Max 400 SB overbore?

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Oct 3, 2002 | 07:56 PM

LD85

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From: Indianapolis IN

Max 400 SB overbore?

Max overbore for lest chance of cracks etc.

What is the most anyone here has overbored a 400? :confused:

Oct 3, 2002 | 08:05 PM

buzzbomb

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From: Urbana IL

Re: Max 400 SB overbore? (ld85)

I've got one right now at .040, but i would'nt go further. :cheers:

Oct 3, 2002 | 09:08 PM

dtorc4

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From: Atlanta GA

Re: Max 400 SB overbore? (ld85)

I second buzzbomb. .030 is ok, .040 is pushing it. When I was shopping around for a short block, I talked to two or three engine builders and they all told me they prefer not to go more than 30 over on a 400 block.

[Modified by dtorc4, 1:08 AM 10/4/2002]

Oct 3, 2002 | 11:49 PM

sinistervette

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From: the corner of walk and dont walk

Re: Max 400 SB overbore? (ld85)

.040 is ok, just harder to find pistons for, .030 is the best bet. I've got 2 400 that are .060, but the blocks are filled with hardblok. I did go .060 on one when I first got into building/playing with the 400's. The machine shop said they would not gaurantee anything with that much overbore! At least I learned the first time! :yesnod: :cheers:

Oct 4, 2002 | 12:35 AM

Wadoka

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St. Jude Donor '03-'04

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Re: Max 400 SB overbore? (sinistervette)

Are y'all using the GMPP Sportsman 400 block, or just whatever 400 block you happen to have scrounged? What P/N are you using right now?

Oct 4, 2002 | 12:57 AM

sinistervette

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From: the corner of walk and dont walk

Re: Max 400 SB overbore? (Matt Black)

Quote:

Are y'all using the GMPP Sportsman 400 block, or just whatever 400 block you happen to have scrounged? What P/N are you using right now?

Mine are regular production blocks, #'s 330817, 3951509. I think the first one I went .060 with that broke was a ????511. I don't remember but it was a fact. 4 bolt block :U ! Some aftermarket blocks have been rumored to go up to.080, but I wouldn't ever go over .060. Just my opinion.......I know, my opinion don't count! :lol: :cheers:

Oct 4, 2002 | 07:18 AM

LD85

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From: Indianapolis IN

Re: Max 400 SB overbore? (sinistervette)

The block is a 2 bolt 3951509 casting. I would like to just hone it to clean it up.

Oct 4, 2002 | 09:20 AM

0ski_dwn_it

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From: St Marys PA

Re: Max 400 SB overbore? (ld85)

If its an aftermarket you can go higher. They are beefed up compared to the stock blocks. I am going .030 over with my 509 casting. Be sure to have the block megnafluxed before you spend the time and money on machining. You can also have them meg the crank if your using a stock crank.