Timing Chain Tensioner Extended too much?

[Captain Obvious]

Coincidentally, I've been messing around with the timing chain and tensioner stuff recently and with that in mind, I'm really wondering why your chain has so much slack in it.

I've compared a brand new timing set with all new gears, chain, and guides to a used set that has run 150K miles. Of course there was a some difference, but even the 150K used set has way less slack than what you have in yours. Now, of course, yours could be worn and stretched more than the used set I have here, but I'm thinking there could be something else going on.

As part of your rebuild process on the engine, did you have the head cut? Having material removed from the head can have a large impact on chain tension.

Also, you said you did not replace the chain or the tensioner. So what did you replace? Did you replace the guides with new, or are the guides used as well? I'm thinking if you got the head cut and reused all the old parts, that's what is causing the issue.

Edited November 11, 2023 by Captain Obvious
more detail

[Patcon]

Decking the block would also add slack.

[Ownallday]

7 minutes ago, Captain Obvious said:

Coincidentally, I've been messing around with the timing chain and tensioner stuff recently and with that in mind, I'm really wondering why your chain has so much slack in it.

I've compared a brand new timing set with all new gears, chain, and guides to a used set that has run 150K miles. Of course there was a some difference, but even the 150K used set has way less slack than what you have in yours. Now, of course, yours could be worn and stretched more than the used set I have here, but I'm thinking there could be something else going on.

As part of your rebuild process on the engine, did you have the head cut? Having material removed from the head can have a large impact on chain tension.

Also, you said you did not replace the chain or the tensioner. So what did you replace? Did you replace the guides with new, or are the guides used as well? I'm thinking if you got the head cut and reused all the old parts, that's what is causing the issue.

I believe the chain I have is the original one as everything I removed internally in the engine was all original so it's never been rebuilt but the engine was running before hand. I had low compression in all cylinders which made me do the rebuild. Do you think the chain will be fine for a 60 mile drive considering I could not force the chain out with my hands when the chain was installed? My head was resurfaced but the guy said not a lot of material was removed. I'll have to call Monday and find out how much they removed. I also do have a 1mm head gasket. The rebuild was mainly bottom end all new, head has new rockers and seals but same guides yes.

[Captain Obvious]

12 minutes ago, Ownallday said:

My head was resurfaced but the guy said not a lot of material was removed. I'll have to call Monday and find out how much they removed. I also do have a 1mm head gasket.

So you had the head cut and are using a custom head gasket that is thinner than stock. Both of those will contribute to the issue you are dealing with.

What about the timing chain guides (not the valve guides)? Did you replace those with new or are they the same ones that were in the engine when you started? This is one of the guides I'm talking about:

[Captain Obvious]

17 minutes ago, Ownallday said:

 Do you think the chain will be fine for a 60 mile drive considering I could not force the chain out with my hands when the chain was installed?

And I'm not comfortable with this. I don't think you should start the engine like that, let alone try to make it 60 miles. It's just too risky.

Edited November 11, 2023 by Captain Obvious

[Ownallday]

10 minutes ago, Captain Obvious said:

And I'm not comfortable with this. I don't think you should start the engine like that, let alone try to make it 60 miles. It's just too risky.

Figures, guess I didn't think about that with the head gasket. The guides are new so yeah I replaced those, the old ones were worn. Okay, guess I'll have to either have to ask my friend to hold onto the car a little longer or pay a really expensive tow truck fee.

[Ownallday]

Went ahead and spent the extra money to get a new timing chain set from Amazon so I'm not waiting, will knock it out Tuesday and hopefully solves my problem and I'll save the other timing chain for a rainy day. I ordered 0.015 cam tower shims too just to be safe but I really don't think I'll need them but just in case I do, do you guys think unbolting the head bolts and not replacing the head gasket is okay or do I need another head gasket if I do that route now?

[Captain Obvious]

The new timing set will certainly help, but depending on how much the machinist took off your head, even with all new timing parts, you might still find the tensioner sticks out further than it should. I've got typical head gasket thickness measurements around here someplace (not handy right now), but I'm thinking your 1mm head gasket is about .020 thinner than stock? So if the machinist took even .010 off the head, you're at a total of .030 from stock. Even with a new timing set, I'm worried your tensioner will still be out more than it should be. Maybe enough to limp you home, but still something you would need to address.

All of this is very fresh in my mind because I'm sitting here looking at my custom chain guide that I'm working on in order to bring my tensioner stickout back to acceptable range with my just completed .040 shaved head.

The .015 shims will help a whole lot, but then you run the risk of having your contact patch on the lash pads or rockers in the wrong spots. That said... I'm no engine builder, but I would be more comfortable with running with an incorrect contact patch for 60 miles than I would for that tensioner sticking out that far for 60 miles.

