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  #1  
Old 07-06-2008, 01:01 PM
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mico mico is offline
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Default Main bearing clearance question

Guys, I have a D1 block that has been line bored, Im using a Clevite standard size bearing. Is there a standard diameter that I should be getting when measured? I get a main of 3.001, crank reads 2.989 which is .012 clearance. When I use green Plasiguage it shows .001 :?
Whats the best way to measure this?
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Old 07-06-2008, 01:23 PM
CutawayAl CutawayAl is offline
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Even experts make a mistake once in a while, I suspect your measurements or math are off. Plasti-gauge is not as good as accurate measurements. Measure the main housing bores. If those are within spec, install the bearings, torque the caps, and measure the bearing IDs. Then, measure the crank journals. All these measurements should be made at multiple points, and obviously must be accurate. If the clearances determined by measuring vary much from a properly done plasti-gage reading, the block and/or crank are not straight. Also, assuming the crank endfloat is ok, and the main journal fillets clear the bearings, the crank should spin easily. If it doesn't, that also could be an indication of a crank/block problem.
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Old 07-06-2008, 01:42 PM
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The block just came from the machine shop. Bored, decked, linebored it was 1/2 filled prior to machining. The crank is a new Scat forged 4.5. I installed the crank with permetex assy lube and torqued to 100lbs crank spins with very little effort (easy). I dont belive that there is a problem with the block or crank. I just need to get the clearances figure out. My mics measure the same as the machine shop on the crank so I assume that its calibrated.
What measurement should I get with the bearing installed and cap torqued?
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Old 07-06-2008, 03:47 PM
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Mike, get you a good dial bore gauge that reads to .0001. Then you can install the bearings & caps & get an accurate reading to compare to your crank journel sizes.
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Old 07-08-2008, 02:23 AM
RobMcQ RobMcQ is offline
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Hey Mike,
Isn't engine building fun?
Main and rod bearings have been one of our biggest sources of frustration over the last decade. Trying to hit target clearances is just a royal pain in the butt! The bearings just aren't very predictable anymore. I used to be an avid supporter of the Federal Mogul performance bearings, and hated the Clevites. However, after F/M switched bearing production to Mexico, they have become absolute pain in the arse, never a consistant size. So, we've been switching back to the Clevite's, and they have actually gotten better than they were in the late 90's.

But, we still end up having to try numerous sets, mix and match .001's and X's, etc to try and get to target clearances. And just because a set is sized at .001, doesn't mean it will be a thou tighter than the STD's. That's only a theory. You just have to install and measure........install & measure...........install & measure..........

We have tried some of the Kings and the ACL's with good results. Some have come back in race engines and seem to be holding up just fine. The thing about 'em is if you hone the housing bores on the split, have the crank on the low, and install the bearings, you almost always end up with a workable clearance the FIRST time. What a f#@king concept! F/M & Clevite have forgotten how to make a damn bearing. So we waste hours upon hours with their crap trying to get clearances. I know Barry has nothing nice to say about the Kings and ACL's, but after all of the problems we consistently have with the F/M & CL's, I don't know why..............

Sorry, the bearing topic will start me on a real rant.
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Old 07-08-2008, 09:13 AM
rmcomprandy rmcomprandy is offline
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That clearance is entirely within the specs of a regular rebuild, grocery getter type engine. They are on the tight side of those acceptable OEM limits.

A high performance or race engine is an entirely different story.
There are some "rules of thumb" however, the biggest parameter on clearance is how will the engine be loaded and the desired clearance depends a lot on the strength of the crankshaft and the type of metal it's made from, whether the block material is on the brittle side or mallable and what weight and type oil is to be used, etc.
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Old 07-08-2008, 12:41 PM
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Actually I don't have a big problem with ACL. They are OK parts. I don't like King though. When we checked them - and I had SERIOUS checking tools back then - the King stuff was all over the map for profile, and the material was nothing like they claimed.

I have a bigger problem with companies that make up stories and lie to customers than with companies that simply don't have the resources to deliver a particular part. King was selling low budget passenger car rebuilder quality parts with marketing claims of them being superior to legitimate race hardware.

Maybe they've learned better....it's been at least 3 years.
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