Another overheating post

[Kevin Estes]

[John H.]

Re: Another overheating post

Kevin -

You don't have a radiator issue, you have an idle airflow (and probably timing) issue. First, make sure your vacuum advance can is working, and you have full vacuum advance at idle - makes a big difference by reducing exhaust gas temperature at idle. You MAY not be getting full deployment of the vacuum advance due to your low idle rpm setting and resultant low manifold vacuum; I'd crank the idle speed up to about 800-900 rpm and check the level of manifold vacuum and how much vacuum advance you're getting at that rpm; you'll get more coolant flow as well. I'd also verify the gauge reading against an I.R. gun "shot" of the thermostat housing so you know what the actual coolant temperature is. The cure may be as simple as increasing idle rpm to "spec" for more airflow, more coolant flow, and higher manifold vacuum.

[Duke W.]

Re: Another overheating post

I agree with John. You've got to set the idle up to at least 750/800. Set it with an accurate test tach - not the car tach. The OEM spec is 700 (750 with CA AIR equipment), but as is typical with SHP engines, that is low IMO. Also. check your vacuum can to be sure it provides full vacuum advance - about 16* - at 8" vacuum.

You may have the wrong can. What is the number on the bracket behind the diaphram housing? The wrong vacuum can and too low an idle speed can definitely cause idle overheating.

The initial timing spec is 10*, so if you have the proper vacuum can which provides the maximum 16* at a proper idle speed a timing light should show about
26* of idle timing with the vacuum can connected.

Duke

Duke