[Mook]

1969 GTO, 468 Stroker, Edelbrock round ports. 200r4 with 3000 stall, 850 Quick fuel carb and 160 performance stat. Temp idling today 85+ degrees ambient temp. Temp hangs around 185-190…..

Temp rose to about 195 driving around town light to light…

Temp rises to 201-205 driving long stretches, when constant acceleration is required.. Temp will lower once acceleration is not needed ie., stop light /stop sign or sometimes going into O/D. Temp also lowers 5-8 degrees when heat is turned on.

This scenario was worst before fatting to primary jets to 83 from 80. This change improved temp by at least 10-15 degrees.

My thought was carb is still running too lean even with the increased jets from 80 to 83, will 84 or 85 make an improvment?

And or Replace stock style 4 core copper/brass?, radiator with Cold Case larger capacity 2 row aluminum type. My thought there is when turning heat on increases amount of coolant receiving surface air flow?

Anyone agree? Anyone have any other ideas / comments?

Thx……

[Dragncar]

I would not be worried with those temps.

[Gach]

Just an idea I would check your timing, making sure it’s not advancing. I’ve seen timing Advance up to 50 degrees. As the rpms go up. In other words lets say you run a total of 36 degrees all in by 2500 rpms. I will put a timing light on it and bring the RPMs up making sure that it’s not advancing to 30 or 40 degrees. It’s possible while the temperature drop at lower speeds is because timing is then around 36 degrees. I put a time and light on it and check it. Making sure it’s not advancing passed it 36 degrees.

[Schurkey]

A 160 'stat in an engine that runs 205 has lost control of the engine temperature. That 'stat is fully-open by 180, maybe a little cooler. At idle or cruise, the engine temp should be within a few degrees of the thermostat rating, so that under heavy use there's additional cooling system capacity that can be used.

SOMETHING, or several somethings, are wrong.

There's two dozen possibilities, ranging from cooling system problems involving airflow, to cooling system problems involving water (coolant) flow, to engine running problems like insufficient timing advance or lean fuel/air mix, to chassis problems like dragging brakes and tires low on air, making the engine work harder than it really should.

How old is the radiator? What fan/fan clutch are you using? Is there a proper fan shroud, and does the fan fit nicely inside--about 1/2 in, 1/2 out of the shroud (1/3 in, 2/3 out may be even better) without huge gaps between fan blades and the inside of the shroud? What is the crankshaft-to-water pump pulley ratio? Have you removed the seal at the windshield-end of the hood?

[steve25]

If you do not have a fully programable electronic ignition system then you need a distributor with vacuum advance to bring in much needed extra part throttle timing.

If you do have the needed electronic system then what is your total timing like from say 2500 to 4000 rpm?

In terms of a 160 stat all it does is go to fully open sooner the a higher temp stat.

So yes it will take a tad longer for your engine to get up to a normal temp level, but your engine staying at around 160 hinges on your cooling system function and the reserve cooling capability it should have.

Something as simple as your water pump impeller to pump baffle could be a mire .025" too large of a gap and then the pump can't move the coolant out to the Rad like it should, and especially as rpm's go up.

If you have a pump that does not have a cast vane type impeller like a stock one then those are flat out crap and it's no wonder you are well on the edge of having issues.

The bent up stamped steel vanes that some replacement pumps have that look like a Alternor fan make for as much cavitation taking place as they do moving coolant, NOT GOOD!!
From another web site this was posted by a well known engine builder.
When dyno testing at full or near full throttle I have seen the Exh temps go up 30 to 40 degrees for every degree of timing that the motor wants and you don't give it!

So let's cut this back a little to a part throttle condition, in this state of running I can see Exh temps being 20 degrees higher then they should be with the result then of that extra heat going right into the cooling system.

[Formulajones]

With a 160 stat and only 85 degrees outside the cooling system is definitely struggling to maintain control.

There are more than likely several factors all contributing. Without more details it's hard to pinpoint any one cause.

