No. The cam gear doesn't ride against the plate.
SB Cam Thrust Plate P5249637 no longer made? Only tensioner now?
- Thread starter dstemmerman
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MopaR&D
Nerd Member
The tensioner rubbing block gets "sliced" up over time running a double-roller chain because the contact area is much smaller; the chain is rubbing on the three small surfaces of the chain links whereas on a stock-type chain the entire width is in contact with the tensioner.
I saw this first-hand on a COMP timing set and tensioner I pulled from my 360 with 25k miles, thin grooves worn into the tensioner pad... this time for my Magnum build I'm using a Cloyes billet true roller and no tensioner.
I have at least 2 spare thrust plates sitting around but if I did need one I'd just get it from the junkyard.
I saw this first-hand on a COMP timing set and tensioner I pulled from my 360 with 25k miles, thin grooves worn into the tensioner pad... this time for my Magnum build I'm using a Cloyes billet true roller and no tensioner.
I have at least 2 spare thrust plates sitting around but if I did need one I'd just get it from the junkyard.
The cam just floats in the bearings. There is no fore and aft spec that I know of. The thrust plate keeps it from coming out, the chain keeps it running true. The Welch plug in the back of the block does nothing but seals up a oil leak.
Thank you!
Duane
Well-Known Member
Then what prevents the cam from trying to go out the back end of the block and why does my milodon gear drive have a Torrington bearing on the front. I believe the thrust force is on the camshaft side, but we have to control end play in both directions no?
Let me think of the rotation. The oil pump/distributor drive gear pushes it forward as it's driven I believe.
nm9stheham
Well-Known Member
No, not the cam gear... it is the thrust plate... which is why it is called that!
I just looked at my 340 trust plate and, despite the light surface rust, it looks like the wear is on the back, not the front, so I have it backwards. If so, then TMM is right, the thickness does not matter for the running cam location.
I just looked at my 340 trust plate and, despite the light surface rust, it looks like the wear is on the back, not the front, so I have it backwards. If so, then TMM is right, the thickness does not matter for the running cam location.
MopaR&D
Nerd Member
That's what I was gonna mention, I noticed that difference when working on big blocks, those need more cam thrust support because the distributor drive gear doesn't "push" the cam forward as it rotates. I think? Lol
nm9stheham
Well-Known Member
I think you hit it on the head TMM, and I have been through that before and figured it out.... I just have forgotten. The reaction at the oil pump gear pushes the cam one way or the other. (I am also pretty sure the lobes are not flat front-to-back.)
Duane
Well-Known Member
Correct I no this because I performed an oiling mod to pressurize oil the camshaft side of the thrust plate. The gear drives are hard on that plate. As Ryan Johnson said to me, milodon has the roller bearing on the wrong side. The cam doesn't thrust in that direction.
But I am pretty sure that the cam gear when bolted on, traps the position of the cam between the thrust plate, so if that plate were thinner, you would have more end play. No spec that I know of.
I do not even think that tensioner plate is thinner. Just looks that way in the pic.
I looked up specs in the manual. The thrust plate and timing gear keep the cam in place. .002-.006 with a new thrust plate and up to .010 with a used thrust plate. "if not within these limits, replace the thrust plate."
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nm9stheham
Well-Known Member
That could well be.. I don't have one to measure... maybe someone does. But if the trhust is from the back, it doesn't matter once things are running. I just thought that a .156" plate would be danged hard to bend a tight 90 degrees as shown and not break.
So, perhaps it would not be all that hard to make a thrust plate, once the right steel is selected.
" A flat-tappet cam’s lobes are slightly tapered to promote lifter rotation. Roller cams feature a nontapered lobe surface. Because the lifter bearings roll across the cam lobes, this virtually elimin........................"
https://www.motor.com/wp-content/up...On-a-Roller-Cams-Lifters-Rockers-Oct-2013.pdf
Interesting that Milodon has the bearing on the wrong side. I think the cam naturally thrusts forward especially because the service manual manual mentions thrust plate wear.
If there is a end play spec in the manual, all thrust plates must be similar thickness.
nm9stheham
Well-Known Member
Seems like that would be the case. I'd sure like to hear a real measurement on the tensioner type..... assumptions and all that ya know....
Let me see if the FSM has a spec.
Kendog 170
Let the boy go !
I am out of my league here but doesn't the cupped washer on the cam bolt control the movement as well. When I tore down my motor, someone must have lost it and used a flat washer. Cam had crazy in /out play until I replaced it with proper washer then play was in spec. somehow cam was unaffected.
Nope no thickness spec in the manual.
Kendog 170
Let the boy go !
I believe the spec was 002"-.010"
Duane
Well-Known Member
Mopar performance used to sell a high strength cup washer for that because the stock ones used to collapse. So yes yours may have came loose.
No the washer does not control the end play. It merely secures the came gear to the came. The end play is control by the machining of the three components combined. The end play is probably just so oil can get between the parts.
In my AMC days, occasionally we would get in a noisy straight six, sounded like a small knock in front of the engine behind the timing cover. The cam would walk back and forth at idle, the factory fix, was a spring and a plastic button, the spring rode in front of the cam and the button, push against the cam cover...it worked well.
Are not the lobes of the cam ground with a slight taper, to help rotate the lifters. This alone is enough to push the cam forward against the thrust plate. If the thrust plate is “step” worn..it does need to be replaced.
I did install the tension-er with my new chain and sprockets a few years back, both the tension-er and thrust bearing where the same thickness. This coming winter when the motor gets a major over haul I will not be reinstalling the tension-er but will be gong with a better quality set or gears.....
Are not the lobes of the cam ground with a slight taper, to help rotate the lifters. This alone is enough to push the cam forward against the thrust plate. If the thrust plate is “step” worn..it does need to be replaced.
I did install the tension-er with my new chain and sprockets a few years back, both the tension-er and thrust bearing where the same thickness. This coming winter when the motor gets a major over haul I will not be reinstalling the tension-er but will be gong with a better quality set or gears.....
Duane
Well-Known Member
I have a brand new one at home. I will measure it when I get home today.
See post #36. We were looking for the thrust plate thickness.
"In my AMC days, occasionally we would get in a noisy straight six, sounded like a small knock in front of the engine behind the timing cover. The cam would walk back and forth at idle, the factory fix, was a spring and a plastic button, the spring rode in front of the cam and the button, push against the cam cover...it worked well.''
Chevy always did that. I think Mr Gasket had a tensioner button available.
"Are not the lobes of the cam ground with a slight taper, to help rotate the lifters. This alone is enough to push the cam forward against the thrust plate. If the thrust plate is “step” worn..it does need to be replaced."
Yes they are.
"I did install the tension-er with my new chain and sprockets a few years back, both the tension-er and thrust bearing where the same thickness. This coming winter when the motor gets a major over haul I will not be reinstalling the tension-er but will be gong with a better quality set or gears....."
Good plan. How many miles on the tensioner? It would be interesting to note the wear. Snap a few pics.
Chevy always did that. I think Mr Gasket had a tensioner button available.
"Are not the lobes of the cam ground with a slight taper, to help rotate the lifters. This alone is enough to push the cam forward against the thrust plate. If the thrust plate is “step” worn..it does need to be replaced."
Yes they are.
"I did install the tension-er with my new chain and sprockets a few years back, both the tension-er and thrust bearing where the same thickness. This coming winter when the motor gets a major over haul I will not be reinstalling the tension-er but will be gong with a better quality set or gears....."
Good plan. How many miles on the tensioner? It would be interesting to note the wear. Snap a few pics.
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