Ethan[ws6]

iTrader: (13)

Just out of pure curiousity, does anyone happen to know what the max valve lift someone could run on a set of 243's? or 241's? I have had a couple of people ask me and I can't seem to find the info anywhere.

Thanks a lot!

wytry

iTrader: (6)

I don't think you can simply determine a max valve lift. The duration of camshafts plays a role (a large one) when it comes to PTV clearances. I run a 232/234 .595 .598 112 LSA cam with 62cc 243's safely. Just an example.

Ethan[ws6]

iTrader: (13)

haha that's exactly what I"m running as well. I know duration throws out issues as well, I guess i just need to hear how big people are going without issues haha

vettenuts

iTrader: (4)

Max lift will be determined by the valve spring/seat/retainer setup and max duration and lobe profile by the PTV. You need to check clearance from retainer to valve seal, coil bind, etc.

Ethan[ws6]

iTrader: (13)

also I should elaborate that this would be a situation where the pistons do not have valve reliefs cut. That's the main thing I'm trying to figure out here. safest lift without cutting reliefs, if not the 100% max down the the .001" at least a solid number that is safe

dudeiwin86

iTrader: (1)

youre missing the point others were trying to make.

if youre concerned about cutting pistons, then that means your concerned about PTV (piston to valve) clearance.
and THAT means you need to be concerned about DURATION and LSA of the cam, not the lift.

duration and LSA play a far more significant role in PTV clearance than lift does.

it would help others (with more experience than I) to guide you, however, if explained more about the heads youre going to use.
stock? milled?

Darkman

iTrader: (2)

Lift is wholly unrelated to piston to valve clearance (PTV), which is related to duration, overlap, and cam timing. The piston only comes close to the valves when it is at, or nearly at, top dead center (TDC). The occurs only twice during an engine cycle. It occurs once as the piston comes up on the compression stroke. On this stroke however, both valves are closed. The second time the piston approaches TDC is on the exhaust stroke. During the exhaust stroke the exhaust valve is open but is already retreating from its maximum lift as the piston rises. The piston can hit the exhaust valve if, and only if, the exhaust valve retreats too slowly. Under no circumstances however, can the piston catch the exhaust valve at its maximum lift.
On this same exhaust stroke, the intake valve is beginning to open (which constitutes overlap with the retreating exhaust valve). The intake valve, can hit the piston if it opens to soon and the piston is at, or nearly at, TDC. However, the intake valve will not hit its maximum lift until the piston is past TDC and is on the way down (the intake stroke).

Thus, the maximum lift of either valve is not a piston-to-valve issue.

garygnu

valve timing events are really importent.big lift don't mean big power.

LilJayV10

iTrader: (39)

Seven inches. Max.

Gordon0652

iTrader: (4)

I ran the MS4 cam on LS1 heads... Do not remember the lift.
Its not so much the cylinder head but the components.

Thats all she can take "i'm tellin ya" lol

LilJayV10

iTrader: (39)

****, if I gave it to her twice!

Slvr00Bird

iTrader: (2)

That makes me feel all warm inside. Have a G5X3 and I was worried about it and PTV.. Still gonna be cautions about it, but that's a relief that there's less chance or less likely that I'm going to have to fly cut since the MS4 is bigger.