I posted this question on another website with no results. Realized that probably nobody is doing this. They are grinding down 312 mains to 292 size and stroking them with offset grind.
My question is can a 292 crank have its rod journals offset ground to a 2.00 size, for a stroke equal to that of a 312, and use over the counter rods and pistons? Rods of equal length to the 312, but with the 2.00 bearing. Pistons?
Is there an internet reference for rod length, bearing size, pin diameter, and for similar specs on pistons?
I know the offset grind of the journals is dependent on their condition. These are currently .010.
Custom made rods and pistons are just cost prohibitive.
Mike

 

Mike,
I've read your post here and in the other website. I believe what you are trying to do is increase your compression ratio?

OK, I'm going down the same road with my 292 right now. I really wanted a set of the 10CC dome pistons that mummert has on his website, but now it states "if enough interest or demand" Well I called him about the pistons and he told me he was not going to have them made as he would have to sell 35 sets to recoup his inital investment.

So I called around and found a company JE pistons out of California. The guy said he needs a new cast of the cylinder and combustion chamber to make the 10.5-1 or 11-1 ratio pistons. After I make the mold and send it to him he will make a set for me at a cost of $900.00 This is just out of my price range! (by the way this JE made the trial set for mummert the guy told me so)

Mummert told me there is no way to get a y block up to the ratio I wanted with flat top pistons.

So now I've decided to have my only 312 crank checked out and if its OK I'm going to remove the 292 steel crank and do the upgrade to a 312 cast crank.

What do you think?

Kevin Bigwin

 

Kevin, if you have a good 312 crank aren't you lucky! That would be a relatively easy way to increase compression and displacement. I would like both, but compression is the most desired. With a .080 over and 312 stroke that would give 318 displacement. The effect on compression would be a little less than might be expected. If I would retain the same rediculous deck height (which I wouldn't), the compression would go up from its current 7.5 to 7.8. That is a 4% increase. So in your case I think it makes mathematical sense that if you have a current compression of say 9, the same increase in displacement would give you a compression of 9.36. If you cut your deck height down to .045 that would kick up the CR even more.
I have been looking at Mummert's site also, and at some of the prices of the 312 stroker rods. Too much, and they wouldn't help in trying to get a 312 stroke out of a 292 crank.
I have been looking for a 312 crank for a long time.
Mike

 

Well I have spent too much time searching rods, and haven't come up with anything feasable. SBC stroker rod of 6.250 length, with small journal of 2.00 is available, but they are expensive also. So much for the stroked crank.
Kevin, Mummert was right on the flat top compression issue. With a 318 displacement, a deck of .045, and combustion chambers of 67 cc, the compression ends up at 9.6:1 according to my figures. Mike

 

hi, everybody makes high dom pistons for the 307 sbc, i've got a couple sets i've been saving for when i build a couple of y-blocks. also 283 sbc pistons are 3.875 bore and they will have more compression height, so you might get away with a shorter rod. now comes the good part. when they ran 289's at indy in 63 they used 292 steel truck cranks to stroke them. this makes me beleive that a 351 windsor crank could be cut down to fit for a 3.5 stroke or mabey go to one of the many stroker cranks for a windsor. i was planning on trying a 400 modified crank myself but i'm sure you could get a scat stroker to swing easier, i'm sure you'll get into the cam fairly quick. good luck, wayne.

 

hi big window, would you be interested in a set of nos Johns pistons, i've got a set left but i'd have to dig them out, i'm not sure if there're 292 or 312. give me a buzz, wayne.