I’m having trouble deciding which way to go with my ‘71 914. Needs very little metal work, but needs paint, interior and rubber, (all of it).

Since I have original motor and trans,

1. Restore, cheapest option $
2. Create a 914 Hot Rod with a 3L 911 motor (which I have)and 915 transmission. $$
3. LS swap with Boxster trans. $$$
4. Create a 914/6 clone $$$$

I can sell the 911 motor and recoup some costs. I’m pretty sure I won’t like the 901 trans. The 1.7 won’t thrill me. The LS will and the Boxster trans would be the best shifting.

What to do...

I'd do #2. Flat 6 sound and fast enough for me.

Do what the heck you want with your car. You do your thing and do it epically and we can all respect that.

Looking forward to an epic build!

Do the 3.0 and use the 901 tranny. Spend some $ changing the gears to better match the engine.

That's what I have and it keeps me happy.

Nothing wrong with a well-sorted 901 side shift in a 3.0 six conversion—so long as you aren't going to treat it like a muscle car in first gear. Can even be made to shift really nicely.

My vote is a mix of 1 and 2. I'd bring the interior exterior back to 1971 specs (original colors if good/you like them), with that 3.0 six you've got. Can make for a very fun car.

I talked to a guy at Sebring last weekend. He has a 2.4l 914/6 GT race car. He said the 901 was garbage, shifts like crap and needs a refresh after every track event. He only keeps it because he has to for vintage class. His is converted to side shift, too. He didn’t think it would last long behind a strong 3L. He said go 915 and don’t look back. He knew Porsche’s and his car is looked after by a premier Porsche race team. He’s run all over. If I go /6 I’d want to do DE events so it won’t be babied. He guaranteed a “money shift” with the 901 and shifter combination. That’s a painful thought and track insurance won’t cover that.

While the 901 would save me substantial money, an engine rebuild will make the trans savings seem like pocket change.

Can the 901/factory design shifter be set up to shift reliably and safely?

I can tell you I have a properly build/upgraded 901 that survived >10 years of time trials and races, and it seems like something is fundamentally wrong with that person's box if it needs that sort of maintenance/rebuild interval. So many early 911s and 914s are raced with that setup (or at least used to be) and not torn apart every event.

914 shifting and reverse lockout can be improved in various ways covered a lot on the board here (search for Tangerine Racing and Rennshift / Rennshifter). The main thing is to first ensure all stock linkage bushings are good and everything's adjusted right. Also the shifter reverse lockout detent plate. These bits are trashed on so many 914s.

With the 901, you would have to be super careful with 1st gear on a 3.0 and plus the 915 has the conventional shift pattern. Getting used to the dogleg pattern takes a while. So there's definitely merit to the 915 swap and I guess one thought is you could always try the 901 first then do the 915 conversion later if desired...

Hot Rod sounds like the best option! That's the route I would go.

Found someone local to work on the project. I’m going with #2. We are going to keep the CIS with some tweaks and go with a 915 transmission. I will start a build thread when we get cracking. A few months of planning and parts acquisition before the real work starts.

Been running a 901 for 31 years and never had a money shift…and it didn't shift all that nicely until 20 years ago—and only started shifting very nicely after some more futzing 10~ years ago.

Will grant that track and racing is another matter, but have also driven 901s in that scenario and they were ok. 915 better? Sure, but still not G50. And even a modern GT3 or GT4 won't prevent a money shift. As for longevity, 901s benefit from billet side plates and intermediate plates, 904 mainshafts, etc—and, for track work, a cooler.

Curious to hear from others with a lot of experience tracking/racing with the 901…is 915 stronger and more robust? Sure. Necessary for a stock 3.0? YMMV, though I might go 915 for a hot 3.0 or 3.2.

It really depends what you want. Our cars are starting to become seriously valuable so you really can't go wrong keeping it "all Porsche".

And, as someone who's just gotten to the "started driving" stage of an LS3/Boxster 6-speed conversion, I would tell you that it has WAY too much HP. It easily overwhelms the tires (245 on 9" wheels with GT flares) making a bunch of that HP unusable.