I would first look at timing. You absolutely need vacuum advance for additional part throttle cruise timing. Engines are much more efficient at light cruise with 44-48 degrees of timing via vacuum advance (10-12 degrees added)

You aren't overheating but running warmer than it should be capable of and many times I see this scenario it's timing related. I'd start with that first, it's cheap and easy.

From there certainly a cold case radiator helps and works more efficiently than a 4 core brass. Your stock mechanical clutch fan if in good working order is worlds better than most electric fans on the market.

Maybe more detail on what you're doing for timing would help us suggest a direction to go

[RocktimusPryme]

What is your fan situation?

Im not going to repeat what others have already said but I largely agree with them.

While there can be dozens of things as others have said, a general rule is, If you heat up at a stop you don't have enough fan. If you get hot while on the move you don't have enough radiator.

Based on your symptoms I would start with the radiator. (I might try some free stuff first like timing changes) Cold Case is a strong option to fix your whole issue. At the very least if it doesn't solve your problem I think it will at least improve it.

Once you know you trust your radiator, it becomes easier to troubleshoot IMO.

[grandville455]

If your just putting around thru town i doubt your even on the main jets yet, mostly still the idle and transfer slots at that point, what's your cruise rpm? If your barely on the throttle, u are not on the mains yet or if u are its very little

[nUcLeArEnVoY]

As others have said, you absolutely NEED vacuum advance for optimum part throttle and/or cruising efficiency. Cruise mixtures are leaner, which require that advance spark to give sufficient time to ignite. If it's too retarded, then the exhaust gases are not evacuating properly and so the motor builds up heat. Most motors of this era will happily chug along on at 55-65MPH on the freeway with up to 52 degrees of timing (that includes vacuum advance!!!) My '79 T/A W72 makes around 48-50 degrees total timing at 60 or so MPH. It would make more, but I have a limiter on my stock vacuum advance since I deleted EGR, which actually cools combustion temps allowing for a bit of extra cruise timing.

Just as an FYI, though, those temps are hardly out of control and were pretty standard for when these cars are new... but they are out of control for your thermostat rating.

Your temps raising during load and sustained higher RPMs is normal to a degree. The engine is working more, which generates more heat. It's normal for a car's temp to climb once you get on the freeway, but eventually it stops climbing once you reach thermostat temp or maybe a bit past it at most. Your temps are higher all around, which is an overall cooling system capacity issue. One thing stands out: you mention 4 row copper/brass. Is it the original? If so, replace it, or recore it if you want to stay original. I don't give a chit how much better built or better performing the factory radiators are. That may very well be true, but the fact STILL remains it is a 50+ year old part, and even the most thorough maintenance throughout its life won't stop it from developing some degree of corrosion and buildup. I just wouldn't trust it. Cold Case radiators are very good, I use one myself and I seldom see the needle go past the first tick on my temp gauge, and I can straight up grip my hand around my upper radiator hose after an hour of driving and just hold it there without getting burned or hurt.

Concerning your fuel mixture, it's good to see that making the change in jets made an apparent difference, but I really do think that people get sort of overanalytical with fuel mixtures and hot running (or overheating), when in reality, cooling system problems are usually a lot more simple to explain. Ignition timing is a far more influential tuning-related component toward engine temp than fuel mixture is, in my experience. I think your problem is a lot simpler than your fuel mixture. Cooling systems, when set up well can account and compensate for a LOOOOT of other poor build choices or issues; whether it be a crappy tune, too much piston quench, and even some pinging. So you mean to tell me subtle variations in fuel mixture where it's a bit too lean is going to cause a massive increase in engine temp that the cooling system can no longer control? Come on now. In that case, we'd be seeing overheating threads all the damn time, because running a bit on the lean side is a VERY easy mistake to make. Too much cam or headers can make you run lean - heck, in the mid 70's, the cars ran lean as hell mixtures from the factory. (And yes, they also ran hot, but that's because of all the emissions crap, low timing, and strangulated exhaust.) I would think you'd experience running and driveability issues with a ridiculously lean fuel mixture that would grab your attention way before the engine temp.

