Hello. I just finished an extensive 2+ year rebuild and upgrade of my engine, and, as this forum has been such a great help & inspiration to me, I wanted to share the experience and some lessons learned. I just got the car back from dyno tuning with Steve Wong and it's running mostly correct. And a disclaimer up front: I am not an expert, so if anybody finds errors with this, please let me know and I'll correct it.

To begin with, here's my car:



Here's the engine:



And here's the at-the-wheels dyno chart:



-Sam

 

Modifications completed are as follows:
- 3.8L Mahle machine-in pistons & cylinders: see post below
- Carrillo connecting rods with ARP bolts
- ARP head studs: see post below
- Webcams 993 Supersports camshafts
- gt3 oil pump: have to machine the crankcase to fit this
- lightweight flywheel: causes embarrassing stalling of course (see details below)
- Aasco valve springs and Ti retainers
- early 964 cylinder head leak fix
- Varioram air intake
- 993 fuel injection
- 993 engine harness: best deal you'll ever get on a Porsche part (see details below)
- 993 DME harness: see post below
- 993 DME with custom Steve Wong tune: see post below
- full 1.75" B&B dual exhaust: see post below
- Clewett serpentine fan belt kit
- custom air conditioning lines: see post below

Special thanks to: Kenny at Autowerkstatt, Loren Beggs, Steve Wong, Henry Schmidt, EMS, Dorian, countless contributors both here and the Pelican forum

 

I used Mahle machine-ins because they're supposed to be a little stronger than slip-ins. Having the case cut for these is pretty straight-forward, but I had a much harder time finding someone who could cut the required o-ring grooves in the case spigots. Unlike the stock 3.6L cylinders which have the o-ring groove in the bottom of the cylinder where it mates to,the crankcase, 3.8L machine-ins have the o-rings inside the case spigots themselves, a location that's difficult to machine. The shop I found also had the good forethought to stagger these grooves between spigots so the walls didn't get too thin in those locations. The o-rings used are 993 RS parts listed in the PET.

 

When installing these, make sure you're measuring to the last thread and not beyond to the domed end:





I made this mistake, and it causes you to not have enough thread engagement with the head retaining nuts because the studs are too far in the case. So 75 miles after rebuild I was on the highway for the first time, put my foot down, heard a loud pop, then heard scary noises and had very little power. I limped to a Kmart parking lot and was towed home. The whole top row of cylinder head retaining nuts on the right side of the engine had pulled off:





I reinstalled all the head studs to the correct depth and put new nuts on them.





Note the head nuts loose in cam housing





Note the lack of thread engagement between the studs and nuts



the horror...

 

This was my biggest hurdle and getting it wrong cost me several thousand dollars and eight months of troubleshooting. You need a 993 DME to operate the Varioram air intake (I've also been told you can get by with the 964 DME and use separate MSD switches to actuate the Varioram valves, but this seems half-a**ed to me). Here's the breakdown of the only non-driveblock 993 DMEs that should work (I'll use a '>' to indicate superseded part numbers):

993.618.123.03 > .06 > .GX: 95' 993, non-Varioram, 55-pin / OBD1, RoW & US, can be chipped to operate Varioram
993.618.123.11 > .KX: 96' to 98' 993, Varioram, 55-pin / OBD1, RoW
993.618.123.85: 993 RS, Varioram, 55-pin / OBD1, RoW

Any 993 DMEs previous to the 993.618.123.03 cannot be chipped to operate the Varioram. And you could theoretically use any of the US 96' to 98' 993 88-pin / OBD2 DMEs to run Varioram in a 964, but they can't be chipped either so you couldn't modify the tune, may have a harder time wiring it to the chassis, and would have to contend with all the emission-related hardware and software.

So I went looking for one of the 55-pin / OBD1 DMEs listed earlier. And I eventually found an ECU refurbisher who would sell me a 993.618.123.03 (Bosch 0.262.203.674) at a decent price. I figured I'd be able to chip this DME to operate the Varioram. This is the unit they sold me (notice that all part numbers are written by hand):



I then purchased a custom chip from Steve Wong that he swagged for my modifications and to operate the Varioram. My thinking was that I'd use this chip to break in the engine, then get Steve to do a dyno tune and make me a more permanent chip. So once the rebuild was complete, this DME and chip did run my engine, but not very well and after taking it to Steve for a pre-dyno tune check, I realized that (a few wiring mistakes from myself aside) it wasn't operating the Varioram correctly. This sent me down an 8 month path where I didn't drive the car, dropped the engine about seven times, and replaced practically every sensor in an attempt to get the Varioram actuation to work.

I suspected my 'hand numbered' DME from the beginning, but was hesitant to replace it, because this was the most expensive component. Big mistake. So after trying everything I could think of, I broke down and went looking for another 993, 55-pin / OBD1, non-drive block DME. They were extremely difficult to come by, and were more than $6k new from Porsche (without core). Eventually I found a 993.618.123.03 DME at a salvager that I had to pay $2k for:



However, this did operate the Varioram when chipped.

I now suspect that the original refurbished part I bought was not actually a 993.618.123.03 (Bosch 0.262.203.674), but something that the refurbisher created from some other similar Bosch DME. I'm fairly confident that it operates fine as a 993.618.123.03, but was not capable of being chipped to run Varioram.

