SBC Gurus: how far can you bore a race only 327

One of mine is already .060 over if I am only running it on the 1/4 how far can I go. I would like to build the motor for a possible drag car project we are putting togehter.

Tim

 

To keep the walls thick enough to provide proper piston ring seal, +.060

 

Cant you go further if you fill the water jackets?

 

Sonic check the block, Hardblock the sucker to the deck, and bore it and 1/8" over if the is enough meat.

 

Only your machinist can tell you the overbore limit AFTER a sonic check.

Smokey Yunick said an engine needs at least .130 for a cylinder wall before losing power from poor ring seal/cylinder flex. But Smokey could have been trying to screw with his competition.

Get a sonic check and post the chart, then we can tell you the max.

 

Since you said race-only. I wouldn't be afraid to go to .100 wall thickness with concrete.

 

Sonic checking is the ONLY way to be sure how far is safe. Be sure to have ALL of the bores checked. You only need core shift in one bore to eliminate a big overbore. .030-.040 is usually safe for any block (there are exceptions), anything over that have it checked especially if your spending BIG money for a race only piece. Better safe than sorry.

Frank

 

Can you even lay hands on a set of pistons larger than .060 overbore. You may want to install your 283 crank into a 350 block and then you would have a 283 with a huge overbore(a Grumpy Jenkins 305).

 

Excuse me 283+350=305 not sure about 327+350.

 

Thanks, I think I'll give this one away and start on another fresher one.


Tim

 

Bore it until water seeps in, then back up a bit.

sorry

 

well, a 265/283 crank(same stroke) in a 327/350 block(same bore) would be a 301/302(depends on who's doing the rounding off) CID depends on how much overbore


how about a 400 block with a 283 crank?

 

Why did you ask?

 

With a concreted block you can get away with cylinder wall thickness as little as .080 since the cylinders are fully supported and the iron is only there as a wear surface really.