Wnts2Go10O

iTrader: (12)

i was reading an older issue of super chevy and they were describing how the diameter of the lifter limits the ramp rate that is useable on a given motor. with a larger diameter not only would you be able to increase the ramp rate but would also give the cam more lift and duration. what do you all think the ramp limit is on the stock diameter lifters? is it just a flat tappet thing or does it also apply to roller motors?

KCS

iTrader: (20)

That refers to flat tappets. The edge of the flat tappet can catch the lobe if it is too agressive. Guys would hone out the lifter bores to accept larger diameter lifters. I think Dodge came with the largest lifters back then, .902 or .905, something like that.

DAPSUPRSLO

iTrader: (14)

This is a good question. What about the bigger diameter bodied rollers and their bigger diameter lifter wheels? Can these allow for more agressive lobes or are they just generally able to take more spring pressure without comming apart? Maybe both?

ecotec88fiero

In theory it would help, but since it is a roller, not much to catch on.

MSURacing

iTrader: (1)

Actually, you want to be careful of not running to much diameter. Yes, with a larger diameter roller you can run a more aggressive lobe, but all the larger roller is doing is slowing down the acceleration of the lobe. And, the side affect of this is that you will now introduce a lot of side load on the lifter. This will wear out the lifter bore fast. Actually, a "mushroom" flat tappet lifter give you the best of both worlds because you can run an incredibly fast ramp withour the risk of sideloading or biting into the lobe. Why do you think so many racing organizations outlaw these types of lifters.

andereck

Because of the added expense to everybody's engine to keep up. Machine work must be done to the block to allow clearance for the lifter. A Chevy is a poor candidate because of how close cam lobes are to each other. A Ford diameter lifter is marginally larger than a stock Chevy and is the norm in oval track racing.

RednGold86Z

[QUOTE=MSURacing]Actually, you want to be careful of not running to much diameter. Yes, with a larger diameter roller you can run a more aggressive lobe, but all the larger roller is doing is slowing down the acceleration of the lobe. And, the side affect of this is that you will now introduce a lot of side load on the lifter. QUOTE]

I disagree with your theory. Take it to extremes to see my point. Imagine a 1mm roller - that would have almost ALL side loading. Then imagine a 100mm roller but with the same small cam, almost no side loading.

Also, as the roller approaches a plane (larger roller), it accelerates faster as the lobe turns. Kind of why when you look at the lobe of a standard roller cam, it looks like it's extremely radical, but actually it's just compensating due to arc's intercepting a circular roller. If you put a larger roller on there, the same angle change in cam lobe yields a larger lift difference.

Wnts2Go10O

iTrader: (12)

Torquemonster TT

Having played with cam ramps to see what we could get away with - let me say this:

when you do it right - the power gain from maximising a 0.904" lifter cam compared to a 0.842" lifter cam is HUGE. By power I'm talking average power over the rpm power band.

It's huge not insignificant. The problem is that very few cam grinders take advantage of this. Every engine has its advantages - but this is one area Mopar has Chev covered. Chev makes up for it by being a lot easier to get good quench and Chev has better heads available.

SlickVert

iTrader: (5)

I believe that the Morel lifters for the LS1/2 have a larger roller then stock.
Bob

Cstraub

iTrader: (1)

.750" as compared to .720" or .700".

Wnts2Go10O

iTrader: (12)

wht difference do they make to the cams ramp rate?

Roarin_8

iTrader: (5)