Assessing an unknown engine

[911hillclimber]

I recently went to PCGB Club Office for an Early 911 register tech meeting.
Mike Champion gave an insight to the early engines and said they can be twisted when taken aparts simply due to age of those castings, Twisted is a rough term, distorted too, but slightly defomed?

IIRC a line bore will need some special shells and those cost dearly.

Really hard to determine if the case is indeed deformed, you will need a very good engine shop for that or simply bite the bullet, dry build the case and put the bar through it.
This may involve replacing the large end bearing too...
Prices all on Design 911 web site for the bits and the sizes you can get.

If the cases are deformed the crank will drag, it will not suddenly come to a halt like it would if a rod was interfering on the case.

I had a hard stop on the crank rotating in my last 3.2 engine rebuild .
Turned out it was the Carrillo rod touching the stock oil pump ...just... and a quick file on the pump cured that.

When turning the crank be sure the rods above the crank are correctly held in their path of travel (ie simulate then going up and down in the cylinders. Gravity deals with the ones dangling down.

You can do this by holding them upright with strong elastic bands on a cross bar, ie broom handle, held up tight by your budding daughter while you rotate the crank at least 3 turns in the right direction of rotation.

I take it you did not dry build the crank in the cases before the rods went on?

[chris68]

Maybe reassemble crank in crankcases, with plastigauge on each half of bearing journals. Might at least let you see where it's tightening up.

[911hillclimber]

Good idea, a tight crank, but exactly where is the spot?
Good thinking from Chris!

[chris68]

Only other thing would be to make sure to follow recommended tightening sequence and torque up in stages checking for free crank rotation after each complete stage. That's probably teaching you how to suck eggs though. Obviously, don't rotate the crank if doing the plastigauge measurement.

[RobFrost]

Only other thing would be to make sure to follow recommended tightening sequence and torque up in stages checking for free crank rotation after each complete stage. That's probably teaching you how to suck eggs though. Obviously, don't rotate the crank if doing the plastigauge measurement.

Thanks, good ideas Chris. One reason I wondered if the bearings aren't standard is because it was tight before I even started to torque up. I'll also assemble without the IMS in case it is the IMS backlash.

[RobFrost]

I recently went to PCGB Club Office for an Early 911 register tech meeting.
Mike Champion gave an insight to the early engines and said they can be twisted when taken aparts simply due to age of those castings, Twisted is a rough term, distorted too, but slightly defomed?

IIRC a line bore will need some special shells and those cost dearly.

Really hard to determine if the case is indeed deformed, you will need a very good engine shop for that or simply bite the bullet, dry build the case and put the bar through it.
This may involve replacing the large end bearing too...
Prices all on Design 911 web site for the bits and the sizes you can get.

If the cases are deformed the crank will drag, it will not suddenly come to a halt like it would if a rod was interfering on the case.

I had a hard stop on the crank rotating in my last 3.2 engine rebuild .
Turned out it was the Carrillo rod touching the stock oil pump ...just... and a quick file on the pump cured that.

When turning the crank be sure the rods above the crank are correctly held in their path of travel (ie simulate then going up and down in the cylinders. Gravity deals with the ones dangling down.

You can do this by holding them upright with strong elastic bands on a cross bar, ie broom handle, held up tight by your budding daughter while you rotate the crank at least 3 turns in the right direction of rotation.

I take it you did not dry build the crank in the cases before the rods went on?

Thanks Graham. I also had to file the oil pump slightly (but different reasons - 964 pump)

I previously assembled it with the old bearings and no IMS and it was a bit tight but loosened with a turn of the crank.

[Gary71]

One reason I wondered if the bearings aren't standard is because it was tight before I even started to torque up. I'll also assemble without the IMS in case it is the IMS backlash.

Do you have the old bearings you could try? Can’t remember if you’ve had the crank ground?

[andytat]

The first time I came across a warped case was about 20 years ago when I
had my workshop in Singapore. We were rebuilding 12-15 aircooled engines
a year and this one particular engine showed no unusual issues while being
stripped down. It was a 2.4 E. Running perfectly, just using lots of oil and
leaking badly. The crank measured perfectly but 3 of the main bearings showed
signs of uneven wear, not through to the copper backing though. So in went
new std mains. I have a habit of rotating the crank when torqueing each pair
of through bolts, just to make sure nothing odd is happening. I had torqued
the first 2 pairs and the cranks turned as it should by hand from the flywheel
end. Upon torqueing the 3rd pair of through bolts the crank needed a screwdriver
through 2 flywheel bolts to turn it. I thought this a bit odd but when torqueing
the next pair of through bolts the crank was solid!
I split the cases and installed the old main bearings and torqued the case
through bolts and outer M8 bolts and the crank once again turned beautifully.

I ended up purchasing an adjustable boring bar, at great expense from the company
that supplied Porsche and had some special holding fixtures made up to keep the
case halves in line, as you can't fit the nose bearing because it interferes with the
boring bar.
I moved back to UK in 2012 and needed a bit of cash and wasn't intending to
rebuild any more engines so the boring bar went to Nick at Redtek.

Sorry for the ramble Rob but it sounds to me like your cases are warped and
unfortunately I don't know any other remedy apart from having them line bored.
You can usually get away with the lightest of touch to bring them back into round.
That way you can still use std outside diameter mains as I'm not sure of the
availability of oversize bearings these days.

Best of luck.

Andy

[Gary71]

Definitely worth a hone. I had my (mag case) line honed just to do the tinniest of corrections. You could see where the hone had touched surface but it literally skimmed it
I used standard bearings and all is good.

You can see it in this pic

[911hillclimber]

Looks a good first move above, but if a full line bore needed Design911 sell std bore, 0.25mm oversize o/d shells for £420 inc vat.
Double the std/std bearings, but at least readily available, but call them first!

Who did the hone Gary?

[Gary71]

It was Rob Walker engineering in Witney.
They did all the machining for me. Now closed unfortunately I believe, shame as those skills are dying out.

[911hillclimber]

Thought so.
He did some work I think for me on my smashed 3.2 via Bob Watson over a decade ago.

[RobFrost]

I woke around 6:30 this lovely rainy Sunday morning with the sudden conviction that the upper half of the case must be hanging up on the larger 964 oil pump, deflecting the case and pulling it tight. I previously filed a little off both halves of the case webs to accommodate it, but it is not possible to place the pump in the one half to test whether sufficient metal has been removed. Within 10 minutes or so I was in the garage pulling the halves apart... only to find that the crank will simply not turn even sat in the one half of the case with the top half removed.

For a moment i thought the nose bearing was crooked, but no. So in spite of all your most helpful suggestions, attention turned to my original hypothesis, that the shells are too thick. I pulled one out and it shows 901.132.50 which looks to be 0.25mm undersize on the inner. So I'm sure that is the issue, as my crank is at original factory spec on all journals. One reason I suspected this issue, is that I bought the shells from a DDK-er believing them to be standard, and not actually verifying the part number myself. Additionally, I did not even get close to tightening the through-bolts. The crank was tight before the case halves were even together.

[neilbardsley]

That is a bit strange

Sent from my 22011119UY using Tapatalk

[chris68]

Nice easy fix if it's only that