I am thinking of building a motor like this for my 914...

Short Stroke 2.8L Six


I already have the 76 turbo engine to use as a core. I can buy JE pistions for the cylinders I have, and get the cams reground to the correct profile. The heads on the motor I have would work fine by adding additional spark plug holes and the insert for the MFI injector. I can buy these to use for intakes instead of the pricey S MFI stacks.


I should be able to get 280HP out of it.

Anyone have any comments, opinions or just want to tell me I am full of ?

those throttle bodies have a fuelrail, so why make provisions in the head for MFI style injectors?

the 76 turbo engine is a 3.0, right?

Step #1
Gather up a whole pee pot fulla money.......
Step#2
Spend it all on a bunch of hard to find parts......
Step#3
Put it all together in a car and then whut?

The parts are not that hard to find. You use a 2.2 E or S crank. It fits in the 76 turbo case. The turbo compression ratio is too low for NA operation, so you replace the pistions with JE pistons at 10.5 to one. You put the correct cams, dual plug, and oversized valves, and MFI.


You end up with a 300HP screamer motor.


By using the 2.2 crank, you lower the displacement to 2.8L, but raise the redline to 9K.

very interesting to think about. but as stated, very expensive, time consuming, and, what is the purpose of the car? Will the mfi pump tolerate the de-stroking, re-camming, and dual ig'n? Even if it did, wouldn't it be peaky, laggy, and so unsuitable for street use?

estimate the $ and time to do it. multiply each by 2. estimate the eventual selling price. multiply that by 1/2. Are you comfortable with the difference?

Selling price is irrelevant. I am never selling this car. There is not enough money in the world to make me sell it.


Time is free.. It's my hobby. Money.. well.. that is another story.

The MFI pump is not being destroked. It just gets configured as an S spec pump.

It's going to be peaky, and a dog at low RPM ranges. It should be fun to drive though.

sorry MFI is a waste of time on that motor....

bigger hp and drivability will come from an ITB EFI motor....

MFI is cool, but alot of money for the cool factor....

crankfire and EFI (not megasquirt) will go further

and who will rebuild your MFI pump and make a space cam for it?

The whole reason for considering it is that I have everything but the 2.2 crank, the pistons, the stacks, and the cams. Beyond that its just a rebuild for me. And its not the first time I have rebuilt a 911 engine.

I was just wondering if anyone thought it would be a fun engine in a 914.....

fun: yes
money pit: hell yes
Cool factor - SCHWING!!!

PEFI/Crankfire > MFI

That sounds like a very interesting engine. Since you have most of the parts, why not? Sounds like a screamer.

Let me know if and when you start builidng it so I can learn me some!

Proven fact that engine is a screamer. Do it. The crank will be fairly cheap. This combo is down on torque (for a FAT 911) but works well in the 914 with a decent geared box.

I have always loved this combo. The only real custom pieces are the pistons (big deal)

Mild cleanup on the intake and exhaust ports is all that is needed.

We do the same thing with 3.6 engines. Destroke them with custom rods and pistons to 3.4. Dont even have to port the heads for a reliable 350hp. Under 10k plus core to build one.


B

I like the Old School aspect of MFI.....


AND PEFI can't match the injection pressure of MFI. More injection pressure means better atomization of the fuel.


And I have a short geared 4 speed with a tall overdrive 5th in my 914 right now. 5th is probably too tall, but I have a F that I can flip for 5th.

YES & NO. Build, thats a big fat yes. As for using it no unless you want it use it to adorn your luxurious ocean front work office. Ya know, next to them Rolls Royce antique aircraft engines or a Wenckel.

Velly plitty.

PEFI can beat MFI in every category. If you want High pressure Fuel injection you can turn up the pressure. You can go up to 100+bar with modern injectors. Stock injectors from the later model Porsches and 911s can handle up to 75PSi without any problems.

PEFI is light years ahead of MFI. You can tune the part throttle much better than your can with MFI. Your fuel mileage and drivability will be much better.

Otehr wise the motor sounds like a cool setup.

