Daytona Crank [w/chain replacement] need help, please.

[Daniel Kalal]

A head-scratcher.

In the photograph, you can see the steel gear that was removed from the crank as part of the conversion from gears to chain. But, here's the deal: It was found that when the new sprocket was torqued, it pulled up against the bearing surface before it did the crank. So we tried the old steel gear. The tolerances are very slight, but even when the steel gear was put back, the same thing happened. The engine did turn before things were removed, although there is evidence on the face of the gear that things were always very, very close.

Note: I've shaded part of the bearing face yellow in the photograph (it's not really that color).
So, what is going on here? Why isn't it pulling up flush?

By the way; this is what the aluminum oil pump gear looked like:

 

[john zibell]

This is the point that aligns the crank to the connecting rods and pistons. That said it is a critical point in assembly. Either the front main carrier is too wide, or the front of the crank section is too short. I'd remove the front main carrier and measure the width. I would compare that to a new carrier, or one that allows the crank to rotate. Unfortunately I can only locate ID dimensions for the mains and no width dimension. That width dimension would be on the assembly drawing, but I don't have access to those. The same problem exists with the crank shaft, I can only find diameter measurements, no length dimensions.

 

[Daniel Kalal]

Thanks John.
Your points are certainly well taken, and for those reasons I am baffled. All the parts are the same.

Has anybody seen such a level of "relaxation" when the crank bolt is removed, that the crank seemingly shrinks? I can imagine that if you were to over-torque the bolt that eventually draw the gear (or sprocket) flush to the crank (by squeezing the aluminum flange and everything else), but that's not a reasonable solution. By the same token, I could add a thin shim/washer between the sproket and the crank, but that seems goofy, and I don't want to risk the sprockets no longer being in plane.

 

[Penis Rotor]

Daniel, the crank is never going to shrink!

First thing I'd ask is how long did it run before you noticed the oil light. Any time at all may of been way too much!

Pull the front main bearing. While the crank may turn it may of damaged the thrust face at the back of the bearing. Jut an idea.

Also have you tried taking the timing inspection bung out and levering the crank forward with a screwdriver? It's been a while since the old girl shat her pants, perhaps there is not enough residual oil to make things easy to spin and with the mucking about at the front the crank may of moved back and now simply be being obstinate and unwilling to move.

In MY EXPERIENCE, which probably counts for not a lot when the crank id pushed fully forward there should be between about 6 thou minimim and 18 thou maximum clearance between the back of the crank sprocket/gear and the front face of the main. This should be determined by pushing the crank FORWARD as far as possible.

As John has said, the end float is determined by the depth of the front journal and the thickness of the bearing, front to rear, they ARE generally well made.

If lubrication has ceased, as you are well aware, damage will start pretty much immediately.

Check the front main and, I'd suggest, the big ends. Any damage? engine out and do it right from the ground up,

Pete

 

[Daniel Kalal]

Daniel, the crank is never going to shrink!

Well, it's a theory... [agreed]

We pulled the front bearing (you can see in the photograph that the bolts have been pulled), and all look just fine. But, clearly, something isn't right, and the only way to tell is to start digging.

 

[Chuck in Indiana]

<shrug> I'd be pulling the bearing carrier and getting out my depth mics. It will surely be obvious when you start checking all the dimensions.

 

[pauldaytona]

Daniel, did you solve it? What if you pull the clutch, that should move the crank forward.

 

[Daniel Kalal]

Daniel, did you solve it? What if you pull the clutch, that should move the crank forward.

Yes; all is well. Thanks. Turned out to be something as simple as interference with the new crank sprokets and the bolts of the oil pump not allowing things to pull up fully. Easily handled.

I've been meaning to post the entire list of part numbers to make that swap. I'll do it with a separate post.