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Bearing clearences

 
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harveyhead01
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PostPosted: Tue Sep 27, 2011 9:26 pm    Post subject: Bearing clearences Reply with quote

What is the proper/best method to achieve the correct bearing clearences? (Rods and Mains)
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William Jones
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1971 Ford Mustang

PostPosted: Tue Sep 27, 2011 9:45 pm    Post subject: Reply with quote

Are yours tight or loose?

Bam

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af2
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1933 Willys Coupe

PostPosted: Tue Sep 27, 2011 10:13 pm    Post subject: Re: Bearing clearences Reply with quote

harveyhead01 wrote:
What is the proper/best method to achieve the correct bearing clearences? (Rods and Mains)


The best method? Inside and outside mics correlated with each other then Plastiguage to make sure the #'s are correct.
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10sec.et
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1969 Oldsmobile Cutlass

PostPosted: Tue Sep 27, 2011 11:28 pm    Post subject: Reply with quote

assuming you have the proper measuring tools....

BEFORE turning the crank, have your finished rods, block and bearings and torque the bearings in place. measure everything and take the crank to the grinder. TELL HIM what to cut the journals to. that is all he needs to know.

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af2 wrote:
It seems we can look at our magical Balls and come up with a fix?

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harveyhead01
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PostPosted: Wed Sep 28, 2011 4:50 pm    Post subject: bearing clearences Reply with quote

I geuss to rephrase my question, say I ordered a name brand crankshaft. I run through all my measuring checks and find out I have 1 main and 2 rod journals out of spec...too tight we'll say. Do I take crank, block and all to machine shop? Or is there something I can do myself?
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William Jones
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Location: Lake city, FL
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1971 Ford Mustang

PostPosted: Wed Sep 28, 2011 5:44 pm    Post subject: Re: bearing clearences Reply with quote

harveyhead01 wrote:
I geuss to rephrase my question, say I ordered a name brand crankshaft. I run through all my measuring checks and find out I have 1 main and 2 rod journals out of spec...too tight we'll say. Do I take crank, block and all to machine shop? Or is there something I can do myself?


If its tight you can buy a X bearing which gives you a little more clearance. When building motors I often mix bearing halves. I might end up using a half set of X bearings (undersized) or just pair the bearings up differently then packaged. Make your measurements if you are tight on 1 but loose on the other swap bearing halves until you get what your looking for. If that doesn't work buy the undersized bearings until you end up with what you want. But if its way off a trip to the machine shop will be required.
What crank is it? I know eagles require some work out of the box. Also if its a aftermarket crank I don't think I have built one yet that didn't need at least a half set of X bearings. But I like my stuff on the loose side.

Bam

_________________
Take the horse out off the barn and let her RUN BABY RUN!!!!!

92 LX 454ci Clevor 9.24@142.53 N/A
71 Mach1 454ci Clevor 10.16@134 N/A 3850lbs race weight "Lost in fire"
03 Cobra Bone stock 12.42
68 Falcon 363ci 10.55@126 N/A
95 GT 363ci 11.08@118 N/A
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af2
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Joined: 01 Sep 2003
Posts: 5558
Location: grassvalley, ca
71227.76 points


1933 Willys Coupe

PostPosted: Wed Sep 28, 2011 5:52 pm    Post subject: Re: bearing clearences Reply with quote

William Jones wrote:
harveyhead01 wrote:
I geuss to rephrase my question, say I ordered a name brand crankshaft. I run through all my measuring checks and find out I have 1 main and 2 rod journals out of spec...too tight we'll say. Do I take crank, block and all to machine shop? Or is there something I can do myself?


If its tight you can buy a X bearing which gives you a little more clearance. When building motors I often mix bearing halves. I might end up using a half set of X bearings (undersized) or just pair the bearings up differently then packaged. Make your measurements if you are tight on 1 but loose on the other swap bearing halves until you get what your looking for. If that doesn't work buy the undersized bearings until you end up with what you want. But if its way off a trip to the machine shop will be required.
What crank is it? I know eagles require some work out of the box. Also if its a aftermarket crank I don't think I have built one yet that didn't need at least a half set of X bearings. But I like my stuff on the loose side.

Bam


I was going to cut some of what William said but left it because it is the way you have to get the correct clearance.

Read his quote a few times and you will see that is the only way without spending big$ to get the clearance you need.
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Big Dave
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PostPosted: Thu Sep 29, 2011 5:25 pm    Post subject: Reply with quote

I agree with William's method as I have done it that way for years. Before I bought my Bore Gauge (you can get a cheapy for about $250) I used an outside mic for the crank and either telescoping snap gages (very easy to use and fairly acurate) and the outside mic again; or I got out my inside mics which were harder to use (I have big fingers and twirling the little knob inside a main cap tended to affect the reading so I would have to average about three readings to be sure).

The bore gauge is the best way as it is fast, accurate and very easy to use. You will be using it on all of your builds, even for your close friends who have to wear name tags so that you know who they are, who just happen to drop by the shop so that I can HELP them with their engine build (I was in a partnership with three other mechanics in a seven bay four lift garage and they were close associates/close freind of the my partners who showed up looking for help, not total strangers off the street though I often wondered).
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Paul P
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1971 Chevrolet Chevelle

PostPosted: Fri Sep 30, 2011 8:35 am    Post subject: Reply with quote

I used an outside mic for the crank and telescoping snap gages on the torqued bearings on my last build. It worked well.
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