Timing Chain and Sprockets

[Matt Wilson]

I'm in the process of cleaning the various engine parts for assembly in my 265 engine build.  A couple of days ago, after cleaning the timing chain and sprockets, I decided to do a test fit of all three parts (chain, crank sprocket, cam sprocket) on the workbench.  Unfortunately, I could not get the parts to fit properly.  The two sprockets are NOS parts, but the chain is new (I believe it's Melling).  If you zoom in on the first photo, you can see that the crank sprocket overlaps the cam sprocket, which is the only way to get them both inside the chain at the same time.  The second photo shows that the chain fits pretty well around the crankshaft sprocket, although there may be some small gaps in some places.  The third photo seems to indicate a more obvious issue, in that the chain meshes well with the cam sprocket for probably about a 110 or 120-degree arc at the top, but then it starts to diverge from the sprocket as you go down the sides, with larger and larger gaps the farther down you go (you can see this in the first photo, too).  I am unable to force the chain into mesh at the sides, so I think there must some slight mismatch between the chain and the cam sprocket that adds up with each successive tooth, to the point where it just doesn't mesh at all on the sides, and consequently, the chain is effectively shortened and therefore doesn't allow both sprockets to fit at one time.

 

Has anyone else run into this issue?  Am I missing something here and doing something wrong?

 

I plan to call the vendor who sold me these parts, to see how this can be remedied, but meanwhile, I wanted see if anyone has had or heard of this issue.

Edited December 30, 2021 by Matt Wilson

[bkahler]

Wow.  Never saw an issue like that before.  Everything seems to point to the cam gear being defective.  I'm really curious as to how this works out in the end.

 

Good luck!

 

[Matt Wilson]

55 minutes ago, bkahler said:

Wow.  Never saw an issue like that before.  Everything seems to point to the cam gear being defective.  I'm really curious as to how this works out in the end.

 

Good luck!

 

Thanks, I'll try to remember to post back here to let everyone know how it turned out. Funny thing is, everything on all three parts looks perfect to the naked eye - very nicely machined, formed, etc., but it just doesn't fit the way it should.  I wonder if it has anything to do with the use of NOS DPCD sprockets with a new chain made by an aftermarket manufacturer.

[bkahler]

If the chain fits the crank sprocket just fine but not the cam sprocket then I would think the cam sprocket is the odd duck.

[Plymouthy Adams]

for sure this is appropriate...TWO OUT OF THREE AIN'T BAD

[Matt Wilson]

1 hour ago, bkahler said:

If the chain fits the crank sprocket just fine but not the cam sprocket then I would think the cam sprocket is the odd duck.

Right, I tend to agree.  Having said that, there does appear to be a little bit of gapping in the last couple of teeth on either side of the crank sprocket, which by the way, is at about the same number of engaged teeth as where the gap shows up on the cam sprocket....so if the crank sprocket was bigger, makes me wonder if would also show a more obvious issue, like on the cam sprocket.  If so, then that would point to the chain as being the culprit, which could make some sense, since it's new and the sprockets are NOS.  Anyway, it's hard to say.  I wouldn't mind trying a NOS chain, if they have one, but I also wouldn't mind trying a different NOS cam sprocket.  I'll talk it over with the supplier.

[Dave72dt]

Have you laid the chain over the old parts or the new parts over the old parts and compared?

[Matt Wilson]

26 minutes ago, Dave72dt said:

Have you laid the chain over the old parts or the new parts over the old parts and compared?

I've laid them out side by side for visual comparison, and have also counted teeth on the new and old sprockets, counted links on the new and old chains, and have taken measurements of tooth and link spacing, and chain length and sprocket diameters (as best I could, using calipers), and they really SEEM to be the same, except that the new parts are the thicker ones, whereas the old parts are the thinner ones (1" vs. 7/8" as measured by chain thickness).  I think there must be some really small difference that adds up with each successive tooth, until it amounts to a difference that's big enough to cause the problem I'm seeing.

 

One more thing I could do is try to fit the old sprockets into the new chain and see how they do.  I may do that at some point, but that will require cleaning the old sprockets, as they are filthy from laying oily in a box in my garage, and I don't want any of that crud anywhere near my new chain, since it's nice and sparkly-clean.  Also, the old crank sprocket is still installed on the 251 crankshaft that I'm not using, but I could probably get a good idea of how well things fit without taking it off the crank.  My hesitation on both those items is just laziness and time consumed to do them. 

