SB Cam Thrust Plate P5249637 no longer made? Only tensioner now?

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dstemmerman

dstemmerman

1972 Dart Swinger Denver
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It seems as though the powers that be think the chain tensioner is mandatory now. Is there a reason a guy can't just buy a new small block cam thrust plate (P5249637) instead of a chain tensioner? Looks like the Mopar Performace version is even hard to find. I could only find the Mancini version. Mancini Racing Timing Chain Tensioners
 
Open a wanted thread if you need one. I wouldn't use a tensioner unless you are using a stock type chain and gears. Double rollers don't need one. The Tensioners are just stock Magnum engine parts. any parts store can help you there.
 
toolmanmike said:
Open a wanted thread if you need one. I wouldn't use a tensioner unless you are using a stock type chain and gears. Double rollers don't need one. The Tensioners are just stock Magnum engine parts. any parts store can help you there.
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Good suggestion. Thanks Mike! Still curious why no one makes the thrust plate anymore.
 
toolmanmike said:
Open a wanted thread if you need one. I wouldn't use a tensioner unless you are using a stock type chain and gears. Double rollers don't need one. The Tensioners are just stock Magnum engine parts. any parts store can help you there.
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Why would you not use one with a double roller. They have some slack in them too, just curious.?
 
Does not seem like it would be all that hard to make a thrust plate from stock plate material... What I don't know is the surface hardness where the sprocket rides.
 
Duane said:
Why would you not use one with a double roller. They have some slack in them too, just curious.?
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The tensioner blocks that rub the chain were made for narrow single width chains. A good doube roller is plenty strong. Just my opinion that they aren't necessary. I put one on my 273 when I built it but I wouldn't do it again.
 
Duane said:
Why would you not use one with a double roller. They have some slack in them too, just curious.?
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There is also some tensioner block wear and that plastic has to go somewhere. Hopefully the oil filter catches it all.
 
Duane said:
Why would you not use one with a double roller. They have some slack in them too, just curious.?
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IMHO.... the rubbing block material is the wild card. There have been reports of them falling apart in not too many miles, and I've take one apart from a 4.7 where the rubbing block material was already brittle and cracking apart in a 10 y.o. engine. And then again, some seem to hold up just fine.

So it's a part that can (and has) failed erratically, with no good rhyme or reason that has been identified to my knowledge, other than possibly the materials used. I am not against them... I've raced 6-7k rally stage miles on engines that have them but they were much better built and of good quality materials, and they didn't fail or put plastic bits in the oil. The reports of what is out there for SBM's now seems erratic in quality/durability.
 
toolmanmike said:
The tensioner blocks that rub the chain were made for narrow single width chains. A good doube roller is plenty strong. Just my opinion that they aren't necessary. I put one on my 273 when I built it but I wouldn't do it again.
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So you are saying the plastic is not wide enough for a double roller.
I did not think strength had anything to do with it. I thought it was to keep the slack that all chain eventually get, from disrupting the cam timing.
 
Duane said:
So you are saying the plastic is not wide enough for a double roller.
I did not think strength had anything to do with it. I thought it was to keep the slack that all chain eventually get, from disrupting the cam timing.
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You're correct. A double roller will stretch less because of it's strength. As the chain wears and stretches the cam timing will change whether it has a tensioner or not and yes the tensioner guides are not as wide as a double roller chain. You can use one if you like. It will work as designed. I just don't think I will use one again for the above reasons.
 
toolmanmike said:
You're correct. A double roller will stretch less because of it's strength. As the chain wears and stretches the cam timing will change whether it has a tensioner or not and yes the tensioner guides are not as wide as a double roller chain. You can use one if you like. It will work as designed. I just don't think I will use one again for the above reasons.
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My car is a drag only car and I am using a milodon gear drive.
I was just curious on why you don,t like the tensioners. Cheers
 
Here is another question related to the tensioner type like shown on the Mancini site...... the plate used for that tensioner looks a lot thinner than the thrust plate used in an LA. That is gonna move the cam back in the block. At some point, doesn't this become a problem with where the lifter ride on the lobes?

Maybe there is enough tolerance so that it is not, but I was wondering what the plate thickness ought to be for an LA. I realized that I don't have one here to measure the thickness.

Edit: Never mind... found one. .156" thick.... 5/32"
 
If you have to line-bore the block for some reason a tensioner might be necessary. I use the Edelbrock timing chains, they are pretty tight and I've never had to use a tensioner with one. 65'
 
nm9stheham said:
Here is another question related to the tensioner type like shown on the Mancini site...... the plate used for that tensioner looks a lot thinner than the thrust plate used in an LA. That is gonna move the cam back in the block. At some point, doesn't this become a problem with where the lifter ride on the lobes?

Maybe there is enough tolerance so that it is not, but I was wondering what the plate thickness ought to be for an LA. I realized that I don't have one here to measure the thickness.

Edit: Never mind... found one. .156" thick.... 5/32"
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Nope, the cam stays it it's position whether the plate is .010 thick or .300 thick.
 
Duane said:
Agreed, that's why I went to a gear drive, takes out all the variables
and never changes.
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Noisy unless you are on the race track and need the timing stability.
 
Plymouth 65 said:
If you have to line-bore the block for some reason a tensioner might be necessary. I use the Edelbrock timing chains, they are pretty tight and I've never had to use a tensioner with one. 65'
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Absolutely!
 
toolmanmike said:
Nope, the cam stays it it's position whether the plate is .010 thick or .300 thick.
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How is that. The end play of the cam and it's running position are determined by a combination of the chain sprocket, the recess machined on the camshaft and the thickness of the cam plate is it not. I though the cam floats between the cam sprocket and the cam plate with each butting against the plate to stay in position.
 
toolmanmike said:
Nope, the cam stays it it's position whether the plate is .010 thick or .300 thick.
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Ok @Duane think about how those work. The front of the block is machined, as well as the cam plate. The machined surfaces butt against each other and the hole in the plate allows the cam snout to protrude but the cam can't walk forward. The thickness of the plate is on the timing cover side and doesn't go inside the block.
 
Duane said:
How is that. The end play of the cam and it's running position are determined by a combination of the chain sprocket, the recess machined on the camshaft and the thickness of the cam plate is it not. I though the cam floats between the cam sprocket and the cam plate with each butting against the plate to stay in position.
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I see what you mean.
 
This cam isn't going anywhere and the thickness of the plate doesn't control it.
Mopar Nats 2015 004.jpeg
 
toolmanmike said:
Nope, the cam stays it it's position whether the plate is .010 thick or .300 thick.
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Hmmm.... confused.... not the 1st time though...! On an LA.... Aren't the lobes are a bit taller at the back than the front so the lifters are constantly trying to push the cam backwards? So the IIRC, the back side of the cam sprocket is riding on the front side of the thrust plate..... and setting the cam location front-to-back, and changing the thickness of the thrust plate would change that location......?? I thought that was the reason for the thrust plate... Or do I have the thrust direction backwards?
 
toolmanmike said:
Ok @Duane think about how those work. The front of the block is machined, as well as the cam plate. The machined surfaces butt against each other and the hole in the plate allows the cam snout to protrude but the cam can't walk forward. The thickness of the plate is on the timing cover side and doesn't go inside the block.
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But is it not the cam gear that prevent the cam from walking the other direction.?
 
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