Main cap clearances

[MI6TA]

Time to plastigauge, what am I aiming for? .002 - .003?

[BIG CAT]

Main bearing clearance?

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[Ryan Stout]

About right. Mines around .002-.0025 iirc

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[Featherburner]

Plastigauge gives a vague inaccurate reading.

[MI6TA]

Main bearing clearance?

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Yeah that's what I meant lol. Too many beers.

and Featherburner what you talking about?

[DMBlack]

Featherburner gives a vague inaccurate post.

Plastigauge is not the best way to measure bearing clearance but it has worked many times on many engines. I am not an engine builder so take this with a grain of salt.

The abbreviated way is to install bearing in the mains without the crankshaft. Torque the bolts/studs to proper spec and measure inside bearing diameter. Then measure crankshaft journal and do the math to get the actual clearance.

Again I am NOT an engine builder, but that is how I understand the correct way to do it. I am sure someone will correct me soon.

[noice]

No that is the correct way to do it. You do need accurate measuring tools though.

[MI6TA]

Very accurate measuring tools indeed. I'll see if pops has tools that exact but I doubt it. Plastigauge will be the way we end up doing. So .002 to .0025 is within the area I'm shooting for?

[Featherburner]

Plastigauge is not the best way to measure bearing clearance but it has worked many times on many engines. I am not an engine builder so take this with a grain of salt.

The abbreviated way is to install bearing in the mains without the crankshaft. Torque the bolts/studs to proper spec and measure inside bearing diameter. Then measure crankshaft journal and do the math to get the actual clearance.

Again I am NOT an engine builder, but that is how I understand the correct way to do it. I am sure someone will correct me soon.Nothing vague or inaccurate about my post. Have you ever compared actual measurements to plastigauge? I have. If you are OK with a plastigauge reading of "about" .0025 but could actually be .001 either way of that, be my guest. But for me, it was worth it to purchase the proper mics and bore gauges and learn how to use them.

[DMBlack]

I agree that is the proper way to get it done. How about instead of just saying that is not the best way of doing it, explain the correct way? That could possibly stop some confusion and be a little more helpful.

[MI6TA]

All right, well I wish I could do it the right way but we don't have accurate enough tools. Today the plastigauge test did not come out well. I'm at around .0017-.002. I'm not comfortable running it that tight so I could use some ideas of what to do. I tried switching a bearing from one to another and then retesting, and it actually got a little worse.

[BIG CAT]

You need a set of extra clearance bearings. For clevit they add a x to the bearing part number. It add a extra .001"

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[MI6TA]

You need a set of extra clearance bearings. For clevit they add a x to the bearing part number. It add a extra .001"

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hmm. I had the crank turned ten under, and bought ten undersized bearings from sealedpower/federal mogul. That's not what you're talking about though is it.

[quik95lt1]

like bigcat said run a "x" bearing it will loosen it up .001....you can always run a half shell for .0005 too.......good street motor I like seeing .0025-.0029 if you are a couple tenths looser on the thrust don't worry about it it wont hurt........in a race motor/hi hp stuff you can run out to .0032-.0034 and still be ok but I wouldn't go any further than that....and anything under .0021 is tight.....general rule of thumb for street stuff is .001 per inch of pin diameter

[MI6TA]

First I've heard of the extra clearance bearings. Seems to be perfect for my case. I suspect that when the crank was turned .01 under, the machine came very close but about .001" off to the perfect .010".

Today we tried seating the bearings all the way in with a mallet and hitting the crank strategically around the journals. It seemed to help our plastigauge readings become more constant, and also proved that the extra clearance bearings are what I need. 1-4 bearings came out .0015" and the Main was .0018ish. Putting me at .0025 and .0028 when the new bearings are in.

[MI6TA]

So, .254mm is .010" I found some "King engine bearings" main bearings at .228mm which converts to .009". Is that what I need?