Plus, you'd want need to do a serious brake upgrade (I have Boxster calipers all around), chassis stiffening, trailing arm stiffening, etc., etc.
I've done all that so I feel like my car is an OK representation of a decent V8 conversion.

To each, their own. My first hand experience? I'd recommend against a V8.

If I could start all over again, I'd do a 6 conversion or a Subbie swap. And I think I'd keep it narrow body. End up somewhere over 200 but under 300 HP. Keep it light and nimble. Focus on handling and braking.

Don't get me wrong, I really like my build. I get to point at it and say "it's got 500+ HP..." It's fun to build, cool to look at and docile when you don't stick your foot in it.

Again, it's all about what you want from your car.

Sounds like you already have "sunk costs" in a 915 that you have on hand so not really an extra cost for your project....that said the 901 has low cost and super availability to go for it. I've been beating on 901's with my 2.7/6 that dyno's 215rwhp. The trans does take a beating and you're wise to have a spare--because surely something will get bitchy sooner or later so consider it as sort of a consumable. I swap between two tranz that have shorter & taller gearing depending on the track I'm going to...A/F/M/S/X for short tracks like Roebling or Summit Point & A/F/N/S/ZA for VIR, Watkins Glen, Sebring, Daytona. Enjoy the build & get on the track!!!

Buy three more cars and do all four options.

A 901 box will be just fine. Whomever you talked to has a screw loose

Chose the right headers, engine mount, sheet metal etc and you will be all set.

Are you farming out all the work? If so, custom engineering will get pricey.

I will be working with a local guy who specializes in air cooled Porsche and he has done this before. I will be involved in the build.

I don’t have a 915 yet. I’ve got a quote for one to my specs. IIRC the 901 requires a pricy and compromised clutch/PP/Flywheel combo to work with the 3.0. The 915 can use a standard combo. By the time I up-grade the 901, buy the special C/PP/Fw combo, I’m more than half way to the built 915. If I hop up the 3.0 in the future, it will support it.

I would like to keep the narrow body. The body on this car is really nice and cutting it up seems wrong. I need to look at wheel and tire combos for narrow body fitment. Would love suggestions for narrow body track wheels and tires that can be driven to the track.

My friend just got a ‘19 GT3 RS. No money shift unless the PDK craps itself in spectacular fashion

I guess no one told your friend that real GT3s have 6MT.

(Just kidding…sort of!)




Narrow body for a track car is tougher, but there's a thread going re: trailing arm ideas driven by a desire to sneak 215/60R15 tires under stock or near-stock rear fenders.

If I was looking for one tire to use on track after driving there on it, I'd probably look at 205/50R15 and 225/50R15 Toyo RA1, or other R-compound rubber. Or 225/50R15 at all four corners. Either way, offset and back-spacing will be critical to sneaking the maximum tire into the fenders with the minimum pull at the outer fender—and I'd look at Group 4 15x7 911R wheels mentioned in that thread or custom race wheels.

Shorter OD of 225/50R15 should help, but I suspect you're still going to need to roll the rear fender lips and/or fenders. Properly set up narrow 914s may not have the ultimate potential of flared 914s, but they can still haul the mail.

If you really don't want to deal with shoehorning, 15x6 Fuchs with 205/50R15 or 205/60R15 R-compound tires would work, as would 205/55R16 R-compound tires on 16x6 Fuchs. There are very good options in 205/50R15 and 205/55R16. I'm less up to date on 205/60R15…can be spotty.

You might want to check your sources and see that indeed the 2018 GT3 RS can be ordered with a PDK. I’ve been in the car....

I hate doing things twice, especially paint and body. If I stick with the narrow body and end up not liking it, adding flares would be re-doing the body. And buying another set of wheels and tires. My goal is to have a fun to drive/track 914/6. I’ve got to decide if I will be happy with a conservative set-up, tire and body wise.

Not quite true. You can use the 901 case from a 70/71 911, and put the 914 side shifter guts into it. Then use a 70/71 911 225mm clutch assembly on the 3.0 flywheel. It all bolts together with no aftermarket parts, and won't cost as much as you think. The only pricey bit is the throwout bearing. And you get rid of the pulley on the side of the transmission, because the clutch is a pull type. Also, there will be no load on the clutch tube because it is a straight pull.

