Roller cam lobe interference with adjacent lifters

[counterman]

I am mocking up my "new" combo on the engine stand, and have discovered an issue with lifter body clearance with adjacent lobes on the camshaft. I am using the Comp 210 hydraulic roller with PBM (Morel) lifters. On a lobe or two, I have slight contact with the adjacent lifter body. The lifters are not tapered at the rollers, and measure a full .8415 top to bottom. The cam lobes are lots wider than the old flat tappet I pulled out. The combination of those two plus block build tolerances is giving me the contact. End play is spot on, so I am going to have to modify something here. Either the lifters or the cam lobes are going to have to be cleaned up a few thousanths. I guess that the cam would be easier to modify, as the lobes are way wider than the rollers on the lifters, giving me room to file the sides of the lobes slightly. Cutting the lifter bodies could weaken the roller area, although I doubt it would matter given the little bit involved. Anyone else have this happen before? Just goes to show that you have to check and recheck everything on these motors to prevent a catastrophe. Thanks, Counterman.

 

[TurboBob]

I think this same thing may have been responsible for my roller cam failure a few years back.

http://www.turbobuick.com/forums/general-turbo-buick-tech/156664-downside-roller-cams.html

Generally, the cam is modified for clearance. Although I don't think a file is the tool of choice.

Perhaps others will chime in.

Bob

 

[Nick Micale]

The first batch of Comp's ductile roller cams had this issue of the lobes being too wide. I installed one of the first cams they made and found this problem, in the car unfortunately, and I talked to Comp about it.

We fired the car and heard this awful noise. Took a while to figure out what is was after we had damaged a couple roller lifters.

If this is a new cam, I would contact them for an exchange.

 

[bison]

I am mocking up my "new" combo on the engine stand, and have discovered an issue with lifter body clearance with adjacent lobes on the camshaft. I am using the Comp 210 hydraulic roller with PBM (Morel) lifters. On a lobe or two, I have slight contact with the adjacent lifter body. The lifters are not tapered at the rollers, and measure a full .8415 top to bottom. The cam lobes are lots wider than the old flat tappet I pulled out. The combination of those two plus block build tolerances is giving me the contact. End play is spot on, so I am going to have to modify something here. Either the lifters or the cam lobes are going to have to be cleaned up a few thousanths. I guess that the cam would be easier to modify, as the lobes are way wider than the rollers on the lifters, giving me room to file the sides of the lobes slightly. Cutting the lifter bodies could weaken the roller area, although I doubt it would matter given the little bit involved. Anyone else have this happen before? Just goes to show that you have to check and recheck everything on these motors to prevent a catastrophe. Thanks, Counterman.

Does the cam need to go rearward or toward the front of the block to correct the misalignment?

 

[counterman]

Thanks, guys. I figured someone else may have seen this before. Bison, I will be taking a closer look later today, once I can get back out to the shed. Thanks, again. Rudy.

 

[counterman]

Okay. In the light of day, it is obvious that the cam needs to move rearward in the block. The lifters on the 4 end cylinders interfere with the cam lobes as I rotate the cam. Cylinders 3 and 4 are okay. I used a pair of flat tappet lifters that I verified to be the proper o.d.. These are nice and square top to bottom, and they eliminate any visual trickery that the roller lifter might cause. The interference is from the lifters lightly rubbing the lobes to the rear of their positions. I am basically at zero clearance to the rear, but with tons to the front. I reckon about .040 off. Looking at the machined thrust area of the Comp piece versus my old flat tappet verifies the same. I have about .040 from the machined surface of the flat cam to the unmachined surface of the front of the cam. On the Comp piece, that same measurment is about .080. There's the problem. Now what? Do I tote the cam down to the machine shop and have .040 taken off the thrust, or do I toss it in the trash and start over--taking my chances that the next cam will be any better? Thanks, Rudy.

 

[TurboBob]

The interference is from the lifters lightly rubbing the lobes in front of there positions. I am basically at zero clearance to the front, but with tons to the rear.

doesn't this mean that the cam needs to move forward?

 

[counterman]

Sorry, Bob, I flubbed the description. I edited the post. Thanks, Rudy.

 

[bison]

Okay. In the light of day, it is obvious that the cam needs to move rearward in the block. The lifters on the 4 end cylinders interfere with the cam lobes as I rotate the cam. Cylinders 3 and 4 are okay. I used a pair of flat tappet lifters that I verified to be the proper o.d.. These are nice and square top to bottom, and they eliminate any visual trickery that the roller lifter might cause. The interference is from the lifters lightly rubbing the lobes to the rear of their positions. I am basically at zero clearance to the rear, but with tons to the front. I reckon about .040 off. Looking at the machined thrust area of the Comp piece versus my old flat tappet verifies the same. I have about .040 from the machined surface of the flat cam to the unmachined surface of the front of the cam. On the Comp piece, that same measurment is about .080. There's the problem. Now what? Do I tote the cam down to the machine shop and have .040 taken off the thrust, or do I toss it in the trash and start over--taking my chances that the next cam will be any better? Thanks, Rudy.

You can turn the thrust surface down the required amount to get clearance then add shim to take up the slack in the front. You shouldnt have to take off too much to get it to clear.

 

[counterman]

Bison, I will get the cam to the machine shop this week, hopefully. You are correct that I will not need much, as I am just touching the lifter to the lobe where the contact is occurring--zero clearance, more or less. The .040 figure would make it right on the money, with clearance aplenty on both sides of the lifters. I also measured the distance from the front of the dist gear to the back of the thrust area on both cams just for the heck of it. You have to figure that the gear location should be the same on both raw castings before any machine work is done. I have nominally 2.130 on the flat tappet piece, and 2.175 on the roller--or .045 difference that way, too. I am just happy that I caught this now, before sticking it back in the car. I wonder how many other cams like this are out there. It would have been easy to miss this, and it surely would have caused trouble shortly. Thanks to all of you guys on this forum! Rudy.

 

[bison]

Bison, I will get the cam to the machine shop this week, hopefully. You are correct that I will not need much, as I am just touching the lifter to the lobe where the contact is occurring--zero clearance, more or less. The .040 figure would make it right on the money, with clearance aplenty on both sides of the lifters. I also measured the distance from the front of the dist gear to the back of the thrust area on both cams just for the heck of it. You have to figure that the gear location should be the same on both raw castings before any machine work is done. I have nominally 2.130 on the flat tappet piece, and 2.175 on the roller--or .045 difference that way, too. I am just happy that I caught this now, before sticking it back in the car. I wonder how many other cams like this are out there. It would have been easy to miss this, and it surely would have caused trouble shortly. Thanks to all of you guys on this forum! Rudy.

Good catch. Every time i assemble one of these engines i find something like this unless its a stocker or i had previously assembled it and worked out those types of things previously.

 

[counterman]

Update! Got the cam back from the machine shop. I had them remove .040 from the thrust surface of the cam as planned. It fits like a glove now, with no lobe to lifter interference. I reshimmed the cam button, and all is good. Thanks, again, to the folks on this forum. Rudy.