[78w72]

I agree there are other pontiac owners with cooling issues... but at 75° it should not be overheating at idle or when moving, especially with an aluminum radiator..

Ive read the 1st gen firebirds dont have ideal air flow, do you have the full shroud and fan is positioned right in the shroud? Are there other pieces that go around the core support ive read about?

Ive also heard that electric fans can restrict air flow and cause cooling issues compared to just the stock fan. One member on here has a 700hp gto that said he tried electric fans & other combos of parts but the best was a stock fan & shroud.

Just some suggestions & things to consider, hope you can figure it out.

[freebird69]

Originally Posted by 78w72

I agree there are other pontiac owners with cooling issues... but at 75° it should not be overheating at idle or when moving, especially with an aluminum radiator..

Ive read the 1st gen firebirds dont have ideal air flow, do you have the full shroud and fan is positioned right in the shroud? Are there other pieces that go around the core support ive read about?

Ive also heard that electric fans can restrict air flow and cause cooling issues compared to just the stock fan. One member on here has a 700hp gto that said he tried electric fans & other combos of parts but the best was a stock fan & shroud.

Just some suggestions & things to consider, hope you can figure it out.

Thanks for the suggestions. Yes, I have the baffles installed as well as a gasket at the core support. I installed the e-fan years ago when I bought the car because it was overheating badly. The Spal didn't seem to have a noticeable affect on airflow but it does help to cool when i turn it on. I have, one by one, replaced every component of the cooling system which has helped and each piece helped in a small way but there has never been a silver bullet cure. I am close now so I'm happy and just a few degrees away from my personal target of not over 190. There are guys that have insisted that 210 to 220 is perfectly OK but I would rather run cooler than that, plus my car runs better at cooler temps.

[Sirrotica]

Just a quick question, do you have the small water pump pulley to overdrive the waterpump? Not only does that speed up coolant flow, and increases fan speed, it pressurizes the system after the water pump to help eliminate steam pockets in the upper recesses of the water jackets. It was a HD cooling, as well as an A/C factory change.

And one other option is to do the 421 modification that opens a blind hole in the cylinder heads to improve water circulation. Done by the factory back in the mid 60s to factory 421 engines to help with steam pockets. The factory hole in most engines was not drilled when the blocks were machined, but drilling it out helps aleviate heat buildup. If you lay a head gasket on the block, and head, the hole is in the gasket, but never drilled by Pontiac. Of course this isn't an easy modification to make, simply because it requires engine disassembly to execute.

[freebird69]

Originally Posted by Sirrotica

Just a quick question, do you have the small water pump pulley to overdrive the waterpump? Not only does that speed up coolant flow, and increases fan speed, it pressurizes the system after the water pump to help eliminate steam pockets in the upper recesses of the water jackets. It was a HD cooling, as well as an A/C factory change.

And one other option is to do the 421 modification that opens a blind hole in the cylinder heads to improve water circulation. Done by the factory back in the mid 60s to factory 421 engines to help with steam pockets. The factory hole in most engines was not drilled when the blocks were machined, but drilling it out helps aleviate heat buildup. If you lay a head gasket on the block, and head, the hole is in the gasket, but never drilled by Pontiac. Of course this isn't an easy modification to make, simply because it requires engine disassembly to execute.

That's a good question. Mine is a 2-groove and measures ~7" dia. I did a quick search and all of the pulleys I see are the same as mine for the short snout WP. I would think that I would need an offset pulley with a 7" dia for the power steering and a smaller for the fan? Anyway, I will look into this further.

[freebird69]

Originally Posted by Sirrotica

Years ago when I had Pontiacs that ran hot, be it a race car, or street car, my go to fan was a nylon 18.375 diameter fan. It pulls more air than any fan I've ever used at idle, and all the way through the RPM range. The fan blades are almost 90 degree pitch, designed to pull maximum air.

Link to nylon fan: https://www.summitracing.com/parts/flx-104465

Dirt track Pontiacs are tough to cool, but this fan was recommended to me by the shop owner that I used to send all my radiator work to. I tried one, and was sold. Another nice thing is they are much lighter than a fan clutch assembly so easier of water pump bearings also. They aren't going to get you any fuel mileage improvements, but keeping the engine cool trumps fuel mileage.

