276 Over Bore Newbi Question

Discussion of the Early Dodge / DeSoto HEMIs.

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showngo
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276 Over Bore Newbi Question

Post by showngo » Sun Aug 09, 2009 4:17 pm

I have read articles stating that the 276 Desoto blocks are “thick” and 0.090” is no problem with over-boring cyclinders. My question is I have a nice gouge in one of my cylinders from the previous owner disassembling it. ( .060 – 0.70 could remove it) BUT if .90 is “no problem” is there any noted problems of having the block bored to the standard 3.720 of the 291 block 0.095 ???. If stroke and everything else is the same as the 276 block.

PS Just a note I have had sets of plates water-jetted to make “log intakes” for the 276-291 at this time it is for the 4, 6 Holly 1-bbl and 4,3 Rochester 2 bbl (due to cost of 97's ect) Guess if its not out there It needs to be built.
Thanks for all the Information, this site is a God-send.

392heminut
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Re: 276 Over Bore Newbi Question

Post by 392heminut » Mon Aug 10, 2009 12:52 pm

Best answer I can give you is have it sonic checked, and then you'll know for sure. Every block is different and yours could have core shift. For the money it costs to rebuild these early hemis, the cost of a sonic check is cheap peace of mind!
Owner of the Poor Man's Hemi Cuda

polyspheric
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Re: 276 Over Bore Newbi Question

Post by polyspheric » Mon Aug 10, 2009 10:52 pm

How deep, how long, how wide, and how far down the wall is the gouge?
If it's below the lowest point of oil ring travel @ BDC ignore it.

showngo
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Re: 276 Over Bore Newbi Question

Post by showngo » Tue Aug 11, 2009 4:44 am

It looks like he "dragged" the rod out so the gouge is from about an 1" = 1.5" from the bottom, all the way out the top....... Fun Fun

johnny5
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Location: St Charles, MO

Re: 276 Over Bore Newbi Question

Post by johnny5 » Thu Aug 13, 2009 8:17 pm

It depends on the casting. The earlier ones may be a little thinner due to water jacket mold changes as the years progressed but you can't tell without sonic checking it. When you bore a motor .090" over you're really just taking .045" of actual material off the walls. That's why alot of people don't see it as a really big deal but I'd only do that to a motor with .200"+ walls to start with. Alot of early small bore hemis can take .120". I'll be sonic testing a 291 soon. I'll let you know how that comes out.

charlie
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Re: 276 Over Bore Newbi Question

Post by charlie » Sat Aug 29, 2009 2:48 pm

YOU CAN HAVE THE BLOCK SLEEVED, INFACT YOU CAN BRING THE BLOCK BACK TO STANDARD BORE, OR ANY SIZE YOU WOULD LIKE.

MOPAR CHARLIE 727-271-5068

George
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Re: 276 Over Bore Newbi Question

Post by George » Sun Aug 30, 2009 10:48 am

If the sonic check shows you can't go bigger, just sleeve the one cylender to what the others would be, not that expensive to do 1.

polyspheric
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Re: 276 Over Bore Newbi Question

Post by polyspheric » Sun Aug 30, 2009 12:39 pm

I agree - do the one. There's a break-even point that somehow doesn't appear in many of these conversations: "what's the cost of replacing the block vs. how many sleeves?"

showngo
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Re: 276 Over Bore Newbi Question

Post by showngo » Thu Sep 10, 2009 9:37 am

Well the answer I have been waiting for ------ IT is now a 291 The thinest spot is the size of a dime and thats .204" thick. I was told that on pump gas I will not have a problem. So there Ya have it. (I was told not all blocks are that thick ) so DO NOT take this as a baseline for all other blocks. Thanks for all the input.

johnny5
Posts: 128
Joined: Mon Dec 05, 2005 3:52 pm
Location: St Charles, MO

Re: 276 Over Bore Newbi Question

Post by johnny5 » Thu Sep 10, 2009 9:25 pm

That's better than most of the blocks used for racing. You're gonna be fine even if you need to go another .060" beyond 3.72".

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