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Old 03-10-2013, 12:22 AM
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350 block .030 over

I was wondering I found a guy selling a 4 bolt Chevy 350 bored .030 over by a reputable machine shop with receipts to prove it. I want to build a 383 stroker but I thought that pistons had to be matched at the same time the block is bored? Would it be a bad idea to buy this block?

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Old 03-10-2013, 01:10 AM
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Chad,that depends.Tell the guy you would be willing to give him a sizable deposit so you can take it to your machine shop to be checked out.Tell your machine shop to mag it and check to bore size to see if they can find a source for piston for the bore size.If your going forged pistons in any event those sizes are larger.
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Old 03-10-2013, 09:09 AM
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For the most part today, due in large part to modern machinery, pistons are much more consistent to a given bore size than in the past. As for forgings, the bore size is the same, the piston is actually a little 'smaller'.

Agreed, if it "measures" correct, it's good. Ask if it was honed with a deck plate. 350s really should be for any application. If not, negotiate a lower price and bore it to .040" over. Pistons are readily available in virtually all configurations and are the same price.

FWIW

Jim
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Old 03-10-2013, 11:21 AM
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What we have been dealing with the foreign imports impact machining QC is in no small part playing a role in sizing.
I agree with PB in terms of you have the option to go to .040 proving it mag's as a good core.But then do have the pistons in the machinist hands for the finished bore size.Forged pistons react differently to heat requiring clearances.It is that reason why you have cold piston slap until the engine warms up.
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Old 03-10-2013, 11:31 AM
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I went and measured the bores they come in slightly under 4.030 at 4.0285 as for pistons forged ones are not required. Building a street engine around 400hp so hypereutectic pistons will do.
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Old 03-10-2013, 11:37 AM
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I'll get my two cents in.

I agree with P-body.
Forged pistons have come a long way since the old TRW's from back in the day. We used to run .008"+ on race big blocks.
Now pistons are made of better materials along with better production. I remember when .002" plus or minus was the norm for production forged piston sizes.
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Old 03-10-2013, 12:43 PM
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Found the I-Con's are a good bang for the buck.Have offset pins for cold piston slap.

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Old 03-10-2013, 07:25 PM
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Quote:
Originally Posted by 1Gary View Post
Chad,that depends.Tell the guy you would be willing to give him a sizable deposit so you can take it to your machine shop to be checked out.Tell your machine shop to mag it and check to bore size to see if they can find a source for piston for the bore size.If your going forged pistons in any event those sizes are larger.
I asked if he would let me have a machine shop have a look at it. He said no so I am going to walk away.
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Old 03-10-2013, 08:48 PM
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Yes.There are deals which seem really good you do have to walk away from.There are just too many out there and if it doesn't seem right,another will come along.

I think you made a smart decision.
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Old 03-11-2013, 01:57 AM
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Quote:
Originally Posted by Chad. View Post
I went and measured the bores they come in slightly under 4.030 at 4.0285 as for pistons forged ones are not required. Building a street engine around 400hp so hypereutectic pistons will do.
You can look at the finish of the bores and tell if they've been final honed or have only been bored in most cases. If there's no indications of the final hone being done (finish quality and crosshatch), it has to be done in order for the bores to be sized correctly and to allow the rings to break in.

You may find you need to have the final hone (re?)done to fit the pistons to the bores. You'd expect to see a 0.030" overbore for a 0.030" piston, the clearances being provided by the piston OD, as mentioned previously.
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Old 03-11-2013, 07:22 AM
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If he won't "back it up" with a shop, RED FLAG!!! I agree, move on. 350 blocks are NOT hard to find. We're not even a "Chevy shop" but we have a couple driver's side dipstick 350 4-bolt blocks around "just in case"... (:-

Jim
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