64SF
Well-Known Member
A friend has a 67 Firebird, 455 engine, Rochester carb. When he sets the timing (vacuum plugged) then reconnects the vacuum line the timing and idle increases without increasing the throttle. Thoughts?
Non MOPAR timing question
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Dreamcatcher
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It advances when the vacuum is hooked up(timing) usually 3 to 400 rpms Normal in most cases.
BeatersRus
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check which port hes coming off of on that carb,
it should be a full vacuum only at speed,not full vacuum at idle.
in other words,hooking the line up while the car is Idling at normal rpm Shouldnt affect it at all.
check the ports and see which one is correct.
retest
it should be a full vacuum only at speed,not full vacuum at idle.
in other words,hooking the line up while the car is Idling at normal rpm Shouldnt affect it at all.
check the ports and see which one is correct.
retest
Dreamcatcher
Will fish for food
Also depends on where the vacuum is coming from. Should be on the carb and some carbs have more than one source. Measure the vacuum on each. The right one will be slower in reaching full vacuum.
Hikin Mike
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Some cars/engines like ported, some like manifold. I run ported on my 69 Firebird 455.
Hikin Mike
Well-Known Member
A recent discussion about ported and manifold vacuum from what I consider a Quadrajet guru: https://forums.maxperformanceinc.com/forums/showthread.php?t=835736
steve340
Well-Known Member
If you connect the vacuum advance to manifold vacuum the rpm and timing will go up - and this is right if the engine is supposed to be this way.
Just adjust the idle speed screw down.
Just adjust the idle speed screw down.
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