JP86SS

iTrader: (1)

Like the title says I am putting a Non-retro hydraulic roller cam (XR-276HR-12) into my 817 406.
The parts arn't going together as expected and I'm looking for some guidance/experience.

The timing chain I bought is for a flat tappet (for early years) and the roller cam has a smaller bolt pattern.
Looking at a lightly used cam gear I had, I was able to install it using the new chain and crank gear.
Tooth profile lined up and looked virtually the same albiet a little bit of wear.

I purchased a torrington bearing and a roller button to use on this as I know the cam will want to push forward.
The torrington makes up the space behind the gear to keep the chain straight and the lobes appear to be centered over the lifter bores.
Q1: What keeps the torrington straight to the center of the cam behind the gear?
(both gears do not have a way to keep it centered and I am bothered by this)

The button that I have "seems" to fit with the larger end fitting into the "flat tappet" gear with the small side out to the cover.
Seeing how the roller cam has a smaller center, the button will not work with the roller gear.
Q2: Is there a different button just for rollers in old blocks?
I must be missing something here, If someone has some insight it would be greatly appreciated.
TIA

sofakingdom

iTrader: (1)

Then you simply bought the wrong cam. You have a step-nose cam for the factory roller system, whereas what you really needed was the original design roller cam, commonly referred to as a "retrofit" since the time the factory finally got wise to the idea about 20 years later than everybody else.

Then you need to un-know that; the sooner the better. THe oil pump puts a MASSIVE load on the dist gear, which in turn, pulls the cam INTO the block.

The non-stepped nose of the correct type of cam, and the "pocket" that must be machined out of the correct timing gear, that it was designed for.

Yes. You have it. It fits fine in the correct cam and timing set that it was designed for.

That's the root cause of the problem, right there: simply, the wrong cam.

Bottom line: get the version of the cam, whose part # will start 12- instead of 08-, and the timing set for that; and life will be good. I ran a 12-432-8 in my 400 for several years for example, and a 12-412-8 in another motor; it all fit and worked like a charm.

JP86SS

iTrader: (1)

Thanks for the feedback.
I used the LT1 cam in my 87' roller 350 for a while and figured I could use it in the 406 since I "hear" you can make rollers work in old blocks .

If the cam is pulling inward I can see the benefit of the torrington (of which I have never seen any notes about machining needed in the gear but makes sense since there is no way to hold it) but why is it suggested to use a cam button and external bolts from water pump housings to reinforce the cover ?

I may just use a solid roller cam I have instead but will probably need some more head work to obtain the lift clearance needed.
Was hoping to avoid that until later and use the current setup for now.

EvilCartman

iTrader: (1)

I'm running a cam out of an LT1 in my block right now. Ordered a timing set for a '92 Camaro with roller cam (smaller bolt pattern on cam), used the cam plate off the LT1, drilled and tapped holes for that, then got some hydraulic roller lifters with link bars to plop in. Some people even just cut the ears off the cam plate and let it spin around, not sure about that one though.

sofakingdom

iTrader: (1)

A flat-tappet setup pulls the cam into the block EVEN MORE than a roller, since in addition to the oil pump load on the dist gear, there's also the result of the bias of the lobes, whereby the rear side of the lobe is taller than the front side, and the lifter isn't "flat" but rather is spherical with about a 5' radius. So if millions and millions of those are running just fine without a Torrington, you can be fairly confident that a roller - with LESS force on that place - won't "need" one either. Which is not the same as saying it's not a good idea, just, not "necessary".

The chain also helps retain the cam.

Yes you can make a spacer out of a cam retainer plate by grinding off the ears. Works fine. Probably a good idea to polish its surface a bit so it doesn't wear on the block since it will probably spin; you could bolt it if your block can accomodate that gracefully, not all blocks can.

The reason for the cam button is that if a roller cam DOES slide forward for any reason (in a wreck while running for example) the result would be even more disastrous that a flat-tappet. It's not "necessary" as such, any more than your car won't work unless it has insurance; rather, it eliminates the chance of REALLY BAD things happening.

In a racing setup with a solid roller and 3 times the spring pressure as a stock flat-tappet though, there's ALOT of force on everything in there, which means the force retaining the cam may not be enough. That's when a cam button with a reinforced cover is indispensable. For a typical hyd roller like the one you have, just one of the little nylon buttons whittled down to where it fits among the bolts, and a stock cover, could probably be enough. Again, like insurance. How much life insurance do you have? Is it "enough"? If you can answer that question definitely, maybe you can figure out if your cam is retained "enough".

Still, in your situation I'd just get the right cam, and be done with it. Trade in your late-model cam for a "retrofit" one. While you're at it, consider having them grind it on a -9 core (billet) instead of a -8 (cast); doesn't cost all that much extra, and makes the cam considerably more robust.

fireturd350

iTrader: (8)

I'm running a solid roller in a 70s truck block without issues. I had just the normal stuff done when machining new freeze plugs, etc. I'm using the heavy duty CompCams 3 piece cover, cam button, and a gear drive. I'm not using any wear plates or torrington.

I also went through 3-4 different cam buttons before I found one I actually liked. I ended up bypassing the solid metal ones for the nylon type that you can adjust with shims and a snap ring.

I vote on getting the right cam.

JP86SS

iTrader: (1)

Yep, retro cam looks to be the directon I'll go on this.
I bet there are more "cobbled" applications out there where people read that its possible but the details are not clear, so they have to make decisions they would have avoided otherwise.
Thanks again,
John