The Stovebolt Site Forums The Shop Area Engine Shop How much over?

I've read & heard a couple times now about boring a 283 out to 302...that's .125" over. I don't remember where or when, but .060" over was the max. number from sometime in the past. Is it just the 283 that can be bored that much?

cm

depends on the year of the block, 58-62 may take .125, 63-67 .060 max .... other small blocks, check availability of oversize pistons, I think some 4" bores are chancey even going .060

Bill

...yep, bored a 283 to a 302 back in 1964 with a Duntov camshaft and couple other tricks. I was hard to beat for about a year then my brothers took it to the dragstrip when I was in the hospital for surgery. Afterwards I was pouring about a gallon of water in it ever couple days......until the truth came out. They ran it hot at the strip and and when I pulled the heads the #3 cylinder wall cracked. It can be done!

Mine is .125 over to 302 with the Duntov cam I think. I know it was out of a 327 'vette motor, does the Dontov sound right? It gives a hell of a lope on that little motor, and makes her quite the screamer (especially with the original rear end...)

Depending on what else you did the cam is a good one. Back in the early 60's a good Duntov (after Arkus Duntov of corvette fame) was about as good as you could get for the street and weekend drags. Back in the day everyone would refer to them as a "three quarter duntov". Ahhhh, the good ole days! ...oh, and heck yes, mine would scream. That jewel just love to turn up the rpms and S C R E A M

back in the day they would call a .125 over 283 a 301.

To call it a 302 you have to cheat about half a cubic inch. I think the actual displacement is about 301.46. The most popular Duntov can was called an "098" from the last three digits of the part number, also known as a "30-30" from the reccomended intake and exhaust valve lash specification of .030". It was the standard high performance option on a lot of the Corvette engines. Valve adjustments lasted about two weeks because of the radical action of the lobe profile. The cam gave a pronounced idle lope, and worked best with big valves, high compression, and a very high-flow exhaust system. It did sound wicked, and once the engine got wound up a little, it gave a respectable power gain. Off-idle power and low-end torque sucked bigtime!
Jerry

Thanks for keeping us "spot on" Jerry. Its been many many years but te 30-30 sounds familiar and ditto the lifter adjustment. I also had a little problem with the rocker studs working out a little till I learned how to pin them. Gosh, thats been a loooong time ago. But hey, it was FUN...and my hole shot wasn't always the best but once the old mule got to kicking it was gone to the barn. On one ocassion I was winding it a little to tight and busted the rocker and the push rod came 1/2 way through the valve cover. Only lost that one by a fender length and the guy wouldn't give me a rematch later on.

Boy, what a memory trip Jerry. Ain't it nice.

I remember back in the late 60's a built 327 I put in a plain jane 56 2 door really screamed - don't recall the cam I put in it, but valve adjustment was a constant job and I was tuning that dam thing every weekend - nothing beat it tho' especially none of the factory muscle cars of the era

Bill

This has nothing to do with your original question but might be of interest to 265 builders. You can bore a 265 .125 over and make it a 283. You can use standard 283 pistons. In fact, the first 283's were just exactly that then later they recast the block to allow for more "meat" on the cylinder walls.

In mid 60's, little brother built a 364 (4 x 3 5/8)in from my spare 57 block using a welded stroker crank and Jahns pistons.
We hit a sand flaw low in 1 cylinder but because it was below ring travel we accepted it as was.
The 58 vette it was/is in stayed around and when he did a more restoration in 99 we stripped and freshened up the engine and installed sleeve in that hole.The sleeve required an additional overbore of .187 and the cylinders were already .125 over so a total overbore of .312 and the cylinder we sleeved just barely broke through in 1 place.
The trouble with big overbores is you never can count on the cyl wall being sound or well centered with the original bore centers.
That being said before the cheap 327 short blocks became available, a lot of "4 inchers" were created around here and I don't ever remember anyone having trouble with thin walls.
We couldn't believe it when the word on the new 327's was don't rebore beyond .030.
I was boring a 327 of the "right numbers" .030 for a friends 66 vette in about 95 and when we hit sand holes in the 3 rd cyl I told him to give this one away and lets start over.
I recently sleeved 2 cylinders in a 50 Studebaker champion that had been parked since 1955 had 26,000 miles on it and these 2 cyls had sand holes that had leaked since new but had sealed off of their own.
There can be a lot of surprises when you start boring Detroit iron.
But then that Stude wasn't Detroit was it?