I was just wondering, why couldn't I bore a 305 out to 4" bore and make it a 350? Aren't the blocks the same? I know that I would need different heads, etc., but what would keep me from doing this if the blocks are, in fact the same?

James

 

The blocks are not the same. The 305 bore is 3.734" while the 350 bore is 4.000". 305 blocks don't have enooough metal to go .060" over usually, let alone .266" over.

The cranks are the same casting, but have different counterweighting.

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"So many Mustangs, so little time..."

 

wow, twice in one year i've heard this question. i am impressed. as has been already stated, it won't work.

 

Is it because the water jackets are closer in a 305 than a 350 or a 400?

Brandon

 

JRoy,

You can bore a 305 block to a 4" bore. By the time you're finished, that areas you haven't broken through will be so thin that you might as well break through. You can continue boring to about 4.500", then press in eight brand new steel cylinder sleeves and bore them up to 4" again. Instead of having a solidly cast cylinder case, with the deck securely held to the crank support webs, you'll have a ten-piece "junior erector-set" engine case, just like your buddies in the Fords with the Romeo 4.6L engine.

Do yourself a favor and find a used-but-nice 350 or 400 in the bone yard and start from there. You'll have more cash in your pocket and be much happier than with a large-bore 305 and much stronger than the "erector-set" type engines.

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Vader
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The spacing between the centerpoints of the cylinders are the same for all small block Chevys. However, the radius of the bore changes to maintain the proper wall thickness. In the case of the 400's, the cylinder walls are siamesed to maintain that thickness.

No, you can't bore out the smaller blocks to a larger bore size. The bare castings are all different.

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hahaha...
i think i was the one who asked that before... i'm glad the guys here told it couldn't be done... my asswipe mechanic had me hoping for nuthin... anyway he's sold me a 4 bolt main 350 since... and yes... i did verify if it was indeed a 4 bolt 350.
i'm tellin you roy, get that 350, you won't regret it one bit. i'd hate to be the one to say this: 305's suck!!! (in stock form that is) it couldn't even run with the 307 in my 71 camaro.

 

Is there a significant weight difference between the two blocks?

 

The weight difference, if any, is insignificant. The blocks weigh the same.
As was mentioned up above the pistons in a 350 will be a little heavier, but you are talking about grams.