Rod side clearance

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1972ho
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Rod side clearance

Post by 1972ho » Wed Oct 25, 2017 2:26 pm

Hey guys I know I ask a lot of questions,but it one of those things when you don’t want to screw up I need many of opinions.So I got my V-6 back from the machine shop and I’m just doing some basic mock up and found my rod side clearance is at .027 but only to one side and about .000 to .001 on the other side.Also with just one piston and rod assembly install without the rings my piston rocks from .003 to .020 above the deck,will that reading square up with rings installed and if it centers would that be about .010 or above the deck.Oh forgot to mention this is a split pin even fire crank one rod per rod journal.Thanks

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Re: Rod side clearance

Post by bill jones » Wed Oct 25, 2017 2:45 pm

-is the side of rod up at the wrist pin boss bound up on one side of the piston---like the rod beam is possibly offset from the lower bearing end--and maybe installed backwards?

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Re: Rod side clearance

Post by PackardV8 » Wed Oct 25, 2017 2:59 pm

I need many of opinions.
Don't need many opinions, just the one fact of the matter. Sometimes here, that's hard to discern.
found my rod side clearance is at .027 but only to one side and about .000 to .001 on the other side.
Nope, should be equal. Find what's keeping it from centering; can only be the pin in the rod (pressed pin?) or an offset rod installed backward.
will that reading square up with rings installed
Yes, the rings will reduce rock. What is the desired height?
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Re: Rod side clearance

Post by allencr267 » Wed Oct 25, 2017 3:20 pm

As long as it isn't less the the crank's end-float.
Check for some clearance when fore And aft & non-binding pin.

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Re: Rod side clearance

Post by joe 90 » Wed Oct 25, 2017 3:41 pm

So long as you can slide the rods sideways and they go click , click , click ....then they're OK.
They're not seized.
Need to rotate the crank first.

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Re: Rod side clearance

Post by 1972ho » Wed Oct 25, 2017 5:24 pm

I thought the deck height was going to be about zero but the machine shop decked the block .004 to .005 plus they checked my crank stroke and found that it is varying about 3.505 to 3.511 not sure which holes those are.And I’ll have to check to see if it is the rod and wrist pin that is stopping the movement.And installed the rods on both sides and the results were the same it needed the beveled side aft it may be the bearing that is stopping the movement.

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Re: Rod side clearance

Post by 1972ho » Wed Oct 25, 2017 6:34 pm

Looks like the bearing is causing this problem I removed the bearing and the rod moves from left to right,Do you know if there is a bearing narrower than a CB-745-HN.

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Re: Rod side clearance

Post by Dave Koehler » Wed Oct 25, 2017 7:18 pm

Is the rod facing the right direction?
As Joe mentioned you have to roll the crank over at least once for the rod to kind of center up and settle in.
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Re: Rod side clearance

Post by 1972ho » Wed Oct 25, 2017 7:27 pm

Yep I rolled the crank over a few times and still no clearance on foreword side of the rod and the rod it self is centered on the wrist pin,any of you Chevy small block builder no of a bearing that is narrower than cb-745-hn

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Re: Rod side clearance

Post by Dave Koehler » Wed Oct 25, 2017 7:37 pm

Rod orientation. What I was getting at is most rods have an offset on the big end. Installed backwards they get confused.
The only time you need a narrow bearing is if the journal radius is larger than normal and the bearing rides up the radius. Usually an aftermarket crank.
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Re: Rod side clearance

Post by 1972ho » Wed Oct 25, 2017 7:55 pm

This is billet moldex crank in a ford even fire v-6 with 2.00 rod journals,when the crank was ground this was the bearing that was used.But it had never been in the block with a piston and and wrist pin installed.

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Re: Rod side clearance

Post by Dave Koehler » Wed Oct 25, 2017 8:09 pm

I don't think the bearing is at fault, especially if only one is doing it. Closer inspection is required.
Rod too thick, bearing tang offset wrong, rod in backwards, too much radius versus the others, etc. Might try another rod on the wonky hole. If the issue goes away at least you are narrowing down the issue.

If you see witness marks on the edge of the bearing you may have to chamfer them if nothing off the shelf fits. Welcome to hot rod engine building.
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Re: Rod side clearance

Post by Dan Timberlake » Wed Oct 25, 2017 8:20 pm

I'd have a look at the fod seated on the rod journal with the cap off.
The bearing insert should have clearance with the radius at each edge of the rod journal, like the right hand side of the rod in this picture.
http://www.grumpysperformance.com/bearingoffset2.jpg

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Re: Rod side clearance

Post by modok » Wed Oct 25, 2017 9:22 pm

1972ho wrote:
Wed Oct 25, 2017 6:34 pm
Looks like the bearing is causing this problem I removed the bearing and the rod moves from left to right,Do you know if there is a bearing narrower than a CB-745-HN.
cb610

It does not matter if the piston is installed or not, unless the piston is the problem.

Should have checked before assembling engine. Now you do not know if it is the piston causing it or not. Even with piston guided rods, the rods still move freely side to side when it is assembled. You have some kind of binding at the bearing/crank radius, or small end of rod is binding against the piston, or the rod is bent or has the wrong cap on it, or sides of rod are not square to the bore of the rod.

Pistons do rock, but piston rock and piston protrusion are usually two different things.
Measure the piston protrusion in the center, OR, at the front and rear over the pin and average those two readings.
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Re: Rod side clearance

Post by joe 90 » Thu Oct 26, 2017 1:03 am

Try the rod on the crank with the crank out of the engine?

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