engine and drivetrain How many of you are running 91mm Pistons or larger?

[jimk]

Thinking with my fingers, but if the rod bushing clearance to pin was a bit snug, could it be that when the rod was finding home center while running, the pin constantly bumped the retainer until the retainer gave out or was dislodged?

[evil02]

5 minutes ago, kaptanoglu said:

Terry at the eponymous Terry Sayther Automotive did the teardown.  I haven't looked at it myself yet, beyond the pics that Terry send me (and that I posted earlier in the thread).

 

  All good info. Thanks for sharing.  Clearances and a/f ratio's all play a part. It was possible parts were hurt during the lean running and it finally gave up..

 

 I'm glad a 3rd party is doing the tear down. I'm sure he knows what to look for.  Anyhow, good luck with the rebuild!

[evil02]

10 minutes ago, jimk said:

Thinking with my fingers, but if the rod bushing clearance to pin was a bit snug, could it be that when the rod was finding home center while running, the pin constantly bumped the retainer until the retainer gave out or was dislodged?

 

Possible but, when they dislodge, it is usually a big deal!

Edited April 3, 2019 by evil02

[jimk]

Just now, evil02 said:

it is usually a big deal!

Which is what the photo shows, a big deal.

[kaptanoglu]

27 minutes ago, Conserv said:

So, at very best, you could pick up 7 hp. Unless you’re constrained by the Kugelfischer’s fuel delivery and you pick up virtually nothing. The imperative for greater displacement in your circumstances — a street motor — seems underwhelming to me, although I act fairly conservatively with an original block.

 

I've done stupider things than this for 7hp ?

 

My thinking is predicated on:

(a) advice that a 92mm bore is very reasonable on a non-boosted tii motor (from Steve, who has done quite a few of these), 

(b) the expectation that I can sleeve it later, if I really want to preserve the original block (which, to a point, I do), and 

(c) tii blocks are readily available

 

If your view is "failure mode with that block is that it goes in the trash", then that is a different calculus.  That being said, while, in clean form, at least, Sputter is a pretty fantastic restoration, it will never be considered "original", given the 73 bumpers and other tasteful, appropriate, but non-original mods.

 

It does, however, have the world's best trunk lid tool box.

 

I do appreciate your input.

 

Last, my expectation is that it must have taken a detonation or some other anomaly to bang loose the wrist pin.  I just can't fathom how a bad install would take 20K miles to manifest.

[evil02]

2 minutes ago, jimk said:

Which is what the photo shows, a big deal.

 

lol,  that's merely a flesh wound..   google wrist pin failures..

[jimk]

14 minutes ago, kaptanoglu said:

Terry at the eponymous Terry Sayther Automotive did the teardown. 

I'd follow Terry's recommendation, it would be tops.

[irdave]

Twenty thousand miles does seem like a long time for an assembly error to show up.  What were Steve's thoughts?

[kaptanoglu]

1 hour ago, irdave said:

Twenty thousand miles does seem like a long time for an assembly error to show up.  What were Steve's thoughts?

 

He is thinking that it must have been a detonation or something like that.  I will certainly be on top of timing/AFR when we bolt it back together. 

 

I can't imagine what else it might have been.

[evil02]

19 minutes ago, kaptanoglu said:

 

He is thinking that it must have been a detonation or something like that.  I will certainly be on top of timing/AFR when we bolt it back together. 

 

I can't imagine what else it might have been.

 

I would possible buy a/f being off.  If you had detonation, detonation marks will be present.

[Conserv]

4 hours ago, jimk said:

I'd follow Terry's recommendation, it would be tops.

 

+1

 

I take back most of what I said: I had no idea all four cylinders were already at 91mm — I, incorrectly, assumed they were at first or, maybe, second oversize. If an extra mm cleans up the problem, by all means go for it!

 

Best regards,

 

Steve

 

[kaptanoglu]

1 hour ago, Conserv said:

I take back most of what I said: I had no idea all four cylinders were already at 91mm — I, incorrectly, assumed they were at first or, maybe, second oversize. If an extra mm cleans up the problem, by all means go for it!

 

5 hours ago, jimk said:

I'd follow Terry's recommendation, it would be tops.

 

For clarity, Steve at TEP has quite a bit of experience w 92mm in these and said “do it.”  Terry offered it as an option but weighed it vs using a different block, given he has not done (m)any 92mm overbores except for race engines. 

 

We’e going to give it a go and see what happens. Pictures coming as it happens. 

[LarsAlpina]

Problems are in the middle. At least to some point.

 

 

Best regards, Lars.