Intake valve lift at BDC

[swampbuggy]

Lets take an NHRA Pro-Stock engine with appx. 1.200" peak valve lift, appx. what would the valve lift be at BDC ? Or a NASCAR Cup engine, guessing valve lift at .875", what might be the lift of that one at BDC ? This thought came to me, don't know why, maybe a dream LOL. But thought somebody might know the answer ? Mark H.

[CamKing]

PS, about .290"
Cup, about .230"

Sorry. These are at TDC

[CGT]

PS, about .290"
Cup, about .230"

Seems like it would be more than that. At what rate is tappet lift per degree descending on that part of the lobe?

[CamKing]

PS, about .290"
Cup, about .230"

Seems like it would be more than that. At what rate is tappet lift per degree descending on that part of the lobe?

That would depend on rocker ratio. I was only looking at the valve lift curves.

[David Redszus]

The valve lift at BDC would depend on duration and lobe center.
Perhaps cam index would be a better descriptor.

[CamKing]

The valve lift at BDC would depend on duration and lobe center.
Perhaps cam index would be a better descriptor.

I based my numbers on a couple of "Not too old" projects, I did.

[zums]

PS, about .290"
Cup, about .230"

Maybe lobe lift
Tom

[CamKing]

PS, about .290"
Cup, about .230"

Maybe lobe lift
Tom

Excuse me, I'm an idiot.

[piston guy]

Tom ,
Not lobe lift , valve lift. Mike knows better

[Stan Weiss]

Mike,
I know these are not your lobes. But looking at these lifter raise ATDC and rocker arm ratios I don't see how they could only be .290" ABDC. Are these that different than yours?

Stan

Comp_TS_Lobes.gif

[CamKing]

Sorry. I gave lift at TDC, not BDC. My mistake.
I'm not used to people asking for intake lift at BDC.

[CamKing]

OK, now let me try this again, with my brain engaged.

PS, about .860"
Cup, about .535"

[swampbuggy]

Thanks Mike for your answers, all the reading came with some good laughter Mark H.

[MadBill]

No offence, but gotta ask: why would anyone care?

[swampbuggy]

Hello Bill, i heard a comment made by someone smarter than me that not too many people are concerned with the lift of the intake valve at BDC. There was some more said, all of which i can not remember. I just thought i would bring it up for comments thats all. This forum is for questions and learning for sure. Thinking about bringing the I.V. back down to its landing on the seat without issues of bounce or ??? . So the more lift at BDC, the more lift that has to be erased between BDC and seat contact, hence the original question. Does this help ? Mark H.