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Old 04-27-2012, 08:53 PM
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Solid roller cam alignment....how to adjust

Hello. Got a new solid roller cam for my sbc....nice piece. However when mocked up in the engine it seems the rollers on the lifters are all lining up towards the rear of the lobes....like the cam needs to be pushed in more. I have a .030 copper/bronze thrust washer behind the cam sprocket, the cam is pushed in as far as it will go, and the gears (cam and crank) line up perfectly with the .030 washer. The rollers are 100% on the lobes....just towards the rear and not in the center.

When I remove the thrust/wear washer, re-attach the sprocket and push the cam back in the rollers are centered on the lobes....so it seems to be off center .030. Is there a fix for this? I've been all over the net and can't find a resolution. I'm wondering if I need a different cam sprocket....if one even exists for this issue. Any feedback is appreciated. Thanks.

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Old 04-27-2012, 11:55 PM
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As long as the lifter roller is 100% on the lobe (including when the cam is all the way out against the cam button), you are good to go.

I suppose if this was bothering you to the point of distraction you could machine 0.030" off the crank gear to allow the thrust washer to be removed from behind the cam gear, and run the cam gear against the thrust face of the block, or machine the thrust surface of the cam gear to compensate for the thickness of the thrust washer, but I wouldn't. If you were to do either, I'd lean towards getting a parallel thrust surface behind the cam gear.

Don't forget to set up the cam button.

Last edited by cobalt327; 04-28-2012 at 12:00 AM.
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Old 04-28-2012, 09:02 AM
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Thanks for the post. I was toying with the idea of having both gears machined for the .030..in effect pushing them both further in towards the block....I guess it does bother me that the rest of the lobe surface is wasted and if the cam does walk for whatever reason down the road I could have a lifter roller come dangerously close to the edge.

If I leave it as is I will be making sure the cam endplay is as close to zero as I can get it.
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Old 04-28-2012, 09:36 AM
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Quote:
Originally Posted by leverhead
Thanks for the post. I was toying with the idea of having both gears machined for the .030..in effect pushing them both further in towards the block....I guess it does bother me that the rest of the lobe surface is wasted and if the cam does walk for whatever reason down the road I could have a lifter roller come dangerously close to the edge.

If I leave it as is I will be making sure the cam endplay is as close to zero as I can get it.
Btw..any reason you wouldn't machine the gears?
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Old 04-28-2012, 10:39 AM
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A roller engine should always use a cam gear with a Torrington thrust bearing. I say that because most of the thrust washer engines I have taken apart have significant wear on the washer and/or the block.
The gear must be machined to accept the bearing.
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Old 04-28-2012, 02:28 PM
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Quote:
Originally Posted by leverhead
Btw..any reason you wouldn't machine the gears?
If the thrust surface of the block wasn't square to the cam/crank centerlines, that would be reason enough to machine it. The thickness of the thrust washer is to accommodate any amount that would be conceivably removed from the block thrust face in order to make it square.

You have to remember- this block was never intended by the factory to use a solid roller cam and lifters, so there may be fitting required to make it "perfect".

Having the roller in FULL contact w/the lobe- including when the cam is fully out against the cam button- is the requirement that has to be met. This includes any possible flex in the timing cover.

As for torrington or thrust washer- I've always used a thrust washer. There's no way to protect against having the small needle bearings from a failed torrington bearing getting into the oil pan, then on to the rest of the engine. YMMV.
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Old 04-28-2012, 03:14 PM
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The Torrington bearing I'm referring to is a sealed unit, not the old style that was introduced 30 years ago. I suggest a timing set from JPP.

http://jpperformance.carshopinc.com/...id/31390/5981T
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Old 04-28-2012, 09:43 PM
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I feel that there's no reason to use a moving element bearing- sealed or not- in this application.

First, if the cam is installed and clearanced correctly, there is no significant friction/wear occurring at the back of the cam gear/block thrust surface. If wear IS seen in this area, it's due to the cam being installed incorrectly, or some other error in installation or manufacturing. And no bearing- torrington or otherwise- can be expected to compensate for a poorly assembled engine and/or faulty manufactured part(s).

And if there WERE to be a high load imposed on that area, for whatever reason, a solid thrust washer has a much greater load bearing surface area than the relatively tiny, and highly loaded points of wear provided by the torrington needles.

If the engine is assembled and clearanced as it should be, either will work. If there were to be a problem, I'd rather have a solid thrust surface than I would a moving element bearing to absorb/transmit the loads imposed on it.

