rdkonkel

iTrader: (4)

Hi guys,
building an '04 LQ4 6liter. Got a few cams layin around and want to know what's the max lift before having any clearance issues.
Have used the .525/.532 with favorable results but would like to go bigger.
This motor is stock long block with a tune, headers, cold air intake etc.
Going in a 4,000lb, 72 truck with 700r4 and 410's with shorter than stock tires so the rear gear will technically be a set or two higher.
Any info from previous builds would be appreciated.
Trying to avoid pulling the heads and flycutting the pistons.

5.3LJimmy

iTrader: (10)

Max lift is in the .700" range.

rdkonkel

iTrader: (4)

Seems pretty high, are you sure .700 can be done on a stock motor/heads?
Only looking for mid to high 500's

5.3LJimmy

iTrader: (10)

Lift has no effect on PTV clearance. When the cam reaches max lift the piston is down in the bore. The valve events are what determines whether or not you will have clearance issues. The LQ4 has dished pistons which have more clearance than the flat top motors. You would have no problem going to a cam with 242/248 duration and as much lift as you want to run.

rdkonkel

iTrader: (4)

That's cool. What about a 5.3, building on of those too

5.3LJimmy

iTrader: (10)

You will kill all of the bottom end power and make a 5.3 completely undrivable long before you run into PTV issues.

93Z2871805

iTrader: (5)

Not true sir. The raised edge on the skirt of the dished LQ4 piston is at the same height as the LQ9/LS2 flat top and would still cause PTV issues.

rdkonkel

iTrader: (4)

If I stay around 230 or less duration and .550 lift do you think I'd be safe?
Has any one got a cam this big or bigger in a stock LQ4 or 5.3?

rdkonkel

iTrader: (4)

5.3 Jim,
I see you have a truck, Currently I have a 5.3 in a 3/4 ton truck with 410's and shorter than stock tires to get a even higher ratio. Also a 700r4. Stock cam with headers and a tune. The stock motor burns the tires through 3rd gear. (combo of power, high gear, and little weight in the rear) I would like to know what is the highest lift/duration I could use in this truck with the 5.3 , also putting a 6.0 in the same type of truck, would the cam be about the same for both motors. no stall

5.3LJimmy

iTrader: (10)

The raised edge will cause a clearance issue with the side of the valve but at the tip of the valve(closest to the intake) the dish has more clearance. I'm not saying that the dish has as much clearance as a flycut piston but it does offer a bit more. If you look at a picture of a piston in a car that has had some PTV contact you can see the "eyebrow" is far from the raised edge of a dished piston.

Fade2blk500

iTrader: (18)

I'm currently running a 234/236 .601 .611 lift on a 114lsa and have plenty of ptv.. makes good power as well

93Z2871805

iTrader: (5)

I have a set of .020 over dished pistons in my garage that are notched, like you said the tip does have more clearance with the dish vs a flat top, however the side of the valve closest to the cylinder wall still protrudes into the raised edge where the eyebrow cuts through, so without flycutting (or a notched piston), you'd still experience valve to piston contact whether it's a flat top or a dish, it would just be in a different area on the piston.

Side question, is that 5.3 jimmy setup you have AWD?

I'd say you would be plenty safe.

5.3LJimmy

iTrader: (10)

No it is RWD.