Hot Rod Forum : Hotrodders Bulletin Board - View Single Post - Pontiac 400 Idles to fast
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Old 09-08-2010, 09:51 PM
beertracker beertracker is offline
quadrajunk a name earned
 
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I think I have solved the problem!

First, I removed all vacuum hoses and plugged the vacuum source at the carb and all vacuum lines. Next I ran the engine and one at a time I reconnected the vacuum hoses looking for a change in rpm; result no change in rpm.

Next I connected my new digital timing light and measured initial advance at 18 degrees BTDC. Centrifugal advance measured 21.3 - 18 degrees = 3.3 degrees @ 2500 rpm. Both of these measurements seem wrong. What do you guys think? Maybe the weights need a little clean up & lube? These measurements are with stock 6x-8 heads, stock exhaust & intake manifolds, stock HEI, dual exhaust. I don't have a vacuum pump so I can't measure vacuum advance but I know vacuum advance works since I applied mouth suction (Bill Clinton style, sorry) and the idle speed increased. LOL!

Eventually the engine will have 4 tube headers, Summit 2802 cam (2200-5500 rpm),stock converter, 2.78 gears for now, 6x-4 heads milled .040", 8.9:1 CR. What do you guys think as far as timing? I am more concerned about this paragraph setup.

Forgot to mention, the vacuum source is ported (above the throttle plates). When moving vacuum source to intake manifold the idle speed increases.

One last question, why is it necessary to go change to a floating valve train when going to a after market cam & milled heads on a Pontiac block? I thought the hydraulic lifters would compensate for changes in head milling height and after market cam lift??

This forum is great! I have learned a great deal about hot rodding!!

Thanks,
BT

Last edited by beertracker; 09-08-2010 at 10:10 PM. Reason: vacuum source is ported vacuum (above throttle plate)
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