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Old 09-07-2015, 09:46 AM   #1
Doctor's Ford
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Default Model B oil leak. Need clearance info

Several months ago I posted all the drama trying to fix a rear main oil leak on my 33 model B sedan. Problem still not resolved, now on m 4th attempt to fix it.

This post is to ask for information on clearances. I understand a very narrow clearance is required between the crankshaft and the bearing. Can somebody provide the following information for the model B engine:

1) Clearance between crankshaft and bearing
2) Front-end crankshaft clearance
3) Is there any other clearance measurement I need to asses?
4) A simple procedure to measure the clearances (I only have regular hand tools)

Thanks barners. There is a day when my engine will work! Got to keep an optimistic attitude
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Old 09-07-2015, 10:44 AM   #2
Jim Brierley
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Default Re: Model B oil leak. Need clearance info

Clearance between crankshaft and bearing. .0015" You might get by with .001" but don't do that if you do any freeway driving.
Clearance between crankshaft and bearing. Not as critical, and not adjustable. Aim for .004"
Oil can leak at several places on these engines. Between the cap and block; around the bolts, top or bottom of bolt, etc. Carefully use sealer at all points, too much can cause problems. Make sure the crank hasn't been modified for some kind of seal. Good luck! Leaks can also occur at the rear of the cam, use sealer on the gasket.
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Old 09-07-2015, 10:52 AM   #3
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Default Re: Model B oil leak. Need clearance info

Quote:
Originally Posted by Jim Brierley View Post
Clearance between crankshaft and bearing. .0015" You might get by with .001" but don't do that if you do any freeway driving.
Clearance between crankshaft and bearing. Not as critical, and not adjustable. Aim for .004"
Please clarify...
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Old 09-07-2015, 11:45 AM   #4
Tom Wesenberg
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Default Re: Model B oil leak. Need clearance info

I think Jim meant PISTON and CYLINDER on his second clearance.

You can use aluminum foil to measure the clearance for mains and rods. Fold the aluminum foil to double the thickness and measure it. Then insert a strip about 3/4" wide and the length of the bearing, between the crank and cap. Then tighten the cap to specs. If this keeps the crank from easily turning, but a single thickness allows easy turning, then the clearance should be good.

A search will turn up the foil method for checking clearance, but be sure to measure the thickness of the foil, as it can vary.

Last edited by Tom Wesenberg; 09-07-2015 at 11:51 AM.
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Old 09-07-2015, 12:25 PM   #5
Patrick L.
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Default Re: Model B oil leak. Need clearance info

Quote:
Originally Posted by Y-Blockhead View Post
Please clarify...






I don't want to step on anyones toe's, but, I think the bottom [ .004"] may be referring to crank end play. If not, someone will correct it.
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Old 09-07-2015, 01:29 PM   #6
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Default Re: Model B oil leak. Need clearance info

OK, thanks all for your answers. These are the numbers I am looking for: crank and bearing 0.0015". I did ask about crank end play, not pistons. Appears the answer is 0.004".

I will try the aluminum foil and plastigauge methods. Did not know about these methods but just watched a couple of you tube videos and I can handle it. Now I need to know the torque specifications for caps and rod bearings on the model B. Anyone has those figures?
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Old 09-07-2015, 01:54 PM   #7
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Default Re: Model B oil leak. Need clearance info

Use the Plastigauge because it gives more information about the clearance across the bearing journal. Plastigauge will indicate a taper whereas the foil will not.

If the clearance at the rear main bearing is adjusted, the center and front main bearings should also be adjusted.

While you have the rear main bearing cap off, remove the oil passage plug from the front face and make sure the passage is not obstructed. Look for the drain pipe protruding into the oil passage as well as look for sludge.

Seal the bearing cap bolts using silicone when re-installing the cap.
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Old 09-07-2015, 01:59 PM   #8
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Default Re: Model B oil leak. Need clearance info

Use the Plastigauge because it gives more information about the clearance across the bearing journal. Plastigauge will indicate a taper whereas the foil will not.

If the clearance at the rear main bearing is adjusted, the center and front main bearings should also be adjusted.

While you have the rear main bearing cap off, remove the oil passage plug from the front face and make sure the passage is not obstructed. Look for the drain pipe protruding into the oil passage as well as look for sludge. I have found residual plugging material wadding) and babbittt in oil drain passage. Plugging material is used by rebuilders to keep babbitt from flowing into the oil drain.

Seal the bearing cap bolts using silicone when re-installing the cap.
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Old 09-08-2015, 11:47 AM   #9
Jim Brierley
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Default Re: Model B oil leak. Need clearance info

Yes,
I was talking about end-play.
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Old 09-10-2015, 08:46 PM   #10
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Default Re: Model B oil leak. Need clearance info

Thanks for the helpful info.
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Old 09-11-2015, 12:03 AM   #11
Kohnke Rebabbitting
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Default Re: Model B oil leak. Need clearance info

Model B Mains should be set to .002-00 Minimum, and .002-50 Maximum.

The rod bearings should be .001-80 Minimum, and .001-30 Maximum.

Use oil on the plastigauge.

Herm.
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