COSTIGAN86

iTrader: (8)

I have a set of ported 799s going onto my LS2 with a ASA cam. Should I mill these heads first? I do not want ptv clearance issues. Cam is .525/.525 226/236. Milling .025 will bring it down to right around 61cc, bringing the CR up to almost 11.5. What would you do?

slt200mph

iTrader: (42)

High compression is free HP. I'd mill them. I have a set of heads milled down to a 11.4 to 1 ratio. Been running them for 5 years now.

slt200mph

iTrader: (42)

High compression is free HP. I'd mill them. I have a set of heads milled down to a 11.4 to 1 ratio. Been running them for 5 years now. Nuff said..

KT2

COSTIGAN86

iTrader: (8)

anybody else?

COSTIGAN86

iTrader: (8)

I cc'd the chambers today and they are 67cc after the port work. At .006" = 1cc, shaving .030" will bring the chambers to 62cc, giving me 11.26 compression. Anyone see any piston-to-valve clearance issues with this?

COSTIGAN86

iTrader: (8)

I'm using stock MLS head gaskets, .051" compressed

yonerhottlt1

iTrader: (21)

With a cam that small, I don't see you having any PTV clearance issues at all. Although it's always best to just measure to be sure

COSTIGAN86

iTrader: (8)

I know that its best to measure, but was hoping to find someone with the same or similar setup and if they had to flycut.

fst100

iTrader: (5)

i thought 243/799 heads were 64cc not 67cc which were 853/241s?

COSTIGAN86

iTrader: (8)

^ you are correct. After polishing the combustion chambers they are 67cc.

fst100

iTrader: (5)

so you have either 241 or 853s then?

427zm

iTrader: (9)

Something to thing about; if you went to the .040 Cometic gasket, you could mill less and still get the same added compression you desire. The other thing this will do is add quench which helps protect against detonation. Tight quench is a great thing for a NA motor. Oh, and as for your original question, I don't think you'll have PtV issues at all with that cam. Intake duration is typically the main thing to concern yourself with. Now, the only way to make sure is to measure.

No, what he's saying is that the back cutting of the valves, and port work increased the chamber size.

COSTIGAN86

iTrader: (8)

Update: I measured and had plenty of clearance. Milled .020" and still have over .100"

fst100

iTrader: (5)

ah ok. so it brought the cc from 64cc to 67cc and now that he milled the heads 0.020" they're now around 63.75cc-ish?

i'm still new to all of the heads and such. so porting the innards of the heads also affect the cc overall, meaning for example 799 heads be 64cc and if i do a home-port job such as removing the lump and bulleting the intake valve area that the overall cc would go up some? sorry for the threadjack btw COSTIGAN86

KCS

iTrader: (20)

The ports and chambers are two different things. Narrowing the guide boss and removing the rocker boss will increase the volume of the port, and will have no effect on the chamber.

mgood613

iTrader: (1)

I am running the howards vs ASA cam with PRC 243/799 Stage 1 heads Milled .030 with .045 cometic gaskets on a LS1.

My PTV was .083 intake and .125 Exhaust

Just FYI, but I would always check.