I blew my engine and I'm planning on a rebuild. Now, I wanted to offset grind the crank and get .060+ pistons to get 6.0L of displacement but a set of custom pistons for the application would be rather expensive. Now, I guess I'll just get the pistons with the .030 or .060 overbore size. Is .060 too much or prehaps not really worth it in terms of gains vs. reliability/risks/etc. ?

 

i'd only go oversize as much as needed to clean up the holes, not to increase displacement.

 

you won't even see a noticable difference in performance going .060 over compared to .030, its a difference of 5 cubic inchs, and isn't worth the block integrity problems. as ede said, only bore it out the minimal amount needed. that way there is still some meat left in the cylinder walls for future builds

 

Indeed. For every increase in overbore size is one less time that the block can be cleaned up via bore. If you are dead set on giving it a bore, .030" is the most common size. If you are dead seat on displacement from that, just pop in a 400 crank (ground to 350 main size) or a special 383 crank and give yourself a merry little 383. (~6.27 L).

"383 Stroker" is funner to say than "6L V-8"

Besides, i dont think all blocks are safe for going .060 over. Have to watch out for the water jackets. Sonic testing will tell youfor sure if its safe. I may be wrong and that my be a problem of 305 versus 350. Anywho, if it were me, i'd go .030 over and stroke-a-tize that chunk of metal.

 

Well, as I said I am a little tight in the budget right now and a stroker kit would be too expensive. I am buying a rebuild kit from summit that includes hypereuthectic pistons for $210. A 400 crank would mean a piston change (more money) and a poor rod ratio if I keep the 5.7" rods so it's out of the question for me. Maybe I'll just settle for a 355cid. It's not what I had in mind at all but unless I gather some deccent amount of money it will have to do. Anybody knows the compression height and valve relief or dish volume for the factory pistons? How about compressed head gasket height? I could figure something out. Please let me know.

 

.030 over is what you want. That way you can take it to .040 over if needed for a second rebuild or if something goes wrong.

.060 is just wasting the block IMO. Not worth it for your application.

 

Ok, I read that the deck clearance is .017" and compressed gasket is around .038". Compression height should yield around 1.568" I still need the cc's for the piston's dishes or reliefs or whatever they have. Any thoughts about milling the pistons? How far could I go? THe objective here is to increase displacement cheap. I was thinking about offset grinding and milling the pistons or maybe a thicker head gasket or both to compensate for the extra travel of the piston while keeping costs down by not having to buy custom pistons. A .060 offset grinding plus .030 over pistons yields 361ci or 5.9L and 363ci or almost 6.0L with .040 over pistons. I need the cc's of the pistons' reliefs to calculate the new CR. Help me here people.

 

C'mon people help me out here.

 

You don't "read" what your block's deck clearance is; you measure it. Every block is different. Sometimes the 2 sides of one block are different from each other. Sometimes the front cyls are different from the rears. The only way to know what it is, is to measure it. I can tell you from measuring a few that most stock blocks are between .020" and .040", with most of them being near .025". But that doesn't matter; if you have the block zero-decked, you fix all of that. Good-bye stock measurements.

The factory piston measurements don't matter at this point. If you bore the block, they go in the garbage. Good-bye. It is now irrelevant.

What matters is what you get to go back in.

Stock "compression height" on an off-the shelf 350 piston is 1.560". You're not getting custom compression height pistons in a $200 kit.

If you're really concerend about what your CR is going to be, down to that level, you'll have to cc your heads. Your factory "spec" is not an absolute number; since as stated above, every engine is different and somtimes every cyl within an engine is different, if you're really concerned about it, you need to measure it.

But, I can tell you, as a rule of thumb, a 350 with typical flat-top pistons, typical .039" head ggasket, 64cc heads (which could actually be anything from about 62cc to 68cc or maybe even more, depending on what valves are in them and how many valve jobs they've had done), and zero deck height, works out to between 10.2:1 and 10.5:1.

Any "offset grinding" and "piston milling" and all that, will cost you more than the difference between a stroker kit and a straight-up 350 kit. If you want more inches out of your existing block, stroking it is the way to go.

Bore your block .030", buy some one of the common readily available 383 kits, grind your block yourself for the clearance (the cheaper the kit you buy, the more clearance work you'll typically need), and you'll have the most inches you can get for the lowest price. Buy parts that add up to 9.000", get your block cut to 9.000", and build it.

Of course if you get a 383 kit, your CR will come out a good bit higher than if you build a 350. If you decide to do the 383, you might want to either leave a little extra deck on there, or get dished pistons.

 

Thanks a lot for all the info. I'll get everything measured and I'll start from there. I'll see if I can get a stroker kit . Maybe I should start a $2 per forum member collect

 

Exactly like RB83L69 said.

Stop spinning your wheels dreaming of obscure ways to try and grab a few cubic inches, all you are doing is wasting your time.

The big surge of early power turn on in stoker motors does not all come from the displacemnt alone, it is due mostly to the mechanics of the longer stroke.

If you try to get extra cubes by means other than stroking as you previously mentioned you will be lucky to get 1hp per cubic inch with absolutely no noticable increase in TQ, a big waste IMO.