I know this works, because I have a 2.4L engine with this clutch setup on it. The only difference would be using the 3.0L flywheel. But you can run anything up to a 3.2 with all factory parts using this setup.

Clay

I look at pete as the authority on many aspects of porsche in general as he is the former editor of excellence and is the editor of 000. That said I have no idea what can be ordered on a GT3. I don't follow much past 1998.

Can't wait to see the build and happy to help if I can

I have a 3.2 running a side-shifter 901 geared to best use the torque/power of the 3.2. It drives fine. I only have 2,700 miles on it but no issues at all. Would I convert to a 915 if I had the extra cash lying around? Yes. But I would likely take it straight to PMS for that conversion as they can do it correctly the first time in their sleep. Yes, there are others experienced in these swaps too. If I hit the lottery one day and have a spare $20K lying around my car would go to PMS for that swap.

Sorry, I was totally kidding about GT3s & PDK. PDK was made mandatory in the 991.1 generation of the GT3 & GT3 RS, which a number of folks—myself included—loudly decried. For me, that move removed my interest in the model—even if it was undeniably better on track and in performance terms. The 991.1-based 911R paid for the development of a 6MT for the 991.2 GT3/Touring, but PDK has been all you can get in a GT3 RS since 2016. For track work, it would be my choice. On the road, I feel PDK removes too much interaction in a sports car—40% of a driver's five primary inputs (steering + shifter + three pedals). And I enjoy heel-toe just a bit too much to lose that dance on the street…it's one that can be practiced at any speed.

I'm with you all the way on not wanting to do things twice. I have to redo my suspension, as it isn't to my liking, and am going to plan the replacement out very carefully. Narrow body for track work is a tough call. There are ways to sneak pretty serious rubber into a narrow-looking car, but I'd probably go M471 flares for a track car.

I ran a stock 901 trans behind my 3.0 conversion. You might not want short gears.

Sort of got to this point by accident.

GT LSV8 w/901
GT 914-6 2.7 w/901 Conv
GT 70 914-6 3.4 w/901

All different animals, my problem is finding time to drive them all

If you want to go all in on a track car and have the cash, do the big engine, 915 trans, etc. Then you won't end up spending the time and money to do good, better best.

The nice thing about 914's is they are a fun car to drive around town, even if they are bone stock.

Maybe one of each.

Steve Timmons/Instant-G took me out in one of his built 911-3.8 conversion cars. Full gas from first to about 4th. Slammed it into each gear. He was showing off a bit but it was his car to abuse as he wished. A 911 trans would have been on the pavement in the first 10 feet. I don't drive my car like that but Porsche moved to the 915 pretty early on for a reason. Most of us don't do it because when all is said and done, it's $10-15K depending on the owners skill or hiring it out.

There are some negatives to a 915. They weigh more, aren't usually as light or smooth shifting and require some specialized parts but it's all part of the journey.

Are you saying the 901 gears are unnecessarily short for the power of the 3.0?

Pick option 3 and sell me the 6

No the torque of the 3.0 worked great for me with standard gears. I had a short geared box at first and didn’t like it.

quote name='maj75' date='Feb 4 2021, 10:40 PM' post='2888482']
[quote name='Van914' post='2888331' date='Feb 4 2021, 12:50 PM']
I ran a stock 901 trans behind my 3.0 conversion. You might not want short gears.
[/quote]


Are you saying the 901 gears are unnecessarily short for the power of the 3.0?
[/quote]

Big trannys come with big weight
My -6 weighs in at 1820 wet with a 901
And gearing like few others F/J/O/S/V

Track cars don’t like extra weight

^ This.

There are plenty of drivers who can—and have—made 901s work (and last) in race cars with fairly serious horsepower. No NA flat six makes particularly impressive torque, let alone down low (check the hp vs lb-ft even among 3.8- and 4.0-liter GT3s with variable cam timing and every other trick in the book…it's usually 500~ hp to 325~ lb-ft). A number of older engines are lucky to make more than 180-200 lb-ft, and it doesn't arrive down low.

