Flat Plane Crank LT5

[mgbrv8]

Freshly rebuild LT5 thanks to a grenaded oil pump. They replaced the stock crank with a flat plane. It still isn't broken in yet. I hope the video and the pics work


Video:
https://www.facebook.com/holger.hove...3/?pnref=story


Pictures
https://www.facebook.com/norbert.vor...7474204&type=3



David Hetrick

[Fully Vetted]

Would this not be the largest displacement engine ever made with a FPC? I know Fords Coyote is the largest displacement FPC for a OEM at 5.2L. Not sure about aftermarket and/or racing applications.

[mgbrv8]

Originally Posted by Fully Vetted

Would this not be the largest displacement engine ever made with a FPC? I know Fords Coyote is the largest displacement FPC for a OEM at 5.2L. Not sure about aftermarket and/or racing applications.

Boy that is a good question. Im going to ask around?


Dave

[LGAFF]

I believe the Lotus GT-1 was 6.0 Liter

Renewing their ties with General Motors, they managed to get hold of a set of 5.7L LT5 V8’s. Lotus had helped develop this engine for the Corvette ZR1 when it was still a GM subsidiary. The engine was fitted with a flat-plane crankshaft and its displacement was increased to 6.0L. It eventually developed 615 horsepower with FIA-mandated 36mm intake restrictors.

[Hog]

"The factory GT1 Lotus Racing team (run by Fabien Giroixs-First Racing )would be the only ones to opt for the Chevrolet V8 instead of the Lotus 3.5 V8 turbo unit." The other privateer teams (GBF UK and Martin Veyhle Racing) stayed with the 3.5 turbo V8. These 3 teams got the 7 chassis that were built.

The flat plane LT5 was eventually replaced by Dodge V-10's in the Elise. Talk about a step----down. The V-10 couldn't match the lackluster performance of the Chevrolet LT5 V8 or the even worse Lotus 3.5 turbo engine. While the Lotus developed LT5 was a good engine, it was competing against race bred engines and apparently did have the top end power that other pure race engines were delivering.

Here are some LT5 pics the Lotus Elise GT1.(at least I think they are LT5 derivatives. Its tough to decipher as the 3.5 Lotus was a V8 as well, though it was turbocharged

[A26B]

The Moldex flat plane crank was coordinated through Jerrys Gaskets, as well as some gaskets & seals. The Main Studs were developed by Todd Pepmeier.

We are glad to have played a small part in the project.

[Jagdpanzer]

Originally Posted by A26B

The Moldex flat plane crank was coordinated through Jerrys Gaskets

Jerry,
Another excellent example of support for the LT5 ZR-1 brotherhood!!
How was Moldex to work with and what was their lead time to design and produce the crank?

[A26B]

Originally Posted by Jagdpanzer

Jerry,
Another excellent example of support for the LT5 ZR-1 brotherhood!!
How was Moldex to work with and what was their lead time to design and produce the crank?

Moldex was great to work with. Modified the damper bolt threads to a more common metric, without issue. Made to lightest possible weight, balanced to bob weight specs provided for rod/pistons used. Nitrided, same journal specs

Lead time was estimated at 12 weeks but ended up being 18 weeks between deposit & final payments.

I wouldn't hesitate doing business with them again.

[Jagdpanzer]

Originally Posted by A26B

Modified the damper bolt threads to a more common metric, without issue.

Excellent improvement to the LT5 crankshaft design.
I always wondered what must have been going through their heads when they decided to go with the M16x1.0 damper bolt lash-up instead of something more practical and readily available like M16x1.5.

[ZRapid-1]

Crossplane Crankshaft


Flat Plane Crankshaft


The Bottom Line

Crossplane Crankshaft Advantages: Smooth, vibration-free performance; distinctive American muscle car burble.
Crossplane Crankshaft Disadvantages: Heavier (harder to rev), requires larger crankcase.

Flat Plane Crankshaft Advantages: Lighter, more compact, more responsive (high-revving), better exhaust scavenging.
Flat Plane Crankshaft Disadvantages: Prone to vibration, lower torque levels.


Good video showing how the pistons move relative to each other:
https://www.youtube.com/watch?v=2AzrOPPZFzs
(Should have added exhaust sounds instead of music in the video.)