Instead of beating a dead horse, I'll suggest the OP do a search here and elsewhere on the subject and then he can make a decision based on his application.

Last edited by cobalt327; 04-28-2012 at 09:49 PM.
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Old 04-29-2012, 01:23 AM
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Thanks for the replies. I've located the part#'s for both the timing set with the torrington bearing and the .030 thrust washer. Lots of info out there, good and bad, about using the torrington bearing.....i've been all over it the last couple days. Main issues are about the bearing blowing out and needles destroying the engine, although there are those who have been using them successfully. From what I can gather, the sprocket with the bearing is already clearanced for a roller cam, where if I use the .030 thrust washer I have to machine out .030 from both gears for the roller retrofit to get the lobes/lifters where I want them.

Machining the block at this point is not an option and not deemed necessary as everything looks good there as far as alignment is concerned. Having the lifters fully on the lobes at all times is my main concern here. Its hard to make a decision with all the conflicting info out there, but it seems there is piece of mind to be had with the thrust washer.

Either way, I dont want the cam sprocket riding against the block if I can help it.
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Old 04-29-2012, 08:51 AM
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I've seen both types used with success and both fail. The "squareness" of the block face is seldom an issue (unless damaged), as it's just as important with a flat-tappet hydraulic as it is with a solid roller, if not moreso. That's an area the factory did a pretty good job. The flat-tappet "forces" the cam to the rear with the "rake" on the lobes, so the gear is "rubbing" the block at all times.

The timing cover plays a role here as well. The stock ones are a bit flimsy. Though they do "work", some oscillation can occur, beating the front of the block. A reinforced version or a more solid "cast" or billet type is prefered. Setting camshaft end-play is important. It's a bit easier in engines with thrust plates. And while the bearing-type sets are available for them, too (Fords, Pontiacs), we routinely rev them hard with no bearing and they live just fine.

Agreed, 100% wheel "contact" is the minimum requirement for position.

Jim
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Old 04-29-2012, 09:33 AM
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The cover I have now is a 2 piece aluminum cover - heavier than stock, but has no re-inforcment inside for a cam button (which is nylon) but seems to work fine. I may change it out with one that has a cam endplay adjustment built in.

P body,
You say you dont' use the bearing type sprocket...do you use the thrust washers instead and if so do you machine the gears for them? Thanks.
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Old 04-29-2012, 11:53 AM
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I use the cheap aluminum covers available anywhere. I install the cam button and measure the standoff from the timing cover mating surface and machine the cover contact point for the button to get .005". +/-.002" endplay. I use Permatex gray sealer and no gasket.
I have seen shims to go between the cam gear and the nose of the camshaft if you really want to move the cam back in the engine, but some diligence on calculating the maximum thickness would be required.
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Old 04-29-2012, 11:59 AM
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Quote:
Originally Posted by leverhead
You say you dont' use the bearing type sprocket..
Not presuming to speak for anyone but myself here, but the application in question is when a thrust or retainer plate is used- like the '86-up Chevy blocks that are machined for a hydraulic roller, or the Pontiac, for instance.

Because a cam retained by a thrust plate tends to be limited in its motion both fore and aft- and there's no flexing of the timing cover to act as a spring to launch the cam/cam gear rearward- there's less chance for the cam to "pound" the gear against the thrust surface. Because of that, wear would be expected to be less than if the cam was being helped by the springiness of the timing cover or if the cam-to-timing cover clearances were greater, allowing a 'running start' for the cam gear to contact the block.

The natural movement of a cam in an engine can be in either direction. On a Pontiac, the distributor rotated opposite of a Chevy, so this tends to push the cam out the front of the block- I suspect this is one reason a thrust plate is used from the factory. On the Chevy, the cam tends to be pulled rearward (or into the block) by the direction of rotation of the cam gear. This can be partially offset by the angle of the cam lobes on a flat tappet cam. But when a roller cam is used, the distributor gear is the only force acting directly on the cam (harmonics are another matter); the lobes do not have any taper to help rotate the lifters and offset the distributor gear's tendancy to push or pull the cam.
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Old 04-29-2012, 01:20 PM
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Yes I saw the cam 'snout' shims but with .030 I wouldn't be comfortable with the cam 'sticking out' of the cam sprocket that far.

Btw, again this is a early sbc retro-fit roller setup....so no retainer plates.
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