And the 901's weaknesses are well known: Hard use of first gear, the side plate, the intermediate plate, and—on track—cooling. And the shift linkage. All of these have been addressed by the factory and/or the aftermarket. There are some really good products for these gearboxes.

The move to a 915 still doesn't bring a "rock-crusher" gearbox, and there's a reason Porsche moved to the even heavier G50. One of my mechanics calls 915s "maintenance items"—in regular street cars—that Porsche finally addressed with the G50.

In the end, though, it'll come down to what a driver wants. Slam shifts and dropped clutches? Expect regular and expensive "maintenance" with any Porsche 911 gearbox…they just aren't designed for it and the weight over the rear axle, lack of easy torque, and torque peak are a recipe for mechanical disaster. There are plenty of cars that are better burnouts and slamming every shift home, as Porsche gearboxes demand mechanical sympathy.

Speaking from experience, the 915 is an expensive slippery slope mess. I have $10k in mine. Between the cost of a core $1k + Martin Bott kit $3k + limited slip $1500 + rebuild and assembly = $10k minimum. Plus different shifter, shift rods, clutch, flywheel, CV's, axles and misc. clutch adapter parts. That's not the half of it. Most reputable Porsche shops with tons of 915 experience can't make the Martin Bott kit work. Wevo stopped making there kit. Cable shifters are also another pain to get to shift properly. I finally gave up with local shops and drove six hours to Patrick Motor Sports in AZ. They went through the whole trans and found the shift rods weren't clearanced correctly. After PMS fixed it, I am totally happy with it. Shifts like a modern car, but more balky compared to a 901 or modern trans. My only issue was shifting from 2nd to 3rd. Half the time 3rd was a brick wall and I would have to fish for it. I am also hearing the parts from Martin need quite a bit of massaging to make them work. Reminds of the Vellios kit horror stories (RIP). After the above 4 years of hell, I love my 915/916 trans. The gears match the motor, but it will never shift as nice as a 901/914 trans. Also for autocross the 2nd and 3rd plane in a 901 is a blast, versus with a 915, your switching plains to go from 2nd to 3rd. However with the Rennshift, all I do is push up to go from 2nd to 3rd. The springs take care of the rest. My 916 trans actually shifts better from 2nd to 3rd, then it does from 1st to second. I heard the 915 balkyness can be improved with lightened gears. PRS914-6 did an article in Excellence using these gears. They have big holes in them!!

^ The above has me thinking 901 > 915, ultimately.

Unless you have big torque. The guy who converted my 914 to a six, and has done many others with 901s and, I presume, 915s, solved that issue in his own ultra-hot 3.5 with a 930 gearbox.

You are the first person that has described the 901 914 as “nice shifting.” More often it’s described as stirring a bowl of oatmeal. I have a couple of more race guys to talk to, but their frame of reference is “weight” and many time “class” which gives no choice in the transmission selection. They also think nothing of going through their 901s after every event. That’s cool for them, they have a “transmission guy” and that’s his job. They also have some rich owner writing fat checks to arrive and drive a sorted car.

The 901 usually shifts lighter and smoother than a 915. 911 and 915 trans tend to be more precise in a 911 since the shift rod is short and direct.

Panelbily hit my approach spot on. 3.0, 901 with flipped 5th, 1st is useless to a 3.0 so start in 2nd and wind it up. Use highest and best possible parts and ignition in the build. Then drive it.

I've been racing 901's in wheel to wheel racing since the 90's
and do not go through my box frequently

certainly not every event

as the motor gained RPM (8K redline) I did start loosing the Intermediate plate
but an upgrade to the billet plate seems to have solved the problem
have not opened my tranny in 3 years now and don't intend to

and Street use or lower RPM never caused that problem

A lot of rich race guys are idiots
but the majority of racers are not rich idiots.

the 901 is the lightest of the porsche trans
and probably the best shifting when all of the shift modifications are made to the linkage and chassis

it is not the strongest

I haven't logged the street miles of others
but Jon posted on this thread and I think Elvira (3.0/6) had tranny problems at the Palm springs event 4-5 years ago. I believe he told me he had thousands of miles and many many years on the trans before it gave him problems.

