A trick to fitting RS heater bypass to 3.6 conversion?

[BarryJB]

Well today was my first start up (my mechanic started it once yesterday before he called me!) and short drive with the '95 3.6 engine in my 85 Carrera... and we have a couple of minor things to finish up, transferring the backup-lights switch pins, getting onion flanges and resonator tips added to the cat outputs, adjusting the throttle cable, and... fitting the RS heater bypass tube...

And the first - and only - "snag" - so far - is that the carbon fiber RS heater bypass tube (I got mine from Fabspeed) doesn't seem to fit. We already changed out the top fan shroud for the recommended 964 part 964.106.403.02 (oddly this 1995 993 engine had the later 993 part which the parts diagrams and lists say it is NOT supposed to have until 1996) and that looks like the right part, size and angle to mate up fine, but the bypass tube won't fit into the bottom space to allow fitment into the lower duct - it doesn't clear either the engine mount gusset or the fuel rail well enough to insert it and maneuver it. It can be rotated so that you can start the pipe into the duct but then there isn't enough clearance to rotate this non-flexible part into position...

All the instructions I've seen say it can be done with engine in... which is where it is!

Is there a trick, or do we need to cut the thing up and modify it - I note others have used this part in their 3.2 to 3.6 conversions and the 964 fan shroud part was the only complication I recall seeing, and we already did that!

Any suggestions greatly appreciated. Luckily with the great weather this can't stop me driving the car this weekend

[Jack Olsen]

Are we talking about the air duct on the left side?

[BarryJB]

Originally Posted by Jack Olsen

Are we talking about the air duct on the left side?

Jack, yes, exactly! I have the Fabspeed version of the factory bypass you show in your pic. By all accounts it is no larger than the OEM part, and I'm sure Mark K. at Black Forest has used this same carbon-fiber piece in one of his 3.6 991SC jobs.

I've seen your beautiful car many times, along with other 911/Carrera 3.6 conversions that also used a similar part (there are three of four on the market, OEM versions are hard to find and $$$$) so that also persuaded me the part should be a no-brainer drop-in - engine in or out of car.

Jae Lee at Mirage is doing the conversion. We both looked at it today and the part is big to jostle in, and we both tried a while, optimistic fettlers that we are. Here's a screen shot of the part from Fabspeed's install video (hope it's OK to mention them here

What do you think? Our plan is to cut it up &/or recontour it for more clearance. It's clearly a close fit between the fuel rail and engine mount gusset - as your pic shows.

[BarryJB]

Only got this one iPhone shot today - shakiness all mine, excited! Somehow I even deleted my first start-up video

[Bill Verburg]

is the connecting duct above the fan .02 or .00?

You need the .00

[Tom '74 911]

Barry -

I ran into the same problem w/my 3.6L conversion. I purchased a carbon RS heat pipe from Maxspeed (basically the same thing as Fabspeed I think) and it does not fit where it goes through the tin because of the engine mount gusset. I think the main difference is that the part is made for a 964, not an earlier 911 and I assume that the engine mounts are different - which is why it works in a 964. . .

I wonder if it works in Jack's car because his engine has been moved forward - maybe just enough to clear the mount gussets?

I hacked my tube all up but wasn't pleased with how it turned out, so I am using some SCAT tubing instead. This is one of the last things I need to work out on my conversion as I don't really get any air flow or heat through the system - I have Fabspeed headers w/heat. There doesn't seem to be enough pressure to blow air to the front and what little air that does make it through is luke warm at best. . . still looking for a good solution as I need heat. . .

Tom

[Jack Olsen]

Tom, one way to improve airflow is to add a Carrera kick panel blower to pull air in from the exchangers.

[Tom '74 911]

Originally Posted by Jack Olsen

Tom, one way to improve airflow is to add a Carrera kick panel blower to pull air in from the exchangers.

