SBC Shaft Mount Geometry with different int/exh lifts

[Warp Speed]

I can't believe that small amount of difference would really matter enough to measure performance wise.

Believe it! LOL

[DaveMcLain]

I can't believe that small amount of difference would really matter enough to measure performance wise.

Believe it! LOL

.030 is .015 each way, come on...

[Warp Speed]

I can't believe that small amount of difference would really matter enough to measure performance wise.

Believe it! LOL

.030 is .015 each way, come on...

His geometry problem, probably not gonna be a factor. Doesn't mean it's correct but.....
I assumed, since you didn't quote anyone, you were referring to Bills post right above yours, (not the general thread subject) in which my statement would still stand.

[lekid]

The latter.
Besides, an engine that really needs the high lift flow could drop 15 HP with a change from 1.7 to 1.65.

Thanks Bill! This is a nitrous engine (400hp jets though a plate), never runs N/A, and from what I am being told by the nitrous gurus helping me, the more the lift on intake the better to stuff as much nitrous as possible as quick as possible. 1.7 it is!

[RCJ]

You should assemble it and see what you have.Using mid lift you are not looking at the cam at max lift.

[kimosabi]

0.825 / 0.760 lift base on lobe x rocker ratio (before lash and deflection)
0.795 / 0.732 after lash

That's a split as they say. You're gonna have to make compromises here so I agree with the "meet in the middle" approach. You're smacking alot of nitrous in there so maybe focus a little bit more on not compromising the exhaust side. Ain't valvetrain fun?

[lekid]

0.825 / 0.760 lift base on lobe x rocker ratio (before lash and deflection)
0.795 / 0.732 after lash

That's a split as they say. You're gonna have to make compromises here so I agree with the "meet in the middle" approach. You're smacking alot of nitrous in there so maybe focus a little bit more on not compromising the exhaust side. Ain't valvetrain fun?

By saying to not compromise on the exhaust side, you mean to sit the difference but pay more attention to the final geometry (rocker sweep) and final net valve lift on the exhaust and tweek slightly if required to get as perfect as possible, even if I lose a little on the intake?

[kimosabi]

0.825 / 0.760 lift base on lobe x rocker ratio (before lash and deflection)
0.795 / 0.732 after lash

That's a split as they say. You're gonna have to make compromises here so I agree with the "meet in the middle" approach. You're smacking alot of nitrous in there so maybe focus a little bit more on not compromising the exhaust side. Ain't valvetrain fun?

By saying to not compromise on the exhaust side, you mean to sit the difference but pay more attention to the final geometry (rocker sweep) and final net valve lift on the exhaust and tweek slightly if required to get as perfect as possible, even if I lose a little on the intake?

Yes that's correct. Pardon my poor choice of wording. If the cam was more even lift both sides I'd say split the difference through and through.

[MadBill]

I'd lean the other way. The intake is more critical for power, needs more lift and is usually heavier so should get the nod re any required compromises. That said, there still isn't enough here to merit much agonizing.

[lekid]

Thanks guys. Very appreciated!

Speedtalk FTW...again!!

[cjperformance]

0.825 / 0.760 lift base on lobe x rocker ratio (before lash and deflection)
0.795 / 0.732 after lash

That's a split as they say. You're gonna have to make compromises here so I agree with the "meet in the middle" approach. You're smacking alot of nitrous in there so maybe focus a little bit more on not compromising the exhaust side. Ain't valvetrain fun?

Yeah, normally I'd say get the intake closest and the exhaust is what it is. With this I'd say split it for dummy up purpose, asses PTVC, then if good err on the 'get the exhaust right ' side of things.

[lekid]

Did the geometry based on the splitting the difference and it is actually extremely close to the 90deg at mid-lift on the exhaust. I did not do the intake yet, still waiting for the new intake rockers since it requires a different offset for this head.

Here is a picture of my exhaust sweep

26828451_10154997561981927_513261982_o.jpg

[redliner]

Did the geometry based on the splitting the difference and it is actually extremely close to the 90deg at mid-lift on the exhaust. I did not do the intake yet, still waiting for the new intake rockers since it requires a different offset for this head.

Here is a picture of my exhaust sweep
26828451_10154997561981927_513261982_o.jpg

What does the sweep measure?

[cjperformance]

Did the geometry based on the splitting the difference and it is actually extremely close to the 90deg at mid-lift on the exhaust. I did not do the intake yet, still waiting for the new intake rockers since it requires a different offset for this head.

Here is a picture of my exhaust sweep
26828451_10154997561981927_513261982_o.jpg

What does the sweep measure?

.065" ish by the look

[lekid]

I did not measure it, but since the valve is 11/32, it looks to me like it is roughly 0.060-0.065".