Edited December 30, 2021 by Matt Wilson

[Dave72dt]

But how does the old chain lay over the new cam sprocket.  It doesn't look like the chain overlaps the edge of the sprocket teeth.  I understand you want to be using all new parts but it's information you can use when talking to the supplier.

[bkahler]

You should be able to wrap that chain all the way around the new crank sprocket.  If it doesn't then somewhere in the mix there is a problem.

[Matt Wilson]

1 hour ago, Dave72dt said:

But how does the old chain lay over the new cam sprocket.  It doesn't look like the chain overlaps the edge of the sprocket teeth.  I understand you want to be using all new parts but it's information you can use when talking to the supplier.

I thought about that, but I doubt I'll be able to do that because the old chain is only 7/8" thick, while the new sprocket requires a chain that is 1" thick.  I'll take a closer look to see, but I doubt it will work.

 

I think the closest I can get is wrapping the new chain around the old sprocket.

Edited December 31, 2021 by Matt Wilson

[Matt Wilson]

1 hour ago, bkahler said:

You should be able to wrap that chain all the way around the new crank sprocket.  If it doesn't then somewhere in the mix there is a problem.

The new chain wraps completely around the new (NOS) sprocket, although some small gaps start showing up at the edges, butI might be able to close those if I pushed on them a bit.   

 

If you're talking about wrapping the old chain around the new sprocket, I don't think I'll be able to do that because the old chain is only 7/8" thick, while the new sprocket requires a chain that is 1" thick.

[bkahler]

1 hour ago, Matt Wilson said:

The new chain wraps completely around the new (NOS) sprocket, although some small gaps start showing up at the edges, butI might be able to close those if I pushed on them a bit.   

 

If you're talking about wrapping the old chain around the new sprocket, I don't think I'll be able to do that because the old chain is only 7/8" thick, while the new sprocket requires a chain that is 1" thick.

 

No, just the new chain around the new sprocket.  A chain is going to stretch so if it basically fits the sprocket now even a few thousands stretching should happen immediately.  It sure sounds to me like your cam sprocket is the odd duck here.

[JBNeal]

I was under the impression that new timing chains these days need to be accompanied with new timing gears so they match pitch.

[billschwindt]

you have mismatched parts. all parts should be purchased as a matched set in one box! 

[Matt Wilson]

3 hours ago, JBNeal said:

I was under the impression that new timing chains these days need to be accompanied with new timing gears so they match pitch.

 

1 hour ago, billschwindt said:

you have mismatched parts. all parts should be purchased as a matched set in one box! 

Ah, I see.  That is making some sense in the context of my issue here.  I'm really surprised the vendor supplied these parts to me.  I'll clean the old cam sprocket and see how it does in the new chain, but I'm starting to suspect (and especially with your comments) that the chain is not right for the sprockets, since they are not matching sets.  Thanks for the input.

[lostviking]

I have to disagree. The chain does not properly fit the crank sprocket. The mismatch is visible in the second picture, as you pointed out. Since there is a lot less sprocket, the small spacing error between the OEM sprockets and the chain never gets as large, but the chain is not correct.

 

Edit: should have read them all, especially your last. Yes.

Edited January 1, 2022 by lostviking

[kencombs]

On 12/30/2021 at 6:07 PM, Matt Wilson said:

I thought about that, but I doubt I'll be able to do that because the old chain is only 7/8" thick, while the new sprocket requires a chain that is 1" thick.  I'll take a closer look to see, but I doubt it will work.

 

I think the closest I can get is wrapping the new chain around the old sprocket.

I just reread this and finally caught the 7/8 vs 1" part.  Clearly not the correct parts.  

[John-T-53]

On 12/30/2021 at 8:35 PM, billschwindt said:

you have mismatched parts. all parts should be purchased as a matched set in one box! 

 

This is the solution. Get a matched set otherwise it'll never be right.

[Matt Wilson]

5 hours ago, kencombs said:

I just reread this and finally caught the 7/8 vs 1" part.  Clearly not the correct parts.  

