Posted By: drag440
How much to mill Indy's SR's - 01/17/09 10:34 PM
I am building a .055 over 440 with BME alum. rods and BME flat top pistons. The pistons are .025 in the hole and the gakets are .040 Cometics for a 4.380 bore. This will give me .065 piston to head clearance for the alum. rods. The pistons have valve releifs, maybe 4cc's? The heads are 78cc's. This is only about 10.6 comp. Thats not going to cut it. I would like at least 12.0. This is going to be a NOS engine with a 350hp Fogger. I think I need to mill the heads to about 65cc's? How much do I need to get cut off the int. side and the gasket side?
Posted By: fast68plymouth
Re: How much to mill Indy's SR's - 01/18/09 02:19 AM
based on what you gave for specs, i get 10.42cr now, and it would take 14cc's off the heads for 12:1.
you cut Indy heads are roughly .006 per CC, so for a 14cc reduction, you're looking at cutting them .084.
better check the V/P clearance before cutting them that much.
cut the intake side .012 for every .010 off the deck.
so, if you cut the decks .084, cut the intake side .100.
Posted By: drag440
Re: How much to mill Indy's SR's - 01/18/09 05:51 AM
Thanks for the info. This engine was already together with stage 1V steel heads at 11.0. Now we are going to alum. heads which need more comp.
Posted By: Dodgem
Re: How much to mill Indy's SR's - 01/18/09 05:42 PM
My SR's too were 77/ 78 as shipped and I think we are at .065 to .070 to get to 67 cc now that took some to 65 so I made them all 67.
Posted By: drag440
Re: How much to mill Indy's SR's - 01/18/09 08:17 PM
I figured the comp. would probably be a little less than 10.6 because I didn't know what cc the valve releifs were so I just figured it with none. I was just trying to get a ballpark idea for now. The heads can only be cut to 62cc's I think, so maybe I will cut them to 68cc;s and moc the engine up with checking springs and check the valve clearance. Then I can order thicker or hopefully thinner gaskets. I think Cometic makes some .027 gaskets. This short block has ben in 3 different cars in the last 15 years. I've run a 312/590 and a 324/650 cam in it, both with 1.6 rockers and had plenty of clearance. This engine has also seen a LOT of NOS over these years. The car it is in now has a 350hp fogger on it. Years ago everyone said to run low comp. with NOS, but now that seems not to be true. Just about everthing that I have always been told to do in a engine is the wrong thing to do now
Posted By: drag440
Re: How much to mill Indy's SR's - 01/18/09 11:19 PM
I just measured the depth of the valve reliefs and they are .250 deep and the pistons are .025 in the hole so that gives me a lot of room.
