dan67

So, my L96 needs to be freshened up bearings, pistons, etc. While I'm in there and have to buy pistons anyway, I was thinking of L77 pistons would be a nice way to increase compression from 9.6 to 10.4. Another thought would be to buy the stock pistons because they have valve reliefs in them to run more lift. Budget build. Looking for 500hp +,823 heads, truck intake, the car weights about 2900lbs, 4L60e trans, 3.55 rear end gears

RB04Av

I don't see why not... after all you're gonna need a fairly healthy cam to make enough RPM to make that much power, and such a cam will want higher compression anyway, so it's probably the right thing to do.

indyjps

Take a look at Silvolite 3517HC, @WS6STORE sells them as part of their packages. Flat top 6.0 gen 4 pistons. Compare to L77, decide from there.
https://ls1tech.com/forums/generation-iv-internal-engine/1909285-new-flat-top-pistons-my-l96-gen-iv-6-0l-2.html

dawgs74

I put ls2 pistons in my l96....with 64cc ls3 heads. ..I'm rite around 11:1....pistons swapped right over

cmysix

iTrader: (2)

You don't need to lift the valve any more then what the head flows. IE: head flows 300 cfm at .550 lift that's all the lift you need lifting the valve higher doesn't get you anymore

Dynamic396

You will have more area "under the curve" (duration from .200" lift to .200" lift) if you have a greater amount of lift for a given duration from .050" to .050". So unless the port flow actually decreases with more lift (which would be unlikely), you will typically pick up power with more lift. That is, up until the point that valve train control becomes an problem, which definitely needs to be taken into consideration..

WE TODD DID

iTrader: (2)

That’s 100% false. Not sure how you came up with that conclusion. The head is still moving air past peak lift flow. You’re lifting the valve before you get to peak flow, why can’t you lift it after?

cmysix

iTrader: (2)

You said it yourself peak air flow you can't flow more air then peak period..... otherwise that would be peak you also don't need lift to give you more duration, duration is ground in

WE TODD DID

iTrader: (2)

What happens if you go past peak? Does the air stop moving all of a sudden?

Dynamic396

If you have two cam lobes, both with exactly the same duration from .050" to .050", say 230 degrees. But one lobe has .350" of lift at the lobe "ground in" (.595" at the valve with a 1.7 rocker), and the other has .380" of lift at the lobe (.646" at the valve), which one do you suppose will get to .200" lift at the valve first, and stay above .200" lift longer? .300"? .400"?

Sodak66

I put ls2/l77 pistons in my L76. might as well while your at it. You guys hijacked the thread, Yes bump up the compression while you at it. You'll make more power and you can still run plenty of lift!

cmysix

iTrader: (2)

We are talking about how much air you can push or suck through a given size hole if you can only get 300 cfm max through that hole I don't care if you lift the valve 12 inches you still only gonna get 300cfm

Dynamic396

It's about getting the valve to peak flow as quickly as possible and keeping it there for as long as possible within a given duration window. That is, more often than not, going to involve lifting the valve past the point where flow no longer increases with additional lift. Unless you have a horrible port design (and they do exist) and flow actually decreases with additional lift (eg. port stalls), the port will continue to flow at max as you continue to lift the valve. But it will have spent a significant amount more time with that amount of flow, and you will have gotten to, say .150" or .200" lift (where flow is increasing very rapidly with increased lift) more quickly, and stayed above that amount of lift longer than you would by only lifting the valve to where flow stops increasing and then returning the valve to the seat.

Corona

👆 Speechless....👍 He Knows the Facts.

WE TODD DID

iTrader: (2)

You can also go down in head gasket thickness.

Dynamic396

Yep. Agreed. I shoot for .040-.042" quench on a street engine.

cmysix

iTrader: (2)

I did a .044 HG and milled .025 on my LS2 that really woke it up

rpturbo

iTrader: (47)

Isn't that in total, less than a 1/4 point in compression? And it really woke it up? .025 mill is a touch more than a clean up pass. My printer paper is thicker.

G Atsma

A .025 cut takes about 4cc out of the chamber. That plus whatever the .008 thinner HG adds gets him an 11.65:1 CR

patSS/00

iTrader: (6)

You don't need valve reliefs if your P to V clearance is otherwise OK, just adding lift has little effect on P to V. Changing exhaust valve timing will have a big effect.