And as for the head gasket... Again, I'm no engine builder, but if you haven't run the engine at all, I'd be comfortable with leaving the head gasket in place if you were to pop cam tower shims in there. Follow the correct loosen and re-tighten sequence and procedure on the head bolts and I'd expect things to be OK. 

Which route to take kinda depends on how quickly you need to get that thing out of your buddy's way.

[Ownallday]

19 minutes ago, Captain Obvious said:

The new timing set will certainly help, but depending on how much the machinist took off your head, even with all new timing parts, you might still find the tensioner sticks out further than it should. I've got typical head gasket thickness measurements around here someplace (not handy right now), but I'm thinking your 1mm head gasket is about .020 thinner than stock? So if the machinist took even .010 off the head, you're at a total of .030 from stock. Even with a new timing set, I'm worried your tensioner will still be out more than it should be. Maybe enough to limp you home, but still something you would need to address.

All of this is very fresh in my mind because I'm sitting here looking at my custom chain guide that I'm working on in order to bring my tensioner stickout back to acceptable range with my just completed .040 shaved head.

The .015 shims will help a whole lot, but then you run the risk of having your contact patch on the lash pads or rockers in the wrong spots. That said... I'm no engine builder, but I would be more comfortable with running with an incorrect contact patch for 60 miles than I would for that tensioner sticking out that far for 60 miles.

And as for the head gasket... Again, I'm no engine builder, but if you haven't run the engine at all, I'd be comfortable with leaving the head gasket in place if you were to pop cam tower shims in there. Follow the correct loosen and re-tighten sequence and procedure on the head bolts and I'd expect things to be OK. 

Which route to take kinda depends on how quickly you need to get that thing out of your buddy's way.

I believe the OEM gasket is 1.2. I've ran 1mm head gasket before on a previous engine with a new chain and it was solid. I actually remember the tensioner sticking out slightly more than normal but wasnt excessive like what I have now. I suppose Instead of the shims I can just get a thicker head gasket and that would solve the cam geometry. What I will do is see how much the new chain and tensioner solves the problem, I think if it throws that tensioner piston back in at least 3-4mm would be good to run as is otherwise I might just look into a thicker head gasket even though I spent $300 on this one lol

[Zed Head]

And, if you lift the cam towers you'll tighten the chain. It's a thing.

https://zcardepot.com/products/copy-of-cylinder-head-cam-tower-shim-set-240z-260z-280z

He has .015" also.  You could stack them.

https://zcardepot.com/products/cylinder-head-cam-tower-shim-set-240z-260z-280z?variant=19278543978609

Also, eBay -

https://www.ebay.com/itm/134138328417?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=r5VbdHh0RZK&sssrc=2047675&ssuid=&widget_ver=artemis&media=COPY

 

Or, looks like this one won't pop out.  

https://jdm-car-parts.com/products/adjustable-timing-tensioner-for-l4-engine-by-kameari?variant=39843755425901

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Edited November 11, 2023 by Zed Head
ans > and, plus added some stuff

[Zed Head]

With a new chain and gear set installed you could loosen the cam towers and raise them to find what thickness shim you need.  That's what I'd do (if I was starting from scratch).

p.s. a thicker head gasket will lower your compression ratio.  Not good.

p.s. 2 - although, raising the towers and cam shaft will also require new lash pads, I think.  You're kind of in a bind, math and calculations are required.

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Edited November 11, 2023 by Zed Head

[Ownallday]

17 minutes ago, Zed Head said:

And, if you lift the cam towers you'll tighten the chain. It's a thing.

https://zcardepot.com/products/copy-of-cylinder-head-cam-tower-shim-set-240z-260z-280z

He has .015" also.  You could stack them.

https://zcardepot.com/products/cylinder-head-cam-tower-shim-set-240z-260z-280z?variant=19278543978609

Also, eBay -

https://www.ebay.com/itm/134138328417?mkcid=16&mkevt=1&mkrid=711-127632-2357-0&ssspo=r5VbdHh0RZK&sssrc=2047675&ssuid=&widget_ver=artemis&media=COPY

 

Or, looks like this one won't pop out.  

https://jdm-car-parts.com/products/adjustable-timing-tensioner-for-l4-engine-by-kameari?variant=39843755425901

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.

.

 

 

Wow that tensioner is expensive, what happens though if it doesn't tension it enough since it stops at a certain point, can't really tell how that one works. Wouldn't the thicker head gasket just make up for what I shaved off though? Especially just going back to OEM thickness head gasket? It's a stock L28 for the most part, n42 block and n47 head with stock efi.