Milling the heads brings the valves even closer to the pistons. As to how much it changes the ratio, that depends on how much is removed and how large the chambers are to start with. On a 351W, I'd think .040 off would be short of a half point in the ratio, just off the top of my head.
Milling the heads brings the valves even closer to the pistons. As to how much it changes the ratio, that depends on how much is removed and how large the chambers are to start with. On a 351W, I'd think .040 off would be short of a half point in the ratio, just off the top of my head.
Hmm. Just doing the angles in my head I highly doubt I'd be able to run the cam I want with stock pistons with the TW heads milled down. I'll look into it more I guess while I get this suspension done.
In the meantime... can anyone recommend a set of 9.5-10:1 compression, notched (for the AFRs... if I get new pistons, i'm going all out with the heads) for a 351w? Something fairly durable but not ridiculously expensive woudl be nice.
HOw much does that usually run? Whats a 'cometic'? Does shaving the heads down still allow you to run 2.02s? How much does that bump up the compression? I like the idea in concept...
Cometics are in the $60-80 a piece range depending on the thickness.
The only issues are the cost and you have to make sure the block face is completely clean.
Other than that . . . they will never blow out and you can re-use them.
The "How-to rebuild SBFs" book states the 69-72s are 9.5:1 while the 73-76s are 8.7:1
On a 69-72, you probably could get away with just taking .030" off which would drop the chamber down to ~56cc and roughly make 10:1 from the previous 9.5:1
Over the giant dish piston, a 56cc chamber and the .029" thick cometics would come out to 9.45:1 from the anemic 8.7:1.
Cometics are in the $60-80 a piece range depending on the thickness.
The only issues are the cost and you have to make sure the block face is completely clean.
Other than that . . . they will never blow out and you can re-use them.
The "How-to rebuild SBFs" book states the 69-72s are 9.5:1 while the 73-76s are 8.7:1
On a 69-72, you probably could get away with just taking .030" off which would drop the chamber down to ~56cc and roughly make 10:1 from the previous 9.5:1
Over the giant dish piston, a 56cc chamber and the .029" thick cometics would come out to 9.45:1 from the anemic 8.7:1.
it really depends on the block casting. a C9 or D0 block will have the 9.5:1 if it's a D1 block it will have the lower 8.8:1 compression. my 73 windsor has the D1 block.....
No matter what the books say, there was a definate piston change from 71 to 72. I have proof of this. One piston from each. Both have dished tops, but the 72 piston is deeper. Only the 69 4 bbl Windsors had the flat topped 10 to 1 pistons.
Yea, I kinda figured as much on the 69's compression ratio, but wasn't sure off hand. I think the deck difference is only about .020 like the 302's were. Nothing a milling can't fix.