Author Topic: How much of an issue is .004 main bearing clearance?  (Read 2486 times)

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fairlaniac

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How much of an issue is .004 main bearing clearance?
« on: October 13, 2019, 07:55:27 AM »
My #1 bearing clearance is .004. All of the others are at .0028-.0031. The journals are at 2.749 without any variances. It's a street engine with a few passes intended at FERR. Is the .004 and issue?

A second question. I have a new Fel Pro rear main seal kit. Never opened but purchased 15-17 years ago. Would you use it?

Thanks!
Doug Bender
1966 Fairlane 427+/5 Spd TKX
1964 Comet Pro Street 427+ (in progress)

My427stang

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Re: How much of an issue is .004 main bearing clearance?
« Reply #1 on: October 13, 2019, 08:36:19 AM »
My #1 bearing clearance is .004. All of the others are at .0028-.0031. The journals are at 2.749 without any variances. It's a street engine with a few passes intended at FERR. Is the .004 and issue?

A second question. I have a new Fel Pro rear main seal kit. Never opened but purchased 15-17 years ago. Would you use it?

Thanks!

Too much in my opinion, if you recheck and get the same numbers, and are using a dial bore gauge, I'd fix it.  If it's Plastigauge, who knows what you have

BTW, if the journals measure the same, and #1 is looser, you either have a bearing issue or a crush (cap) issue.  I'd measure the saddle ID first, it'd be a shame to spin one because it was loose in the cap.  Did you try swapping bearings around to see if clearance followed the cap oir bearing? 

Also, I just did a 461 that I couldn't get a set of FMs to do what I wanted, these were rod bearings, but STDs were loose, .001s only gained me .0005, Used a set of Clevites and they were perfect, so could even try a brand swap. 

As far as the rear seal, it'd likely be fine if it feels soft and was bagged in the box, but how do you know.  Might be cheap insurance to buy a fresh name brand
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Ross
Bullock's Power Service, LLC
- 70 Fastback Mustang, 489 cid FE, Victor, SEFI, Erson SFT cam, TKO-600 5 speed, 4.11 9 inch.
- 71 F100 shortbed 4x4, 461 cid FE, headers, Victor Pro-flo EFI, Comp Custom HFT cam, 3.50 9 inch

Barry_R

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Re: How much of an issue is .004 main bearing clearance?
« Reply #2 on: October 13, 2019, 09:07:50 AM »
Speed-Pro 146M1 for a Cleveland should snug it up a touch - - we do that fairly often on standard size cranks.  Just buzz off the tangs.

Truth be known a one thou variance might never be noticed since old engines run just fine like that forever, but I prefer to have a bulkhead end bearing snugger then that.

CaptCobrajet

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Re: How much of an issue is .004 main bearing clearance?
« Reply #3 on: October 13, 2019, 09:11:17 AM »
Yes......too much.  Having .004 on the front main is a healthy bleed on the system also.  I agree 100% with Ross that you might want to check that housing bore.  If it is within .0005 of the high spec, you can tune up the cap on a surface plate with some 180 to 220 sand paper with parts washing fluid and get it to 2.9420.  If it is that, or smaller, that part is fine.  You would need to recheck your clearance once you tune up the bore.  I keep .001 bearings here both non-coated and coated.  Let me know if you want me to send you a pair of each after you check the housing bore.
Blair Patrick

WConley

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Re: How much of an issue is .004 main bearing clearance?
« Reply #4 on: October 13, 2019, 10:32:53 AM »
If you are losing oil pressure, you could just tighten up the front end accessory belt  ;)

Seriously, I agree that you should address that #1 bearing clearance.  Blair is giving you a nice option to do it right without much pain  :)

On the accessory belt, at Ford back in the day, we were doing a routine teardown of a 3.0L durability test engine.  There were no reported issues or noises in the car.  Imagine my surprise when the #1 main bearing cap showed up in the bottom of the pan!  Those two cap bolts were fractured during initial assembly (bad batch of bolts, it turned out).  The engine didn't care.  We determined that the tension from the serpentine belt was enough to keep it from knocking or losing too much oil pressure.  Makes you wonder what other amazing screw-ups are running in stock engines...
A careful study of failure will yield the ingredients for success.

