What is correct cam end play for Gen VI, and how do you set it?
 

I know the Gen VI motors use the step nosed cam with the retainer on the front of the engine, but I just installed my roller cam for a mock up with the correct GM retainer, and it seems like it has a lot of end play to me. I don't have a dial indicator handy at the moment, but when I checked it with feeler gauges it looks like about .050. Is that way out to lunch? If so, do I have to install shims behind the retainer to adjust it.

Thanks!

What gear do you have install?
I have a step nosed cam, cam plate in front the block, with gear set with torrington trust bearing, when it was all new i have .003-.004'' of end play, now after 80h runing i have .010'' of end play that i think that is ok but i am not an expert.

I think it is a cloyes, and it has the torrington thrust bushing. It is a double roller that was designed to work with the GM Gen VI cam retainer.

Here are a couple of pictures that illustrate exactly what I am talking about:

Here is the nose of the cam protruding from the cam retainer. It is pushed forward as far as it can go. Notice probably about 0.10 of the cam nose protruding through it.

http://i1224.photobucket.com/albums/...211_212731.jpg

Here is a shot of the cam after I push it back towards the rear of the engine. Note that it goes all the way back so almost none of the step is showing:

http://i1224.photobucket.com/albums/...211_212741.jpg

It doesn't seem like there should be this much rearward play in the cam to me. What limits how far back in the block the cam can go? Is it the rear plug?

Do I have a problem here or not?

fixx
 

it needs to be measured once the gear in installed with a dial indicater..

the cam gear controls how far back it can move. you need to see what you have with the gear on.

guess we were typing at the same time!

Does it matter if the chain is on as well, or can I measure it with just the cam gear?

Does anyone know what measurements I should expect?

.003 to.005 is the norm. if you just want to check end play you dont have to have to put the chain on.good luck

On mine thats the end play i have when the gear set was new, now i have .010'' after 80 hours of running dont know if is that too much, the extra end play that i have come from the torrington trust bearing.

.010 will not hurt . if theirs no gauling . .010 is not enough to cause the lifter from one side to touch the lobe from the other side. nor will it cause spark scater.

Pretty sure it's more than that based on what I saw before with the gear on it, but I will get a dial indicator on it today. How is this corrected if the end play is too much?

are all the parts new? check out the end play and let me know.

Everything is new, but cam gear has 30 hours on it.

Checked it again with the cam gear installed and torqued, and now I have ZERO play. My cam gear does have the built in Torrington thrust bearing, so maybe that is by design, but I was expecting it to have a few thousandths.

sorry ive never used the Torrington in a gen 5 or 6 so im not sure if .000 is enough end play i would think .002 or .003. I allways hse the stock thrust plate and have no problems good luck...

Does it turn freely when it was torqued in place without chain?

I remember mine when it was new at .003'' i canot fell the end play by hand you nead a dial gauge to see them.

Also on mine i open up a litle the cam edge plate dia because the gear does not turn freely when torque in place due to the rear retaining bearing ring (you can see them in the iner side dia of the bearing near the bearing cover) was a litle thicker then the bearing, that is was cause the 0 end play and the restriction if you heve one when you turn the gear by hand.

Thats a trust bearing and you need .003-.005'' end play, if they are too tight it wont last.

Sorry i dont have anny pic to show you what i am trying to explain hope thats can help you

Super MX,

The cam does turn freely, but I can feel a little bit of resistance when I turn it. This seems to be the case whether or not the gear is installed and torqued down, so I don't think it is because of the gear / torrington bearing. I pulled the cam back out and inspected it, and all seems fine there - cam journals don't have any burrs or high spots. Temp in my garage is about 45*, so it may just be the fact that the assembly lube is thick. I don't feel any binding at all when I turn it, just a little drag - in other words, it's not like you can just spin it and take your hand on it and it will continue to move. You have to continue to apply a little bit of force - maybe a foot lb or two at most. Probably normal - I talked to Bob Madera about it yesterday and he said he doesn't think I have a problem. He said in general you don't even have to check end play with a Gen VI cam retaining system.

I wish I had another cam handy to compare it to. What would really be nice would be to have the old cam that I was running before - it ran with the same timing gear for 30 hours with no issues at all. That would be a good comparison to make.

