: Overheating only when idling
Jul 18th, 03, 11:16 AM
I have a 1969 Camaro. It has a 327, 40 over, 262XE cam, exhaust manifolds, stock water pump and pulley, and stock 4 blade fan. The rad is 4 core with an original (very expensive) cap, and 160 thermostat. The car temp is great when moving. But as soon as I stop at a light, or heaven forbid traffic, the temp runs up over 190 to the dreaded 200+ level. It's getting to the point I am afraid to pull into the drive-thru's. My thought was to change the fan to 5 or 7 blade since I figure I need to keep air moving through the rad. But I really wanted to keep everything as stock as possible. What are my options? Thx in advance.
Jul 18th, 03, 11:38 AM
What pressure cap are you running? If you are only running about a 5-7 you need to jump to at least a 13-15 to lower your boiling point. If you go to a 21, you want to make sure your radiator can handle the pressure.
Jul 18th, 03, 11:42 AM
You have a timing ot air flow problem. Since you're trying to stay stock check your initial timing and see where it's set. Remember to disconnect the vacuum advance and plug the source. Factory setting is about 4 degs btdc. and may be too low for your modified engine. Be aware increasing the initial timing could cause part or wot pinging which is bad for the engine. If you advance your timing do it 2 degs at a time and then go test drive.
210 degs isn't going to kill your mill but that's about where I would say the safe zone ends. Make sure your shroud is installed properly and that you don't have anything obstructing the front of the rad core. I would also run a 180 stat as opposed to the 160.
I bet your answer is in the timing...
Jul 18th, 03, 12:23 PM
dumb question..do you have a fan sroud? Is the car actually overheating or just get hot?
Jul 18th, 03, 09:34 PM
My stock 4 blade fan wasn't pushing enough air on my 327. I hated watching my temp rise at lights. I got a new flex fan that pushes double the air my crapy stock fan pushed. 180 is the magic number.
Jul 19th, 03, 04:18 AM
Do you have a good factory fan and shroud setup where the fan blades are partialy inside the back of the shroud? If not, you need one. If you do have a correct shroud and fan, I think you might benefit from a correctly set up manifold vacuum advance on your distributor. The manifold hookup allows you to have more advance at idle which helps lower the engine temp. You might need a different canister as the stock one was emissions calibrated. Just search the archives or ask and I will post more info.
Jul 19th, 03, 04:13 PM
I know you want to keep that stock look but the fan is not enough for your application.
A good alternative that will more than double the airflow is a new technology flex fan (heavy duty series #17XXX only) from http://www.derale.com/flexfans.shtml . They are available from Summit Racing for around $50 but are backordered because I have been sending everyone over :D
While this is not exactly stock, it does ad in appearance and certainly you will love the performance. YOu should be able to run an 18" in the stock shroud you have. I run a 17" with my 69 ragtop/air/400hp+/traffic/95*days.
Jul 21st, 03, 01:38 AM
Just got back from the weekend. Thanks for all responses. Answers to a few questions; yes I have the stock shroud installed and it is the stock waterpump, I am running the distributor vacuum off the base of the carb, the advance is set to approx 10 at idle before advance, and the cap is high pressure (not sure exactly) because it has never released a drop even when "overheating". It sounds like the timing and vacuum thing are under control, and the answer is in the fan. Should I even bother with a stock 5 or 7 blade, or just spring for the high performance. I just want it to look stock and will paint the aftermarket black if I go that route. Thx again.
Jul 21st, 03, 10:04 AM
Could the problem be the vacuum source for the distibutor? If I recall corectly, the vacuum advance should be on a ported vacuum source so that at idle, no vacuum is applied to the distributor. Can anyone verify my thinking?
Jul 21st, 03, 10:58 AM
The only thing the vacuum source is doing at this point is adding vacuum advance to the initial once the car is running. That should in no way cause it to heat up at idle.
As for the stock fan not being adaquate, why is it still on the car after 33 years? Is the surface area of the 4 core that much more that it requires the air flow through it increased to be effective? If so this is a good lesson in matching components.
69rag - if you want a replacement fan and clutch that will look somewhat stock (won't fool the numbers guys) Summit sells a Flex-a-lite 5 blade and clutch for it for about $60 or so for both pieces.
Jul 21st, 03, 03:34 PM
the vacuum advance does nothing at idle when hooked up to the carb in it's original 69 "emissions style" setup. The high temps at idle can be lowered by using a pre-emissions style vacuum advance hookup to the manifold vacuum. That is how it was hooked up before emissions controls were put on cars in the mid-late 60's. Cars will run cooler at idle when hooked up the older way but some times it requires you to change vacuum canisters depending on the amount of vacuum you have at idle.
Jul 21st, 03, 05:34 PM
I bought that Derale heavy duty flex fan and I wasn't happy with it. It did ok, but not better than the 18" straight fan that I got out of the boneyard.
My big straight fan drains a little more HP than I'd like, but let me tell you--I was in a parade on the 4th of July with 90 degree temp outside, and my car never got to 190.
My car is a 327, 30 over, HE268 cam and headers. I also have the shroud, good cap, 4 core radiator and now no more cooling problems.
Jul 22nd, 03, 01:49 AM
Thanks for all the input. I am a little confused by all the vacuum and canister talk. I do not have power brakes. The only thing running off my original, cast, 4-bbl, intake vacuum is the tranny. Are you saying it would help with cooling to run the dist. off that as well? If so, no problem. As for the fan, I am not concerned about horsepower loss. I may opt for just an 18" 5 or 6 blade fan and try it. What's to lose? I just can't figure out how the factory kept things cool with the old 4 blade. Does 40 over make that much difference?
Jul 22nd, 03, 04:36 AM
I would agree that a 18" fixed BB fan would/could move more air than the Derale heavyduty depending on design as one poster provided, but these fans can take up to 45HP and I do not consider this small! This could add to overheating issues at cruising speeds given the right circumstances. See my test of years ago at http://carnut.com/ramblin/dyno.html which does not include the derale models. I am not knocking these fans but if they work for you then just do it even tho you should not need such a beheamoth beast! There is no reason that a Derale heavy duty would not work for this application in my opinion. My 69 ragtop is 400hp+, air, and lives in heavy traffic in Hotlanta and has a 17" Derale with stock shroud and never comes off the thermostat cycling point.
Full time manifold vacuum will actually help your cooling cause, not degrade it! A static timing of 6 to 10 degrees with a limit of 22 degrees at idle with vacuum advance is typical on most performance engines. The increase in timing will help "tip-in" throttle response as well.
The "overboring" does not appreciably contribute to heat production or "cooling problems" per se, however the additional compression or cubes due to this physical change would obviously up the HP ante and this is what causes waste heat!
Jul 23rd, 03, 01:41 AM
Up to 45 hp! Even if it half that, it's very significant. What about a clutch fan? I guess I will opt for the aftermarket. But with regrad to the vacuum. I was planning to tee off my power brakes to the tranny outlet at the back of the intake. Where exactly should I move the distributor line? Remember I have the original cast 4 bbl intake.
Jul 23rd, 03, 02:03 AM
69Rag, the article that I posted covers a 18" bigblock fixed, clutch when cool and clutch when hot tests. Even fully cooled clutch fans can take alot of hp!
Now, for one of my constant whining arguements on clutch style fans. Does the clutch in the test work correctly? How can you tell? It appears to but as you can see by the tests results who knows? This is why I will not use them. You have to make up your mind if you have one that is correct or not.