I've been thinking of doing that - it would fix the air flow issue. I still need to figure out why the air coming from the rear is only luke warm though. I'm not convinced that the Fabspeed headers w/heat have big enough boxed sections to heat up enough air. . . My last motor was a 2.7L w/backdated heat and SSIs - they worked great!

[DW SD]

I'm not seeing part .00 when searching through the catalog. Only this one: Pelican Parts - Product Information: 964-106-403-02-M100

You could always return the part and buy the orange ducting? Actually, I'm in Leucadia and have some new extra ducting in my garage you could buy, if you'd like - I was going to use it for brake ducting, but it is a far back-burner project. Given a little time, I could help fabricate the aluminum adaptor that you see in my photo.
Hi to Jae.
Doug W (with silver widebody early car)

[Tom '74 911]

Looks like Doug beat me to it - here's a pic of my SCAT tubing heat tube. . .

Doug - do you get enough air flow through yours? Did you add later footwell blowers?

[Tom '74 911]

Sorry to keep adding posts instead of condensing. . . but I just noticed that the photo I just posted shows the engine mount gusset that conflicts w/the tube where it goes through the tin pretty well. . .

[DW SD]

I'm getting sufficient flow. Bear in mind, I only hooked up one side (left heat exchanger) and have mine piped directly to the driver's side defrost outlet under the window. Here in San Diego, that's all the heat I've needed.

If I'd do it all again, I'd buy two marine inline blowers (setup for suction) and keep the engine bay totally clear. There is a thread somewhere on that approach. That builder just put wire mesh over the heat exchanger inlets to keep out pests seeking warmth.

Doug

[BarryJB]

Wow you guys are up early (non-PDT denizens forgiven )! Thanks to you all, I think the fog is clearing to a light mist now...

Hope I don't miss anyone here re responses:

Bill, I have both the 964 (02) and the 993 (00) fan shroud parts in hand - and the Fabspeed bypass tube looks like it mate fine with the 964 (02) part, which was SUPPOSED to be what was factory on my 1995 non-VR mill, but it had the 993 (00) part (in theory only 1996-8) which has the mating end (upper end, pointing left) less close to vertical - but that isn't where it won't fit, it's at the bottom by the engine mount. Just ain't enough room!

As an aside I read in a Rennlight article (Fitting a 964 RS cup heater bypass pipe to a 993TT) by Bob Brooks that if you want to put this 964 bypass tube in a 993TT you do need to keep the 993 (00) part. Once and if I get this thing in, I'll report on which upper shroud part worked on mine.

Tom - strongly suspect you've nailed my issue. I've retained the stock headers and H/Es, heater crossover and cats so I'm stuck with the lower tube location and engine tin. As I wanted to retain A/C I had a 993 engine mount modified. A buddy kindly CNC'd up two lugs and welded up those and a Rennline brace to it… and I suspect that has mullered the space that using a 3.2 hanger (for no A/C) provides - which is maybe why it fits on Jack's car? So I think I'll see if the original heater pipe used with the electric blower fits at the bottom and maybe try some elegant hacking there - or at least attempt to adapt the part elegantly. Since these photos, Jae added a bracket for the coils to the left arm.




I already have footwell blowers that work and Jack's suggestion was my plan. I bought half-a-dozen from Sean at Autobahn years ago and swap them out for a M^2 rebuild once I can't stand the squealing any more. Only two have burned up in the 15 years I've had the car.

Doug W, the part you mentioned is the part that supposedly fits the Fabspeed tube, which form-wise looks like all the other CF aftermarket parts and Jack's OEM plastic bypass (which would have been my choice if I could have found one for reasonable $).

The two different shroud tops are listed as shown below. Looking at both parts together (as I said we had both in hand) on the 964 part the hole slope is a bit nearer to vertical.


I think I'll mess with the part some first and if I give up I'll see if you want to part with some of your hose! I've got access to fab but thank you re your offer to help out with an ali part. Will indeed say hi to Jae - he's been up at Cosworth building engines for Singer quite a bit this year, of all the reasons for the transplant on my car to be a bit delayed, can't think of a better one!

