Lifter considerations and possible long term issues.

[BVHOG]

I was getting ready to do a cam swap on a new Mil 8 and when I looked at the cam it struck me just how much bigger the lobe is than that of the twin cam.  The possible problem I see with this is the lifter roller speed will be greatly increased at a given rpm. We are not talking a small amount here either.
I feel the moco dropped the ball on this one as they had the opportunity to use a larger roller lifter and grind cams accordingly.  What do  you think, potential problem? No?

[wfolarry]

I don't see it as a problem I see it as an improvement. 

[BVHOG]

I don't see it as a problem I see it as an improvement.

In what way?

[No Cents]

  I'll take a stab at it.
With a bigger rounder cam lobe the lifter will ride better on it vs a smaller tighter lobe.

Ray

[1FSTRK]

The larger diameter base circle will decrease the side load on the roller and lifter bore at a given valve lift. This should put things more inline with the automotive size cam lobes that the lifters were originally designed to run on.

[FSG]

The larger diameter base circle

can someone post what that actually is ?

[wfolarry]

The larger diameter base circle

can someone post what that actually is ?

Which one? They're different sizes.

[FSG]

all 4 then, FI, FE, RI & RE

[BUBBIE]

 

Aren't the Lifters in the M8 type "C's"...

I just posted in another thread: IMO that the only place for the "C's is in the Trash Barrel...

Comp 850-1 are Very reasonable Under 70$ for set of 4 and with That, you can afford an Often Change IF Needed/Wanted...

I have had my latest set in for over 10,000 miles and sounds like a sewing-machine... Ten thousand is a low number as I expect to do another 15,000 miles...  Then just replace them as that is a Very Cheap investment Hopefully BEFORE they go bad...

signed....BUBBIE

signed....BUBBIE

[wfolarry]

[smg id=2939]

[smg id=2935]

[smg id=2937]

[smg id=2936]

[smg id=2935]

[smg id=2934]

RI 1.501  FI 1.427  RX 1.363  FX 1.512
This is just a quick measurement with calipers. Close enough for what you want.
FSG feel free to fix up the photos.

[1FSTRK]

Larry won't the calipers be picking up some of the ramp when measuring these lobes?

[FSG]

Close enough for what you want.

  I can see why they have different BCDs, I wonder how close the after market are doing the cams.

What has the profiler told you about the M8 Cams?

[attach=0]

[wfolarry]

I haven't measured it yet on the stand. I need the timing specs for the cam to input into the program & go from there. I'll probably do it over the weekend. I'll post them up when I do.

[BVHOG]

I still feel Harley could have used a much better lifter but then again that's nothing new . And is the side load really that much less to offset the huge increase in roller speed.   Time will tell

[Admiral Akbar]

I still feel Harley could have used a much better lifter but then again that's nothing new . And is the side load really that much less to offset the huge increase in roller speed.   Time will tell

Didn't know 15% was huge..(FX)    Only 5% RX

[1FSTRK]

The Automotive cams that these lifters were designed to run on have a .776 base radius which would yield a BC of 1.552 without the ramps and rev to 6200 with the factory revlimiter.

[BVHOG]

The Automotive cams that these lifters were designed to run on have a .776 base radius which would yield a BC of 1.552 without the ramps and rev to 6200 with the factory revlimiter.

Since when have you seen an automotive application abuse lifters like the V-twin motor does?

[HD/Wrench]

  I run a Little M dart block with hyd rollers in it. 150 on seat 490 open. Spin it to 7600 on the 1-2 and 7400 on the 2-3  and 7400 on the 3-4 . But hey its just a little NOS guzzling engine .. HA HA

[1FSTRK]

The Automotive cams that these lifters were designed to run on have a .776 base radius which would yield a BC of 1.552 without the ramps and rev to 6200 with the factory revlimiter.

Since when have you seen an automotive application abuse lifters like the V-twin motor does?

Not sure why a lifter would know the difference. Spring pressure, rocker ratio, and as you pointed out roller rpm would be the same in either application. The thing that separates the HD from the auto application is oil pressure and supply to the hydraulic unit and that has nothing to do with the roller. Personally I think the larger base radius on the cam the better, one of the advantages of the Twin cam over the Evo.

[flh canuck]

I suspect that the larger cam radius has more to do with the geometry of a single cam in the center of the cam chest having to actuate the valves for two separate cylinders while still using stock twin cam lifters.

If they utilized a single cam with a smaller base circle and lobes, the cam would have to be positioned higher in the cam chest making for some funky pushrod angles... Or I suppose they could use the present cam location but then the twin cam lifters would have to be sunk further into the block to make it work... Or I could be entirely way off base (circle) here 

[Admiral Akbar]

I suspect that the larger cam radius has more to do with the geometry of a single cam in the center of the cam chest having to actuate the valves for two separate cylinders while still using stock twin cam lifters.

If they utilized a single cam with a smaller base circle and lobes, the cam would have to be positioned higher in the cam chest making for some funky pushrod angles... Or I suppose they could use the present cam location but then the twin cam lifters would have to be sunk further into the block to make it work... Or I could be entirely way off base (circle) here