Right, well, to clarify - the chain outside thickness is 7/8 for the old one and 1" for the new one, but the old sprockets are nominally 1/2" thick, while new ones are nominally 1" thick.  When I purchased the parts, the vendor told me these two configurations existed, and they recommended I buy the thicker one, as it's more durable (makes sense).  See the first photo (not sure why it posted above all the text) showing crank sprockets for the two configurations - the 1/2" having a single row of teeth and the 1" having two rows.  The parts they sent me are all two-row parts, but obviously they don't mesh well with each other, probably because they are not a matcing set from the same manufacturer, as others have suggested.

 

For everyone's info, as a follow-up to a suggestion, I cleaned the old single-row cam sprocket and inserted it into the new two row chain to do a test fit.   Aside from only having one row of teeth, it fits really well all the way around the entirety of the sprocket, with uniform tooth spacing and gaps, as shown in the second photo.  This could point to the chain being the odd man out, but I think I just need to get a complete matching set.   I just wanted to try this out for more information 

Edited January 1, 2022 by Matt Wilson
Forgot the photos the first time

[Matt Wilson]

33 minutes ago, John-T-53 said:

 

This is the solution. Get a matched set otherwise it'll never be right.

I will ask for this.  Now, to be sure I understand, are you saying I need a matching set, as in all three parts made to fit each other specifically (like a differential ring and pinion)?  That's what it sounds like based on billschwindt's comment about needing to be in one box.   Or do they just need to be all made by the same manufacturer, such as all Melling parts or all Chrysler NOS parts, even if they're not necessarily in the same box?  I just want to be sure what I'm supposed to ask for.  Thanks. 

[Dodgeb4ya]

The 1954-56 DT parts book for the 23" and 25" engines show the timing chain and gear sets changed design in 1954.

Went from a early type chain and gear style....chain with a center groove guide.... and gears with a center cut groove for the chain guide.

The later new replacement chain and gears are made with out the center groove guide chain and no groove in the cam and crank gear.

And I believe this later style set is narrower too.

This applies to factory Mopar OE parts.... now days replacement cam chain and gears who knows... not me.

[John-T-53]

On 1/1/2022 at 12:47 PM, Matt Wilson said:

I will ask for this.  Now, to be sure I understand, are you saying I need a matching set, as in all three parts made to fit each other specifically (like a differential ring and pinion)?  That's what it sounds like based on billschwindt's comment about needing to be in one box.   Or do they just need to be all made by the same manufacturer, such as all Melling parts or all Chrysler NOS parts, even if they're not necessarily in the same box?  I just want to be sure what I'm supposed to ask for.  Thanks. 

 

I would talk to Melling and ask them. I'd guess that if you get Melling gears alone they are made for use with their chains. It's probably not that much cost difference, and perhaps even cheaper if you just order a complete timing set rather than individual gears, sans chain. But you'll have to ask your supplier.....good luck.

[Matt Wilson]

On 1/2/2022 at 12:06 AM, Dodgeb4ya said:

The 1954-56 DT parts book for the 23" and 25" engines show the timing chain and gear sets changed design in 1954.

Went from a early type chain and gear style....chain with a center groove guide.... and gears with a center cut groove for the chain guide.

The later new replacement chain and gears are made with out the center groove guide chain and no groove in the cam and crank gear.

And I believe this later style set is narrower too.

This applies to factory Mopar OE parts.... now days replacement cam chain and gears who knows... not me.

That's interesting.  The two-row (thicker) timing set with the center groove was billed as being more reliable, and if so, I figured this would be the type used in later years, but your parts book indicates the opposite.  This agrees with that fact that the non-groove (thinner, single row of teeth) was what I found on the engine when I dissembled it, and it was from an early 60's Power Wagon.  It seems like it would be the other way around, but it is what it is.  Thanks for the info.

[Matt Wilson]

5 hours ago, John-T-53 said:

 

I would talk to Melling and ask them. I'd guess that if you get Melling gears alone they are made for use with their chains. It's probably not that much cost difference, and perhaps even cheaper if you just order a complete timing set rather than individual gears, sans chain. But you'll have to ask your supplier.....good luck.

Yeah, that's a good idea.  I've already contacted the vendor who sold me the parts I have, but meanwhile, I'll look up Melling to see what I can find.