[skinny035]

I have a 65 with A/C that runs fine, even during hot weather. However, when it idles or slow stop and go it will overheat. I've tried all of the recommendations. I am running an 18" clutch fan with a shroud and want to go to a 19 or 19.5 fan..a heavy duty clutch would be fine or I may just run without a clutch. I want a 19 or 19.5 inch fan with a deep pitch part number recommendation. One other thing, there is a 3/4 gap between my radiator and the fan shroud. I have seen 65's at car shows with no gap? One I saw had an indentation on the shroud so as not to interfere with the radiator bracket, as mine does. Any help is appreciated...Mainly, I need a fan part recommendation. My 18" clutch fan ain't doing it.

[Sirrotica]

If this fan doesn't pull enough air to stop the temperature creeping at idle, you have a problem beside the air speed, and volume of air.

Link: https://www.summitracing.com/parts/aaf-all30095

Summit has spacer and bolt kits to get the fan properly positioned in the shroud, so check their offerings while looking at the fan.

I've used it on race cars as well as street driven cars and it's hard to beat the price, and the volume of air it pulls at lower engine speeds. Also it weighs next to nothing so your water pump bearings have a lot less strain on them. You also lose the clutch fan and all the headaches, extra cost, and weight.

Hopefully you have A/C pulleys already on your engine to increase the rotational speed of the fan and water pump as well as water pump pressure in the top end of the block and heads. All the details add up and you have to have all the correct components to work as a system to keep a Pontiac Strato Streak V8 cool in the summer.

[turbo69bird]

Did you check the operator plate to impeller distance?

[skinny035]

Yes, I've done everything

[Speargun]

Originally Posted by skinny035

.... One other thing, there is a 3/4 gap between my radiator and the fan shroud. ....

You want to close up that gap.
Any gap between the shroud & radiator will allow the fan to pull air through the gap instead of through the radiator.

What do you consider "Running Hot / Overheating"?
Technically, as long as the coolant isn't boiling, it's doing its job.
Personally, I don't like to see higher than a steady 210* - 215*, but 195* to 220* is considered normal and the temp gauges didn't go into the red until 245*.

A bigger fan should help if it will fit & you'll want a clutch to match the fan diameter & pitch. I.e. more pitch = heavier clutch.
Running without a clutch, or with a screw ran through one, will move more air, but, depending on the fan you're using, you may sound like a Cessna going down the road.

You have two problems at idle... Air speed/volume & coolant speed/volume.
Both are reduced and whatever you can do to increase them, will help with cooling.
The only real options to improve coolant flow are:
1: ) Remove the thermostat
2: ) Install a smaller pulley
3: ) Install a better radiator. (Cold Case)
4: ) Install an inline electric water pump

Improving air flow tends to be easier & less expensive.
1: ) Seal all gaps around radiator/shroud
2: ) Bigger fan (Diameter &/or pitch)
3: ) Stronger fan clutch
4: ) Spal electric fan as a pusher

Tuning can affect the temps also.

[skinny035]

Past 240 and it pukes...ive got the best water pump that Butler performance offers. Ill close the gaps with some insulation. It just doesn't look nice at a car show. Also, as mentioned, my friends shroud has an indentation for the bracket that let's the shroud sit up tight. I am running the "stock" 18 inch clutch fan for A/C cars which is actually 17.5 inches. I need a recommendation for another fan. I read online that there is a 19.5 inch notched fan? I need a larger fan with more aggressive pitch. Does anyone have a part number?

[Speargun]

I don't have a part number, but the best fan I've used was a 18"-19", 7 blade fan from a '76 Chevy C-20 Camper Special with a 454.

I've also had good luck with a Derale 18" with a heavy duty clutch.
https://www.summitracing.com/parts/der-17118

What to look for in a fan.
Larger diameter - A larger diameter fan can move more air.
Increased pitch - Moves more air per revolution, but requires more power
More blades - may be quieter and offer smoother airflow.

[tom s]

Have you checked your timing?Simple thing that can cause our pontiacs to over heat.I had a loose dizzy retard itself and it started running hot a idle.Retimed it,made sure it was tight and no more issue.FWIW,Tom

[70GS455]

3991431

https://www.classicindustries.com/pr...xoCWRgQAvD_BwE

[65 Lamnas]

The “notched” fan is for 1965 cars P/N 9779004, 1 year only and used on GTO with H/D fan option, and on Tempest/Lemans with A/C. It’s also found on certain 1965 full size cars. It’s 19-1/2” dia.

[fyrffytr1]

Do you have the radiator seal kit installed? And, do you have the hood insulation pad? My 67 would run hot. I removed the hood insulation for another project and didn't reinstall it right away. My car ran much cooler without it.

https://www.opgi.com/gaskets-seals/e...c-G240434.html

[skinny035]

Good question...I have the seal kit installed but there is a 3/4 inch gap between the top of the radiator and fan shroud. Also, I do have that pad on the hood and I always wondered if that could contribute to the heat. Ill remove it and see if that helps. Thanks

[skinny035]

Update. I bought a 19.5 inch fan with a extre duty Hayden fan and IT WORKED!!!! I drove it around and parked it and opened the hood and let it idle and it never got over 190. HOWEVER, I closed the hood (which has insulation) and it started climbing again...any recommendations? Should I remove the insulation? Or just drive around with the hood up? Lol

[b-man]

I would remove the insulation.

[73ta]

You need to recalibrate the fan clutch thermostat from it's factory setting to a lower temperature more inline with your thermostat and desired running temp. With it's default setting, probably doesn't fully clutch until temp is already too high sitting in traffic with no air flow.

[skinny035]

Do I make the coil tighter or looser on the fan clutch to make it come on at a lower temp?

[RocktimusPryme]

Originally Posted by skinny035

Do I make the coil tighter or looser on the fan clutch to make it come on at a lower temp?

https://www.youtube.com/watch?v=oSexUZHcmZ4

It depends on how you look at it, and can be a bit confusing in text format. I give a visual in this. Basically the inner tang of the spring needs to turn counter clockwise.

You can accomplish it in multiple ways but the easiest is just to bend the outside spring tang a touch.

[cmoc-bob]

Fast Monty's Garage on YouTube did a good presentation on connecting both cylinders head outlets into the heater/cooling system.

He also showed his test results, and the "more flow" isn't always better. Note the part(s) where we regulated the cal head flow into the cooling system. And the effect hose sizes had......

You can pump too much fluid too - and the heat exchangers don't have time to work.

Look at some modern cars and note the smaller radiator hoses, outlets, etc. Effort to slow things down.

Fast Monty also did some good tests on electric fans.

DeWitt's makes some quality radiators too - they note the BTU capacity of what you are buying.

Good luck !

[nUcLeArEnVoY]

Only one other post recommended to check Ignition timing. More Ignition timing at idle improves temps. Are you using your vacuum advance on manifold or port vacuum?

[vertigto]

Interesting...having a similar issue.