I agree, if enough coolant is moving through to begin with, then a smaller pulley will do no good, and the problem lies elsewhere.  With that huge pulley, it just isn't moving fast enough, as observed by myself and others.

Miker also brought up a good point, and that is when it occurs.  If it is not at idle, then a pulley change will not fix it because when you're cruising down the road, a fan is not even needed and the pump speed is more than adequate.

Myself, I had an issue at idle.  When I drag race, I increase the idle speed to 1000rpm, which helps me to leave more consistently.  I never experienced the problem while idling at that rpm in the staging lanes.  I swapped to a smaller pulley, and the problem seems to be solved at normal idle speed, in normal traffic situations.



Lawrenceville, GA

one last thought is 200 is not over heating,with a good rad and presure cap210at a stop sign is not going to hirt the engine,with air cond i would always shift to nat a light.

What comes to mind, is it boiling and are you using the factory gauge as an indicator? A lot of movement on a factory gauge might only be a small rise in temp and if it is not boiling then there is less to worry about. The only way to be sure of what is happening is with a quality gauge that is properly calibrated. My factory gauge has gone all the way over to the last mark when it is over 100deg stopped in traffic and the car has not boiled with a 13lb cap. I always check the release pressure on the cap to make sure they are working correctly.

Go on line and look at US Radiator they make an exact model with all kinds of fin and tube options. Should be all you need and more.

US Radiator in Vernon Ca. is who made the one for me. I had a 3 row and I stayed with 3 but with a lot more fin area. I also had them add a AT cooler in the bottom in case I change transmissions. Great folks to work with...

56 Vic, B'Ville 200 MPH Club Member, So Cal.

I certainly agree that radiator performance is much more responsive to air flow than water flow. Without going into heat transfer theory, it's because of the difference in specific heats of air (.24) and water (1.0, or .85 for 50/50 antifreeze).  However, if the water velocity through the tubes drops below a certain level, radiator performance will quickly degrade.  This is based on my experience as a "cooling systems engineer" years ago and also from some data I have from radiator manufacturers.  The following data for a specific radiator shows the relative performance of a given radiator when varying tube velocity. The baseline is 100% at 100 feet/min tube velocity.

(tube velocity, feet/min), (performance, %);  (200), (105%),     (150), (102%),     (100), (100%),      (60), (97%),    (40), (95%),    (30), (92%),    (15), (84%),    (10), (80%),    (8), (75%),    (5), (65%)

As you can see, increasing or decreasing the water tube velocity from 100 feet/min has little effect on radiator performance.  However, when tube velocity drops below 30 feet/min radiator performance starts dropping significantly. This could be an important issue for radiator performance at idle when water tube velocity is at a minimum. At 5 feet/min tube velocity, radiator performance is only 65% of what it would be for 100 feet/min.  For less than 5 feet/min, performance drops to 0 quickly.

Bill Newland