914-6 engine rebuild/upgrade options - opinions?
 

Hi,
I have a 1970 matching # 914-6 I'm restoring and am at the engine rebuild stage, Over the years i've accumulated a few engine parts and would like more power than the 110Hp (When it last run the only mod was E cams). The use would be street only and I'd like it to run on 91 also I don't want to mod the 2R Case in any way that can't be reversed (bar internal changes) and it should to all intents and purposes look stock (hence using the webers) So I've considered the following options:

Option 1: Original 66mm non counter weighted crank, pauter rods and AA 86mm JE low Pomp P & C, 2.4 heads E cams, Webers

Option 2: Change to a 70.4mm crank, 2.4E Mahle 84mm P&C (which i have in my collection), Pauter rods, 2.4 Heads, E cams & Webers

The case I'd line bore, piston squirters, bypass mod, case savers (strangely already had IM bearings fitted)

Questions:

1. Has anyone got any feedback on the AA 86mm JE low Comp P&C set?
2. I have some 84mm Mahle Cylinders, would it be better to bore them to 86mm than use the AA provided ones?

Thanks for your input

Cheers Neven

MHO. As you're aware, the 914-6 engine is a base 911T engine. Drop the engine and put it in storage. It'll cost more to bring it up to your/needed specs. Can repurpose the Webers for an upgraded engine.

Start with a better structure; stronger crankcase, large valve/port heads, etc. In the meantime, keep watch on the various classified ads.

Sherwood

Agree, 2.0 to 3.6 all ballpark cost about the same to build, put the little T engine away on a skid.
I've got a 3.0 twin plug with Weber carbs, easy 250hp in my 914.

Over the 25+years I owned a 914-6 street car, it got a new engine (saved the # matching) every time I needed money for the family vacation. 6-7 if memory serves.
I never felt the 3.0+ engine was what my car deserved.
It had a 2.4 S MFI, all sorts of 2.0, 2.2, 2.4 combinations. The most fun, easy to drive, octane safe engine was a 2.7 RS spec engine with Solex cams and 40mm Weber carbs.
A real 200hp, great torque and no detonation issues even without a front cooler.
2.7 cores a relatively inexpensive, rebuild costs are basically the same as the original engine and all the ancillary items, exhaust, flywheel, intake manifolds and sheet metal all transfer easily. Even the ignition harness and 3 pin CD are applicable.

Id agree with henry on this one.
Especially since he had direct experience of it not needing a cooler.
He helped a friend with a 914 (Ethan) plan out the rebuild on his 914-6 motor I rode in it and the car is a complete blast.

That said i did once drive a 2.4E powered one and it was pretty good fun also.

HI Neven,

I have a 914 that is a 6 conversion. The last engine I had in it was a 2.7 with RS pistons, Mod S cams and Webbers, very similar set up to Henry with a little more cam. It was a blast and I would highly recommend. I also have shorter 3rd and 4th gears, which are great for the street. The one issue with the 2.7 is it would get to 230deg on a 75 degree day driven easy. It really needed more cooling. I previously had a 2.4MFI E spec engine. That engine did not get as hot even on warmer days. As you plan your engine choices think about cooling needs. You probably don't want to cut a original 6 to put in a front cooler but you might look at options for a cooler in the rear.

john

I have to agree with others here. Unless you are going to Concour your car and trailer it to shows, (in which case go with the stock 2.0 build) I would shoot for a 3.0 or 3.2. I did the 3.2 with 964 cams and SW chip and Ben McFarand's heat exchangers and muffler in my '71 914-6 and it just drives great. Plenty of power and torque. I opted to keep the Motronic injection and love it. No fuss, no fuel smell, reach into the car and turn the key and it fires right up. No changes to the chassis to accommodate the engine. I did add and external oil cooler up front to keep it cool in the summer in CA, but otherwise, no real issues.

The challenges I see with 3.0 and larger engines in the 914-6 chassis is the extra torque on everything. Trans, axles, trailing arms etc.
There is also the challenge of ignition options (3 pin CD is not compatible).
Flywheel requires something special and the aluminum motors weigh more.
Larger engines generally generate more HP (cool) but now cooling becomes an issue.
All of these conversions are available but why open that can of worms.
2.4/2.7 bolt right in. No need to reinvent the wheel.

One though: at 145mph, the stock 914 chassis starts to dance. 200hp will get you there (been there, done that) so how much bigger should it be?SmileWavy

The dancing (driving stress) can be reduced at 145mph or with torquer engines by reinforcing the chassis. There are chassis solutions available for quite some time. The stock chassis is fine for 4-cylinders and blvd. cruising; not so much after that.