I'm probably way overthinking this whole thing, but it's the little things like this that keep me up at night. :fear:

For sure you still have a litle restriction due to lube thickness
But on mine i was feel more restriction when the gear was torqued on vs non torqued. So thats why i have work a litle the cam retening plate due to the imperfection of the torrignton bearing.
If you have already run 30h with that gear and cam you are probably ok.

Just make sure you have no differrance when the gear is on non torqued vs the gear torqued on.

Measurements
 

I still wasn't quite convinced that I don't have an issue, so I set my mind to trying to get some answers. First thing I wanted to do was figure out what timing set I have. After some investigation, it looks like it is the same thing as the ones that Summit and Jegs both carry under their house names. For example, the one Summit lists is PN SUM-G6617-B => http://www.summitracing.com/parts/su...b/media/images

It is a double roller set that has an entrained thrust bearing built into the back of the gear.

http://i1224.photobucket.com/albums/...5_213333-s.jpg

Jegs also sells one under PN 20425. Jegs tech support couldn't really tell me much about required end play for their sets, but the guy at Summit claimed that these were designed to be run with zero end play. I wasn't completely satisfied, so I took it by a local speed shop that builds a lot of racing engines. His opinion was that at zero end play, you don't really have any way of ensuring that there is no excessive preload on the bearing, which could lead to failure. He thought I should have 0.002 or 0.003 at least.

So I took my micrometer out in the garage and took some measurements.

First I measured the depth of the nose of the cam protruding from the retainer. I got 0.115".

http://i1224.photobucket.com/albums/...215_210656.jpg

Next I measured the depth from the face of the torrington bearing to the surface of the gear that rides on the nose of the cam. For this I got 0.120".

http://i1224.photobucket.com/albums/...215_210740.jpg

That would indicate that I actually have about 0.005" PRELOAD on the bearing.

Just for grins, I took another measurement of the depth of the back of the gear that mounts on the nose of the cam, and got 0.107". I laid a straight edge across the face of the thrust bearing and slid a feeler gauge, and it sits between 0.002 and 0.003 above the edge of the gear. So that should give me a total stacked distance of about 0.109 - 0.110. Theoretically, that should show up as about 0.005 end play, so I am a little confused by this measurement.

I am going to try mounting a different timing gear on the cam that is in the engine, and I am also going to try a different Gen VI cam just for grins to see if I can isolate the problem.

You should invest in a dial indicator with magnetic base. They can be used for all kinds of things and pretty inexpensive.
http://www.amazon.com/inch-Dial-Indi...+magnetic+base

I have one - that is how I determined that there is zero end-play. I was using the mic to figure out why.

I guess the way to correct this would be to mill about .007 from the cam retainer.

just my worthless opinion but you dont want zero endplay because although the torrington bearing can carry the load, the step of the cam would be forced against the retainer which would be steel on steel and with no clearence it would push out any oil and heat up quick. I try to stay away from the house brand stuff for timing sets as they have been all over the place on measurements. also check the retaining plate to make sure that it is perfectly flat on both sides and you dont have a burr or deformation causing a tight spot.

I think thats an option that you can do, Make sure that the inner edge of the bearing is not thicker than the rest of the bearing surface, is what i have fond on mine and is what cause the zero endplay before i work on the cam retainer.

I solve the problem by openning up a litle the cam retainer plate hole diameter to clear the (inner edge thicknes of the bearing).

If you put a strait edge on top of the bearing can you see if you have a thicker part on the bearing?

Be very careful when using your caliper to measure the step as you are. If the caliper isn't held perfectly perpendicular, then your measurements will be in error. A depth mic would be best. Unless you have a base that mounts to your caliper, that'll work too when using the depth rod. Or use the other end if possible. Thatl'll give your a larger surface for a more accurate reading

Exactly what I was thinking. No way measuring with a caliper will be trustworthy. What I'd do at this point is get some .005 shim stock and put it under the gear/cam interface and see what you have for end play when tightened up. Then you can make an accurate judgement on how much to cut the plate.

FYI. If needed you can run the thrust plate under a surface grinder to reduce its thickness. You might also try another thrust plate I have seen them vary as much as .003 pretty rare though.

