Attention all builders! I have a discussion going in another forum about the maximum recommended overbore size of a 460 (or 429)
All my books say no more than .030 over, and even that is with a sonic check and core shift inspection!
Realistically, can you safely go more than that size, and still get pistons to fit?
I appreciate any and all input, to end this thing! Thank you.
Mark

 

I've gone .060 over with no sonic check or problems. Dave McLain said .080 and he's bored a lot of 385s.

 

I would agree with george, I have done .060 without any problems. I have sonic checked a few blocks, mostly DOVE-A's and found that the average thickness is to be around .240 to .320 on the out side/in side of the block and alittle less on the deck. One of the machenist that I use has done a few .110 over bores on a few 429/460 blocks, just have to pick through the castings and start sonic checking in hopes of finding one with the right amount of material in all the right places. The tricky places are in the front and rear of the block.

 

Engine Systems in Tucker, GA bores a lot of their stroker 460's .080" over. I have also heard that the 1979 and newer engines(all external balance engines), are not as thick as the pre-'79 engines. I plan to pour my block and bore it to 4.437" and put a 4.5" crank to make a 557. I have one hole now that has a heavy wall sleeve in it. I bored it .125 over to press the sleeve in and didn't have any trouble. I broke a rod and sent a piston through the cylinder wall. It looked to be about .250 thick where it broke through. Dave

 

To the best of all my knowledge and reading, .080 over is the safest to go. I'm sure you can go over, but depending on what your doing with the motor is it really worth the risk. I went .040 over on mine and haven't had the slightest bit of trouble.

 

My DOVE block is .060 over and my engine builder told me I could go as much as .120 over on that block! You gotta get the old iron when they built 'em beefy because they didn't know any better -- or did they?!

 

I've heard of stroker kits for 460's up in the 8xx cubic inch range, so big bore's must be possible. A 5 inch bore and 5 inch stroke yields 785 cubic inches, so there must be a way. And that with a D0VE or an SVO block.

 

My friend who truckpulls, built a 4.75" stroke stock block that was poured and it didn't hold up. With the stock deck height, you can't get a long enough rod in it. The angle gets to extreme with a large stroke and a short deck height. The results is a hole in the side of the block. 557 is probably a good safe max cid for a stock block. Dave

 

I am actually wanting to keep a stock stroke, with flat tops, but I want a maximum 'safe' overbore. Of course, I will still have it sonic checked...
Mark

 

I've gone .125" with early blocks(D0VE). I have 3 D1VE blocks at .080 & sonic checked ok for another .010. I must agree a 557 is about it. Stock blocks don't like more than a 4.500 stroke

 

Forgive my sleepiness to do the math, but what displacement would I have with .080 overbore on stock 460 rods?
Thanks, anyone!
Mark

 

477 c.i.

 

Hey, thanks for that! It seems to be a familiar number... Is that because it is a common overbore on the 460?
Mark

 

Common over bore is .030, it makes a 466

 

Here's a quick link to determine displacement

http://www.customengines.com/cube_calc.html