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post #1 of (permalink) Old 10-16-2000, 10:10 AM
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How do you Plasti-gauge?

I'm getting ready to assemble my 350 one of these nights after work and I have never Plasti-gauged an engine before. I have assembled a couple engines in the past but my brother always did the Plasti-gauging and I didn't pay much attention. He said he was going to show me how it's done on this rebuild, but I have a feeling it will be at his convenience, probably after the new year some time. I don't want to wait that long.

The engine is a 1979 350 4 bolt block with a cast crank 0.040" under stock on the bearings. Everything is ready to go and I have all the right bearings for reassembly. I have one stick of green (.001-.003") Plasti-gauge. All you have to do is cut the stick, place it on the bearing surface between the crank and bearing, tighten the cap down to spec, then pull it all apart and hope you measure about 1.5, right?

What are the minimum and maximum acceptable limits?


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post #2 of (permalink) Old 10-16-2000, 04:48 PM
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Re: How do you Plasti-gauge?

I would like to know what too do too, cause i haven't ever rebuilt a motor but i have swapt them out

post #3 of (permalink) Old 10-17-2000, 08:20 AM
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Re: How do you Plasti-gauge?

Just moving this thread back up to the top...

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post #4 of (permalink) Old 10-17-2000, 12:23 PM
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Re: How do you Plasti-gauge?

Correct, be sure there is no assy lube or anything on there to ruin the reading. Also, main readings can sometimes vary around the bearing because the blocks are not always straight. I think .0015" is way to tight. I think from memory the mains should 2.5-3.5, and rods 1.5-2.5? I personally have never put a motor together that was tight. Even if I get all the parts machined "perfectly" the motor ends up loose. My last motor was the tightest one yet and it was .0035 mains, 2.5 rods. I had one motor @ .006 mains.
The only measurements that I find accurate are the piston to bore.
It's funny, the book will say be sure to check the clearance, but what do you do when it's too loose? I'm not going to re-grind the damn thing, and I don't want to buy a crank enlarger.

Chevota
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post #5 of (permalink) Old 10-17-2000, 10:16 PM
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Re: How do you Plasti-gauge?

This might be dumb question what do you do if the clearence is to tight???

post #6 of (permalink) Old 10-18-2000, 10:12 AM
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Re: How do you Plasti-gauge?

Me thinks you have to take the part back into the machine shop and have them polish / hone it up a bit more. My brother had to take a couple of rods back in when he was rebuilding a Pontiac 400 last year when they Plasti-gaged too tight.

Now, the question of the day is what to do if you have too much clearance?

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post #7 of (permalink) Old 10-19-2000, 09:29 AM
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Re: How do you Plasti-gauge?

If you have too much and you really want to fix it, you have to have the crank reground down to the next size and cross your fingers.

Chevota
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post #8 of (permalink) Old 10-19-2000, 10:15 AM
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Re: How do you Plasti-gauge?

Chevota -

I put the block on an engine stand last night, wiped the cylinders with a clean cloth, then gave them all a coat of WD-40.

I think I'm going to Plasti-gauge the shortblock tonight or tomorrow. Here's what I'm going to do...

1) Remove the main bearing caps. These are still on the block to keep them from getting mixed up (I have them marked, too).

2) Wipe everything with a fresh rag and some carb/choke cleaner (good idea or no?) to remove any honing oil, metal shavings, etc.

3) Install engine side of crank (main) bearings.

4) Carefully place crankshaft on bearings.

5) Cut off 1/2" long piece of Plasti-gauge and lay it on the bearing journal parallel to the axis of the crank.

6) Install lower (oil pan side) bearing into bearing cap. Tighten to torque spec.

7) Unbolt the torqued bearing bolts and remove the cap; measure the Plasti-gauge with the included scale.

Steps 5-7 get repeated for ALL the main bearings AND rod bearings.

Am I forgetting anything?


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post #9 of (permalink) Old 10-19-2000, 11:02 AM
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Re: How do you Plasti-gauge?

Sounds good. I'd clean the bores and entire block with Berrymans Brake Cleaner. Don't use the "Non-Clorinated" stuff. Fresh cut bores can really hold a lot crap, you'll probably go thru a lot of paper towels on those. Be sure to wipe the bores and journal surfaces with oil ASAP after using the brake cleaner, because it cleans so well the metal will rust instantly.

If you mix up the main or the rod caps your screwed!

I install the bearings in the mains and put the caps on the block without the crank, then hammer them down in place with a heavy rubber mallet. You could bolt them down but I'm lazy. This will seat the bearings so you will get correct readings when you do it with the crank. Be sure the surface between the journal and the bearing is dry and super clean, same with the rods.

Chevota
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post #10 of (permalink) Old 10-19-2000, 11:17 AM
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Re: How do you Plasti-gauge?

Thanks for the help! It's not as hard as my brother made it sound... he's always got a negative tone about things that he feels he should assist on.

I'd bet $20 that he's going to tell me "The engine's going to grenade!" after I put it back together without him Plasti-gauging it for me. He'll probably be mad, too. He's kind of quirky like that...

I'll just have to mention the bad rod nock (really bad) in the 455SD he put together a while back. OOPS [img]/wwwthreads_images/icons/blush.gif[/img]!

<font color=red>TOO MUCH POWER</font color=red> isn't enough.
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