unexplained tensioner length difference

[mskala]

Complicated question: I just changed cylinders/pistons without splitting
the case, and after putting everything back where it was, the 1-2-3 side
chain tensioner doesn't extend nearly as much as before.

Side-stepping the usual discussion of whether to use the guards or go
pressure fed, I've been using the guards for a long time. The instructions
say to have 1/8" space below the guard. I know I had at least that much
before, and now it is only 0.065".

So, trying to make sense of this; I had to use the thicker base gaskets
(0.020" instead of 0.010"), and I didn't measure the cylinders to see if
they are different height, but could either of those cause my chain to be
'tighter' at room temp by a significant amount?



If it makes sense, then I will need to run without the guard on this side
and check in there again later.

Thanks,
Mark S.
2.2L -> 2.3L

[Amstaff]

are they completely pumped up?

[Jcslocum]

The answer is yes, if the cam is further from the centerline the chain will,be tighter or the other way round, looser.

[mskala]

Thanks for answers. For now I will run without the guard as after playing
with it there is not enough space. If the guards installed without enough
room below them, I believe as the temp goes up they will turn into 'solid'
tensioner and stress the chain.

Tom, I do not understand your comment as the 2 sides of the engine are
totally independent, and also the bleeding process uses the top reservoir
of oil above the check ball, so dunking the whole thing in oil would not
change anything.

[Amstaff]

According to Wayne's book the way to pump the tensioners up is to submerge them in oil and pump the shaft until they pump up.

[mskala]

No, that's not correct. You must be talking about the later pressure-fed tensioners.

[Hawkeye's-911T]

Hi Mark

Do a search on John Walker's & Grady Clay's posts on tensioners. I am presently going down a somewhat related road with respect to chain tensioners. These gentleman give a lot of info which may help answer some of your questions.

Cheers
JB

[mskala]

Familiar with John Walker's procedure. I have searched without luck for specifics
of my exact question. This is not a chain-tensioner issue, I would have posted
that in the general technical forum. Seems like nobody really quantifies these
things. I'll have to try some math.

[Walt Fricke]

New chains?

If concerned, and the chain seems normally tight with these tensioners (and it should - see below), you could try smaller idler gears to compensate for the increased distance the cams are from the IS shaft due to the thicker cylinder base spacers. That spacing will also affect how the chain housing fits to the cam carrier with the big O ring. The O ring allows some misalignment, which you may not have noticed.

The oil in the tensioner has nothing to do with the tension it puts on the chain. The tension comes from the stout spring inside. The oil is part of the shock absorber (really spring vibration or harmonic absorption, which is why the Brits call shocks dampers) function of the tensioner. The same is the case for the pressure feds.

You could add a half link to the chain. But that might be too much - you don't want the idler arm too high up and close to the chain housing.

How about you plane each side of the guards so they are the thickness of the pinch bolt head? That should get you the clearance you need. No real magic in 1/8" exactly.

I've not seen anyone say they went to the trouble of making an equation: For every X increase in cam distance from IS shaft, you will get Y movement of the idler arm end, and Z increase in tensioner extension.

Is the issue the same both sides?

[cgarr]

I assume you did not change the chain ramps? There is one different one if placed in the wrong place can cause a tight chain.

[mskala]

Chains, ramps, and gears are all the same and in the same places.

Actually, from what I can tell, leaving some gap is absolutely critical (I'm going to
assume 1/8" is safe as that is what the guards have been advertising for years.)
As the engine heats up it will be equivalent to the chain being shorter, and the
piston will go down. Without this gap you are probably going to 'stretch' the
chain and possibly destroy the guard and let it loose inside the motor.

The guard is as small as it can possibly by already. I'm sure with enough thought
another style of piece could be made and safely fit in there, but I'm leaving
everything alone and will check on it at the end of the season.

This is only happening on the left side, so I have to assume that the height group
of the cylinders may have been different on each side of the motor before.

[mskala]

Well, I accidentally may have found the answer. Looking through my box of
gaskets, I see the bag of head seal rings and there's 3 still in it. So, while
assembling the left side I left out the seal rings. At least I found it before too
late. Today I opened it up and put them in. Now, the chain tensioner on the
right is down similar to the left.