Then you don't know MFI..... It atomizes fuel far better than EFI because it runs at a much higher pressure.

Pacific Fuel Injection can convert any 911 T pump to S spec.

And I like the fact that the car will be period correct.

Oh.. and I also have to think about the cost of getting my tach rebuilt with a 10K scale.

Had a 2.8L in my 914-6 ... real screamer - mucho fun - unbeatable except for a 900cc Ninja. Key was, IMHO, the GE80s which really wake up the engine and the 40IDAs which tune all the pump to the low end acceleration ( vs 46s at the top end ).

Will freshen the engine over the winter, twin plug, etc and stick in my race car for a sprint engine - vs the more endurance 2.7L twin-plug that's currently in there.

It's fun ... do it !!!

If you are talking carbs.. I have a set of 914/6 carbs sitting in a box at home.


GE80s huh....

Clay - Sounds great to me. I think it would be a fun build and fun motor. *Whisper* "Build it and they will follow....."

Sounds great. I do have a 2.0 E motor sitting as a long block and the MFI with
intake. Should you get serious, get in touch. Dimitri

Want to trade the MFI parts for a set of 914/6 webers complete with linkages and manifolds????

Second the GE80 cams. They suit a 2.7 really well. Start pulling at about 3500.

I think you are right that MFI will get you much better fuel atomization than a programmable system.

I do question though that with such a custom setup that you will have optimum tune with an MFI system though. You can't just go add a bit more fuel at one space in the map with MFI... You could dremel your space cam I suppose - but that would take brass balls. A PEFI system will also get you an ignition system for pretty much free as well.

Your mileage will vary, since you're fuel map will be different....

I like the GE80 cams, but I think he should do some more research for cam selection.


B

Sure, it's that easy.
Racers that have these monsters shouldn't have to spend 20-30 K
to have them built, eh?

Hey Clay - I say go for it and offer these opinions - keep in mind I know NOTHING about that specific combo But I know these are general things that apply to that type of engine.

1. If you really want to spin 9K - and I am all for it as I built a 289 Ford for a guy that did just that years back - you do NOT want cams that start coming in at 3500rpm. You will never get to 9K. You will want BIG cam profiles that come in around 6-6500rpm. I know of no cam grind that can make solid power over a 6000rpm band and even if others claim they would - I would require dyno sheet proof to believe it.

2. Use the smallest piston compression height possible and the longest rod you can sqeeze to a point. Determine first a rod to stroke ratio in the 1.8-2.0 range. Then see if you can fit a piston in there with a 1.1" compression height (that is about my minimum without going to smaller tool steel pins which then open a Pandora's box regarding extra oiling). If you can get a 1.1" CH piston and a 1.85 or 1.9 R/S ratio, that would be your best bet. That way the piston is as light as possible and the rod - well get that as light as possible too.

Sounds like you already have internals all lined up other than the JE pistons, so #2 may be a mute point (as you are already set on your rods), but for the money, maybe consider adding a nice, lightweight I-beam rod into the mix at max length up to a R/S of 2.0. Then you minimize side loading of the piston skirts while also minimizing mass - between the long dwell and just the fact you want to turn 9K there will be a LOT of acceleration seen by the pistons/pins/rods.

3. If you really want to spin, then build it and forget the nay-sayers I built a bottom end capable of 9K, but cammed the car for 4500-7500rpm because I knew I just didn't have the balls to spin my own car that high for fear of disassembling a lot of high $ parts in a bad fashion. It has been easy for me to build engines that do it for others, but I don't have the money to run stuff that highly stressed, nor the desire to re-bearing the motor every season.

Good luck - sounds like a bitchin' project!

Build it. Rippin ass fun.

I think my 2.5 has GE80's (Greg?) Comes alive at 3.5k

I'm building a 3.0 MFI motor now.

Oh yea! Don't listen to the nay say'ers Clay!

(whispers)... go the distance......if you build it you'll have fun.....

That would be one major boogie down the road engine, MFI RAWKS!!!

