Main Bearing Clearances - 460 Ford Forum
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post #1 of 44 (permalink) Old 07-21-2007, 03:32 PM Thread Starter
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Main Bearing Clearances

I am putting my engine back together and checked the main bearing clearances. Crank is ground .010 under. Bearings Clevite 77 MS-1039P-10

#1 - Crank Journal = 2.9892 - Clearance = .0034"
#2 - Crank Journal = 2.9891 - Clearance = .0034"
#3 - Crank Journal = 2.9894 - Clearance = .0044"
#4 - Crank Journal = 2.9894 - Clearance = .0034"
#5 - Crank Journal = 2.9891 - Clearance = .0036

Measured using mics with bearings installed and caps torqued.
This is on a 460 build, expecting 500 HP, 550 TQ, 6000RPM

These clearances seem loose to me. Any advise?

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post #2 of 44 (permalink) Old 07-21-2007, 04:06 PM
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post #3 of 44 (permalink) Old 07-21-2007, 04:12 PM
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At that RPM and power level I'd have it line honed smaller or get a different crank.

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post #4 of 44 (permalink) Old 07-21-2007, 05:42 PM
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For that sort of rpm level I think you would be a lot better with a full .001 less bearing clearance. Since you're at .010 on your bearings and crankshaft you have two options as Randy said, getting another crank and having it ground to fit your block, in your case .009 undersize. Or have it line honed to make the housings .001 smaller than they are right now.

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post #5 of 44 (permalink) Old 07-21-2007, 06:25 PM
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I agree with what both Randy and Dave have said.

Furthermore with the way bearings are nowadays, in terms of quality control in regards to sizing, you can probally go buy a different brand of .010" bearings, say Federal Mogul for example, and come up with a totally different set of dimensions. Then if you consider coated and uncoated bearings, that will change things again.

We cannot build an engine around here, without having several sets of bearings on hand to choose from. It's a trial and error deal nowadays, and I don't care if it's a Ford, Chevy or Mopar engine that you are building.

The performance enthusiast who is building his own engine, and is the type of guy who maybe builds only one engine in three or four years, should NOT expect that one set of rod and main bearings that comes in a stroker kit from Hawks, Flatlander or others, is going to provide the correct clearances out of the box.

Before you go adjusting your block main journal i.d. smaller, or before you go find another crankshaft, may I suggest that you buy another set of bearings, of a different brand and try them.

Hope this helps,

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post #6 of 44 (permalink) Old 07-21-2007, 06:28 PM Thread Starter
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Yes I'd like to see a full .001 less. According to my manual, the factory specs are .001 to .002.

I guess another option is to grind the crank to .019 under and get a set of .020 under bearings.

Probably line honing is the right way to go.

I'll discuss with the machine shop on Monday.

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post #7 of 44 (permalink) Old 07-21-2007, 06:34 PM Thread Starter
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Sorry Charlie, I must have been posting my response when you posted yours.

I am surprised that you can find that much difference in bearings.

Problem is as you know, I can't return the bearings once they have been opened.

But I'll discuss that with the machine shop on Monday as well.

Thanks

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post #8 of 44 (permalink) Old 07-21-2007, 06:38 PM
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I already had a big difference between the MS 1039 P and the MS 1039 V. Both from clevite but found out that the eccentricity is different. Don't know the V is with a 10 undersize avalible or not.

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post #9 of 44 (permalink) Old 07-21-2007, 08:48 PM
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When I do stroker kits I offer an exhange on bearings for just that reason. I try to keep the odd sizes in stock - but for a .010 under crank you are in trouble. Line hone or another crank...

I set up .009s and .011s for the Chevy stuff back when I was at F-M, but they were not going to let me do that for the less popular applications

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post #10 of 44 (permalink) Old 07-21-2007, 09:06 PM
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:lol: Ok guys, I am missing something here. How can you make the block journals smaller by honing? And are his tolerances between the block and bearings, or between the bearings and cranks? I would think they are between the bearings and the crank!?! I know I sound ignorant, but I am not a pro, I am just a little confused. I'm thinking that if you put the caps on and torque them down, then hone the block, you are going to make the "hole" bigger?!?!?! :roll: Please, tell me what I am missing!!!!!! :roll:

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post #11 of 44 (permalink) Old 07-21-2007, 09:47 PM
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He cuts a little bit off the main cap first - then hones the hole to a slightly smaller diameter - more bearing crush and hopefully a teeny bit tighter clearance....

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post #12 of 44 (permalink) Old 07-21-2007, 09:51 PM
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Randall,

What you do is;

1. Cut some (very small amount) off of the bottom of the main caps. Sunnen makes a machine for this.

2. Then bolt the caps back on and the hole should now be eliptical, with the 12:00 to 6:00 dimension be smaller than the 3:00 to 9:00 dimension.

3. Then you go back and line hone the block to the low side of the main housing bore spec. This will tighten up the main bearing clearance.

Hope this helps,

Charlie Evans
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post #13 of 44 (permalink) Old 07-21-2007, 09:53 PM
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Ok, Got it. :lol:
I did a search and was checking out some of the machines, Kinda thought about it after i asked and thought you might do that but I wasn't really sure.

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post #14 of 44 (permalink) Old 07-21-2007, 10:11 PM
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King makes an .009"....you may want to check with them...they may offer a .011" also .
You could have a set of .010" coated...it'll take uo about .0005"

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post #15 of 44 (permalink) Old 07-22-2007, 12:38 AM
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Crank

Your crank is dead on what I want my grinds and new cranks to mic. About 5 tenths under is what I consider perfect. After checking thousands of factory cranks for many years, this is what is coming out of the factories as the typical std. What they have and we do not is a full stock of hand fit bearings. For my own use I love .003 to .0035 but I do not use ant piss for oil.
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