Bill Verburg

There are 102 sets compatible w/ stock 993 rods just be sure to check before buying,

There are also difference in wrist pin and and wristpin o/s

currently FVD might be the best place to got the right parts

if the engine is already apart there s really very little reason not to get the 109mm base bore ins, they're much more reliable and for sure you can get the 993 rod versions w/ correct L/R pi o/s and a tad more compression to boot.

boomboomthump

I was aware he stepped away from the day to day a few years back but wasn't sure what happened after he passed away last April.


Thank you both for your input thus far. Taking notes.

boomboomthump

And you know that is exactly my background before I moved on to more expensive hobbies and found my way here.

I've always said, the air-cooled flat six is essentially just three old Harley motors connected together. So I'm not intimidated one bit.

ch3tman

To support your future planning... courtesy of @geolab :

Spec:











​​​​​​​Install Notes:

boomboomthump

Via some more researching, the camshafts that Patrick MS sells (and I had reference above) are actually the Web Cams you noted. I had mistakenly assumed they made them in-house.

Confused about something on these and the description. On the Web Cam website it says "993 RS Euro Hydraulic Rocker design. See part # 95-002 if you need a groove added to the mains" which is an extra $95 charge to machine the groove. Why is this needed if the description says it's a hydraulic design? On Patrick MS website it reads a bit more explicitly: "If 993 Hydraulic - Add Labor Part Numbers: 95-002 - Machine Oil Groove In Camshaft Main".

Lastly, since I'm keeping power-steering (street car, not a track car) that I want the "P/S" end main (seems obvious). Options are "none, P/S, Scavenge, or both". Presume "scavenge" is specific to turbos? (guessing oil scavenger pump maybe?)

boomboomthump

@Bill Verburg Since I have a '98 (v-ram) can you confirm, my exhaust valves are already the same size as the RS motor (43.5mm)? I believe the pre v-ram cars had slightly smaller valves (42.5mm). So if I did RS valves, it's only the intake valves that I'd need to do, correct? RS had 51.5mm vs 50mm v-ram (or 49mm pre v-ram).


Perhaps beyond the sizes I'm overlooking something like material/finish or maybe there's other reasons to throw another chunk of change at exhaust valves? I had figured this would be part of the costs, so if wise to spend money there I will. But when looking at the sizes, it crossed my mind that perhaps the exhaust side could be forgone. Maybe wishful thinking. $$$$


EDIT after some light night researching via options on FVD: Yes, it seems the exhaust valve is uprated on the RS vs standard varioram cars beyond them being the same size. Yes, I should replace them and baseline everything from new.

95_993

Boom boom,

One thing I didn't see on your list or discussed yet but may be obvious. Since you're starting with a vram gen motor, you will also need the earlier 964 style cam sprockets with the dowel pin so you can dial-in jn the cam. My early 95 happen to have them. This also requires cams have the woodruff slot machined to accept the woodruff key used with the earlier sprockets

One other point about head studs. When I was talking with Steve Weiner a few years back regarding my top end rebuild, he noted the turbo head studs are the way to go if you are replacing.

boomboomthump

I had come across some various mentions on the head studs which is why I asked. What type of build do you have on your motor? Perhaps consensus on an RS-spec motor is that they aren't needed. Still in my thoughts though.


As for the cam sprockets, no I had not seen that mentioned previously? I'll have to check and see if there are part number differences on the sprockets on a '98 vs earlier vs RS. Interesting that the X51 retrofit does not include sprockets. It includes the RS camshafts and the sprockets are "removed/reinstalled" vs "removed/replaced".

Kein_Ersatz

I'll check with my builder, but I do not recall one was used / discussed / called out in the parts list. My builder does have contacts with other air-cooled builders and he can get "specials" from some of those mentioned in this tread (headers for example).

The twist in my 4.0 build was 9M heads. That then caused a rethink on some top end choices, but bottom end was the GT3 path. For HPDE longevity (relatively) we opted not to push the RPM envelope.

