I’m currently building a large journal 327 and just bought high compression 350 piston heads for it. I understand that the pin height between 327 and 350 Chevy engines are different along with the strokes being different. If I use the 327 crank and rods with 350 piston heads will that work? Or will I lose too much compression. They are rated at 12.5:1 with 58cc heads which is what I’m using. Thanks!
I guess it’s just the top of the piston, not a piston head. Got nothing to do with cylinder heads, that was bad phrasing on my part.
Well the rod length is the same on a 327 and 350, the crank is where most of the stoke difference is. The wrist pin is also higher on a 350 piston to add a little more stroke over the 327. question is what type of piston top are you using? Flat top, dished or pop ups? You could in theory make a 350 piston work in a 327 as it would not put the piston above the deck height of the block, your creating a bigger chamber as the entire piston is slightly sunken down in the cylinder. I dont know how that would run to be honestly. Clearance wise it should work, but performance wise that one not sure of.
We’d have to revert to the math formula that’s contained within. Get one. Lot’s of useful stuff to learn.
I don't understand why you would buy 350 pistons if you are building a 327. The difference in the stroke is 0.23 inch. To me that means that the 350 pistons will set close to 1/4 lower in the cylinder at TDC. Maybe you got a "deal" on the 350 high compression pistons but you may have been better off with 327 flat top pistons.
For a zero deck height block, the 350 piston will sit below the deck by half the difference of the stroke of a 350 vs a 327 crank. (3.48-3.25)/2=0.115" That would add about 24cc to your effective combustion chamber volume. Not gonna work so good.
We still don’t know the pop up volume of the pistons to say if this is true. (This is why none of us can answer OP’s question as asked) What will hurt is the quench. But again, what is the expectation of this engine. Cruzing around or racing?
You said 12.5/1, regardless, it just wouldn't work. But go ahead and do it, we'll be here waiting for your next post.
If in fact the pistons are 12.5:1 they may/ may not have the standard 350 wrist pin height (compression height). I guess i would start by confirming that before crunching numbers.
I have a 327 with a 1/2" stroker, 5.7 rods, bored .060" with 1.425" piston pin height, 18cc dish pistons. It comes out to 389".
No... a 327 stroke (3.250") and a 383 Piston (1.425" piston pin height) would need a 5.955" rod, which would be a custom length (with a 9.005" deck height after machining). That would leave the piston .005" in the hole. They do make 6.0" rods, but that would need a 1.470" piston pin height, also custom. A 3.25" stroke and a 6.125" rod would need a 1.250" piston pin height (with a 9.005 deck height), which is not good for piston stability or wrist pin to ring interference. The compression height you're looking for is 1.675" (+0.010"/-0.000"). With a 327 crank, 5.7 rods and a virgin 9.025" block, the piston will be in the hole 0.025" and be stable and live long. Don't get caught up in the long rod vs. short rod discussion or custom length rods. Use what fits off the shelf. Here's a good place to get help with piston pin height for your rod length and stroke. They have calculators for all kinds of engine and racing math... http://wallaceracing.com/Calc-Piston-Pin-Height.php
The Jalopy Journal
