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Rod Bearing clearance

 
Old Jun 16, 2019, 10:01 AM
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Rod Bearing clearance

Have Manley H beam rods with acl bearings, stock used crank. Nothing wrong with the crank just uogradimg the rods and pistons. In the process of checking clearances with plastigage, one of my clearances came up at .001. Has anyone had a issue with too tight of clearancea with this combination? If so what setup works best as far as bearings goes?
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Old Jun 16, 2019, 10:50 AM
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I think i have these in order top being cylinder 1 and the bottom being 4 . but either way this is all of my rod journals. Im going to go find some green plastigage to get a close reading but my thoights thus far are that I need bearings with more clearance. Thoughts?
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Old Jun 16, 2019, 11:00 AM
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have it checked with a proper bore gauge... plastigauge is not the most accurate of things
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Old Jun 16, 2019, 11:05 AM
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First of all, stop using plastigauge. Buy a micrometer set and some telescoping gauges, they're not expensive and are way more accurate than plastigauge.

If your clearance actually is that tight, companies do sell extra clearance bearings that add another .001" of clearance. I wouldn't run an engine with a rod clearance any lower than .0015". I usually shoot for .002-.0025" on builds that aren't crazy.
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Old Jun 16, 2019, 11:08 AM
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So to find the clearance with a mic and bore gauge....measure the crank with the mic and measure the rods with bearings ing them (torqued) with the bore gauge and the difference of the two is the clearance?
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Old Jun 16, 2019, 11:23 AM
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Yes.
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Old Jun 16, 2019, 11:27 AM
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Splendid. Appreciate all the input. I'll do it with better tools.
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Old Jun 16, 2019, 02:04 PM
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Don't order other bearings until you measure those properly. Good bet the clearance is fine the plastigauge just got smeared a bit when removing the rod from the journal. Plastigauge pretty much sucks. It's difficult to use properly, and it's not really accurate anyways.
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Old Jun 16, 2019, 02:11 PM
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So..... Got wut I was able to find. A bore gauge set, a micrometer and a digital caliper. Measured the rod journals with the micrometer. 1.775 across the board. Went down to a rent a shop by me and put rods with bearings in a vice and torqued to 60lb ft. Used the bore gauge (as best as able as it does NOT have a gauge on it. At the parts store now lookong for one.) Inside the end of the rod. And measured with the digital caliper. Rod one gave a measurement of 1.998. Good. The other 3 all gave me a measuement of 1.775 the exact same as the rod journals.
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Old Jun 16, 2019, 03:06 PM
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Hopefully you didn't mar the sides of the rods in the Vice...

What rod bolts are they? 60ftlbs seems tight..
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Old Jun 16, 2019, 03:15 PM
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Didnt damage the rods at all. Used lots of padding. I thin we had some spandex gloves with rubber on them laying around. Put a couple of those on each side of the rod in thw vice. 60 is the spec the machine shop gave me. Manley gave me the same spec for the arp2000 bolts im using.
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Old Jun 16, 2019, 03:17 PM
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Im pretty sure my measurments arent off. I tool my time and measured several times trying to get different values but it all ended up the same in the end. I wanted to find a dial bore gauge just to be extra sure but I think I just need an oversized set of bearing to fill in 3 the bad ones. Or too tight ones.
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Old Jun 16, 2019, 04:21 PM
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You need to measure the rod big end without bearings. Make sure it isn't undersized and over crushing the bearing.
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Old Jun 16, 2019, 04:30 PM
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What is the bore of the rod supposed to be without bearings? I cant find that info anywhere yet.
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Old Jun 16, 2019, 04:33 PM
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