Yup Tom if I can't do a nice job with the RS bypass pipe I'll go that way. I though about adding a tube blower too if output seemed puny, like the ones some folks use for brake cooling, adapting the stock electric fan wiring. By all accounts, with factory RS cars (blower deleted, by-pass pipe installed) the blower wiring was just taped up and and zip-tied to the fuel rail... so might be handy to keep it the same way...

Thank you everyone, a game plan has emerged!

[Bill Verburg]

All I can say is that I have a c/f version and an oe plastic version they both want the 964.106.403.02 duct and both have worked fine in both by '76 w/ 964 & 2 different 993 engines and w/ both of the 993 engines I've used in my 993.

I install the end at the tin first because it is hardest, then the top, on the top I use this handy little 90* awl to get tube end to mate w/ the duct gasket duct


The oe plastic one is much easier to install than the c/f one

[BarryJB]

Well that's definitely encouraging Bill, so I will persist with the cf part; can readily see that OEM plakkie part would at least flex a tad. I am curious as to whether it would have allowed engine insertion if it'd been installed while engine was out of car, I never thought to ask Jae to do that of course. Perhaps my engine hanger means the mill and hence tin etc is sitting a bit further aft. I get the impression most folks use the 3.2 hanger and forgo A/C, but I don't know if that choice even affects the longitudinal position of the engine. It is maybe an inch lower at the rear, by the add-on bosses on the hanger and a stack of washers each side.
But you've helped me decide now - it's gonna fit, one way or another! Will post any relevant or amusing consequences...

[uwanna]

Hey Guys,
I am looking for something a little different. I need to find the fan shroud cover for a 964 that has no outlet, just a cover. Smart Racing used to sell a fiberglass one, but they are no longer around. Any ideas where one could be had?

[BarryJB]

Originally Posted by uwanna

Hey Guys,
I am looking for something a little different. I need to find the fan shroud cover for a 964 that has no outlet, just a cover. Smart Racing used to sell a fiberglass one, but they are no longer around. Any ideas where one could be had?

If you mean these things, you can get them from Fabspeed et al (I don't think our esteemed host sells them) - or just make them. There's a thread on Rennlist about why the top one (which just snaps into the flexible port on the standard top air duct) is perforated... not sure anyone had a great answer
cheers
Barry

[uwanna]

Originally Posted by BarryJB

If you mean these things, you can get them from Fabspeed et al (I don't think our esteemed host sells them) - or just make them. There's a thread on Rennlist about why the top one (which just snaps into the flexible port on the standard top air duct) is perforated... not sure anyone had a great answer
cheers
Barry

Thanks for the reply. Many years ago, I just cut the air outlet off and covered it over with foil tape. Looks like crap! Here's a pic of what I am looking for. Smart Racing's product or something like it.

[BarryJB]

Well, at the expense of looking pretty stupid...

It appears there was indeed a "trick" - after digging the original plastic duct piece (that connected to the electric blower) out of the "junked" box, with the engine installed, it was easy to insert the OEM part; and then inspecting the lower receiver with a flashlight instead of in shadow revealed an internal ridge about 1.5cm down.

Comparing the lower part of the OEM part with the Fabspeed bypass pipe, it was clearly much shorter - so quite simply, the carbon fiber piece needed 2cm trimmed off the end...


The part of the pipe below the ridge (that mates into the lower receiver) on the OEM part is about 1.5cm; the bypass pipe extends 3.5cm past the (somewhat less sharply defined) ridge. So untrimmed, the bypass pipe wouldn't go in far enough to allow it to be rotated into place - doh!

A bit of bent awl work (I have one of those, Bill) et voilà! Trimming the part tomorrow, will post success pic later next week.

[NoEardGoat]

Success Pics???