I've read the advantages of flat plane cranks versus conventional cross plane cranks- better scavenging, lighter mass, etc albeit at the expense of increased vibration. That said, I wonder if there would be any improvement/reduction in the oil consumption in my GTS motor due to the splashing and misting caused by the cross plane crank. It looks like the splashes per rpm would be half those of a cross plane but not sure if it really matter in mist formation due to the GTS' longer stroke.

I've had good success with a vacuum system but wanted to get advice on the use of a flat plane as I may some day want to open the motor up to drill oil drain holes for the pistons.

Thanks,

Joe

 

 

Hi drnick:
I have one of Colin's early vacuum systems and am quite pleased wit it.

All the best,

Joe

 

i had that system as well. made my own AOS (air oil separator) as well. good breather baffling and that should be all you need. i never burned/sucked in any oil. flat plane would sound nice, but you are looking at re doing the ignition firing order as well. maybe even differently clocked cams due to the pistons orientation being changed? not sure, but i just read where a guy put a flat plane in a Z06... stupid expensive custom stuff. but it does sound nice.

 

I must admit that I saw the same article this am and that's the motivation.............https://jalopnik.com/some-mad-genius...ank-1829362964

Happy 9/28 day!

 

Camshafts need to match the firing order.

So at bare minimum this would mean:
1. One off crank
2. One off set of cams - unless the blanks Colin had made could be made to work.
3. Standalone ECU

One thing to ponder, will this crank be designed around stock 928 rod bearings? If not, new rods are needed.

The 8 different length intake runners of the stock intake are bad enough with a stock engine and batch fire ignition / fuel. Going through all this work and keeping that would seem silly.

I love the idea just for the crazy sake of doing it.

 

What about using 944 cams? As an inline 4 they are running a flat plane crank, so would have the correct lobe clocking for a flat plane 928 motor.

 

the firing order is still wrong as that cam is made for 4 firing events per cycle...you'd be firing 2 at TDC simultaneously

though i have wondered if a 944 crank could work for this in a 928 block since the bore pitch is the same. would need a lot of work to fit a 2nd rod on each journal though (or get skinny rods)

though really, if you could jam a set of "180-degree" headers under a 928 body it would give you all of the sound and power benefits without having to change crank/cams/etc.

 

If you were serious about this, you'd be much better off buying a fully-sorted factory flat-plane crank engine such as the Ford Voodoo used in the GT350/GT350R from eBay along with its ECU.

 

That is certainly a consideration. I could do the swap and have my GTS motor to boot.

 

Here's an excellent article showing the many things the Ford engineering team did building the engine.

Ford Voodoo Development...

Like Erik stated, there's a lot more to it than 'simply' changing the crank.

 

you would be better off making headers to make it scavenge like a flat plane motor. It's been done before. The best person to pose this question to would be Bob Norwood. I can ask him next week about the gains from converting the 928 V8 to a flat plane..

 

 

What's the theory that crankcase gas flows would improve with the flat plane crank compared to a cross-plane crank?

 

Its a novelty. Nothing more. The 2 valve SS camaro with a cross plane still bests the 4 valve flat plane Mustang is almost every performance metric.

No doubt a flat plane is cool but for all practical purposes it justs a novelty.

Cant we just leave well enough alone....928s are fine and quite enjoyable as built...upgraded parts from later model are cool but when you start with sillynesss like custom cranks and cams you run the risk of ruining the car and making a 1 off noone else cares about and in the process spending more money for a lesser result.

In short...if you want a flat plane buy a mustang...it will be cheaper, perform better than a homebrew and actually worth something when you are done playing with it.