Flat Plane Crank LT5 - ZR-1 Net Registry Forums

mgbrv8 · 05-21-2016

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 · 05-21-2016

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 · 05-21-2016

Quote:

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 · 05-21-2016

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 · 05-22-2016

"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 · 05-22-2016

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 · 05-22-2016

Quote:

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 · 05-24-2016

Quote:

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 · 05-24-2016

Quote:

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 · 05-24-2016

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.)

05-21-2016	#1
mgbrv8 Join Date: Jul 2009 Location: Texas Posts: 793	Flat Plane Crank LT5 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 Last edited by mgbrv8; 05-21-2016 at 04:12 PM.

05-21-2016	#2
Fully Vetted Join Date: Sep 2012 Location: Rockwall, Tx Posts: 1,510	Re: Flat Plane Crank LT5 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. __________________ _________________ 1994 AB/Grey #141 430 RWHP/392 RWTQ FBI Lyposuction / Secondaries relieved of duty / SW Long Tube Headers / Corsa Exhaust / FIC SS Injectors / MSD Coils / Lightweight Pulleys / Corey tuned B & M Shifter / Aluminum Flywheel / Samco Hoses / Shelby Series One's / C4 No Flex Frame Stiffener BBC - Bling By Carter: Custom ZR-1 Center Caps / Custom Plenum Plate / Air Box Knobs / TB Cover / Oil Filter Cover

05-21-2016	#4
LGAFF Join Date: Mar 2007 Location: Crystal Lake, IL Posts: 7,194	Re: Flat Plane Crank LT5 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. __________________ LGAFF 90 #966-150K miles-sold 92 #234-sold 1987 Callaway TT #17 1991 ZR-1 #1359 Last edited by LGAFF; 05-21-2016 at 10:28 PM.

05-22-2016	#5
Hog Join Date: Jul 2010 Location: Woodstock, Ontario, Canada Posts: 1,275	Re: Flat Plane Crank LT5 "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 __________________ peace Paul ZR-1 Net Registry Member #1494

05-22-2016	#6
A26B Join Date: Dec 2003 Location: Arcadia,OK Posts: 3,394	Re: Flat Plane Crank LT5 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. __________________ Jerry Downey JERRYS LT5 GASKETS & PARTS http://www.jerrysgaskets.com 1994 *ZR-1, Black/Black, Lingenfelter Aerobody, 416cu in, 3.91 gears, coil-over susp, Brembo brakes, etc. 2016 Black-Red, 3LT-Z51 Auto 8-speed. Last edited by A26B; 05-22-2016 at 01:50 PM.*

05-24-2016	#10
ZRapid-1 Join Date: Sep 2010 Location: Bethany, CT Posts: 119	Re: Flat Plane Crank LT5 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.)