Practical Advice on 930 Top End Rebuild

sand_man · 11-01-2005, 06:07 AM

Well gang it looks as though my 1987 930 with only 42,000 miles on the clock is suffering from a broken head stud. Sounds like an early VW Beetle engine or a not-so-loud Harley under load. I have the following mods:
-B&B Headers
-K27-7200 Turbo
-B&B I/C
-STOCK waste gate spring
I do have a copy of Wayne's engine building book. I haven't torn the engine down yet. My question is this: Can I get by just replacing all the head studs and fasteners with the upgraded ARP stuff without having to replace the pistons/cylinders/rings and having the heads rebuilt? In other words, am I safe re-using the parts if they check out okay? I want to be practical. I want to avoid a "while you're in there" fiasco! Surely (don't call me Shirley) with such low mileage some of these parts can be cleaned and re-used...no? I mean if I have to replace some stuff I will, but if it were 1987 and I were taking this car back to the dealer for service, what would Porsche do to fix it?

hobieboy · 11-01-2005, 08:04 AM

The P&C will need to come out to replace the head studs so at a minimum, you'll need to remove the cam tower with the head as 1 piece, then pull the P&Cs.

Given this situation, I'd at least inspect the P&C and rings for tolerances. And I'd at least take the heads apart and inspect all the parts - spring, guides, rockers, ... then decide from there.

If you are confident, you don't need to open up the bottom end.

sand_man · 11-01-2005, 08:14 AM

Thanks hobieboy. Yes, I realize that I'll have to at least tear the top end down/apart and I'm not at all opposed to doing that, it's just that I don't want to get into replacing a bunch of parts just for the sake of replacing them.

hobieboy · 11-01-2005, 11:15 AM

I was like you 2 years ago when I rebuilt my top end... I ended up replacing all the exhaust valves, rockers (I installed new cams), rocker arm bushings and a valve job. I even decided to not touch the head studs. I also check deck height, head volume, etc to know my exact compression ratioAll these because I had an oil leak which was confirmed to be from the $5 oil pressure switch & nothing else

So yes - I don't subscribe to blindly changing everything. Though I really should have changed (instead of just check & confirmed its in spec) the valve springs as the car is a track machine - the too-frequent-visit-&-stay-at-redline caught me with me this year

So I'm doing a full rebuild this winter + EFI

sand_man · 11-02-2005, 12:19 PM

Any advice from Wayne or Henry Schmidt on this? I'm really torn. I plan to take the heads, P/Cs, and rods to a machine shop for inspection. I will use the Supertec head studs and fasteners. I will also use Raceware or ARP rod bolts. I just don't know if I need to split the case. I know once I get to the short block it's really not that much more to go the whole distance...just don't know if it's really necessary!

WERK I · WERK I's Garage

Splitting the case? Why not diassemble the rods from the case before making your decision. The rods can be removed without splitting. Inspect the rod bearings for wear and contamination. If they're showing signs of excessive wear or stress, you can be reasonably assured the mains need refreshing and if the crank needs to be miked.

DonE · 11-03-2005, 04:17 PM

Take the extra time (it took me about 20 hours to split, clean and reassemble) and split it. Replace the main bearings and take the rods and crank to the machine shop. This does not make sense to go this far, spend the kind of money you are going to have to anyway, and not go all the way. The machine shop will be invaluable for the rebuild and if you have a good shop, everything will go together perfectly (and you'll feel good about it too).

Henry Schmidt · Henry Schmidt's Garage

The weak link in the 3.2 & 3.3 engines is the poorly designed connecting rod. The problem, The rod bolt is too small to handle the weight of the piston and rod at higher RPMs.
I would rebuild the rods using ARP bolt and nuts, reuse the Ps & Cs and do a freshen up on the heads. I like your thoughts about head stud

.
The real dilemma is do you split the case to replace the rod bolts. For me there is no dilemma. Split the case (I know, opinions vary) replace the main and rod bearings, install racing chains and if you budget allows GT3R oil pump. Sell the turbo pump and you're more than half way there.