JUST REBUILT MY 327/365; CAR STARTS BUT IDLES VERY ERRATICALLY; CAN'T GET IT RUN FOR MORE THAN A MINUTE OR TWO; MANIFOLD VACUUM READS 3 TO 4" HG; ANY IDEAS WHERE TO START WOULD BE APPRECIATED.
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Re: LOW VACUUM
What is your timing? Advancing the initial timing may help you smooth out the idle and get the vacuum advance (if equipped) to kick in some more advance. Also you need to confirm that that the vacuum advance cannister works and can advance the timing. Duke has posted and written some helpful information about the recommended vacuum cannister for the high horsepower / low vac engines. You might want to search the archives.
Doug -
Re: LOW VACUUM
I HAVE THE TIMING SET AT 8DEG ADVANCED; THANKS.Comment
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Re: LOW VACUUM
Garth:
It sounds like your tappet clearances are set too tight. Absolute minimum clearances for both intake and exhaust valve tappets should be .023", with .030" being the "recommended" clearance published bt Chevrolet. Initially, .026" was recommended, but that was later changed to .030", due to fuel injection vacuum issues. There is a good amount of debate about the "optimal" setting, but .025" has worked very well for me. This yields good driveability, and should provide about 9 - 10 in-hg @ idle (750-850 RPM).
I am certain that there will be more responses to your post, including detailed instructions.
Joe
PS: Please explain the procedure that you followed, in adjusting your clearances.
JoeComment
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Re: LOW VACUUM
Garth,
Are you setting the timing at 8* with the vac advance line disconnected? Does it smooth out a little when the timing is set higher?
Is the engine huffing any black smoke from the exhaust? In other words, is it running extremely rich? Carb problems?
(turn your caps off)Comment
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More!
That is, assuming that you don't have a massive vacuum leak somewhere. After warmup, if "choking" the carburetor with your hand on the air horn results in a significant RPM increase, that is a very good pointer to a sizeable vacuum leak. Likely culprits then, would be carb-to-intale, and/or intake-to-head gaskets. Use the motor oil squirt test to verify.Comment
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Re: LOW VACUUM
THE CAM IS A CRANE "BLAZER"; SPECS VERY SIMILAR TO ORIGNAL; FOLLOWED CRANE INF; SET AT .024 COLD; INTAKES SET WHEN EXH VALVE STARTING TO OPEN; EXHAUSTS SET WHEN INTAKE 2/3 RETURNING TO CLOSE.THANKS.Comment
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Re: LOW VACUUM
Sorry about the caps; I set the timing statically; I can't get the car to run long enough to set timing with a light; car is smoking a lot; white smoke. ThanksComment
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Re: More!
I tested the intake manifold gasket and carb base with starter fluid, no increase in idle; thought it may be internal so I'm replacing the gaskets tonight with GM gaskets and RTV front and rear.Comment
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Re: LOW VACUUM
White smoke? Hmmmm. Could be oil or steam from an internal coolant leak? I'd set the timing about 4 or 5 deg higher just to get things sorted out. New engines sometimes need a little more lead until things are correct. Then set it to specs later.
If the smoke is white, that would pretty much eliminate a carb flooding problem. Give the dist a yank and we'll go from there.Comment
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Re: More!
Garth:
I don't like the white smoke! Assume no oil residue in your coolant reserviour?? Did you perform a compression test? Pull all 8 plugs, keep them in order and label them 1-3-5-7 and 2-4-6-8, let us know what they look like.
White smoke could be steam, or could be oil, too. If you see any plug that is very clean and white......bad sign, which might mean coolant leak. Hopefully, you'll find oil fouled.
JoeComment
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Re: LOW VACUUM
When I pulled the manifold off last night it did look like oil build-up on top of the intake valves.Comment
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Re: More!
Last night after pulling the manifold I did find oil build-up on top of the intake valves; I found the two middle plugs were dark and sooty while the other plugs were wet.Comment
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Re: LOW VACUUM
Garth,
The oil that you have found in the intake ports can't be a good thing but I don't think that an intake gasket leak would prevent the engine from running. You mentioned that you can't seem to keep it going for more than a minute or two. I think I would begin at the beginning and see if indeed you have an engine by taking a compression test before you go any further. May sound elementary but at least you would then know you have the basic elements.
Many things can cause extremely low vacuum readings, including ignition timing, but so can cam timing and poor ring seal etc.Comment
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Re: LOW VACUUM
I almost hate to ask this, but did you degree the cam at installation? I assume this is a fresh rebuild?, one other thing that can screw up an idle is using an incorrect gasket between the main body and the throttle plate of the holley carb.Bill Clupper #618Comment
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