Just for grins, last night I ran over to my buddy Tim's with my gear and cam retainer and did a little measuring and mock up on a step nosed cam that he had laying around. I installed the cam retainer and gear on his cam, and torqued the cam gear down as specified, and immediately noticed that it seemed to have a little more room around the retainer. Sure enough, we were able to shove a .003 shim between the retainer and the face of the cam, so .003 end play with that setup, just like it should be. I measured the nose of Tim's cam, and came up with 0.238, versus 0.234 that I got on my cam. On my billet cam, you cannot get any feeler gauge in there.

I stacked the retainer on top of the face of the thrust bearing as it would mount in the block, and measured the depth back to the gear face where it rests on the stepped nose of the cam, and after several careful measurements, concluded that I have 0.235 in this dimension. I verified that by measuring the thickness of the retainer (0.121) and the distance from the thrust surface to the gear face (0.1314). My cam measures 0.234, which means I still have preload on the thrust bearing. I can confirm this by the fact that with the cam removed from the engine and the retainer and gear installed on the cam, I can feel some drag and stiffness when I rotate the retainer against the thrust bearing on the end of the cam.

I am wondering if it would be better to shim the gear off of the nose of the cam with some .004 or .005 stock, or have some material removed from the retainer. FWIW, when I pulled the retainer off the block yesterday, one of the ears broke off, so I will need to get a new one anyway. I am leaning towards the shim - anyone know where I can find some stock this thin?

Dont know if you can find the shim to do what you need , let us know if you find that shim.

I might just try to find three 0.005 thickness washers that have an ID close to the cam gear retainer bolts. Also thought I could even cut up an old shim gauge and stick the pieces in there.

fixx
 

like mentioned..you can surface grind the outside of the plate to achieve the clearance needed..

Just to be clear, my suggestion on the making up shim material for under the cam/gear interface was for mock up only. You will need to surface grind the retainer to the right thickness once you know how much to remove, and then remove the shim material.

I agree. Shim to check. Grind to use

Honest question - why is it necessary to take material off of the retainer versus simply shimming the cam gear out with some 0.005 shim stock? Are we concerned with shearing the cam gear bolts? I don't see where the shim stock itself can actually go anywhere, since it will in effect be entrapped behind the gear.

Question for some of you that have a machinist or engineering background - should a Torrington thrust bearing have end-play on it, or should it in fact have zero end-play or even preload? They are, after all, designed to take "thrust" up against their surface, hence their name. Also, from what I understand, roller cam's tend to try to spit the cam out the front of the engine versus having it walk back towards the distributor as with a flat-tappet engine, so it seems like the cam retainer is going to have the majority of the pressure on it.

You need some clearance cold to leave room for the metal to grow and not get into a interference situation. Plus it is impossible to know for sure if you have zero clearance and not actually negative clearance (interference).

The reason I would not want to shim under the gear in application is I'd be afraid of creating runout in the gear with my home made shim. Surface grinding will be quite precise.

BT, my line of thinking is that since I have determined that the problem is with the step not being deep enough on the cam, I could be in a situation where the cam gear is out of alignment with the crank gear. If the cam gear is now 0.004 closer to the engine, wouldn't that throw off the alignment for the chain? Decreasing the thickness of the retainer does not address this, but installing a 0.004 shim behind the timing gear does. I could easily check for runout with a dial indicator against the timing gear.

FWIW, at lunch I ran by the engine shop and measured another Gen VI cam. I got 0.238, just like the other one. Installed the gear and retainer and had plenty of clearance. Was able to get a 0.005 feeler gauge in between the cam and retainer.

Your chain won't even notice .004" misalignment. If you were able to purchase a stamped, hardened shim made for the snout of the cam I might consider do that. But to make one out of random shim material and expect that to hold up under the pulsation of cam lobes/harmonics and not disinigrate/fall apart is risky in my estimation.

Have you researched getting a thinner thrust bearing?

why not just have the nose of the cam cut back .003?

How do you go about doing that? They would have to cut back on the step, not the face of the cam.

I dont think a spacing shim would hurt anything between the back of the gear and the cam step face, if that shim is well built!