N4cer

iTrader: (11)

I'm doing a heads/cam swap on my LS1. Here's the heads specs:

Absolute Speed Stage II 5.3L
Valves
Intake: 2.05
Exhaust: 1.57

Lift Intake Exhaust
.200 144 117
.300 204 157
.400 236 194
.450 277 209
.500 293 218
.550 304 222
.600 306 224

And cam specs:
Comp Cams
Duration: 224/224
Lift: .581/.581
LSA: 112


I'm concerned about piston/valve clearance issues. I called Comp Cams and they said I might need to flycut the pistons. But the guy was very unsure. Does this sound like I need to fly cut with valves that big? What about if I went to a 7.35" pushrod? I know the guy that had these heads before me had a 228 duration cam and ran 7.35" pushrods, but he wasn't sure why he did that. I have a pushrod length checker, but want to be prepared as well. Surely someone has this combo!

Any help that my fellow members can give would be greatly appreciated. This is my first build-up and I'm lost.

KY Z28

iTrader: (1)

hey man whats up? I recognize your car from kyhorsepower.com!

I am not sure about the flycutting, what head gasket will you be running? Stock or thinner (say .040)? Also, have the heads been milled any at all? What is the chamber size?

The only reason you would need to run a shortened pushrod is if in fact the head has been decked or you have a thinner gasket, or both. This would basically move the rocker assembly closer to the lifter (in overall distance) and require a shorter pushrod to maintain proper valvetrain geometry.

Hope that helps some!

N4cer

iTrader: (11)

Hey man. Nice to see another KY LS1 owner on here. There's a few of us on here actually.

The cc on the heads is 66cc. Basically it seems that Absolute Speed removed a lot of material to give room for the large valves and to increase breathing. So it brings compression back to normal. They're not milled any, apparently.

I'm running a stock GM head gasket.

I'm waiting to see what the previous owner ran and why he chose 7.35" pushrods. Maybe I need to go that direction, but I hope not.

KY Z28

iTrader: (1)

if i remember right, one reason to run the 5.3 heads was because they offered a little more piston to valve clearance over a 241/243 head. If this is the case and the heads are not milled, I think you will be in good shape with a 224 cam. Duration is what you have to be concerned with when it comes to piston to valve clearance, so I think you should be ok

But just to be on the safe side, be sure to check the clearance with clay when you install everything. I am waiting on new heads and a cam from TSP myself. Even though they said I was good to go, I am still going to check it to be sure!!

where you located in KY? if you need any help, just let me know

bigdsz

iTrader: (1)

With 2.05 intakes I think you will probably need to cut. I've got AS 5.3L heads non milled with 2.02 valves and had to notch with a 228 cam. I only had .045 clearance. The 7.35 push rods are necessary to get the correct valve train geometry, ie having the rockers centered in the middle of the valve stems. This has nothing to do with notching. I also have the 7.35's.

N4cer

iTrader: (11)

Seems like this is getting a little too complicated. I'm considering getting rid of these and going with some Patriot LS6 style heads. Or even stock LS6 heads.

bigdsz

iTrader: (1)

Stick with the AS heads, from your numbers they flow very good. Just make sure you degree the cam and measure for clearances 8-10* btc and clay. That 205 valve is the concern. Also you might want to call Brian at TEA/Trickflow he might give you some insight on the necessity of notching. There was a thread recently on AS that he got in on.

GuitsBoy

iTrader: (4)

I think it might depend on your gasket, but I wouldnt think you'd need to notch with that small a cam, with unmilled heads. But then again it depends on if the valves were hung lower than stock too.

PREDATOR-Z

True it depends on what valves are there.
IMO 66 cc 5.3L beat the purpose of running 5.3L heads.
Sell those and get a set 59 cc PP LS6 style with 2.02 valves, that will boost your SCR and DCR and no notching needed.

Or you can get a set of PRC/PP stage 1 243 casting (LS2/LS6) with duals and run a .040 Cometic. That equals to 61cc (aprox). You'll get better quench, better compression both dynamic and static.

Those big valves are counter productive for that cam.

N4cer

iTrader: (11)

That's the direction I was thinking of turning. Or what cam could I run instead? And the PP/PRC "LS6 Style" heads are supposed to have a welded-in smaller combustion chamber that could collapse. So is that a bad idea too?
You think 59cc heads are fine on 93 octane then?
Maybe go with Livernois instead?
Basically, I'm thinking that I'm very limited with these heads that I have now, and I don't like that a bit. I want heads that will allow me to go to a bigger cam if/when I decide to.

PREDATOR-Z

PP LS6 style have no recent issues (haven't read any bad things in over a year.)
Gunnar is superb at customer service.
The 59 cc will work on 93 octane with tune. Or get the PP true LS6 casting (243s) with 64cc. They will work well with no flycut or other issues.

Xtnct00WS6

iTrader: (8)

I agree about the valves. Aftermarket designs can decrease PTV clearance 2 ways: the diameter and the margin.

Just a little FYI:

I have the Patriot Performance 243 (2.02 and 1.57 and milled .010) with a TR 224 on 114 with +4 and my measurements with a dial indicator were .130 on the Intake and .103 on the exhaust. That seems a little close for a little ole 224/224. But, according to Tony from AFR, you can add .015 to those measurements making it .145 and .118 which is still kinda close on the exhaust but within spec.

I was concerned from the get go so I had a local machine shop take about .015 off of the intake valve margin (part that hangs down into the chamber after the contact point) because it was huge. The ferrea was about .040 thicker than stock valves at the margin. If I didn't do that I would have had about .115 on my original measurement for the intake valve. Ya just gotta measure.

N4cer

iTrader: (11)

So then, what cam would you recommend for these heads?