LS flat plane crank for street use?

[PackardV8]

Currently on auction on BAT is a nice-looking '06 'vette https://bringatrailer.com/listing/2006- ... rvette-11/ described as having:

a modified LS-based V8 featuring a Sonny Bryant flat-plane crankshaft, Carillo rods, Wiseco 12.5:1 pistons, CNC ported LS7 heads, and more. The engine now revs to 8,250 rpm,

Anyone here have street experience with such a build?

Yes, Ford makes it work with very light pistons and much motor mount science, but would an aftermarket shop have the science?

the seller states the car has been taken to track days and driven a few thousand miles since the engine work was completed.

Since it's only gone a few thousand miles since the high-dollar build, maybe a bit much for the street?

[Mark O'Neal]

Seems kind of pointless, even if it didn't have any issues.

[FC-Pilot]

Seeing first hand how bad Ford struggled with theirs you could not pay me enough to put a flat plane crank in a v8 I would own.

Paul

[GRTfast]

Seeing first hand how bad Ford struggled with theirs you could not pay me enough to put a flat plane crank in a v8 I would own.

Paul

They do sound really cool though.

[CGT]

They do sound really cool though.

Really really cool.

[LoganD]

Seeing first hand how bad Ford struggled with theirs you could not pay me enough to put a flat plane crank in a v8 I would own.

Paul

They didn't struggle because of durability, they struggled because of NVH. This necessitated a compromised crankshaft, flywheel, and damper....and that hurt durability.

If the GT350 hadn't been offered with a manual, it wouldn't have been an issue.

[Orr89rocz]

Skip the flat plane and do 180 deg headers

https://youtu.be/mJ_gDDkTKUM

[BigBro74]

To each his own- I dont think flat plane 8's sound all that great (Merica')

[cv67]

Agree..high rpm may sound neat but wont last too long

[FC-Pilot]

Seeing first hand how bad Ford struggled with theirs you could not pay me enough to put a flat plane crank in a v8 I would own.

Paul

They didn't struggle because of durability, they struggled because of NVH. This necessitated a compromised crankshaft, flywheel, and damper....and that hurt durability.

If the GT350 hadn't been offered with a manual, it wouldn't have been an issue.

I got to do some testing on the GT350 before it’s release and worked beside and with the team. I can’t say too much other than I had fun testing the car, and I would not put a flat plane crank in my own V8. NVH issues can create durability issues, and that all I have to say about that (in my best Forest Gump voice).

Paul

[LoganD]

Seeing first hand how bad Ford struggled with theirs you could not pay me enough to put a flat plane crank in a v8 I would own.

Paul

They didn't struggle because of durability, they struggled because of NVH. This necessitated a compromised crankshaft, flywheel, and damper....and that hurt durability.

If the GT350 hadn't been offered with a manual, it wouldn't have been an issue.

I got to do some testing on the GT350 before it’s release and worked beside and with the team. I can’t say too much other than I had fun testing the car, and I would not put a flat plane crank in my own V8. NVH issues can create durability issues, and that all I have to say about that (in my best Forest Gump voice).

Paul

Yea, I mean to curb NVH they don't even use a "real" or "ideal" 180 crankshaft or the corresponding firing order. Ferrari got around the NVH issue by simply removing any direct contact between the driver and powertrain and using fancy engine mounts. If you put a camera on a 458 engine while you're thrashing it the engine is vibrating and moving all over the place.

While I commend the effort and admire the risk factor in pursuing such an engine, by the time they compromised the thing and added the heavy ass flywheel and all that, the benefits of having that crankshaft were gone. BMW realized that would happen when they designed the S65, and that's why it's cross plane. I think the S65 would have been flat plane if they'd decided to forego the manual in that generation M3.

[CGT]

What engine related issues does the GT350 have? I hadn't heard of any, and they are specific to the 6sp cars alone?

[LoganD]

What engine related issues does the GT350 have? I hadn't heard of any, and they are specific to the 6sp cars alone?

Can you even get a GT350 with an automatic?

The reason Ford (and BMW) was so concerned with NVH on a manual transmission flat plane V8 is because you physically touch the shifter. If the engine mounts are soft enough to isolate the vehicle from the engine vibrations, then the shifter moves all over the place. This isn't good for perceived quality. You could theoretically fix this issue by having a vehicle mounted shifter, but generally this results in crap shifter quality, and it was probably out of the question for the GT350 as retooling the trans and shifter would have been expensive.

If you've ever been in an F430 with a manual (so rare!), you'll know exactly why they were concerned.

[FC-Pilot]

What engine related issues does the GT350 have? I hadn't heard of any, and they are specific to the 6sp cars alone?

The issues I am familiar with were in testing where we were hard on everything any time we touched the track. I do not know what they might be seeing in normal street use. They/we went through a good number of engines in testing. Much more than the former GT500 engine platform. They had a few 90* crank engine that they kept around when they were low on engines. They never had issues with them.

Logan is right in that one of the big hurdles was the harmonics coming through the shifter. Once they worked through a bunch of the other issues that one hung them up for a while.

The next car is going to be "stupid fun" to drive.

Paul

[MadBill]

I read a quote by a Pro Stock crew chief that tried a flat crank ~ 15 years back along the lines of: "It didn't make any more power and it vibrated so bad the tach looked the size of a dinner plate."