As I "heard" it, the GW 4.0 builds used custom internals (crank, etc.) not the OEM GT3 path to get 4.0, if that is based in fact, that may then introduce a damper pulley to balance/match a "custom" crank and eliminate "track car" / Elgin cam idle vibrations :-).

MB965

Your stock/original head studs should be fine with 3.8. If you wanted to to replace, the factory Turbo Dilivar head studs are what Rothsport used on my 4.0 engine.

As 95_993 stated using the pinned cam gear is a good upgrade. My Web cams came with the cam sprocket keyway machined, but without the factory cam alignment tool slots. This allows adjusting cam timing vs fixed when using the factory tool. It also provides a mechanical pin cam sprocket lock vs the factory friction lock.
The machined oil groove is too improve oil flow at that camshaft bearing location, so I was told by Web. Very knowledgeable people I spoke to at Web before and after I purchased.

MB965

The GW/Rothsport 4.0 build does use the factory GT3 RS 4.0 stroker crank. The 80.4 mm stroke and 102.7 mm bore is how they get to 3996 cc. Also uses the RS 4.0 countershaft and GT3 oil pump. Rothsport has ATI build a damper tuned to their specific build parts. Necessary for addressing the harmonics on a highly modified engine.

Bill Verburg

The intake valve on the on the RS is 1.5mm larger than a v-rams and is Na cooled, the exhaust valve on the RS is the same size as the v-ram but is Na cooled, I vaguely remember but need to look up that the v-ram and n-vram intakes may have been Na cooled as well w/ hollow exhausts.

But remember that the port sizes and intake manifold tube sizes also changed, n-vram and v-ram are 43/39 RS is 46/42, the RS intakes tubes are also a few mm larger in diameter. So not sure that a bigger valve helps any, the Hot ticket is the Extreme heads that Mike used or the 9M heads that K/E used

for street use you don't need all the trick pieces, one thing not mentioned is that the stock 993 injectors are on the edge @~320hp they flow 235cc to 260cc/min, Bosch has some 310cc/min to 348cc/min for a little more head room

most important is to make sure that the guides are up to snuff , modern Al, Silicon-Bronze w/ a good seat pattern,

I'd also want a separated cat bypass a ta min, but 993tt mufflers flow better than stock or RS too.

Here's the parts list for the 3.8 kit that Porsche used to sell to update a base 993 vr-am
X51 kit for M64/21-part number 000 044 100 00 (no retrofit anymore, designation part number falls in repair kit cat.)
993.102.050.41 pulley
993.106.051.80 wheel hub
993.103.915.70 piston cylinder set slip in 107mm
999.707.152.40 o-ring x6 102x2mm RS is 110.72x3.53mm 999.705.022.41 993.104.035.44 cylinder head
993.105.409.42 intake valve
993.105.419.42 exhaust valve
993.105.246.41 camshaft
993.105.247.41 camshaft
993.110.722.00 intake connection x6
993.110.723.40 sealing ring
993.110.181.43 intake manifold x2
993.618.124.85 control unit
993.111.045.10 muffler
993.111.046.10 muffler
993.618.124.78 resistor
this kit could be ordered in three different versions, the above, version for option M529 and for 97- tiptronic

Bill Verburg

I think that Rothsport gets the ATI dampers from Neil Harvey, he developed the machining necessary to use them on the GT3 crank, I'm sure that Jeff tweeks them to suit.

Bill Verburg

You would know they look very different

here's Mike's

boomboomthump

I had come across that part number last night. Presumed it was just an updated part number. Looks like you can order it on all the Porsche dealer sites and the description does say "retrofit kit". Delaware Porsche sells it for $13,950. I had planned to email them and get the scoop on contents. I had seen a partial listing elsewhere (someone selling the kit via that part number on a European auction site a few years ago). Did see that it included a DME (I'm assuming they charge you a core to swap yours out with one that is loaded w/ the new program). Had not seen that the kit also included new mufflers. Did spot the new intake manifolds too.