Roller Lifter questions

Guest · Post by **Guest** » Tue Feb 08, 2005 6:34 pm

I know with a flat tappet cam, lifter diameter can make a big difference. Does the same hold true with rollers? Is there much to be gained going from a SBC .842 to Chry dia .905 for instance?

Also, any thoughts on tie-bar vs something like the Jesel "Dog Bone" or grooved bores? Are they lighter or otherwise worth the machine work and cost?

la360 · Post by **la360** » Wed Feb 09, 2005 4:24 am

The diameter of the lifter body in the case of Roller lifters makes no difference to the valve timing at all. The diamter of the roller is a different case. If memory serves me correctly, there are 0.750", 0.840" and 0.875" roller wheels in lifter's these days , but I would check with the lifter , and your cam manufacturer regarding the exact sizes, and what your cam is ground for. My memory can be a little shady at times with these things. As far as how much it will affect your valve timing, I haven't done any comparisons myself as yet, but I am certain there are some guys on here who have. IHTH's
AL...

CNC BLOCKS · Post by **CNC BLOCKS** » Wed Feb 09, 2005 7:31 am

Going from a .842 to a .904 lifter the wheels are quite a bit bigger and they change the seat timming avents which change the overlap avents as well and on most cams using .904 lifter the lobes have to be side cut as well. you should let the cam grinder know what size wheel you are using.

The bigger wheel picks the lobe up quicker and come off the lobe later.

Guest · Post by **Guest** » Wed Feb 09, 2005 9:07 am

Thanks La and Carl. that helps. Sounds like the larger wheel can change the timing if put on a cam designed for smaller but not much difference if the cam is designed for the wheel. There are other compromises such as the need to cut the lobes etc. If you are trying to keep entire valve train light for high rpm, maybe going with the smaller lifter is a reasonble choice though I recognize every change affects something else so has to be designed as a package.

Jack

CNC BLOCKS · Post by **CNC BLOCKS** » Wed Feb 09, 2005 9:41 am

We use the .904 Jesels in two of the blower engines we build and maintain only they are over 1200 over the nose and the .904 use a bigger wheel as there is less tracking and a bigger axel.

Lasher... · Post by **Lasher...** » Wed Feb 09, 2005 9:59 am

Crane has an example of the difference a larger wheel will make. The example given was thier R280/500 lobe. If the roller were changed from a .750 diameter to a .810 diameter the change would be:

Lifter Rise.................. Duration increase with .810 Roller.

.020........................... 0.8 Deg
.050............................1.3 Deg
.100............................1.6 Deg
.200............................1.7 Deg
.300............................1.4 Deg
.400............................0.9 Deg
.500............................0.0 Deg