But, I'm sure that the intent is that these seal rings would squeeze down and
the head and cylinder would be touching either way. So now I'm confused in a
different way.

[Walt Fricke]

Mark - I have the same confusion - you are correct that the CE rings should have zero effect on heights and such, since they crush until the heat is tight against the top of the cylinder. But these are the larger, earlier ones, right?

However, perhaps in some way you can't discern you didn't get that bank torqued all the way down, or something got in there to prevent pulling everything all the way down, and the loosening and redoing got rid of that?

An evil thought - if the cylinders on that bank are not all of the same height, I can see how torqueing once might leave the cam carrier tilted a little toward one end, and on redoing toward the other end, or somewhere in between. This is a mag cased motor? Many engine builders recommend making sure that the spigot surfaces are dead even with the crank centerline, and that is part of every rebuild. I realize you didn't split the case, but perhaps relaxing the tension on the head studs could also allow a relaxation distortion to occur? I guess you put a level across the cylinders when you installed them and snugged them down with something?

And did the same when you put the heads on across the tops of the heads? The cam could have been a little high, and the squish of the large O ring seal to the cam carrier could accommodate a little upward or downward misalignment? Maybe one of the guys who rebuilds lots of engines for a living has more light to shed on this.

Though I'd accept victory and move on if this were mine, and just keep an eye on possible leaks which might happen if the cylinder tops are not all at the same crank distance.

[mskala]

This is a good point. Many more checks were done on the left side as that
was first and of course it was necessary to prove valve clearances and such.
On the left side I definitely put the straight edge (from the stomski sprocket
aligner) on it to prove cylinders were the same. I probably didn't do that on
the right side. Eyeballing underneath, all 6 look the same where there is a line
on each cylinder about a mm from the head, so I could get a good idea if things
were out by more than a few thou. But all looks good.

One thing I did, was when the dial indicator was still set on intake 4 valve and
on the overlap I figured I would torque the head nuts another 5 pounds or so
to see if that moved the sprocket, turned it slightly due to the taut chain, and therefore moved the valve. No movement at all. (removed and reset proper
torque then). So I'm sure that I'm not in the middle of compressing anything.

Note that I never separated the heads from the cam housings, and also the cam
moved freely. So unless there is some good idea I will move forward. Also I
found out when first apart that these heads have a chamfer, so probably none
of the area inside the CE ring is making contact, but the 84mm birals I took off
didn't seem to have a problem with that.

[Walt Fricke]

Heads have chamfer on the sealing surfaces? I don't think they should, at least not any of the CE ring heads. The 3.2s did as part of not having CE rings, but you couldn't put those heads on your case unless it was an SC case or later, and it can't be that or the Birals wouldn't fit.

I don't know enough abut the 2.0 heads, which have an actual gasket between head and cylinder - but would you have those if they even have a chamfer? I can't imagine the crush rings not making contact. Obviously you didn't see signs of distress in this area on disassembly - no burn marks or carbon deposits in odd places.

Odd, but all's well that ends well.

[mskala]

Heads are a later version. May have always had a chamfer or been added later,
but that's what I found.

I decided I could put the air into the compression tester through the spark plug
hole. Only leakage through the usual areas, so I guess I'm going ahead.

[Walt Fricke]

2.7 heads would, one would think, have a chamfer (or at least not have a bit of flat) to cover the 3mm extra width on each side. Wouldn't that produce a sort of wedge shaped opening all around? But the head and cylinder would still meet and seal beyond that with '84s, wouldn't they? And the old fat CE rings do their job?

Same with stock 2.4 heads reworked to run with 85, 88, 89, or anything in between done for a race motor.

This sounds like a question for one of the professional engine builders, who have seen all sorts of combinations.

Are these the heads and same size cylinders as before?

[mskala]

early head chamfer?

Previous query about the head. I think it was originally from 2.4 but modified.
I took off biral 84mm cyl and put in 86mm biral AA cylinders. That's why I think
if it was okay before it's going to be okay now.