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Bore gouge was measured at being ever so slightly over 0.5mm and engine machinist recommended the Alusil Liner (as per Strosek Ultra/ Ake suggested). None available from manufacturer but I have found one in Sydney!
He also said that my pistons/ remaining bores were fine to re-use, so just one new piston and liner will have that fixed, very happy about that!
I did think that the liner was a good way to go, but thought a rather complex process and no one locally would be able to do, but machinist says he has done liners before.
Other issue that I found was no 2 and 6 big ends.... hmm, not good! He thinks they may polish out (as it has just gone into the copper layer)! If not crank grind or maybe a S/H crank may be best?
That isn't going to "polish out". It also has been hot enough that it is probably not very straight.That damage doesn't happen very often on a pure street driven car....my guess is that this engine saw some track use.
Luckily, these cranks are very robust and stock standard/standard cranks are plentiful....and will work great as long as you use it only for street use.
If the engine is going to be used for more track use or driven for extended periods of time at higher rpms, you probably will want to make some changes.
That isn't going to "polish out". It also has been hot enough that it is probably not very straight.That damage doesn't happen very often on a pure street driven car....my guess is that this engine saw some track use.
Luckily, these cranks are very robust and stock standard/standard cranks are plentiful....and will work great as long as you use it only for street use.
If the engine is going to be used for more track use or driven for extended periods of time at higher rpms, you probably will want to make some changes.
I’d agree with that summation, I got a crank off a fellow Rennlister who raced the 928, the crank was free but the repair was around $500. It’s possible to repair that crank for sure. Mine was slightly bent but welded and straightened. That’s what the guys at Crankshaft Rebuilders do for a living. It may just clean up with a grind down to the next oversize. Another of the jobs I did, the crank rod journals were eggy and needed a regrind from that. Those guys are in Victoria btw. I have a good spare crank from an S2 which is good and I’d sell it for $100 plus freight, the downside is that you will need oversize bearings and they are not cheap.
Look how blue to con rod got from the failing bearings. That thing was glowing red. You should replace it. If you add up all the work this engine needs, is it still worth saving?
That isn't going to "polish out". It also has been hot enough that it is probably not very straight.That damage doesn't happen very often on a pure street driven car....my guess is that this engine saw some track use.
Luckily, these cranks are very robust and stock standard/standard cranks are plentiful....and will work great as long as you use it only for street use.
If the engine is going to be used for more track use or driven for extended periods of time at higher rpms, you probably will want to make some changes.
To my knowledge my car has never been tracked!
The crank is still to be measured and upon first inspection my engine guy was reasonably confident that it would polish out, if it does not I will get it ground and oversize bearings, if it is indeed easier to get a S/H crank I will do that.
My car will be for road use and possibly maybe a club "track" day, which will be sedate.
I’d agree with that summation, I got a crank off a fellow Rennlister who raced the 928, the crank was free but the repair was around $500. It’s possible to repair that crank for sure. Mine was slightly bent but welded and straightened. That’s what the guys at Crankshaft Rebuilders do for a living. It may just clean up with a grind down to the next oversize. Another of the jobs I did, the crank rod journals were eggy and needed a regrind from that. Those guys are in Victoria btw. I have a good spare crank from an S2 which is good and I’d sell it for $100 plus freight, the downside is that you will need oversize bearings and they are not cheap.
If I need a crank will take you up on that - does your crank need a grind or has it already been ground to 1st oversize?. I have a price for some oversize big end bearings are they are not too extravagant!
Cheers
Look how blue to con rod got from the failing bearings. That thing was glowing red. You should replace it. If you add up all the work this engine needs, is it still worth saving?
The rod is black, it will be measured and checked to see if ok.
That con rod is not OK ( excessive friction heat has discoloured the metal surface ), neither is the crank , its had a high RPM episode( a previous owner ) with insufficient oil pressure at high RPM & the 928 engine ( all ) will starve no 2 & no 6 con-rod bearings of sufficient protective oil pressure ,this is avoidable with correct oil viscosity , meaning at high Oil temp & high revs ( sustained ) minimum oil viscosity of 20w-50 is required , naturally the last century Porsche cars ( engines ) suffered this fate because of lots & lots of silly humans advocating the use of low oil viscosities in these engines from the late 1990's onwards, like the use of 5w-40 engine oil in our Australian climate & what you see is the consequence of that
The previous owner/s really did sell you a hand-grenade
If I need a crank will take you up on that - does your crank need a grind or has it already been ground to 1st oversize?. I have a price for some oversize big end bearings are they are not too extravagant!
Cheers
The mains have been ground 0.25 mm and the rods were ground 0.50 mm. The crank should just be ready to use, from memory one of the better shops linished it and checked it but I used a different crank as I’m running non factory bearings. Just the inspection and linish cost more than $100. The price is just token. (It’s been oiled and bagged for years, I hope it’s rust free still, it should be) Personally I think your crank will clean up with a re-grind as long as you have a really trust worthy shop to do that work. There is grinding and then there is grinding. You can screw it up.
That con rod is not OK ( excessive friction heat has discoloured the metal surface ), neither is the crank , its had a high RPM episode( a previous owner ) with insufficient oil pressure at high RPM & the 928 engine ( all ) will starve no 2 & no 6 con-rod bearings of sufficient protective oil pressure ,this is avoidable with correct oil viscosity , meaning at high Oil temp & high revs ( sustained ) minimum oil viscosity of 20w-50 is required , naturally the last century Porsche cars ( engines ) suffered this fate because of lots & lots of silly humans advocating the use of low oil viscosities in these engines from the late 1990's onwards, like the use of 5w-40 engine oil in our Australian climate & what you see is the consequence of that
The previous owner/s really did sell you a hand-grenade
My first thought looking at those bearing surfaces was 10W-30...
Exhaust and Intake valves, are AE or Schoettle ones any good or should I stick with genuine ones?
There appears to be little choice when it comes to valve springs, genuine is all that I have found?
Long time between posts... it has taken over 12 months to collect all the parts that I needed and for machining work to be done! Re-assembly has begun!!
It's working out to be a very slow process but progress is being made.....
In the end more work was required as I went along, but I do not regret going down the route I did. It is a 928 and these are now worth a lot more in Australia!
Cams also needed regrinding due to pitting, so yes this engine did not have the best care in the past, but it certainly will now!
I ended up getting the 4 new pistons from 928 Intl as they did turn out to be the same tolerance group! Picked out the best ones of mine and the new ones.....
Replacement rods were sourced for the 2 "burnt" ones, crank was ground 0.25mm all will now be good!
Just right now beginning the process of over bore one cylinder (28/42). Block got the first cut a few minutes ago.
apparently I found the last OS piston in the free world. And the company in France took every advantage to make me pay for it. (almost $600).
2 1/2 years later my engine is complete again and back in my car, running sweet!!
Anyone who has rebuilt a 928 engine knows what a pain it can be, but persistence pays off!! 😎
04-17-2018, 09:40 PM
