Advice re vacuum leak?
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Cargo Master
Joined: Apr 2001
Posts: 2,697
Likes: 46
From: Vancouver
Advice re vacuum leak?
It can't be anything else, at this point. There is no leak on top of the manifold; carb, spacer and pvc are okay, so the leak must be at the head-intake interface. It seems to me that because of the FE's design, a leak at that point would suck oil and show up as smoke. I dread taking off that manifold. Any ideas about how to conclusively determine the cause of the problem would be appreciated.
Eric
Eric
Post Fiend
Joined: Feb 2000
Posts: 5,130
Likes: 8
From: Brea CA
Advice re vacuum leak?
Hi Eric, I guess I’m not up to speed. Did you make any recent changes to your engine? That manifold is a back breaker, have you tried retorqueing it down first? Maybe disconnect and plug all your vacuum lines, then spray carb. cleaner everywhere until the leak sucks it up and the engine tells you. Guesses are transmission modulator, power brake booster, vacuum advance (or retard), choke stove, the carb. itself, incorrect pcv valve. Have you replaced all your vacuum hoses? My experience with manifold leaks is that usually only one bank will be leaking. It will draw in oil and blow out smoke on the affected bank, you can tell what side if you run dual exhaust. Good luck!
Barry
Barry
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Cargo Master
Joined: Apr 2001
Posts: 2,697
Likes: 46
From: Vancouver
Advice re vacuum leak?
Barry, I had it apart for a cam change, and to replace the 4V manifold with a 2V. I put the manifold on very carefully. I've tried everything you suggested except re-torquing. I'll try that and report back.
Eric
Eric
Tuned
Joined: Jul 2001
Posts: 430
Likes: 0
From: Deatsville, AL
Advice re vacuum leak?
I've seen the 428 CJ/SJC gaskets leaking at the bottom when they are used with the standard manifolds. It was a bad vacuum leak.
You may have to tear it down and look.
Bob
'66 7 Litre, top loader, 3.25 Traction-lock, Sidewinder Intake, SCJ Exhaust
'88 F150 LWB 4x2, XLT Lariat, 302, 5 speed, 3.08
'99 Ranger, 4x2, 3.0, 5 speed, 3.73 posi
You may have to tear it down and look.
Bob
'66 7 Litre, top loader, 3.25 Traction-lock, Sidewinder Intake, SCJ Exhaust
'88 F150 LWB 4x2, XLT Lariat, 302, 5 speed, 3.08
'99 Ranger, 4x2, 3.0, 5 speed, 3.73 posi
Thread Starter
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Cargo Master
Joined: Apr 2001
Posts: 2,697
Likes: 46
From: Vancouver
Advice re vacuum leak?
The smoke test showed no leaks, so I tried an experiment. I removed the carb and covered the holes with duct tape, removed the distributor, put my stethoscope (heater hose) in my ear and down the dist hole, and cranked the engine for 20 seconds. When I stopped, I heard a hissing for 5-10 seconds apparently coming from the underside of the manifold. No wonder I couldn't find the leak before. So, with the proof that I hadn't wanted to find, I went ahead and did it.
I think if I end up in hell I'll be carrying around a cast iron FE manifold for the rest of time.
Eric
I think if I end up in hell I'll be carrying around a cast iron FE manifold for the rest of time.
Eric
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