I went ahead and ordered an Allstar Performance ALL30095 nylon fan that appears to be a rebranded and exactly the same as the Flex-a-lite. It was 93 degrees here the day I ordered it but now only low 70's so I may not get another chance to properly test it this year. I do appreciate the suggestion because it looks good and inexpensive.

[Sirrotica]

Originally Posted by freebird69

I went ahead and ordered an Allstar Performance ALL30095 nylon fan that appears to be a rebranded and exactly the same as the Flex-a-lite. It was 93 degrees here the day I ordered it but now only low 70's so I may not get another chance to properly test it this year. I do appreciate the suggestion because it looks good and inexpensive.

It is an excellent piece, I first started using one in 1978 when I had problems with my 69 GP 428 dirt track car cooling. It was one of a few suggestions made by my very well respected local radiator shop owner, that I used when I had my garage, and service station business.

His father started the radiator shop, and he was the second generation owner. My father also preceeded me, owning and operating his own auto repair garage, and our fathers knew each other very well.

The material the fans are made from is a fiber reinforced injection molded piece, so they are strong, but a little more forgiving in a crash when they get in contact with the radiator, such as what frequently happens in short track racing. The blades have a tendency to break, rather than saw a hole in the radiator core, like a metal fan does. You'll never probably test that property, but I had occasion to a few times. You could still repair the tubes with a composite fan, whereas a metal fan would completely trash the radiator.

The blades also tend to flatten out slightly at speed, but when coming back to idle they go back to the nearly 90 degree pitch and pull a huge amount of air at low speeds, and idle.

Hopefully this, along with overdriving the waterpump with a smaller A/C style pulley, and the fan will get you where you'd like to be as far as engine temperature, when the ambient temp, and humidity are on the high end.

[freebird69]

So here's where I ended up with my fan situation. To summarize, I have been trying to find a fan that works better than my stock 5-blade flex and here is a list from best to worse:

1. Derale 6-blade flex
2. Stock 5-blade flex
3. Flexalite 6-blade flex
4. Nylon 6-blade flex
5. Pontiac 6-blade clutch fan
6. 428 Pontiac clutch fan

So the Derale is the winner and it's what I will use.

[HWYSTR455]

Idle timing is critical to keep idle temps down. You need a minimum of 12 degrees initial, 14-16 is better, and 8 vacuum helps when on top of that (vacuum can on manifold source, not ported). Obviously, you need to curve the distributor accordingly to control total timing.

Look at the service manual on how to set initial timing for cars before about 1970, they tell you to remove the vacuum hose to distributor and cap it off. What happens to the initial timing when you plug the hose back in? Yeah.

As a loose example, newer cars run 22-26 idle timing. Or more.
*
The 5 blade (and 6 blade) OE clutch fan with shroud and a good clutch and AC pulleys should cool even the hardest to keep cool cars/engines.


.

[HWYSTR455]

Originally Posted by 68 Firebird

HEI curved conservative 10 initial 32 total(comes in at 3500, Heavy HEI springs)) 14 from VA on ported.

There's your problem.


.

[KS circutguy]

Originally Posted by HWYSTR455

Idle timing is critical to keep idle temps down. You need a minimum of 12 degrees initial, 14-16 is better, and 8 vacuum helps when on top of that (vacuum can on manifold source, not ported). Obviously, you need to curve the distributor accordingly to control total timing.

Look at the service manual on how to set initial timing for cars before about 1970, they tell you to remove the vacuum hose to distributor and cap it off. What happens to the initial timing when you plug the hose back in? Yeah.

As a loose example, newer cars run 22-26 idle timing. Or more.
*
The 5 blade (and 6 blade) OE clutch fan with shroud and a good clutch and AC pulleys should cool even the hardest to keep cool cars/engines.


.

I found this to be true even in the 70's looking for a solution to a problem that didn't exist.
IE; I tried a aluminum flex fan to replace stock steel and fan clutch.
It sounded like a blower, and sucked a bunch of HP to run.
Went back to stock setup.
Working in a speed shop you'd be amazed how often people would waste money on upgrades [cooling]that don't work because they were trying to cover up another existing problem.
Timing,lean jetting etc.