Mobile One consumption question

[75Carrera]

Good thinking, everything you said is right. But I still hold some hope it can be worked out without another tear down.

Thanks George..

[aigel]

If there is a noise when the engine is warmed up, there is no oil change that will fix that. Good luck,

George

[JeremyD]

Where did you get the jugs?

[Zeke]

If I read all this correctly, you rebuilt a motor using the old cylinders and new pistons. This means maybe you honed the cylinders for the rings to seat. So, they have to be somewhat large in the realm of specs, if in spec at all.

On the biral and cast iron cylinders I have repistoned, I used a larger pistion and bored/honed the cylinders with respect to the new larger pistions, usually 1 or 2mm bigger. That way, if I wanted .002 on the skirt, that's what I got from the machine shop. And always very accurate.

Using an old cylinder and buying new pistons of the same size as the originals is sketchy, AFAIC. And, I'm no engine builder by any means even if I did a couple. Still, I wouldn't go that route. I think that's why people buy these things in sets. Do you have any idea of what the skirt clearance is?

Anyway, rings are what contain the compression and the oil on their respective sides, correct? So, at 1500 miles, the rings should be seated. They should be seated in the first 100 miles, if not sooner. Now, maybe your mechanic was thinking like I'm thinking (and took several peoples's advice) and did not hone the clys. So, how do you break in rings on smooth, shiney clyinder walls? This has been a question around here for years.

That's why people buy these things in sets.

[75Carrera]

It was a complete 86 3.2 from German Auto Dismantlers in Georgia. The bottom end was solid with some special rod bolts and a good leakdown and compression. The jugs and pistons were existing. It was decided they would be fine with the top end we did.

I want to eleminate every possible remedy before assuming the whole jug/pistion assembly had to be replaced ($4200 on Pelican) plus labor. *I think I can hear my heart beating...

[Early_S_Man]

Donny,

Did you hone or use a glaze breaker on the used 3.2 cylinders? Were they Nikasil or Alusil? Did you measure them, or just go by appearance? The measurements were critical, and may well been the root of the problem, here ... kind of like Bruce Anderson's horror story about the brand new piston/cylinder sets that were manufactured to worn-out specs!

I have never heard of anyone putting a new set of pistons in old cylinders without honing or using a glaze breaker!

There were several options besides the $4200 one you mentioned, including boring the 95 mm cylinders out to 97 mm and getting them Nikasil coated ~$1000. 97 mm JE 9.5:1 forged pistons are also around $1000.

[aigel]

Donny:

The pistons were not new?
They were re-ringed?
If that's the case, were the ringlands carefully measured to make sure they were within spec?

I am asking because if the ringlands are out of spec, it can lead to broken rings during break in. The new rings see high forces during break in and if the ring sits in the land too sloppy under these forces, it will snap.

And as others have wondered, I also do, what has been done to the cylinders to assure proper ring seating?

Good luck, George

[Halm]

Donny, let me restate my experience with Ross pistons: During break-in with 30W non detergent dino oil and then afterwards with standard 20-50W oil, I never got more than 800 miles per quart. On cold start-up, the car would smoke so bad I had neighbors complain.

Do a search on Ross Pistons, and I suspect you will see that you are not alone.

[75Carrera]

Thanks guys...

[JeremyD]

Originally posted by 75Carrera
It was a complete 86 3.2 from German Auto Dismantlers in Georgia. The bottom end was solid with some special rod bolts and a good leakdown and compression. The jugs and pistons were existing. It was decided they would be fine with the top end we did.

Special rod bolts would indicate a prior rebuild - any idea on how many miles? Did anybody measure the cylinders? What happened to the existing pistons and why were they not used?

You do have some options - and I have been in your shoes - and it sucks.

[75Carrera]

If all this leads to a tear-down I'll most likely go with double checked mic barrel measurments, hone and a set of J&E Pistons to match the bore spec. I suppose I'll have to stand for the parts and hopefully my wrench will stand for the labor. First we'll see if any plugs are wet or fouled, do a hot leakdown and compression again.
History isn't really clear but chasing the piston numbers they came from Motormeister (not good news). Why the originals were replaced is a mystery. Might be MM's standard MO.
Today will tell the story...

[Porsche_monkey]

Originally posted by 75Carrera
History isn't really clear but chasing the piston numbers they came from Motormeister (not good news).

Let me guess how this is going to end....

[wyawn]

Anymore news on this? I'm currently rebuilding my '86 3.2. I'm very curious to see how this turns out.