intermittent miss
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Senior User
Joined: Feb 2005
Posts: 468
Likes: 9
From: Alabama
intermittent miss
I have a 66 F-250 that I have just put a 300 from a 65 donor truck in. The engine is a Fred Jones reman. Block is a 75. All accessories are from the 65.
Engine had a miss. I removed the head and found a couple of press in studs had backed out. Replaced press in studs with treaded ones. Rebuilt carb and replaced plugs and points. Engine ran great in donor truck. Pulled engine and put in the 66. Engine now has a intermittent miss on the #4 cylinder. Holds
18 lbs of vacuum then drops to 15 when it misses. I suspect a lifter. Any input would be appreciated.
Engine had a miss. I removed the head and found a couple of press in studs had backed out. Replaced press in studs with treaded ones. Rebuilt carb and replaced plugs and points. Engine ran great in donor truck. Pulled engine and put in the 66. Engine now has a intermittent miss on the #4 cylinder. Holds
18 lbs of vacuum then drops to 15 when it misses. I suspect a lifter. Any input would be appreciated.
Elder User
Joined: Sep 2008
Posts: 563
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From: DeKalb, Ill.
If the plug wire suggestion above doesn't pan out, I'm thinking a stuck valve.
This site can help interpret vacuum readings.
http://www.users.bigpond.com/ergoff/vac1.htm
Let us know,
Murph.
This site can help interpret vacuum readings.
http://www.users.bigpond.com/ergoff/vac1.htm
Let us know,
Murph.
Thread Starter
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Senior User
Joined: Feb 2005
Posts: 468
Likes: 9
From: Alabama
Thanks guys for your replies! Changed plug on #4 cylinder. All plugs are new.
Points and condenser new. Removed Head and replaced press in studs with tread in ones on valves that the studs had backed out. Replaced all lifters.
Replaced head and engine ran great. After installation in 66 the engine has this intermittent miss?
Thanks for all ya'lls help!
This site is great!
Points and condenser new. Removed Head and replaced press in studs with tread in ones on valves that the studs had backed out. Replaced all lifters.
Replaced head and engine ran great. After installation in 66 the engine has this intermittent miss?
Thanks for all ya'lls help!
This site is great!
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Logistics Pro
Joined: Jan 2002
Posts: 4,907
Likes: 39
From: suburban atlanta
You can hook a timing light to the #4 plug wire to see if you are losing spark.
What I am getting is that it ran fine before you transplanted it. Nothing mechanically changed from spot to spot. The valves, lifters, etc should all work as well in this truck as the other one. No?
If that is so, you likely have an electrical problem, such as a missing ground wire, or loose connection, or you could have a vacuum leak that is only now showing up on #4, because #4 was marginal, or is the 'leanest' cylinder. The others are just a little richer?
Check your work. Stuff just doesn't stop working... Ask Murphy. ... and he was an optimist. Now, if you needed to take a load cross country in this thing, for sure it would be Murphy's associate at work. "It always breaks just when you need it most", or, as they say "Watch this". Not. Sorry for the hapless humor attempt.
tom
What I am getting is that it ran fine before you transplanted it. Nothing mechanically changed from spot to spot. The valves, lifters, etc should all work as well in this truck as the other one. No?
If that is so, you likely have an electrical problem, such as a missing ground wire, or loose connection, or you could have a vacuum leak that is only now showing up on #4, because #4 was marginal, or is the 'leanest' cylinder. The others are just a little richer?
Check your work. Stuff just doesn't stop working... Ask Murphy. ... and he was an optimist. Now, if you needed to take a load cross country in this thing, for sure it would be Murphy's associate at work. "It always breaks just when you need it most", or, as they say "Watch this". Not. Sorry for the hapless humor attempt.
tom
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Logistics Pro
Joined: Jan 2002
Posts: 4,907
Likes: 39
From: suburban atlanta
Check the brake booster for leakage, and make sure the carb is tight on the intake. Had a 300 that wouldn't idle for beans, and the power brake booster had a flaky valve that was letting in excess air, then not, then doing it again, etc. Could not find that miss for a bazillion dollars... Someone else did later on.
tom
tom
