915 to G-50 conversion 1986 Coupe’

[Fredie]

Hello all,
This is a shout out to anyone that can help.
I am in the process of converting my 86’ coupe’ Hotrod from a 915 to a G-50.
I am simply tired of the 915 that is inadequate for my NA 3.9 liter 993 based engine that puts down some nice power.

Here is what I have done:

.5) Engine and trans are out
1) CMS rebuilt a really nice box for me with a SBH and a longer first and better second.
And all the other nice bits etc…
2) I have all the bits installed being shifter, pedal box etc..
3) 3.2 style engine “tin” for a 993 3.6 install into g body car.
4) 3.2 engine console and crossbrace
5) PMS transmission mount adjustable.

Here is what I am finding:

1) even though the trans has been shortened, when I put just the trans up to its mounts, it seems to project rearward too far.

This is what I am hoping to accomplish:

1) I did all this dog and pony show so I did not have to hack the torsion tube. This is now just a street car and I would rather not chop and convert to coil overs. I do not mind if the engine goes back a bit. In fact the 930 sat further back. And, the center of gravity argument is a wash considering the G-50 is heavier.

Bottom line
Can anyone enlighten me as to what I am missing? Pictures, common experiences…
I get conflicting answers from various sources. And mostly, no one ever answers their phone or returns voicemails.

Thanks in advance

Regards,
Steve

[winders]

What model G50 gearbox is it?

[Geneman]

ask matt monson also.

[Fredie]

G-50 01. From a 3.2 Carrera.

[-Levi-]

I researched this for months when I upgraded my 3.0 to a 3.6 993 engine. The consensus I got from experts who do these for a living is it’s a coin flip if the g50 will fit without cutting. Even with the SBH work, some simply just don’t fit without pounding sheet metal or cutting t tubes.
Patrick Motorsports has done this conversion many times so it may be worth a call into them. Rothsport told me to just cut the tubes from the start. Fwiw, I just kept my 915.

Keep us posted and good luck

[PeteKz]

If it were me, I'd cut the tubes and whatever else is necessary. Then I'd use coil-over rear shocks without torsion bars. That way you don't have to weld in new torsion tubes and other stuff. Remember that if you move the engine back in the car, there's not much room to do so before you hit the rear cross member. Try to keep the engine where it was.

[winders]

Originally Posted by PeteKz

That way you don't have to weld in new torsion tubes and other stuff.

Even if you go with coil overs you still need to reinforce the cut torsion bar tube because the trailing arms put a lot of force at the inner mounting points. Also, the transmission is supported by torsion bar tube.

[Tyson Schmidt]

You can do it without cutting the torque tube, but it pushes the the engine back about 1/2”-3/4”.

If you use a stock trans mount, the nose will touch the tube. It can be clearances at the high spots, and a bit can be remove from the small snout on the nose cover as well.

I usually use a removed nose cover and mount for fitment purposes first.
I would do this with your adjustable mount as well to get the room to have the drivetrain as close to stock location as possible. You’ll need about a 5mm gap all around to avoid contact under load.

[Matt Monson]

Originally Posted by Geneman

ask matt monson also.

I’m not a ton of help here. I can tell you how much they are shortened, but know very little about the finer details of cramming one into a car.

Just going from my faulty memory, I do believe the 930 has a different engine mount, that might be the trick to moving it enough to install without doing torsion bars. I believe Patrick may make a new replica version to avoid struggling to find a good used original. I suspect if you rang them on Monday and asked about it they could tell you for sure if that’s the fix or not.

[spuggy]

I believe an '86 close enough to the changeover probably has both the G50 mounts and the 915 mounts on the body. Are you trying to use the factory G50 cross member?

PMS makes a cross member to mate 915 body mounts to the G50 (eg for earlier cars). It's slotted, which gives you more leeway when fitting. Also accepts aftermarket 915-style transmission mount pillows like the WEVO ones, which some view as a win over the bonded-in G50 mounts/no firmer options.

My 930/60 was already a tight squeeze into the '77 with a 915, pulley very close to the rear body cross-member. With a SBH G50, it would not go in.

Relieving some of the rosette welded plate over the TB casting buys you 10, 15mm or so for the nose of the G50 to go into. Don't know how much you can take off the G50 nose casting, but taking too much won't make you happy

https://forums.pelicanparts.com/porsche-911-technical-forum/440191-verify-g50-shortened.html

[Fredie]

Hello to all that have contributed. Thank you! I have been out of town working so apologies for not staying engaged.
Much of the above information is very helpful.
I have purchased several of the Patrick Motorsports parts for the conversion.
As I understood the whole purpose of shortening the bellhousing was to not have to cut the torsion tube.
I will mate the trans with the engine after I get back to my home and my little workshop and jack it in to see how it looks.
I’ll post my results when I get them.
Thanks again,
Steve

[Fredie]

Hello again. I am happy to report a successful outcome. However, it’s a lot more work than what I had anticipated
Here is a list of how I was able to get the SBH G50 transmission to fit in my 86’ coupe with a 993 based engine.

1) cut with die grinder the outer two layers where the g50 touches the torsion tube. Ball peen hammer until arms and shoulders are sore and continue. See pictures.

2) relief cut and pound in are where small snout touches torsion tube. Re-weld to seal up and for strength. See pictures.

3) Orient the PMS cross member as depicted in pictures.

4) Use the 1989 turbo clutch slave cylinder hose. It’s about 3/4” longer than the standard 3.2 carrera hose. And by all means connect the solve cylinder to transmission as you are jacking up the engine and trans back in the car. Also use a power bleeder to make life easier as well. This is also a good time to connect the starter cable as well as the drive shafts. Drive shafts just finger tight for now.

5) the engine cross brace needs to be bent about 3/4” forward. See picture. It has a bit of an arc to it.

6) the tunnel factory stamped and spot welded sheet metal cross brace under the 915 shifter needed to be relieved a bit in order for the g50 shifter to fit. Not hard. I just used a multi too to carve out the forward 1” or so.

[Fredie]

And a few more shots. For some reason they are out of sequence but I hope the point gets across.
Also, the whole area should be cleaned up with a flappy disc grinder for more clearance and a clean finish. Follow with primer and stone guard or rubberized undercoating and paint if need be. I left mine beige because the area around it was the same.

[Fredie]

I hope this will shed a bit of light for anyone wanting to attempt this project. I can say the whole shooting match cost more than the car when I bought it some 21 years ago. And I already had the transmission and shifter.
Regards,
Steve