Timing Chain Tensioner Extended too much?

[Zed Head]

Just noticed that CO covered what I was talking about.  Missed it in the flurry of posts.

 

I'd measure the head thickness (you can do that while it's installed) then do the math on the the headgasket and see what should be.

Meanwhile, order new timing gear - sprockets, guides and tensioner.  All three can have wear.

[Patcon]

You can also use the chain guides to eliminate slack. They are slotted for that reason. I might consider enlarging the slots to avoid messing with cams towers and valve geometry. Atleast temporarily

[Ownallday]

1 minute ago, Patcon said:

You can also use the chain guides to eliminate slack. They are slotted for that reason. I might consider enlarging the slots to avoid messing with cams towers and valve geometry. Atleast temporarily

That's actually a very good point and idea. I can't remember if I messed with the direction of the guides but definitely worth a shot. And assuming the tensioner slides in a little more with the new chain I may consider what you are considering with enlarging the slot to make it more even with the tensioner.

[Zed Head]

[Ownallday]

1 hour ago, Zed Head said:

Just noticed that CO covered what I was talking about.  Missed it in the flurry of posts.

 

I'd measure the head thickness (you can do that while it's installed) then do the math on the the headgasket and see what should be.

Meanwhile, order new timing gear - sprockets, guides and tensioner.  All three can have wear.

Will measure and see how thick it is. I actually remember seeing the OEM thickness of the head somewhere. Already replaces guides but I have an entire kit coming Monday and will install Tuesday. I'll update how it goes Tuesday night

[Jeff G 78]

When I built my L28 race engine, I milled 0.050" off the head.  By modifying new chain guides, I was able to get the new chain set and tensioner installed with zero stick out.  I tried to reuse the old chain and gears and I had quite a bit of stick out, but with a new timing set, it was all the way in.  You can slot the guides more than normal to take up additional slack.

I'm guessing that the combination of an old chain and gears, worn guides, a 1mm head gasket, and a milled head have added up to WAY too much stick out.  Take the time and fix it right.  Even if it means pulling the front cover with the engine installed, I'd replace the guides and timing set before starting it up.

[Captain Obvious]

6 hours ago, Ownallday said:

Will measure and see how thick it is. I actually remember seeing the OEM thickness of the head somewhere.

I took a look back through some of my notes and here's a couple points of interest:

Stock head thickness is 108mm (4.252 inches).
Couple USED head gasket I measured - thickness approx 0.045  (1.15 mm) 
NEW head gasket I measured - thickness approx 0.055  (1.40 mm) 
 

[Captain Obvious]

6 hours ago, Jeff G 78 said:

I'm guessing that the combination of an old chain and gears, worn guides, a 1mm head gasket, and a milled head have added up to WAY too much stick out.

I'm thinking the same thing. Stackup of a whole bunch of things.

So I test fitted my .040 shaved head and I still had too much stickout even with a whole new timing set. Even with filing the slot longer on the slack side guide wasn't enough to bring the tensioner back to home. I'm surprised you were able to do a simple slot lengthening with your .050 off and ended up with the tensioner all the way in. With my guide, there wasn't sufficient extra meat on the edge the guide to file the slot as long as it need to be. Maybe your guide was a different brand than what I used?

I eventually had to take some more extreme measures with the guide. I'll post pics when I get a chance.

[Jeff G 78]

7 minutes ago, Captain Obvious said:

I'm thinking the same thing. Stackup of a whole bunch of things.

So I test fitted my .040 shaved head and I still had too much stickout even with a whole new timing set. Even with filing the slot longer on the slack side guide wasn't enough to bring the tensioner back to home. I'm surprised you were able to do a simple slot lengthening with your .050 off and ended up with the tensioner all the way in. With my guide, there wasn't sufficient extra meat on the edge the guide to file the slot as long as it need to be. Maybe your guide was a different brand than what I used?

I eventually had to take some more extreme measures with the guide. I'll post pics when I get a chance.

Here is mine after the new timing set with 0.050" milled with a FelPro head gasket.  Notice the slot on the top of the guide.  There was about 1/4" of stick out with the used timing set.

[Captain Obvious]

10 hours ago, Jeff G 78 said:

Here is mine after the new timing set with 0.050" milled with a FelPro head gasket.

Yeah, that looks a whole lot better than mine did when I mocked it together. I put mine together with a used FelPro head gasket so there was a little bit of crush there, but I also had my head cut .010 less than you did. In any event, if mine looked like that after just opening up the adjustment slot, I would have been good with that.

Maybe there are just differences between manufacturers of chain guides.

[Captain Obvious]

@Jeff G 78, I also see you are using an eccentric bushing on a modified cam gear. Did you find that you needed to adjust the cam timing after you had the head milled?

That's my next step and I'm in process of figuring that out now. I've got a cam gear modified to accept one of those GM style eccentric bushings, but I won't really know for sure until I have a real head gasket installed and the head torqued down. In theory, the milling of the head would retard the cam, so I'm thinking I might be able to just use one of the built in adjuster holes (either 2 or 3) to advance it back to where it should be.

I also don't like the sloppy fit of the eccentric bushing on the cam locator pin. Bushing designed for a 1/4" pin, being used on a 6 mm pin. If I find I do need to use an adjuster eccentric, I'll probably make my own.

[Jeff G 78]

1 hour ago, Captain Obvious said:

@Jeff G 78, I also see you are using an eccentric bushing on a modified cam gear. Did you find that you needed to adjust the cam timing after you had the head milled?

That's my next step and I'm in process of figuring that out now. I've got a cam gear modified to accept one of those GM style eccentric bushings, but I won't really know for sure until I have a real head gasket installed and the head torqued down. In theory, the milling of the head would retard the cam, so I'm thinking I might be able to just use one of the built in adjuster holes (either 2 or 3) to advance it back to where it should be.

I also don't like the sloppy fit of the eccentric bushing on the cam locator pin. Bushing designed for a 1/4" pin, being used on a 6 mm pin. If I find I do need to use an adjuster eccentric, I'll probably make my own.

The GM eccentric bushings worked great, though they take longer to dial in than an adjustable gear. The beauty is that I could use any timing set with no extra cost. The bushings were like $8 from Summit and can be reused over and over. I had no problem with the fit. I did have to make a plug to put behind the washer. The bushings are thin enough that they can walk out past the cam pin. The plug held the bushing in on the pin. 

I used a Made in USA Cloyes timing set that included everything for less than $90. I think I got it at Summit as well.