I bought an aluminum timing cover and it says that it can't be used with a roller timing chain. I think the only reason is because of a lack of clearence between the timing chain and cover which doesnt allow the cam to walk. I was thinking of sticking it in the milling machine and milling the pad down till I got the proper clearence. How much does the cam need to be able to walk? Thanks, Scott

a non roller cam is built to be pushed to the rear of the block. A roller isn't so it needs a bearing or thrust washer.

But you have to have a deep enough cover to clear the chains no matter. Double rollers are just thicker. You wouldn't want the cover to be hitting the timing chain.

I think that's what you're asking.

Sweet so I can just take off material until until it clears! What push's the cam to the back of the block anyways?

Sweet so I can just take off material until until it clears! What push's the cam to the back of the block anyways? The cam is held back by the way the lobes are ground--the lifters put rearward pressure on the cam. You don't want the cam to walk forward, .006 clearance I think would probably be alright. Bob

Unless you're married to that timing cover I'd just get a deeper one. You can media blast an old one and paint it whatever color you need and a new seal is not much either nor is the gasket. In fact you can do without the gasket altho they're so cheap why bother.

There's a zillion one and two piece aluminum billet or not covers, chrome and whatever out there.

You might not hear anything either with non fired rotation or even on start up. When things heat up clearances could change. Also chains stretch with time. I wouldn't want to pull all those accessories or worry the entire time about it. But that's just me. Grind away and let us know what happens. Or take a rubber hammer to it and hope the seal doesn't leak. We'll all learn something one way or the other.

So are you saying that the lobes are angled back a degree or two and are'nt perpindicular to the centerline of the cam? This would mean the lifters would have to be angled also or else it would cause excessive wear. This can't be right is it!? That would cuase the pushrod to bind in the guideplate slot it seems.

the lobes are slightly tapered, some forward, some back. The distributor gear also pulls back on the cam. The lifters are not flat on the bottom but instead have a convex face. The curve is similar to what you would have on a 6-ft diameter circle. If you stick a cam in a block and look down the lifter holes you'll see that the lifters are not centered on the lobes at all. Between the taper, the off-center and the convex face of the lifters the lifters rotate continuously. If they stop rotating the game is over and the lobe is gone.

Tom

If the people who made your timing chain cover can't manage to build in clearance for a roller timing chain, why would you think they're competent enough to put the seal or the bolt holes in the right places?

Be very careful with that piece.

The lobes on a flat-tappet cam are all tapered; all the same way. They are not parallel to the axis of the cam. They're taller in the back than in the front. Also, the lifters aren't "flat", they're concave. And, the drag of the oil pump on the dist gear, which is consoderable, is designed to be applied to the cam in the rearward direction. All of that helps retain a flat-tappet cam rearwards. The rear surface of the timing gear should be held flat up against the front of the block 100% of the time while the engine is running.

A flat tappet cam has an enormous ability to "walk". In fact it can come out until the bolts hit the timing cover, as there's nothing really holding it in. But, the forces from all those other things, as well as the tendency of the chain to try to run straight when at any kind of RPMs, keep that from happening.

Roller cams don't have the taper; all they have holding the cam inward, is the dist gear. The original design roller uses the same chain (roller or not) as a flat-tappet, and a cam button to hold it in. A factory roller setup uses that retainer plate thing, and the timing set is offset differently, to make up for the different thickness at the front of the block from the addition of the plate. That may be what they were talking about, although it seems to me that the end result of the factory roller setup puts the timing chain in the same plane as a flat-tappet setup would. I can't imagine anybody making an aftermarket timing cover that won't fit those cheap "truck roller" chains that everybody uses in street hot rods, which are the same width as real roller chains.