum advance canister was not holding vacuum and so it wasn't working. I'm now looking for a vacuum advance canister and/or replacement distributor. Both seem rare at this point. I adjusted the fuel mixture at idle with the port from the carb capped, I'm guessing the leaking canister was also creating a vacuum leak.

This all came into view after I installed the air conditioning just as the hot weather hit - close to 100. It looks like I committed the cardinal sin - adding new components as another one fails, helping to mask another problem.

I have a thermal heat thermometer and that's a good idea to check various areas.

I appreciate you taking time to answer this thread. It really helped me out. Thanks

[Sirrotica]

Originally Posted by INchief

OK, thanks for the explanation on the heat rejection area. That makes sense and I hadn't really thought about why cars have reservoirs. I agree with getting the other issues solved before looking to increase the cooling system.

I did find some issues with timing and I'm working those out. I found the initial engine timing was off (sitting at 0 degree BTDC) and adjusted it to spec. The mechanical advance is working based on checking the timing through 2400 RPM.

I also found my vacuum advance canister was not holding vacuum and so it wasn't working. I'm now looking for a vacuum advance canister and/or replacement distributor. Both seem rare at this point. I adjusted the fuel mixture at idle with the port from the carb capped, I'm guessing the leaking canister was also creating a vacuum leak.

This all came into view after I installed the air conditioning just as the hot weather hit - close to 100. It looks like I committed the cardinal sin - adding new components as another one fails, helping to mask another problem.

I have a thermal heat thermometer and that's a good idea to check various areas.

I appreciate you taking time to answer this thread. It really helped me out. Thanks

A member on here specializes in older ignition systems and has a lot of obsolete older parts for them. His member name is "Sun Tuned". You might reach out to him to see if he can help you out with a vacuum advance canister.

Link to member: https://forums.maxperformanceinc.com...r.php?u=143447

I'm always happy to attempt to help other members...........

The experience I've gained from over 5 decades of racing Pontiacs, and wrenching on them for my living doesn't do any good if not shared.

[peters23]

Another thing to look at, if you happen to have the heads off:
Check the coolant passageways that connects to the intake manifold on the front. My 1960 heads had a lot of flashing in this area that I ground out with a die grinder. You might need an extra long bit to get in there. Leaving that sort of stuff in there can and likely will decrease flow.

[INchief]

Thanks to everyone that provided input. You got me back to basics and not over thinking the issue. The bottom line is that the engine ran "warm" after overhaul but it was still ok and I wasn't thinking much about it. Then it just went downhill from there.

The initial timing was at "0" TDC (which probably explains running a little warm) so I adjusted that to 5 BTDC. Checked it at midrange RPM and all was good. That led to a leaking vacuum advance, which I found an NOS (Sorenson) one from a local enthusiast . The fittings on the vacuum canister from the previous mechanic were not correct and also leaking. Got a 45 degree fitting for the cannister that takes a 3/16" brake line on the outlet side and got it sealed up. Got timing set to spec, replaced the vacuum canister and vacuum line, idle mixture adjusted. It's 85degrees today - running 160-165 with no a/c and 170-175 with a/c on. Highway, street cruising, stop and go, it's all good. Cheers! It's time to take a break.