Over heating sbc

[Michael F.]

Re: Over heating sbc

Now I've bought a Ralley 350 Olds with the same problem.

Isn't there an Olds Forum? I am sure they would be more likely to answer your questions.

[John H.]

Re: Over heating sbc

Years ago I had my 1965 327/365 engine rebuilt. I spun a bearing. That's what happens when you drain the oil and replace the filter but don't refill the oil in the same day. Yeah, the memory doesn't get better with age. The shop said they shot peened the pistons to expand the skirts and replaced the bearings and rings. After that the engine would run cool as long as you were moving, but let it idle and the temp would climb quickly and boil over. No changes to the radiator, probably the same water pump, but I did change cams. I never figured out what was wrong, I sold the problem. Any ideas? Now I've bought a Ralley 350 Olds with the same problem. Tried different radiators, fans and shrouds no effect. This engine seems to have a very radical cam (loop and no vacumn at idea, probable the W31. Can a cam effect cooling as I describe?

Robert -

You might find this article on ignition timing and vacuum advance useful:

http://www.lbfun.com/warehouse/tech_...101Article.pdf

[Robert K.]

Re: Over heating sbc

Thanks, this has been an outstanding reply. Yes there is an Olds forum and I did post there. One response was cam timing the others 2 clutch fan. Clutch fan it is not. I tried clutch fan, no clutch just spaced. Aluminum fan and electric fans and 3 different radiators. I believe it to be internal to the engine, I am sure it was on my vette some years ago.

What would be the effect of advancing the timimg on the cam and conversely retarding it. Any effect on water temp?

Thanks again for all of the great comments. Lots of food for thought.
Bob

[Timothy B.]

Re: Over heating sbc

Robert,

IMO, the net effect changing camshaft valve timing advancing the cam valve events will make the engine produce more torque at lower RPM's. You close the intake valve earlier so the engine makes more dynamic compression pressure.

Retarding the camshaft has the opposite effect in that the engine will make more top end power.

Advancing the SPARK timing will help the motor run cooler because when lighting the fire earlier combustion energy will be consumed by the engine and less heat transfered to the exhaust. When retarding the spark some of the energy is exhausted out the valve because the burn is still going when the exhaust valve starts to open.

I am sure you will get a better explaination but that how I understand it.

[Duke W.]

Re: Over heating sbc

Thanks, this has been an outstanding reply. Yes there is an Olds forum and I did post there. One response was cam timing the others 2 clutch fan. Clutch fan it is not. I tried clutch fan, no clutch just spaced. Aluminum fan and electric fans and 3 different radiators. I believe it to be internal to the engine, I am sure it was on my vette some years ago.

What would be the effect of advancing the timimg on the cam and conversely retarding it. Any effect on water temp?

Thanks again for all of the great comments. Lots of food for thought.
Bob

Forget the cam timing, even though it sounds like the engine may have some ill-conceived aftermarket camshaft.

LOOK AT THE SPARK ADVANCE MAP! WHAT ARE THE OE SPECS? POST THEM!

Then measure it with a dial back timing light and Mighty Vac and report the results

Is it an emission controlled engine with ported spark advance?

What is the year and engine ID - horsepower of whatever is required to ID the specific engine configuration.

You'll never get a handle on this from me or anyone else unless you can provide some DATA! None of use have ANY IDEA what we are dealing with.

Duke

[Mike G.]

Re: Over heating sbc

Robert, two basic issues to cooling, air flow and water flow, you seem convinced that air flow is not an issue so rule out water flow. If the water pump is not turning fast enough at idle it can cause the over heating that you describe. I would suggest, while the engine is idling and when the temp spikes, raise the engine speed to approx 2000 rpm holding it there for a minute or two. If the temp gauge starts to drop, then it could very well be a flow problem.