And yes, what's your fan situation? You mention your idle hangs around 185-190, so if it's not climbing any higher, then your fan situation may be adequate.

[SRR]

Sounds like maybe the power valve?

[steve25]

What is your hot idle vacuum like?

Just keep in mind that with a Holley type carb that the jets are the FINAL level of fuel enrichment once the power valve is open all the way.

Most Cam’ed up motors will make more vacuum off idle then at idle once a certain rpm is hit.


You might try out a lower vacuum power valve in either the primary or secondary side of the carb depending on how deep into the throttle you are when the temp starts to climb.

[Mook]

Originally Posted by Gach

Just an idea I would check your timing, making sure it’s not advancing. I’ve seen timing Advance up to 50 degrees. As the rpms go up. In other words lets say you run a total of 36 degrees all in by 2500 rpms. I will put a timing light on it and bring the RPMs up making sure that it’s not advancing to 30 or 40 degrees. It’s possible while the temperature drop at lower speeds is because timing is then around 36 degrees. I put a time and light on it and check it. Making sure it’s not advancing passed it 36 degrees.

I will check the timing once I return from Norwalk… I know I have no vacuum advance… its locked out

Thx

[Mook]

Originally Posted by Schurkey

A 160 'stat in an engine that runs 205 has lost control of the engine temperature. That 'stat is fully-open by 180, maybe a little cooler. At idle or cruise, the engine temp should be within a few degrees of the thermostat rating, so that under heavy use there's additional cooling system capacity that can be used.

SOMETHING, or several somethings, are wrong.

There's two dozen possibilities, ranging from cooling system problems involving airflow, to cooling system problems involving water (coolant) flow, to engine running problems like insufficient timing advance or lean fuel/air mix, to chassis problems like dragging brakes and tires low on air, making the engine work harder than it really should.

How old is the radiator? What fan/fan clutch are you using? Is there a proper fan shroud, and does the fan fit nicely inside--about 1/2 in, 1/2 out of the shroud (1/3 in, 2/3 out may be even better) without huge gaps between fan blades and the inside of the shroud? What is the crankshaft-to-water pump pulley ratio? Have you removed the seal at the windshield-end of the hood?

Radiator is maybe 8 years old… thinking of adding a Cold Case ….I have one of those fan clutches that is not engages by temp…. I

I will check the fan shroud situation also

I am running the small a/c water pump

Not sure what the windshield-end seal is

Thx a bunch…

[Sirrotica]

If you think the fan clutch is faulty, or want to test it, roll up some cardboard from a box into a tube, and try to stop the fan with it by letting it drag across the fan blades at idle. If you can stop the fan with the radiator warm, it's free wheeling, and not pulling enough air.

Using the heater to cool the car is indicative of not enough radiator, or too little air movement.

You might also want to use an infrared gun on the top inlet of the radiator, and the bottom outlet. Expect right around 30 degrees between the two. If your not getting that much, and the fan clutch is working properly, the radiator doesn't have enough capacity to reject engine heat. Either has scale insulating it, or it's too small.

Using a lit cigarette to hold in from of the radiator to see how well the fan is pulling is another old time trick radiator shops use. The smoke will tell you pretty well whether the fan is doing it's job.

Using the small waterpump pully will also increase the speed of the waterpump, as well as the speed it rotates at. Pontiac used the small pulley on A/C cars as well as heavy cooling system packages.

Maybe some of this old time basic info will be helpful in solving the problem, good luck.

[Schurkey]

Originally Posted by Mook

I will check the timing once I return from Norwalk… I know I have no vacuum advance… its locked out

That's nuts on a street-driven car. That's the FIRST thing you should fix. You need significant additional advance at part-throttle, and sometimes at idle.