Eric - what rpm do you run out of room (the engine noses over) coming on at 3500?

I know a few people who have had variously-built 2.8s in early 911s and 914s. The 2.8 is or was the max displacement for one particular class of SCCA racing, which is one of the reasons it was so popular.

Dave Ferguson had a 2.8 race motor in his Six. Awesome car--completely amazing. After he had Woods go through the carbs and the distributor, he would only quote the power at "something over 300 HP". It was a race motor, and required race gas and frequent maintenance and possibly frequent freshenings.

The 2.8 has a reputation of being a high-strung money-sucking pain in the butt of a motor. And being fun enough to be worth it.

I noticed that the people who built their 2.8s out of 2.7 motors (mag case) were more unhappy with them than those that built them on aluminum cases. Ferg used an early sand-cast aluminum case for his motor. I would assume that the 3.0 liter alu case would hold up as well as that one.

--DD

Dave is right about the case ... early aluminum is the strongest / best. Mine was built using a later mag case and it only lasted the predicted 60K miles - but God, it was a FUN run and I'd do it again - for the street !!!
Have a sand cast for the next ( race ) 2.8L engine.

Comes on HARD at 3500 exactly but I still have the old rev limiter in there... A friend is bringing over some 7300 rotors.

Gary Boss from the Mid-West runs this engine in his PCA racecar and he is incredibly fast. Go for it!!!!
van914

don't follow the other sheep, go for it!

Why screw up a turbo motor?
IMO N/A sux, but I'm a little biased.
A peaky, hard to drve high revving motor is fine on the track but a PITA on the street.
A turbo motor with 1 bar in a 914, now that is going to get er done!

Like I said, I'm biased.

Thanks Eric.

Clay, I dunno the cam specs on those GE80s but I bet they are done at the 7300rpm range to, or very close to done. Not 9K. I couldn't find specs on google, just this

...GE40 and GE80 cams, which are aggressive non-turbo cams with lots of overlap.

Lots of overlap implies tight lobe center, so that will be a peaky cam. My cam has 106deg l/c with 99deg intake (very rough/peaky) and has TONS of overlap. Makes higher peak power but my range is only 2200rpm between max torque and max HP. I don't think the GE80 will get you to 9K and be making power.

Just a little more fuel to support Brad's comment to think about the cams a bit more if 9K is your goal. My WAG is that you will need something in the 275deg @ .050" range and up to get there. That is a MONDO cam profile.

If you build it tho' I want to witness it around 9K for sure. I haven't heard a 6 up there yet - many a V8 and it is a whole new experience...

906 cams for clay....

Fast high reving motors are cool but expensive. You can't get away with cheap parts. Valves, springs, rods pistons, etc will all have to be carefully selected to reach the power levels at the rpm levels you desire.

You will have to run some pretty expensive valvetrain. Titanium valves and valve retainers, dual valve springs, custom cams with lots of lift, etc.

When you change rod stroke ratio you have to carefully examine the relationship between piston speed and port size/airflow capabilities. A port designed around, for example, a 1.6:1 RS ratio will have a larger volume because the piston will pull harder on the intake charge, than a port designed with a 1.8 RS ratio. These are things you will have to take into account when altering the operating parameters of an engine.

Piston speed will be determined by RS ratio, you should check the mean piston speed at the selected rpm limits just to make sure you don't exceed the design parameters of the rods.

AS far as camshafts go lots of lift will be your friend. Be prepared for that. Also you are looking for a peak torque in the 6500 range. Be prepared for the compromises.

Please don't take these warning as discouraging as they sound. A properly built engine will last for a long time and make the proper amount of power.

I have to agree with Sammy about the turbo engines they make better power than NA engines and they can make a better powerband for street engines. Huge cams and ports make it very hard to get a street car away from a red light or stop sign. I know it is cool when your engine thumps like a jackhammer at a red light , but when you have to rev to 4K to leave that red light it is kinda annoying. If it is a limited use street engine it may be doable, but you are the final judge of what you can tolerate.