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Not terrible.
It's frankly a bit difficult to be too choosy about '85/'86 bore/piston condition.
There's a few dirt scratches here and there.
As long as those are minimal in the bores, I'd measure the piston to wall clearance and go from there.
Semi-retired, as of Feb 1, 2023.
The days of free technical advice are over.
Free consultations will no longer be available.
Will still be in the shop, isolated and exclusively working on project cars, developmental work and products, engines and transmissions.
Have fun with your 928's people!
Came out of a 86.5 I'd hoped could be used to replace the one ruined with blasting media. Luckily we didn't pay yet. Now we are trying to see if any of it is keep before it goes to scrap.
Turns out it was even worse. My son was taking it apart for inspection when he called me over to see the 'work' that had been done.
The oil pan had been welded, too. And there was silicone all around the were the pressure sensor attaches to the block.
But the thrust bearing was perfect.
And the search goes on.
Best guess PO ran over a curb.
Welding slag, some JB weld and doubled up crush washers. Lower oil port on the block was milled of ground away That ain't right
I cannot figure this one out. Did they weld on a block of aluminum or grind it down? Why?
Not terrible.
It's frankly a bit difficult to be too choosy about '85/'86 bore/piston condition.
There's a few dirt scratches here and there.
As long as those are minimal in the bores, I'd measure the piston to wall clearance and go from there.
The bores are really nice. The block isn't. See above.
How do you measure piston to wall clearance? Feeler gauges? Never done that.
Which side of the pistons the pictures are taken from? And from which bank (1-4 / 5-8). Wondering if one side shows more wear because of the piston pin offset they fixed with the 87+ models.
I suspect you cannot simply swap the lower (cradle?) part of the block, which is a shame. You have one nice top half, and nice bottom half. I would at least set them together and have a look at alignment. More common way to measure the bores is to use a telescoping gauge. Then you use the same micrometer to measure that and the piston. You only care about the difference. Grainger 54XJ15 is about $50.
How do you measure piston to wall clearance? Feeler gauges? Never done that.
You're frightening me.
How can you possibly "rebuild" an engine without the basic tools/knowledge?
In order to measure the bores of the block, you need a dial bore gauge.
And you need a 4" "calibration ring" to be able to zero that bore gauge.
And you need a "high end" micrometer that can measure the pistons with-in tenths of thousandths.
At the tolerances of a 928 engine, a snap gauge or an inside micrometer is virtually useless.....a set of feeler gauges would be more accurate.
Bore gauge.
About 50 years old. (Bought it the first week my shop was opened.)
Mitutoyo, made in Japan.
Calibration ring.
Gold standard of calibration.
High end, old school, micrometer.
Also about 50 years old.
Mitutoyo, made in Japan.
Today, I'd buy a digital one, if I was starting out.
Those gauge setting rings are the shizznit for calibration. In theory a set of gauge blocks will also work to get an absolute measurement of a bore, though I haven't had the courage to actually assemble a motor with piston-bore clearances that depended on my own measurements.
You're frightening me.
How can you possibly "rebuild" an engine without the basic tools/knowledge?
In order to measure the bores of the block, you need a dial bore gauge.
And you need a 4" "calibration ring" to be able to zero that bore gauge.
And you need a "high end" micrometer that can measure the pistons with-in tenths of thousandths.
At the tolerances of a 928 engine, a snap gauge or an inside micrometer is virtually useless.....a set of feeler gauges would be more accurate.
Bore gauge.
About 50 years old. (Bought it the first week my shop was opened.)
Mitutoyo, made in Japan.
Calibration ring.
Gold standard of calibration.
High end, old school, micrometer.
Also about 50 years old.
Mitutoyo, made in Japan.
Today, I'd buy a digital one, if I was starting out.
Didn't mean to scare you. I have a machine shop for all that.
08-24-2021, 05:39 PM
How would you rate the condition of these pistons?