 

To run a Varioram intake on a 964 you need a 993 DME and it's harness. The issue with the 993 harness and DME is this:

- 964 DMEs and harnesses are 55-pin / OBD1
- all Rest-of-World 993s are 55-pin / OBD1
- 95' US 993s are non-Varioram and 55-pin / OBD1
- 96'-98' US 993s are Varioram...and 88-pin / OBD2 with secondary air pumps, 4 O2 sensors, and check engine lights

In short, finding a 55-pin 993 DME harness here in America is kinda difficult. So I used one of aforementioned 88-pin US ones that I got cheap as a salvage part. The hard part was then converting this to be the 55-pin harness that I needed. I can elaborate on the details of this process if it'll help anybody. Suffice it to say that I compared the wiring diagrams for the harness I wanted vs. the harness that I had, then made the changes necessary to do the conversion. It was very tedious work that took a couple months, I'd recommend just buying a new harness from Porsche instead, but in the end the conversion did work for me.

 

In addition to the 993 DME harness, you also need a 993 engine harness. Luckily, there was a recall on these harnesses for fraying or fires or something, so there's a harness "repair kit" available from Porsche that actually contains a whole new harness for just ~$130 (a fraction of the cost of just buying the harness outright). The part number for this 'repair kit' is: 000 043 204 61

Note that in order to adapt this harness to a 964, a couple modifications need to be made including the wires for oil pressure, and the vehicle speed sensor on transmission.

 

From the beginning, I'd planned on having the car dyno-tuned to properly incorporate all of the modifications. However, I first wanted to break-in the engine and work out any major kinks, so I had Steve Wong swag an initial chip for me so I could do this. Unfortunately, between the wonky ECU, some wiring errors, and not having taken the time to figure out what my compression ratio was, the car ran pretty poorly during this period.

It goes without saying that you want to have everything on the car "mechanically correct" before you invest in dyno-tuning, because any wasted time on the dyno is very expensive. Well, despite my efforts, it took two full days to tune my car. A lot of time was wasted because I had accidentally installed the distributor off by a tooth or two (still not sure how to do this right, it always seems to jump when I install it), and because there was detonation that had to be diagnosed to my new pistons being high compression (which I didn't know because I hadn't calculated my compression ratio during the build).

 

I've wasted way too much time and money with these stupid lines. Stock 964 lines won't fit with the Varioram, and stock 993 lines won't fit with the 964 engine bay. I ended up getting 911 Design in Montclair, CA to make and install some custom lines that fit. They also fabricated the plate where the AC lines fasten to the compressor. This plate optimizes the orientation of the custom lines and routing, but also rubs on the oil filter slightly. I could look at using a shorter AC belt, but I’m also getting a spacer fabricated for the oil filter console so I’ve got some proper clearance.



Custom AC lines fabricated by 911 Design and routed around back of engine bay








Custom lines around back of engine. Note fitting touching oil filter


Custom fitting plate on compressor made by 911 Design




Hoseman lines, interfered with spoiler mechanism.

 

Lightweight flywheel + 993 DME = stalling
Still trying to fix this. Experimenting with adjusting the Idle Control Valve, will probably talk to Steve Wong as well to see if he can do anything. May resort to mid weight flywheel if necessary.

 

This exhaust was recommended to me, and (apart from custom fabrication) it doesn't seem like there are many alternatives for the 964. Beginning with the good; I have little doubt that this exhaust goes a long way in helping my engine make the power that it does, the construction seems fairly good quality, and under certain conditions it sounds pretty cool. On the other hand, that drone everybody talks about is very real and the I found the fitment to be kinda poor. I had to modify the muffler bracket because the holes didn't line up, the mufflers don't sit quite level, and I had to trim my bumper where the mufflers were melting it.







I'm going to deal with the droning eventually, but will probably keep the headers.

And it's worth noting that this exhaust is loud enough to make your neighbors hate you:

 

Power Window Relay - This part was bad and draining my battery. A new one from Porsche is ~$120 and I'm told it still has a tendency to fail. I was recommended a VW part that's ~$7 and seems to work just as well: 141-951-253-B-M206

Porsche workbooks - get these, they're invaluable, I have them as PDFs on an iPad

Checklist for removing/installing the engine - make & use this, write all the necessary torque specs on it so you don't have to look them up. Send me a PM if you'd like a copy of my well-used one

Compression ratio - cc your cylinder heads so you know what you're dealing with

gt3 clutch & pressure plate - don't bother with these, there's no need and the clutch pedal force required is painful

Rothsport oil line check valve - expensive, but no more smoky starts

Avoid accidentally redlining your engine while trying to start it the first time after rebuild - Yup.

 

- Head work and bigger valves - 9m massaged, xtreme, ?
- Match flow between air intake / heads, and heads / exhaust
- New Pistons to lower compression ratio - 993 RS, 9m, JE (recommendations?)
- ECU - later 993 or Motec (hoping more advanced ECU might solve flywheel stalling problem)
- exhaust - back to stock 964 or 993 to fix drone, cat bypass

 

Sounds like a roller coaster of a build. But the important question is are you finally able to enjoy it?

As for your exhaust... Good fences make good neighbors.

 

Wow epic intro!
welcome and glad you made it - way to persevere!

Steve W ca definitely help with the Lw Fly wheel stall.