LSX_240

iTrader: (4)

Stock bottom end Ls1, 243 Milled .035, Cometic MLS .041, MS3 at 113. Checked PTV several times and the clay looks like the valves are CLOSED when it hits. Had a friend come over and double double check with the same results. Is this normal or are we doing something wrong? Any help is much appreciated.

td1168

iTrader: (2)

What exactly do you mean when you say, "the valves are closed when it hits?" Stock bottom end has flat top pistons. There is no way the piston can hit the valves when they are closed.

LSX_240

iTrader: (4)

The impression on the clay is of closed valves. As if the valves are no where near the piston (or the clay for that matter) when they are opening.

JustAFooL

iTrader: (45)

You have to see the marks in the clay where the valves hit. It should be obvious but you sound like you have done this before? I'm also confused on what you are saying..

JustAFooL

iTrader: (45)

Did you touch the bottom end?

td1168

iTrader: (2)

The impressions are going to look that way. Just take a machinists ruler that reads in 1/64ths and measure the thickness of the clay at the impressions. You have to know how to read the ruler.

LSX_240

iTrader: (4)

Its stock bottom end. Im just as confused as you are, its hard to explain. The marks on the clay are of valves closed. The clay was big enough it touches both valves and the dead area above the valves. The valves opening never touch the clay. Its almost like the timing is off but both dots line up perfectly.

JustAFooL

iTrader: (45)

The impressions resemble a half moon. Just cut it in half and measure the thinnest spot on the clay..

LSX_240

iTrader: (4)

I didn't measure it because its obvious the valves are closed. I ran out of daylight but ill try again later and cut the clay with a razor blade and measure with a digital caliper.

JustAFooL

iTrader: (45)

Something is off, that cam and milled 243s, you should definately be seeing those valves

LSX_240

iTrader: (4)

That's why Im here. Ill Measure it to get an exact number. Ive done this once before and it didn't look anything like this.

poltergeist 02

iTrader: (65)

Why don't you degree the cam? That will tell the true story of what's going on.

LSX_240

iTrader: (4)

Don't have the tools and didn't think about it at all. Could it be that far off?

poltergeist 02

iTrader: (65)

Are you using solid lifters to check with the clay?

LSX_240

iTrader: (4)

No fresh installed ls7 lifters. Might it be collapsing them? Is there enough collapse to make THAT much difference?

poltergeist 02

iTrader: (65)

Yes. If I remember right, the travel of an LS7 lifter plunger is about .180" to .200"

JakeFusion

iTrader: (7)

That's most likely going to be too close, even with stock valves. You're already tight with that cam to begin with, and you're essentially removing .050" of clearance via milling and gasket selection.

You are collapsing the lifter. Use an original lifter modified to solid or use a dial indicator riding on the lifter body to check ptv.

JustAFooL

iTrader: (45)

Don't know why I didn't think of a lifter. I took one of my old ones when I checked and took the "guts" out of it. Before I did though, made a little Mark with a Sharpie. Wootton hardware store and bought washers that would fit and filled to the line. Don't forget to magnetized the washers before dropping in, suck for one to end up in the bottom end

01ssreda4

iTrader: (96)

Doubt this combo will work, how you ended up with it is beyond me. An MS3 type cam is likely going to give just adequate PTV for a stock engine (given manufacturing tolerances). Once you start shaving heads and adding thinner gaskets well you've effectively un-engineered the design of the cam more or less.

LSX_240

iTrader: (4)

01ssreda4 Im doing a "high" compression nitrous build. The heads are hand ported. I have a feeling my ls6 intake and ported stock throttle body are going to be the main issue. Ill try the solid lifter idea tho.