Mating a VW Type4 engine to a Porsche 901 transaxle

[Supernine]

Hi, Newbie to your forum and looking for help.

We have a 1970 2.2L 911 (blown) engine with matching 901 transaxle. The engine suffered a timing chain adjuster failure and bent valves. It will take much $$$ to rebuild over the next years.

We have a 120hp Type4 VW bus engine that we would like to install mated to the 901 transaxle to run in the meantime. This conversion is a bit similar to a 912E Porsche and less similar but close to the 914 2.0L midengine setup with a 901 derivative.

There are issues we face and hope that within the community here, someone will have done this conversion and provide much needed advice and guidance.

Some of the issues we're aware of are:
we cannot use the 228mm Flywheel and Clutch Assembly from the bus due to the diameter being too large with the hump and larger diameter caused by the Ring Gear.

There is also the issue of the Pilot Bearing both size and location. This may not be a big deal that a reeming and larger Pilot Bearing won't fix.

Next, the thickness and diameter of the Pressure Plate. 120hp likely needs 225mm but perhaps 215mm might work. Then there's the thickness of the Pressure Plate face(not width), plus the style that will work with the unique Throwout Fork and Release Bearing of the 901 Transaxle built only in 1970-71. Then, are the Clutch Disc splines different versus the Input Shaft ones

Then, there's the Starter issue of both Reach Depth and Meshing with the Ring Gear.

Type4 engine would need longer mounting studs to mate with the 901 transaxle.

There may be other issues we are not yet aware of and we want to be certain of exactly what parts we need before ordering. It is our hope that we may be able to find a VW parts solution in order to keep costs at a minimum given that we are located in Canada. We face a brutal exchange rate due to our devalued $, we face heavy duties and taxes on imports and now, starting this month, face a 25percent Tariff surcharge on all products coming to Canada from the USA. As a result, say $1000. USD by the time we receive it translates to between $3000.-3500. $CA.

So, if someone in the Community were to have done this conversion and would be willing to advise and guide us, we would be incredibly grateful. Thank you. C

[Bruce.m]

Your best bet is a 914 flywheel. Its deeper & suits the 901 (& 914) bellhousing. You can use the matching 215mm clutch too.

However if your 901 gearbox is actually the 911 code gearbox (between the 901 & the later 915), then it has a pull-to-release clutch. The gearbox has a different release fork & throwout bearing. I believe you can retro fit the earlier release fork & bearing but there will be a number of parts involved. I can’t remember if the belllhousing needs modified for the release arm pivot & retainer.

Most of the parts should be available 2nd hand, although the release fork does wear at the pivot.

Also, the 901 & probably the 911 gearbox uses lower gear ratios more suited to the 6 cylinder engine. The 914 gearbox has higher ratio gears suited to the lower rpm type4 engine.

[Bruce.m]

Also, on the 914 the pilot bearing is fitted to the flywheel. On a bus, it’s fitted in the crank, so the pilot bearing would need removed from the crank

[Piledriver]

On a 901-914 trans the bus 228mm flywheel just needs a pilot bearing installed, given the ring gear is the same I would be surprised it there is a fit issue there. (its best to put the pilot in the flywheel in either case, very minor machining required)

As Bruce noted, the throwout setup is different, the gearing is lower, but a "120hp bus engine" indicates it has had some work done on it (cam, heads, etc) that not be much of an issue, would be down to details like what parts/work was done.

The bus starter is used on the 914 901 trans. Same part#.

Might be worth picking up a used 914 transmission, the early side shifter ones usually go cheap. Same clutch setup.

There may be another option... If in USA Kennedy Engineering makes/modified flywheels and clutches etc, they could probably set you up with a Porsche 225mm "pull" flywheel to use your existing trans/clutch as is on a T4. (912E: not sure which setup they used)

The more involved matter would be are you going to use stock T4 cooling & make engine tin and a rear mount like a 912E or use a "Joe Cali" conversion to use a T1 cooling setup (can be made or bits bought off the shelf from CSP)

Fabricating the surrounding tin is not horribly hard but has to be right, have to keep the hot air from getting recirculated.

Beautiful 912 with a T1 conversion on facebook, search for Thomas Simpson porsche 912. He put a big T1 motor in it but a T4 is actually narrower, and can ~easily get upright cooling as previously mentioned.

[Supernine]

Thanks, appreciate the info.

The setup is going into a 1975 911 chassis with square tubing frame and a 1957 356A Speedster body. We are hoping to stay with the Type4 VW bus engine tin work and modify to close al gaps.

The 1970 911 901 transaxle is rebuild and will use original 911 support. We were told we cannot use the 1979 2.0L bus flywheel due to larger 228mm diameter with big ring gear. Is this wrong.? We would love to use our T4 228mm Clutch Assembly if it will work and do ok with 901 Release Bearing and Fork setup. If yes, do we still need to reposition the Pilot Bearing? We don't want to be Clearancing our 901 trans and weakening the casing.

On another note, we are new to forums. We are. not being notified of replies or answers here. How do we fix this?
Thanks

[Supernine]

Thanks Bruce,
we are certainly grateful for your input and information.

Our 901 transaxle is from a 1970 911T built for the German market and imported to Canada years ago. The release Bearing setup was only avail in the 911s in 1970-71. The bearing alone is brutally expensive at over$600. ea.

Living in Canada means we face many financials hurdles visavis exchange rate, heavy duties, Taxes, shipping and now possible tariffs. There are no more vintage parts suppliers/recyclers left here and used parts are either non existant or priced beyond reach. So, we are looking for the least expensive way to go. Obviously, if we could use our current VW Type4 Flywheel, Clutch, PP and Rel. Bearing, that would suit us best.

Originally, our hope was to swap in our Type4 VW 2.0L bus engine for 2-3 years as we rebuild our 911T 2.2L engine but given our latest discovery of costs of the parts for rebuild, that may not happen, at least for a longer period of time. So, the Type4 setup is where we are focusing right now. So any and all help is most appreciated.

Thanks
SN