Rebuilding 3.6L... advice on upgrades

[wastintime]

Hey everyone,

Well, the date is set, November 10th I'll have to stop driving my baby and rebuild the engine. It didn't leak any oil on the track which was a huge surprise, but it's back to leaking like a sieve during city driving, so that rear main seal's gotta be replaced.

Since I have to completely disassemble the engine anyway to replace the seal, I figured I might as well make sure the engine as perfect, any parts that need to be fixed or replaced will get attention.

Also, I'd like to have a little fun with the engine, and try to gain a little performance. I'm going to get a set of cams from Webcam, work on the windage myself, powder coat and/or polish several engine parts, and install a dual outlet GHL header system, and put a 6-speed G50 gearbox in the car. I looked at 3.8L kits and mass flow sensors, but they're just too expensive for too little gain IMHO... so I was wondering if anyone on this board might have some neat ideas or interesting things to do while I've got the engine apart. Any ideas would be great.

Thanks,
Andrew

[JTO]

What car does this engine live in?
Troy

[Rick Lee]

I assume this is a 964 3.6l, no? I'v never once used 6th gear in my 993 and I drive it like I stole it. Save your money and maybe just go with regearing. By rear main seal, do you mean flywheel seal? That does not require much more than engine and flywheel removal, certainly not a teardown. But if you're pulling it all apart, I'd send the heads out to Steve Weiner, who (from Rennlist postings) seems to have the cure-all for weak valve guides.

[wastintime]

yes, the car is in a '92 C2. The gearbox change is kind of my pet project and I really want to do it. Most of the people I've talked to who have done it absolutely love it and it's something that'll make the car a little bit more distinctive, plus getting an extra gear and maintaining the same final drive ratio will be cool.

The oil is leaking from the inner rear main seal, I think you're talking about the outer rear main seal. The crankshaft has to come out to replace the inner seal, so unfortunately the engine has to be completely disassembled....

[Bill Verburg]

As Richard pointed out the engine does not need to be disassembled to replace a rear main, the flywheel needs to come off but that's it.

Assuming that the engine is an early 964(sounds like it from the leaks), you will need new p/c w/ the goove for head gasket sealing anyway, 102s aren't going to be much more expensive.

993ss cams or Groupe B cams are good choices and will give a lot of bang for the $ but you will also need to go to larger valves 52mmI & 43mmE undercut ss would work nicely, when used w/ phosphor bronze 935 style guides and some nice AASCO valve springs/retainers your valve train will be in good shape. More agressive cams will require individual throttle bodies on the intake and aftermarket($$$) engine management software. The list price of the MAFs that I have seen is way to high to be cost effective, bmaybe if you get a very good deal.....

The cylinder base is gasket is likely missing from an early 964 as well(another likely source of leaks). This does require total disassembly of the engine to rectify as the block walls for the spiggots will need to be machined for o-rings. Replace the rod bolts w/ ARP or Raceware while in there.

You will need a custom chip to wrap it all up in a nice running package.

Whille a nice close ratio 6spd like a G50/21 is desireable and doable, it is not the simplest swap and will require major mods to the rear of the car such as coil overs, cut outs of the tunnel/rear seat area, reinforcment of the rear suspension area, custom trans mounts, custom hyd clutch, etc.

[Bill Verburg]

Strike that trans talk from my last post, the 6spd in a '92 C2 is a very straight forward dropin. Do use a G50/21,31,32 or 33

[Mike Feinstein]

V-ram?

[wastintime]

Both my mechanic and Holbert's Porsche dealer in PA tell me that the engine has to be completely disassembled, so I'm pretty sure that's correct. It's not really an early 964... it's a '92... lol, it never had a single oil leak until a Porsche dealer in Cary NC did factory recall service on the engine and then the rear main seal started leaking... at least that's what the PO said... go figure.

[widebody911]

Upgrade your rod bolts and head studs to ARP or RaceWare.

[jerrykrug]

How many miles on the engine?

[Bill Verburg]

Not 964 engines received all of the upgrades untill late in the '92 model run. Even well into the '93 run the distributor vent wasn't oem.

Assuming that the p/c are fine then the top end upgrades and chip as outlined above will give you a nice pop in hp. I would also recommend B&B or SSI headers if you go forward w/ the cam/top end upgrades.

[wastintime]

68k miles on the engine...

yes, we're doing the dist. vent upgrade, and installing GHL headers.

[ScottKelly911]

Bruce Anderson had some suggestions about upgrading the 3.6 engine quite easily. Jerry Woods extracted an extra 69 hp using IDA 46 carbs or PMO 50 carbs, mild cams (GE 100's I think), a pair of permatune cd units and headers. But with all that you'd spend to do that, if you're just doing it for fun and not going to track the car, I'd just get a supercharger from TPC. They have kit that will give you 380hp without having to change your compression ratio by using very mild boost. Everything that I've read says it's a great kit and very reliable. check out the site www.tpcsuperchargers.com If you are planning on tracking the car, I suggest picking up Bruce Anderson's Porsche 911 Performance Handbook, it has a few different ideas.
;D Scott aka Mouse

[wastintime]

the car will definitely be tracked... i'm waiting to do all of this until after another track event at Roebling Road in Savannah, GA. The problem is I don't want to make it a full track car so that it's no fun to drive in town, and I don't feel like spending tons of money for these improvements. That supercharger does look pretty darn interesting... I probably won't do it right now, if for no other reason than that it's pretty expensive, but it's definitely something to think about for sometime down the road. I'd be really interested to see what kind of reliability people noticed after installing that kit.

[Kahuna]

If I was you, I would pay attention to Bill's advice. His 3.8RS engined Carrera is unbelievable. He has been messing w/ the 3.6 mods for 10yrs now.

[JeremyD]

Maybe a stupid question, maybe not - but one of my goals in the future is to find a 1990 - 19902 C2 engine that needs a rebuild - then rebuild it as a twin turbo - if you are machining anyway - and changing p & c's - then I could lower the compression ratio, new rod bolts, head studs, etc.

Is that duable with a stock 3.6? I read somewhere that the crank on the early 3.6 was the most stout. correct?

[Bill Verburg]

Is that duable with a stock 3.6? I read somewhere that the crank on the early 3.6 was the most stout. correct?

Anything is doable, to get it done right is the trick. If you want a turbo, buy a turbo. Trying to make a silk purse out of a sows ear is foolish.

No, the 964 crank is not the stoutest it is arguablythe worst because of the requirement of an external harmonic damper. The 993 is heavier, stiffer and better oprimized to resist whip at high rpm. The downside of the 993 crank is the narrow rod journals which necessitate 993 or aftermarket rods. This is not all bad as even the stock 993 rods are stronger than the 964 pieces and there are reasonably priced beefed up oem versions available before going the high line route to Pauter/Carillos.

All turbo engines and all 993 engines use the the same high temp alloy for their head castings. No 964 or earlier N/A engine uses this special alloy.

[JeremyD]

Thanks Bill - I figured you'd come through with the correction. Appreciate it...