Sherwood

No doubt there are lots of solutions if you want to strengthen a 914 chassis. If this was a 6 conversion I would think it would be a no brainer. With a factory numbers matching 6 I think you might not want to be modifying too much.

john

Actually, aero issues are the problem at that speed. Air under the nose, lift at the back as well as chassis flex. Of course there are wings, air dams and chassis stiffeners (I've done each extensively) but a stock 914-6 is collectible and demands a modicum of originality.

Then some of us do silly things to a 914 like this...Right Henry.

http://forums.pelicanparts.com/uploa...1610420647.JPG
http://forums.pelicanparts.com/uploa...1610420647.jpg
http://forums.pelicanparts.com/uploa...1610420647.jpg

Thanks Henry, you hit the nail on the head, FYI I have put in a chassis stiffening kit and the car is fitted with antiroll bars but my approach to keep close to the original, hence will probably go 2.2 and try and rebuild it to how I think Porsche should have in the first place (not crippled it to not compete with the 911T). I'm not aiming for a 145MPH racer otherwise I would have started with a 914/4

Cheers Neven

Not a racer. Just needed to move it along. It was a stock 914-6 with a slight flare, 4) 7x15 Fuchs with 205x60 Pirelli P7 and a stock 2.4 S MFI engine. Gearing was modified but 30 years have done a number on my memory.
It was late Saturday afternoon, a friend burned a piston in a 356 during qualifying.
We located a new Shasta piston and my goal was to drive home, pickup a piston and get back in time to replace the piston, in the rain, groveling on the ground late into the night so the car could run on Sunday.
That drive saw the high speed run and the lane dancing at 145 mph. Scary but memorable.
123 mile each way in 2hr and 40 minutes.
The point is 180+ hp power is all the motor in a stock 914-6.

http://forums.pelicanparts.com/uploa...1610594393.png

Neven, Nothing substantial to add here but my opinion- I have a stock bodied six with a 2.4 S built motor with Mod Solex cams. It is a very entertaining street car.

I have nothing against the bigger motors in 914’s and there is a lot of merit in the aluminum case 3.0 and bigger motors, but There is just something about the smaller motors that fit the spirit of the 914 in my opinion.

There is also merit in shelving the original motor, but if it were me, and your original cases are serviceable, I would build a short stroke 2.2 with The 2.4 heads and use Mod Solex cams with somewhere around 9.5 compression. Work with the Mahle jugs that you have. They can be bored and/ or Nikasil plated if necessary. Use the Mahle pistons if you can get them up towards the 9.5 CR. If not, go JE. All on the original cases with the machining mods you listed. Essentially your option 1 except keep you Mahles and go 9.5 and Mod Solex.

The fast Revving nature of these 66mm stroke motors coupled with the light weight chassis is just a sweet combination that channels the spirit of the 60’s factory race cars. The Mod Solex cams deliver really smooth torque as low as 2500 rpm with a real nice surge starting about 4500 rpm that continues building right up to 7400 rpm. Oh, and no additional oil cooling needed beyond the stock cooler and visually the whole thing is indiscernible from the original.

There is some resistance among the cognoscente about investing in mag case motors from the longevity standpoint, but in my view these cars are toys and probably won’t see 40,000 miles in our lifetimes. No reason that a sound, well built mag 180 hp motor won’t provide at least that much reliable service.

Any questions on how to do this right, just ask Henry for help. He has a soft spot in his heart for these cars ( and a shop full of all the right trick early 911 stuff) and he will do whatever he can to help.

One other recommendation- Install a side shift trans with a shifter kit from tangerine racing. 901’s can actually shift really nicely (once out of first) and this completes the driving experience in these cars - big fun!

Henry, I know you did this setup on a 3.0 a while back...would this work with a GT engine lid? I’m looking for ideas on my future 2.7 similar to your specs listed in post #4

http://forums.pelicanparts.com/911-engine-rebuilding-forum/419698-front-oil-cooler-pressure-side-not.html#post4059220

http://forums.pelicanparts.com/uploa...1611635532.jpg
http://forums.pelicanparts.com/uploa...1611635532.jpg

More air is always better. We used the small hole technique in an attempt to direct suction from the fan through the cooler.
I used this same technique on my street six but I did notice higher engine tempts on hot days at idle. Full throttle and cruise the cooler worked but sitting still was a challenge.

Good info, thanks.
I'll probably try under the rear trunk first and see how it works, can always move it if needed. I have a large Setrab with dual Spal fans I'll put on a thermo switch.

That looks like a RX7 cooler which has been a common choice for a 914 front cooler. Now the cooler of choice for the lower budget crowd is the MB oil cooler which is just a little bit smaller but easier to connect. The RX7 had smaller connector bungs that many weld and make bigger, the MB cooler already has bigger metric threaded bungs.
You could use either one for Henry's trick, but the MB cooler gives you something easier to install in the lid or one day in the front of your 914.

We used the RX7 cooler because we liked the idea of a built in thermostat.