Rebuild or Long Block Decision-Looking for Input
 

I am dealing with low oil pressure in a 930 and after a bit of forensic work I think the next option is either to go through the engine or do a long block replacement. Mine is a twin plug, cammed up with head work and I have found a nice similar set up long block from a reputable builder built the right way. Cost of the longblock would be $12,000 and I would get $4500 trade in on my core. I am guessing the low oil pressure is likely a main bearing issue. I don't have a knock yet. Looking for a range of cost if I did the rebuild. I know there isn't enough info here but my assumption is that the $7500 net cost of the rebuild could be eaten up fairly quickly in building myself. Again, looking for first impressions to help with my decision.

i think your right. both ways will cost about the same, you save on labor if you DIY but save time with the rebuild. still have to swap a lot of parts that might need some work and $$$. did you try to shim up the pressure relief valve? might be a temporary fix. How many miles on the engine?

The positive side is, you already know what you own and fixing what you own is always the less expensive way to get completed. All long blocks build the same.
Bruce

I actually did shim up the relief valve about 5mm. Interestingly there were a couple of washers already there which suggests the PO was chasing the problem. Car came out of a bankruptcy auction so no history was available. The car is a 1989 with 44,000 miles and the engine is a 78 which was rebuilt and modded but no idea of miles. No knock, no noises, good leakdown just low oil pressure (34 psi at 5000rpm just checked with a mechanical gauge.

not too, too bad but yes, time to fix right

JMHO,......

'89 930's are worth really good money these days and I'd recommend keeping it a matching numbers car. This means rebuilding your current motor while its still undamaged.

Take it apart, address the issues, do it right without cutting corners and you'll have a solid, reliable car for many many years.

Low oil pressure can be caused by many things and only detailed forensics will help you diagnose the problem so it won't recur.