If you want burn outs... buy a muscle car
and if you want to spend more money... thats fine too
but the 901 is not a crappy transmission

brant

I’m going to reach out to Dr Evil to price having him build a bullet proof, great shifting 901.

Would converting my tail shifter to side shifter make a difference in shifting precision?

Converting to a side shifter is a Big improvement
The 3 shift rods (internal) are extremely easy to convert once the box is opened

But you have to replace the actual shifter and all of the linkage also

All of the trannys are $$ to rebuild

I would need the complete side shifter assembly from a 72+?
Is there any improvement with aftermarket shifter combinations and the side shifter?

You are very convincing. I’ll price out the 901 with all the modifications and the clutch flywheel set up to mate to the 3.0. And compare it to the 915.

Last question for tonight, would you NOT buy a /6 conversion because it had a 915? Because when I sell it, for sure there will be complaints if it has a 901. So more or less sellable with 901 v 915?

Yes. The shifting is only as good as the weakest link (pun intended) so concentrating on the linkage that connects the shifter to the trans makes a big difference. Minimum is all new bushings and bringing tolerances back to spec. Better is Chris Foley's/Tangerine racing linkage and firewall bushing. Icing on the cake is JWest shifter.

When I was a kid, I used to help out a buddy by riding his horses a few days a week. ☺

You are very convincing. I’ll price out the 901 with all the modifications and the clutch flywheel set up to mate to the 3.0. And compare it to the 915.

Last question for tonight, would you NOT buy a /6 conversion because it had a 915? Because when I sell it, for sure there will be complaints if it has a 901. So more or less sellable with 901 v 915?

Tail shift is the worst. Most of us 914 nuts that are happy with the 901 are running a side shift trans with after market firewall bushing and a tighter trans console solution like Tangerine racing. The rennshift with its spring loaded center, eliminates fishing for gears. I used a rennshift with my 914 trans. I only switched to a 915 because the gears in the 914 trans didn’t match my euro 3.2 motor. I bought a kit to convert the rennshift from a 914 trans to a 915 trans.

That’s probably the disconnect. I was thinking about my tail shift 901 and everyone else is thinking about their experience with the side shift 901.

I just looked at Tangerine Racing’s site. Their shift linkage looks very nice. They say it works with the Rennshifter. Is that a worthwhile upgrade?

Real 914-6, all things being equal, I suspect most buyers will value a car with a 901 more highly than one with a 915—the latter is the kind of "major" mod that raises that "what else was done to this car/what was its past life?" question.

Six conversion? I don't think 901 vs 915 has much effect, but this thread has only confirmed for me my preference for the 901.

Mine is a side-shifter with new bushings throughout, a Weltmeister shifter (gasp!), and a custom straight rod from the firewall back to the transmission made possible by the six conversion. I look at the Rennshifter and Tangerine's setup, but I have to say it shifts so nicely I see no need for either. At all. And I have driven a lot of cars over the years. They used to highlight how meh my 914's shifter was. No longer. It shifts just fine...quite nicely in fact.

Yup. Thousands of miles including DE's and AutoX.
The tranny started making nasty noises, kinda like I had straight cut gears only worse. Drove a few hundred more miles home without any problems.
Tore down the tranny and found this.
Click to view attachment
Click to view attachment

Yes! The transmission was still working when it looked like this inside.

Drive it more, then decide. Enjoy it from the driver's seat more than the shop stool or keyboard. Then your decisions will be based on what you actually feel and that will tell you what to do next.

My 901 has a totally different set of gears. First is Ca so its not useless. I don't remember the codes for the other ones but I had second gear cut off and replaced with something that made sense. Third to fifth are a gradual flow. I'm not interested in any competitive driving and the range of gears works well for me when we go on a day tour.

Saying that, I've needed to drop down to first to pull up some steep hills with tight turns and I'm thankful that I can do that without any grinding.

"I would need the complete side shifter assembly from a 72+?"

From a 1973 or up for side shift.