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Old 06-08-2015, 07:08 PM   #1
JBohannon
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Default Model A Lower end

For the first time I am going to pull the pan on my 28 Model A and see what condition the bottom end is in. I am doing this for 2 reasons. At higher engine speeds I get a terrible vibration and it feels like engine is going to come apart. Also I have a bad rear seal leak. My compression is ok and the car runs ok but I think it is time I see what condition it is in. Any ideas on what I should look for when I get the pan pulled. Should I check for extreme looseness in the rods or use plastigage? Thanks for any help.
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Old 06-08-2015, 07:21 PM   #2
Mitch//pa
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Default Re: Model A Lower end

ck for crankshaft end play
this can be done with the pan on
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Old 06-08-2015, 07:57 PM   #3
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Default Re: Model A Lower end

Thanks Mitch what will that tell me how much is too much.
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Old 06-08-2015, 08:17 PM   #4
Mitch//pa
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Default Re: Model A Lower end

i believe the spec is .003-.008
to much end play can contribute to a rear main oil leak and vibration.
of course many other things can cause that also.
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Old 06-09-2015, 12:18 AM   #5
Tom Wesenberg
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Default Re: Model A Lower end

Usually the center main is the first to go, so I'd check that one first.
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Old 06-09-2015, 06:46 AM   #6
JBohannon
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I was under the assumption that most of the vibration would have been from a bad rod bearing but I am now reading in this and other post that it might well be the mains also? Any thing else to look for.
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Old 06-09-2015, 07:56 AM   #7
BILL WILLIAMSON
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Default Re: Model A Lower end

Some average, completely stock Model A's, many time has vibrations/rattles, that sounds as if you're "tearing" up the engine, usually above 45 MPH. Many small things can cause "disastrous" sounding noises. Minerva had a bad noise for about a week, once! The locking knob for the windshield slide bar was NOT TIGHT enough. The tail pipe hanger can cause BAD noises sometimes. If you rig up a rubber hanger on the pipe, it helps a lot.
On crankshaft end play, it helps prevent some wear on the bearing thrust area, IF when you're waiting at LOOOONG stop lights, put it in neutral & let the clutch out. With the clutch pushed in, it puts a LOT of pressure on the thrust area of the MAIN BEARING & causes extra wear.
You can get a FAIR idea of lower end bearing condition, by holding the idle to about 900 to 1100 RPM & "feather" the speed, UP & DOWN, slightly & listen for KNOCKING type sounds. A rod knock can be narrowed down by grounding out 1 cylinder at a time. If you SUSPECT a loose CENTER MAIN, usually it quiets down SOME, when you ground out # 2 or # 3 & will quiet down completely, when you ground out # 2 & # 3, AT THE SAME TIME, while "feathering" the throttle. Claude, (RIP) our REAL GURU, had a rebuilt engine with a center main knock, SOMEONE FORGOT TO ADJUST THE CENTER MAIN!! The shim pack was TOTALLY undisturbed!!! After adjusting it, the engine sounded "PRIMO"!!!
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Old 06-09-2015, 05:22 PM   #8
Chuck Sea/Tac
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Default Re: Model A Lower end

Correct me if I'm wrong, but I don't think a bad bearing will cause a vibration. Or at least a loud knock way before that? Has this engine ever run smooth? I think the vibration is u joint, out of balance crank/rods or pressure plate ect.
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Old 06-09-2015, 05:35 PM   #9
Patrick L.
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Default Re: Model A Lower end

Quote:
Originally Posted by JBohannon View Post
For the first time I am going to pull the pan on my 28 Model A and see what condition the bottom end is in. I am doing this for 2 reasons. At higher engine speeds I get a terrible vibration and it feels like engine is going to come apart. Also I have a bad rear seal leak. My compression is ok and the car runs ok but I think it is time I see what condition it is in. Any ideas on what I should look for when I get the pan pulled. Should I check for extreme looseness in the rods or use plastigage? Thanks for any help.




What does high engine speed mean ? And, does this vibration happen while sitting still in neutral or only when driving ?
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Old 06-09-2015, 06:31 PM   #10
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Default Re: Model A Lower end

I always sit at a light with my foot off the clutch, also helps me from getting T boned people like to run red lights hear. also I start up the motor with my foot off the clutch, I like to get some oil in there before I step on it
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Old 06-09-2015, 08:30 PM   #11
JBohannon
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Default Re: Model A Lower end

the vibration is the same in neutral or driving. It starts at mid throttle. I think my laymen thoughts are it is in the rods?
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Old 06-09-2015, 08:43 PM   #12
Tom Wesenberg
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Default Re: Model A Lower end

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the vibration is the same in neutral or driving. It starts at mid throttle. I think my laymen thoughts are it is in the rods?
That's exactly what my 29 Tudor did when I bought it. The center main was gone completely.
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Old 06-09-2015, 09:48 PM   #13
BILL WILLIAMSON
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Default Re: Model A Lower end

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the vibration is the same in neutral or driving. It starts at mid throttle. I think my laymen thoughts are it is in the rods?
Model A's have so much stuff that's mounted almost solid and/or metal to metal & some noises are almost impossible to find/correct. Each car has different personalities/sounds. Once in awhile I ACCIDENTALLY find/correct a noise, after it's driven me NUTS, for month. Minerva had a loose vertical wood piece, behind the R/H quarter window, that would only noise off @ 40 MPH, in second gear. I almost NEVER found that sucker! I used to know the part # for that individual wood piece. BUT, I DO know the part # for the oil pressure sender for Early Jaguars--PT-1801/06 & the short stepped radumator hose fur a Jag-XKE is--C15099! The English made POOR rubber. I hope their condoms are better.
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