Engine idle temperatures

[Steve_D]

Engine idle temperatures
A while back we all joined in with Stigs frustration about engine temperature at idle.

I’ve just seen a post about timing on Chevytalk which covered the subject of ‘Should I connect the dizzy to ported or manifold vacuum?’

Someone posted a link on the matter in which the author says ported vacuum was only created in an attempt at emissions control prior to cats and it should not be used.

It also indicates that;-
· Full vacuum advance should be in at idle or the engine will run hot.
· Engines with big cams have low vacuum and may be too low to activate the vac. advance. If this is so then a low vacuum can should be fitted to the dizzy.

So does either of the above apply to Stigs or anyone else’s problems?

I’ve posted the link for you to read.

Ported vacuum is taken from the tube up on the side of Holley carbs.
Manifold vacuum connects into the carb baseplate.

According to Desktop Dyno my engine, when complete, will produce about 14 inches of vacuum but the MSD billet dizzy needs 15 to operate the vacuum advance so I will need to change mine.

[url]www.andersonlimited.com/forum/viewtopic.php?t=2484[/url]

Steve

[gtrclive]

I have disconnected mine because my modified Carb has no Ported Vacumn point, and after reading one of Holley's own books on tuning they say only connect it to Ported Vacumn.
Have something like 45-50 degrees advance on tickover if I remember correctly with it connected to Manifold Vacumn. Would like to reconnect it due to better mid range torque and MPG, but still am not sure weather to ??

Will now have to phone an Expert to confirm.

[Steve_D]

Clive
With manifold vacuum you should see at idle your initial static timing of 10-12 deg, + 15 deg. of vacuum. I can’t see where 45-50 degrees could come from unless your static was very high or the centrifugal is coming in early due to weak or wrong springs.
Steve