vacuum leak

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Jan 1, 2012 | 05:44 PM

nikwave

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From: maui

vacuum leak

i just finished putting the engine together after the rebuilt and had low vacuum (12-13)and a tapping?noise on the passenger side cylinder head.cylinder heads are rebuilt by pops and cam/lifters are new compcams.i took the intake manifold out hoping i didn't seal it properly and put it back in again but nothing changed.so yesterday i took the cylinder heads out and found cylinder 1,2 and 6 were really black ,the rest were ok.the whole ignition system is new.so i think is something in the heads/lifters.the valves feel tight in the guides ,but i found some chips missing in some of the valve guide bases,i dont know if that can cause a leak? what do you guys think.thanks and happy new year!

here are the pictures:

ford fe cylinder heads - a set on Flickr

Jan 2, 2012 | 10:22 AM

MIKES 68 F100

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From: Antelope Valley ,CA

My valve guide seals fit over the guide , but i don't think that will cause a vacuum leak .
did you check carb mount before removing ?
squirting around carb with carb cleaner or starting fluid ? if rpm increases you found leak

Jan 2, 2012 | 11:36 AM

nikwave

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From: maui

im going to check the carb ,i did rebuilt it too and put a new carb to manifold gasket.thanks!

Jan 3, 2012 | 02:20 AM

nikwave

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From: maui

update :i found a lifter with 2 small cracks on the smooth part of the body,would that make the lifter not hold pressure thus causing low vacuum ?

picture of leaky lifter:

PC290098 | Flickr - Photo Sharing!

Jan 3, 2012 | 04:26 PM

mikeo0o0o0

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From: Stanley, VA

I've never seen a lifter fail like that. But if the crack goes through to the inside of the chamber I could see where that would cause the lifter to collapse. That would account for the "ticking" sound.
How radical is the camshaft? The more radical, the lower the idle vacuum will be. Also, off a tooth on the timing will change the vacuum characteristics of an engine.
Did you run a compression test before you pulled the heads?
You need as much info as possible to accurately diagnose the problem.

Jan 4, 2012 | 11:40 AM

nikwave

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From: maui

yes i did the compression test ,all cylinders were between 145-150psi.the timing chain is new from compcams,so is the cam xe262.speed demon 750 vac sec,crane cams dist. and ignition box.timing set at 14,max timing at 38.and when it starts it sounds like needs more timing for some reason.

Jan 4, 2012 | 12:54 PM

MIKES 68 F100

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From: Antelope Valley ,CA

did you adjust the mixture on carb ? this will change your vacuum .
good start point for mixture screws is 1 1/2 turns out then hook vacuum gauge up and adjust in/ out half turn at a time till you get max vacuum . match both sides !