Heo

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Re: How much of an issue is .004 main bearing clearance?
« Reply #5 on: October 13, 2019, 09:07:04 PM »
If you are losing oil pressure, you could just tighten up the front end accessory belt  ;)

Seriously, I agree that you should address that #1 bearing clearance.  Blair is giving you a nice option to do it right without much pain  :)

On the accessory belt, at Ford back in the day, we were doing a routine teardown of a 3.0L durability test engine.  There were no reported issues or noises in the car.  Imagine my surprise when the #1 main bearing cap showed up in the bottom of the pan!  Those two cap bolts were fractured during initial assembly (bad batch of bolts, it turned out).  The engine didn't care.  We determined that the tension from the serpentine belt was enough to keep it from knocking or losing too much oil pressure.  Makes you wonder what other amazing screw-ups are running in stock engines...

I repaired a Mercedes Diesel that had pieces of a crushed ballbearing in the oil pickup. Somebody at the factory must have put it there
The customer told me he had low oilpressure when it warmed up.Strange since it had only run 100000 miles so i started with the pump
Its easy on them you just unbolt the sump no need to lift the engine. There it was, a crushed ballbearing



The defenition of a Gentleman, is a man that can play the accordion.But dont do it

fairlaniac

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Re: How much of an issue is .004 main bearing clearance?
« Reply #6 on: October 14, 2019, 06:08:03 AM »
Thanks for the replies. I moved bearings around and the issue sticks with the #1 cap. I'll check the housing bore hopefully later today. What is the spec/tolerance on the housing bore?

FYI - I am using a bore gauge, not plastigage.

thanks!
Doug Bender
1966 Fairlane 427+/5 Spd TKX
1964 Comet Pro Street 427+ (in progress)

My427stang

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Re: How much of an issue is .004 main bearing clearance?
« Reply #7 on: October 14, 2019, 08:06:35 AM »
2.9412 - 2.9420, or like Blair said, under 2.9420...I like to see it on the lower side for a little more crush, be sure to check both sides of the oil feed to check for taper.

I have a little dressing file I will pass over the block surface too, sometimes there can be a little raised edge that bites you.  If a very light cleanup in that area doesn't do anything, unless you have a ton of taper, cleaning up the cap will likely get you there.  Glad to hear Blair brought it up, go easy though, you aren't machining the cap, you are just dressing it

Also be sure you have a good set of main bolts and are torquing with lube and an accurate wrench, when you are counting thousandths, things change quick!
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Ross
Bullock's Power Service, LLC
- 70 Fastback Mustang, 489 cid FE, Victor, SEFI, Erson SFT cam, TKO-600 5 speed, 4.11 9 inch.
- 71 F100 shortbed 4x4, 461 cid FE, headers, Victor Pro-flo EFI, Comp Custom HFT cam, 3.50 9 inch

cjshaker

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Re: How much of an issue is .004 main bearing clearance?
« Reply #8 on: October 14, 2019, 06:48:58 PM »
Like Blair mentioned, if you decide to dress the bottom of the cap, I'd make sure to use a surface plate...something that is perfectly flat and true. Doing something like that on a garage bench is sure to cause a flatness issue on the bottom of the cap. That's definitely not a good thing. Any machine shop should have something like that in their shop, whether it's an automotive machine shop or not. I purchased a surface plate and a couple of straight edges from my local machine shop, owned by a friend of mine. You need those things more often than a person thinks. Very handy to have around.
Doug Smith


'69 R-code Mach 1, 427 MR, 2x4, Jerico, 4.30 Locker
'70 F-350 390
'55 Ford Customline 2dr
'37 Ford Coupe

machoneman

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Re: How much of an issue is .004 main bearing clearance?
« Reply #9 on: October 14, 2019, 07:54:52 PM »
Like Blair mentioned, if you decide to dress the bottom of the cap, I'd make sure to use a surface plate...something that is perfectly flat and true. Doing something like that on a garage bench is sure to cause a flatness issue on the bottom of the cap. That's definitely not a good thing. Any machine shop should have something like that in their shop, whether it's an automotive machine shop or not. I purchased a surface plate and a couple of straight edges from my local machine shop, owned by a friend of mine. You need those things more often than a person thinks. Very handy to have around.

A old piece of thick glass (heavy-duty store windows, display case, etc.) works well here.
Bob Maag