Overheating Issues, Perplexed

[olddog]

Originally Posted by elmariachi

On this issue of revving the engine, I don't see any noticeable difference when I do that. So while the pulley change may help, I am not counting on it exclusively.

If I get it up to say 100*C and kill it but leave the electric fan running for a couple minutes, the temp gauge climbs on up to 110C. But I can then start it again and immediately the pump exchanges the radiator and block water and it immediately drops like a rock by 10-15 degrees. Then I kill it again, wait with the fan on for a coulpe more minutes, start it again and I can get it from on down to 85C, all in less than 4-5 minutes doing this. To me this suggests that the radiator is capable of cooling, either it doesn't have the volume or the time to do so. EDIT>> or the airflow is still too low.

If reving the engine does not drop the temp from when it was idling, then the problem absolutely is not a lack of water flow, in my opinion. Do not waste time on the pulley changes. You may get into problems at higher rpm.

On another post, I think you compared radiator sizes. If the radiator is of adaquate size for the engine, that is ruled out.

By turning the engine off and letting the fan run, then restarting you simulated what more air flow will do for you.

You also took the engine heat out of the picture. So, either the engine is making too much heat (lean, or timing issue) or there is not enough air flow. I think you proved the timing. If you measure the header temp you should be able to prove that it is not too lean at idle, at which point you will have eliminated everything, but air flow. There were many comments on things like opening the hood to see if it cools down. Have you tried any of these? I recomend you focus on air flow improvenents.

One other nagging thing that most every engine builder comments on from time to time is cylinder wall thinkness. I think it is pretty well documented that thin wall will cause overheating issues. I would think that would be when making power not idling. Maybe someone can comment on this.