Chet1185

I didn't look in a manual, thought I would post here instead.

What should the main and rod bearing clearances be for a stock rebuild? I bought plastigage to make sure its right but I'm not sure what they should be.

Also, I took my block to the machine shop and they said the cylinders are pitted from rust so it needed bored .30 over. Now when I go to size the rings what does the gap need to be?

95 TA

RamAir95TA

Is this a stock or performance rebuild? What are your intentions?

Chet1185

I just want stock for now because its my first time. only difference is bored cylinders

shoebox

I know you have been to my website many, many times...

http://shbox.com/1/engine_specs.jpg

Chet1185

Lol, yes I have. Whats the production and service limit?

RamAir95TA

Production limit is what the clearances were set at on the assembly line.

Service limit is the maximum clearance before action should to be taken.

Chet1185

Ok, thank u very much.

Chet1185

Why is the service limit inbetween the production? I would think it would have to be greater to need to be serviced

ACE1252

I would not sweat worrying about the differences between the production and service limits. There is only 0.0003-0.0005" difference between them, on the upper tolerance, depending on which bearing you are looking at.

When I replaced my bearings, I kept the number 1-4 mains close to 0.002" and #5 was around 0.0018" when measured with plasti-gage.

Here are my threads from when I was dealing with my problems. Got lots of good advice from multiple people here on this board. I have multiple pictures in there too. Do an advanced search for my user name(threads started in LT1 section) and you will find all the stuff I was dealing with back around 2009 for my rebuild.

https://www.camaroz28.com/forums/lt1...ctures-713070/
https://www.camaroz28.com/forums/lt1...arings-746672/

cardo0

Piston bore clearance has gotten more complicated. U need to measure the piston at a designated location (specified by mfr) with a micrometer >4" first. Then use a bore gauge to measure the the cyl bore at least 3 locations in the bore and at least 2 different orientations 180 degrees apart. The different between the two gives u the piston clearance.
Problem is that most clearances are called out in tenths (0.0001") and most reasonably price bore gauges read only 0.0005" or worse. The good old days of measuring piston clearance with long feeler gauges (tape gauges) are gone.
I believe most hobbiests just buy thier pistons form the machine shop doing the bore and hone and trust them to check the clearance. And one of the best machinists at work doesn't even blink an eye to do so - his reasoning is the quality of new pistons is so much better than decades before and the new tooling is so much more accurate.

BTW my forged TRW pistons in my old GTO were hand hone one at a time with taper gauges and mark for each cyl. That engine ran great.

Hope this helps more than it hurts.
cardo

Kevin Blown 95 TA

Did you mean to say that?

Kevin Blown 95 TA

There's truth to that - I miced my Mahle forged pistons and they were all identical as far as I could tell. They took a very slight bit of balancing, but they were all the same size which made the machinist's job a lot easier. having all that stuff the same for each cylinder is part of the foundation for a good running engine.

ACE1252

Oops, I did miss a 0. Good catch! I'll correct the post. That would be quite the swing if it was what I originally posted.

Chet1185

took stock engine to machine shop and the cylinders were pitted from rust, which is my fault for letting it sit uncovered but i didnt think i would ever be using it. block is being bored 30 over but the machinist said they left a few thousandths to match the new set of pistons i bought.

i went on shoebox site and looked at what the clearances need to be and i have the plastigage already. for example crank bearing #1 should be .020-.051 mm. so as long as its in that range i would be ok right?

like i said, this is going to be my first time building an engine so i need as much info as possible. thanx for the replies

cardo0

There is no end to the details but don't get frustrated. It's still a small block Chevy and will run with a lot of imperfections. Just something to be aware of when reasembling is the little ball that drops out of the oil galley has to go back in. I believe it is unique to GEN II where GEN I's had a plug. Well your a long ways from that piece now but just want to remind you since a long time may have been since dissembly.
Your doing good and keep the questions coming.

What are using/doing for a crankshaft? Stock? Stroker? Any machine work?
cardo