Roller cam wear

Something I just ran across over on the BritishV8 website, this is claimed to be a TA cam but I can't verify that, at least not yet. Bryan Phipps is the source. I've asked for specifics on lift, duration, and spring pressure, as well as TA's response and am awaiting more info. You can see what the issue is and it looks to me like the lobe is soft. Pretty much has to be an early production piece for a Rover engine. No idea what lifters were used with it, but I suspect if the roller seized that could also be the cause. I'll post more info as I get it.

Jim

 

Interesting, All roller cams are supposed to be 60 Rockwell. Maybe as you mentioned, the lifter wheel acted up. Got pics of the lifter?

 

Does that seem more pronounced on the downhill side ? Maybe roller losing contact and slamming down.

 

Probably had the garbage Morel lifters

 

He posted the spec sheet TA296R-HL and it's a .650" lift profile but what jumped out at me was the valve lash. At .022 and .024" (hot) that seems to me to be excessive. Even big bore long stroke motorcycle engines tend to run around .oo6-.010" or less and they see more severe heat cycling. That has to be hammering the lobes. You can't tell from the photo which side of the lobe we're looking at but the smearing seem to start right about where the ramp starts if it's on the lift side. Spring pressure could also be a factor. He said he had the TA lifters and they showed no damage.

Jim

 

Yes, but why only one lobe. Maybe that one had excessive lash compared to the rest.

 

IIRC roller cams are case hardened and @ .650" lift they more than likely had to reduce the base circle to get that much lobe lift and they could of ground the case hardening off in spots or ground it thin enough to make the grooves?

Remember when we were discussing roller cams for your engine? We discussed how the cam blanks are preformed so the cam grinder wouldn't have to grind so much off of the cam so the case hardening wouldn't be ground off. Like if a cam blank would be just made on a lathe it would need to be ground twice, once to get it close for heat treat and after it is heat treated so the case hardening isn't ground off.

Take a close look at that thing, they definitely ground the base circle a bit smaller than how the blank was made. The way they did it looks like a cool way to leave a bit more metal on a reduced base circle grind but could of ground the case a bit thin or totally off in spots?

 

Just curious if as a precaution they could redo the case hardening to cam after final grind is completed?

 

They can but there would be a risk that when it is heated up the whole thing can get warped and may need straightening afterwards?

The journals are probably finished ground right before the lobes are so the lobes are inline with the journals all in one setup.

 

The lifter hole is cocked, one side has more wear than the other. Maybe the lifter was loose in the hole cocking the lifter. Need to see that lifter, that is probably what the problem is like Demko said Moral lifters, roller in lifter is failing cocking the roller.

Fast ramp roller cam.

 

TA lifters

 

I'll pass that along.

 

He was running 175# of seated pressure.

Jim

 

When I spoke to an engineer at Johnson about roller lifters for my 350, I picked his brain about solid verses hydraulic, he said there hydraulic lifters are superior to any other hydraulic lifters that there is no need for solids for street or occasional race, he went on to say that with solids, the lash you need to run smacks the hell outta the valve train on street or occasional race engines.
He said on full race engines, not a big deal with solids where your rebuilding often.

 

Mark, did he say anything about WHY you need to run so much valve lash with solid roller lifters? I'm having some trouble understanding why you would ever want more than about .008" If you could get by with it, about half that. Plenty of engines run that tight with solids. Why would a roller make that much difference?

Jim

 

Jim I think it’s the extra weight of the rollers that raises the lash spec. Just a bunch I could be wrong.

 

He wasn't specific on how much lash should be run with solids, what he was saying was kind of a blanket statement ABOUT solid lifters and the lash that has to be taken up, albeit small, that wears the valve stem, rocker, pushrod, roller wheel, face of a flat tappet, or cam lobe.
It makes sense to me, for anything to make a ticking, clacking, banging, or knocking sound, there has to be room (clearance, or lash) to accelerate and hit the other part.
My analogies may seem weird, but its kinda how I think

 

Mark, don't forget to factor in the cushion of oil the parts hit before there is metal to metal.(a little analogy adjustment)

 

After a long history with motorcycles and other engines that run solid lifters (and need adjusted occasionally) I can say with some authority that the valve lash setting represents the point below which "ticking" goes away. Primarily due to the oil film but also dependent on the ramp. On some engines this can be less than .004", in rare cases even as little as .002". Those engines don't make any valve noise at all that you can hear. The ONLY advantage of a hydraulic lifter is the elimination of that occasional adjustment. As a general rule of thumb any time you go over about .012" you will start to get valve tick and this means as mentioned, the parts slamming into each other. Might as well be banging on them with a small ball peen hammer. So why would you double that? It's just asking for trouble.

I can see where a very large diesel engine might use such a clearance. Like a container ship engine or something. But not here.

Jim