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ok when my engine is idling the RPM are Oscillating up and down from 700-1,000 i have ran 3 carbs on it 2 Q-Jet's and a holly 600cfm i have checked for vacuum leeks and have found none the timing is set to 18 all in by 3,000 when i am running it above 1,300 RPM's the oscillating stops.
Sounds like a lean surge...have you fattened it up yet?
well 1 of the Q-Jets was off my buddys car and it was doing the same thing on mine
i have a base timing of 18 and all the timing is in by 3,000
vacuum is reading from 20 to 15
and the vaume is @ 22 @ 1,500
it is a bbc 402 with a edlebrock performer 2-0 intake
all so throw the base timing down to 16
the Distributor is an HEI
i set it to 10º no help just makes it run rougher
i dont know what the totle is right now.
I tried the carb spray right at the intake "nuthing"
What is the lowest idle you can get? "i guess 750rpm" but becus of the vac going up and down it is hared to set the air/fule mixture i set the screws 1 1/2 turn out if i back them all the way out nuthng happens if i turn them all the way in it will stall out
I might be wrong, but it sure sounds like a vacuum leak to me.
Quote:
Originally Posted by DennyW
yeah it did that to the 2 q-jets 800cfm and the holley 600cfm
Quote:
Originally Posted by DennyW
yeah i am shure of that. i all so added a super thin smear of RTV around every intake port and i am runing MR. gasket ultra-seal i am LOST and it is late to i am going to give it a try toarow with my frend
well if it stop at 1300 then you past you idle trans slots or very close?? so it may need more fuel ? hard to think a big block would need that?? and it can have a in take leak to ? if the heads and block was cut the intake will not sit down on the china walls .this will stop it coming all the way down .you some times at the very least cut the bottom of the intake for this .and the intake can leak from the lifter valley to ??????
Before overkill sets in; try either the carb spary or non-chlorinated barkecleaner spray (preferred) as a slow, very slow dribble among the venturi'is as it runs. It will either pick up what you're missing or choke it down to a stop. At least you and us will know where to go.
Quote:
Originally Posted by pat mccarthy
i did have the block and heads cut but olny .005 to cleen them up. I all so added a super thin smear of RTV around every intake port on the intake and heads
i did the carb spary thingQuote:
Originally Posted by nitrowarrior
???Might it be the Distribuor??
yep you did say that i have not ever seen any big blocks that square up at .005 .but still easy to check the intake look and see if there is any gap in the front and back of the intake were you put the rubber things that blow out or RTV them that is the china walls look and see if there is some gap from intake to block ?Quote:
Originally Posted by BBMonte
Get a vacuum gauge, they are pretty cheap. Hook it up to the intake and read the movement of the needle.
:HMMM:Quote:
Originally Posted by BigTruckDriver
i have one
Does sound like super lean or a vacuum leak... you said vac is at 22"? Then over lean more likely.
How much cam you got? Might just want a higher idle?
Two cents...
-Chris
my cam is 216/216 @ .05 .515 lift
vacuum is reading from 20 to 15 @ idle
and the vacuum is @ 22 @ 1,500
i thought u want the highist vac when u are tuning your carb?
If you're running power brakes and I'm assuming you are, I'd plug the line to the brake booster and one by one check any and all vacuum lines. A leaky cannister under the dash could cause your problem.
cam looks tame enough... yes, you want highest vac at lowest revs (or whatever revs you want idle at)...
Did it run ok in the past? Are all the cylinders firing (plugs, wires, caps)?
-Chris
this is a rebilt engine and it isnot in the car yet thats for next year
Sure your not runnin' Injected Alcohol? :LOL: :LOL: :LOL: J/K
Quote:
Originally Posted by pro70z28
umm? i dont think so
one of my frends was telling me it might be my vavles there not closing all the way? when i set preload i did 1/2 turn on the wrench. what do u guys think?
well what would that do?
well yeah that dusint sound like what i am doing
well me and my friend were looking at the engine and tring to figure out what is up with it. well i tried to spray carb claener down the carb in little squirts and it seemed to smoothe out but when i tried propane or mapp gas nothin.... i am tring to beleave it isn't a vac leak becuse i have seelant on every thing. so i think it is a leen out on the idle but on 3 carbs?
a another thing i am thinking is might it be that my timing set is off?
i posted befor the site whent down and just wont to make shure ppl see this