Reverse rotation engine and porsche 930?

[ZachZ]

I hope that one of you guy here knows if this would work. I know that boats use reverse rotation engines. insted of fliping the transaxle could I use a reverse rotation engine?

[Dave Peterman]

In Theory it should work. Over the last 2 years I have worked on a friend's
wake board boat it has a Ford 351 W with reverse rotation.

My concerns are reliability it seems to break often.

Cam selection is going to be a bit tough. But Lee at Holman automotive may be able to help you out. He grinds them

The Boat Engines don't run very high RPM 5000 max on my freinds boat

[Russ Noble]

But why? What's wrong with flipping the transaxle?

Do you need a high motor position? Is this for a sand rail?

[ZachZ]

It is for a v8 914 porsche. I dont want to flip it upside down because the engine would be on the ground, not to mention the CV location is just right for an upright transaxle. Isky cams sells everything needed to make a SBC run in reverse rotaton, (cam, distributor gear, and timing gear) and they will even custom grinde a cam to any specs.

This has me a bit cousious. I wonder if this would work on the UN1? The delorean warehouse is about 3 miles from me here in texas and they can sell me a new UN1 for $2900. I wouldnt mind trying this as an experiment, but it sure is a ton of cash to blow without really knowing if it would work.

[Jac Mac]

Whatever you do, make certain that you use a 'New' as in brand new,never been run before Crankshaft, axles-torsion bars-shafts-cranks etc do not take kindly to suddenly being told that they should start working in the opposite direction ( Bit like Humans really ). Bearing that in mind your input shaft is obviously going to be subject to rev rotation plus all helical gears will need to be considered as to which direction the thrust will be directed.

[Jim S.]

I would agree with Jac Mac. One other thing is the ring and pinion is designed to take load on the load side of the teeth not on the coast side.
I think I would flip the ring gear and differential instead of reversing the engine rotation.

Good luck at what ever you decide.

[Big-Foot]

Most engine's crankshafts are drilled to oil the bearing in a specific direction of rotation. Putting oil to the bearing "after" it has already endured the shock loading of combustion is a quick way to destroy the bearings.. Camshafts - It's been a long time (probably 25 years now) since I've seen one, but there is/was a company that was selling direct gear drives for American V8s. These were to allow you to run a standard camshaft in a reverse rotation engine. Not all engines that were reverse rotation were used in boats. Many were used in Super-Modifieds on asphalt oval tracks..

[ZachZ]

Guys I am not worried about the engine what I am more concerned with is if the 930 or un1 would be able to run backwards. Are the gears cut in a way that it wouldn't work or would it work. I'm sure that someone on this site knows.

[Russ Noble]

How much ground clearance do you need? There are plenty of guys here with 5" ground clearance at the back with flipped trans and reasonable driveshaft angles. What diameter rear tyres do you plan on?

I would tend to flip it, fit a shallow sump with wings and run a skid plate under it if necessary. KISS.

[Jim S.]

I believe Renegade Hybrid and Powerhaus can do the machining needed to flip the ring gear within the case if you really feel that you can't flip the trans itself. There are more trans shops that can do this I just can't recal the names off the top of my head.

[Russ Noble]

Originally Posted by Jim Sheren

I would agree with Jac Mac. One other thing is the ring and pinion is designed to take load on the load side of the teeth not on the coast side.
I think I would flip the ring gear and differential instead of reversing the engine rotation.

Good luck at what ever you decide.

And if you flip the ring gear and use a normal rotation motor, the side thrust of the crown wheel is then taken by the opposite side diff bearing, which in a 930 is smaller and there is also the question of whether the case on that side is strong enough not to flex. That side was not designed to take any side loads and it's not possible to easily beef it up as in the case of a billet side plate with the normal setup. It is generally acknowledged the billet side plate is the first step in beefing up a 930 to take V8 torque.

There again torque transferred into the tranny will be limited by your wheel grip. You still haven't told us what wheels and tyres you are running!

There's only one solution that sees the loads in the transaxle transferred in the direction it was designed to cope with. Anything else will compromise transaxle strength. But if you're only running skinny tyres it wont matter. IMHO.

As Jim said, good luck with whatever you decide

[Howard Jones]

You intend to run the engine mid-engine orientation right? Engine in front of the gearbox correct?

You can run a Renault behind a Chev without any internal modifications except a correctly splined clutch friction disk center. Chev to Renault 21 bell housings as well as internal modifications are available from several sources in England. Start with Tornado. If you remain below 350 ft/lbs and treat it like it's your own money the gearbox will holdup pretty well.

If you are interested in a Porsche then call California Motorsports (sponsor on this forum) and ask away.

As another alternative you might think about a Audi. No need to flip these either. Have a look at the Diablo kits and related websites as well as a search on this site. Search "Audi transaxles"

For my money I would start out with spending the money on a Porsche G50 XX and saving money on power with a low cost motor. The engine can always be upgraded later but it's a bitch to reengineer a gearbox install after the fact.

[ZachZ]

Does anyone have a ball park figure on how much money it would cost to have a UN1 shipped to me with the shift linkage and a bellhousing for a SBC?

[Gregg]

Zach, I sent you a pm.

[Wayne M.]

I ran into the same problem running corvair trans in the reverse rotation. Putting power to the coast side of the ring gear produced gobs of side thrust. Like that technical term.... Gobs?? Enough to push the cast iron case apart. Also the syncro rings didnt like going the wrong way either. The grooves in the syncro rings are actually threads and tend to screw them selves onto the cone slowing the gears to the same speed. Running them in reverse are much less effective. Having a reverse rotation engine is not a big deal at all. I talked to several cam companies and they all can grind what ever I wanted in a reverse grind. Keep in mind the rotation direction of the dist and the oil pump, they have to turn the normal direction.

Wayne

[Joz]

ZachZ,
I have found a few UN1's by using this link Junk Yards and Used Auto Parts Directory and the prices have been from $125.00 to $500.00 depending on year and condition.

Joz

[Pete T]

If this is for a 914, it is a mid engine, like the GT40, and reversing the engine rotation would turn the transaxle in the correct direction. That would be the purpose of using a reverse rotation engine. You need to flip the ring gear if you use a standard rotation engine.

I don't see why it wouldn't work. The Corvair engine spun the opposite direction as most engines and Crown (one of the old mid engine Corvair kit manufactures) took advantage of it by mountng the engine in front of the late 4 speed Corvair transaxle. This way it spun the trans and diff gears the correct direction. Kelmark made a kit that had you spin the transaxle 180 and it put the drive power on the coast side of all of the gears. They had some reliability problems because of this.

[middy]

I think that if you reverse the engine rotation, you also have to replace the stock ring gear and pinion with a custom reversed r&p (teeth in opposite direction) otherwise you'd be putting power to the coast side of the teeth.

Am I right?

[middy]

Originally Posted by Russ Noble

And if you flip the ring gear and use a normal rotation motor, the side thrust of the crown wheel is then taken by the opposite side diff bearing, which in a 930 is smaller

According to Porsche Parts catalogue, both side bearings (taper roller bearing) are the same size (well, at least on the long bellhousing 930, not sure about the short bellhousing 930)

and there is also the question of whether the case on that side is strong enough not to flex.

930 case is made of aluminium, not magnesium. You know, hewland DG300s have removable side plate on both sides.

That side was not designed to take any side loads

Please cite your source.