Roller cam end play: Why is the spec for this so tight?

[PRHeads]

The LA cam lobes measured larger at the front edges of the lobes which means that the taper and the pressure on the lobes push the cam forward.

You’re 1/2 right.
On an LA, between each grouping of 4 lobes between the journals, the lobes taper in each direction 2 & 2.

 

[1 Wild R/T]

I always thought it was to keep the lifter body from hitting a neighboring lobe, not to keep the roller wheel centered on the lobe.

The cam would need more than .250+ end play for that to be a possibility....

 

[Doorkicker]

What is the issue with the nylon button?
My first roller cam engine had an aluminum button. Have two engines with the rollerized button, and most recent used the nylon button, but it is fairly new/low miles.

I had one split and drop into the pan. Honestly it was probably a one off manufacturing issue.

 

[451Mopar]

I had one split and drop into the pan. Honestly it was probably a one off manufacturing issue.

Thanks. I used one of the nylon/plastic type trying to make the valve train a bit quieter.

 

[Geoff 2]

The thrust on the cam [ whether it wants to drive forward or backwards ] is determined by the angle of the helical oil pump drive. Whether it be a separate drive as in Chrys V8 engines or a helical gear on the end of the dist like Chebbies & Pontiacs have. The taper on the flat tappet cam lobe/lifter base contributes a SMALL amount of offsetting force, but only a small amount. After a few thousand miles of use, the taper has worn away & contributes little if any opposing force.

 

[Kern Dog]

The taper on the flat tappet cam lobe/lifter base contributes a SMALL amount of offsetting force, but only a small amount. After a few thousand miles of use, the taper has worn away & contributes little if any opposing force.

 

[RemCharger]

View attachment 1984099

Again, why can't we agree, like, thanks and laugh all at the same time?

 

[Tony Tee]

The tight tolerance should keep the timing sprockets and chain perfectly aligned.
But axial loads between the camshaft and intermediate shaft gears should also shove the camshaft towards the rear of the block.
60 psi of oil pressure requires a good amount of load to turn.

 

[dvw]

This picture shows the results of bronze gear wear when keeping endplay to .008" 14 years, 1250 runs, HV oil pump, 5w25 oil.
Doug

 

[gkent]

After a few thousand miles of use, the taper has worn away & contributes little if any opposing force.

Ha, ha, ha, ha, ha, ha, ha, ha, ha !!!!!

 

[ckessel]

Can't we all get along?

 

[gkent]

There are questionable statements and then there are downright stupid statements !

 

[Geoff 2]

Yes, coming from you...

 

[Geoff 2]

It should be obvious, even for gkent, in the pic below, that the high side of the lobe [rt side ] will wear first.....because....it is in contact with that


high side of the lobe while the left [ low ] side is NOT in contact. The high side wears away from contact until it is level with the low side. The drawing could be better showing more of a gap between lifter & lobe on the left side, which is how it is in reality.

 

[1 Wild R/T]

If you lobes are wearing your gonna have a problem.... After your post yesterday I pulled out a couple old (15K miles +) used cams today & measured them... They both still have taper.... The reason I kept them is they hadn't flattened any lobes, they still ran well... If the taper is gone the lifters slide across the lobe rather than spinning... When that happens the lobe isn't long for this world...

 

[Gunner1]

Roller cams just like cranks will windup and snap back as a big lift high pressure spring loads the cam lobe face near a .600 or better lift. This causes multiple orders of harmonics. Hard on chain and gear drives. Also the movement is harder on bronze gears I use to order billet Chevy cams with the gear and rear bearing machined off nd a cast cam piece pressed on. Made it easy to run stock cast gear.

 

[Kern Dog]

If you lobes are wearing your gonna have a problem.

Yeah. It isn't like the lobes wear off the taper and then just stop wearing.

... After your post yesterday I pulled out a couple old (15K miles +) used cams today & measured them... They both still have taper.... The reason I kept them is they hadn't flattened any lobes, they still ran well... If the taper is gone the lifters slide across the lobe rather than spinning... When that happens the lobe isn't long for this world...

I agree.
I've torn down engines that had a lot of miles on them, October 2024 was a 383 that I got for free. I marked all the tops of the lifters and pushrods and had a buddy spin the engine over with a long ratchet. You could see the lifters and pushrods stay almost still until the lifters were on the cam lobes opening ramp, then they SPUN, then down the closing ramp they slowed and stopped.
Old engine, visible wear and the lifters and pushrods still spun. If there were no taper, the lifters would not have spun.

 

[66 Sat]

It should be obvious, even for gkent, in the pic below, that the high side of the lobe [rt side ] will wear first.....because....it is in contact with that


high side of the lobe while the left [ low ] side is NOT in contact. The high side wears away from contact until it is level with the low side. The drawing could be better showing more of a gap between lifter & lobe on the left side, which is how it is in reality.

View attachment 1984628

Can you explain why cam manufacturers would make cam lobes with a high side that is designed to wear away after a few thousand miles so the lobe is flat all the way across?
This doesn't make any sense at all to me.

 

[gkent]

It should be obvious, even for gkent, in the pic below, that the high side of the lobe [rt side ] will wear first.....because....it is in contact with that


high side of the lobe while the left [ low ] side is NOT in contact. The high side wears away from contact until it is level with the low side. The drawing could be better showing more of a gap between lifter & lobe on the left side, which is how it is in reality.

Sit down and be quiet !!

 

[Doorkicker]

Can you explain why cam manufacturers would make cam lobes with a high side that is designed to wear away after a few thousand miles so the lobe is flat all the way across?
This doesn't make any sense at all to me.

lol... doesn't make sense because that's not why there's an angle.