brad8266

iTrader: (23)

I am going to have a stock CI block with flat pistons with 2 cc of valve relief. Cam size is 231/237 .575 .575 112 +3 or 4. I want to get my dcr up a bit more by going with .040 gaskets and running a set of milled 5.3L heads.

My question is how much can I mill the heads before piston to valve becomes likely? I would guess I could mill them quite a bit considering this isnt a monster cam in duration or lift. What you guys think?

Xtnct00WS6

iTrader: (8)

The 5.3 heads have smaller valves than the 241 or 243 castings so if your worried, I'd put in LS6/LS2 valves to maximize your ptv clearance. Aftermarket valves will kill your ptv clearance. Check out this to comparison between Ferrea (.060) and stock ls2 (.020)


As for milling, I'm going to guess somewhere in the neighborhood of .015 with that cam.

Is there anyway you can measure now and get a baseline to see where you're at with the 5.3 heads?

brad8266

iTrader: (23)

I was looking at some 5.3 heads that have larger valves already which are aftermarket. I was thinking if i couls mill the heads down .018 that would get me roughly down 3 cc to 59.5, which would help a lot as far as DCR goes. I am just not sure what other affects advancing the cam will have, other than raising compression. I guess the 2 cc of valve relief would give me a bit more room to work with when milling the heads.

hammertime

iTrader: (1)

If you haven't seen this thread yet, there is some good info here.

Predator is usually right on with head, cam and valvetrain recommendations.

On another note, since your pistons already have valve reliefs, and that cam should clear with a stock head, I can't imagine you'll have any piston to valve clearance problems unless you go to a larger diameter valve that doesn't clear the existing reliefs.

brad8266

iTrader: (23)

I hope to use 5.3L heads with larger valves and want to mill them too. Thanks for the link.

JPH

iTrader: (2)

valve reliefs in the pistons, you should have plenty of clearance. most reliefs are atleast .150 deep.

brad8266

iTrader: (23)

yeah the reliefs are .165 intake and .107 exhaust

Think i have room to mill the heads .030? That would get my DCR where i want it as while at the same time keeping overlap centered at TDC. Most cams come ground with 2 degrees advance already right?

JPH

iTrader: (2)

2 to 4 degrees is standard, depending on cam manufacture.

brad8266

iTrader: (23)

Ok, so my 112 LSA cams ICL would be 110 if I install it dot to dot as long as it has 2 degrees ground in already?

PREDATOR-Z

I think with .030 mill and bigger valves it will be tight on exhaust

brad8266

iTrader: (23)

The valves are 2.055 1.600, what ya think?

JPH

iTrader: (2)

degree it, it's the only way to find out. it should repeat what the cam card says along that everything else is in order. a new timing chain would be a good idea, if you don't already have one.