LT5 race engine
 

ZR-1 gang

I've got a question. Many years ago were some race engine build. I mean those which rev. up to >8'500 rpms.

Does anybody have some data sheets, performance numbers and pictures of these engines? I'd like to know with what cam specs, displacement, compression ratio etc. these LT5's did run.

Sam

Re: LT5 race engine
 

all I know is that they were solid lifter motors and the engine failed prior to the Silver State Classic....

Re: LT5 race engine
 

Thanks
Some performance numbers would be very interesting to see. If I am not mistaken they did have a 180 degrees crank, didn't they?
Every information about these engines is very wellcome. Especially the specs.

The reason for my request is we are going to build up a race LT5 for a racing team and look for components to get the most possible performance output. The first draw we've build is running with individual runners and pulls with stock cams about 550 crank HP by 7'500 rpm.

For the race season 2015 we want to increase the performance as much as possible. The same about revolutions. +9'000 rpms is the goal. Did anybody ever try cams with a 255 duration and a 0.500 lift?

Sam

Re: LT5 race engine
 

Yes, that's what's in my 427. Not big enough. I need +20 degrees, and +.030" lift to breathe >7000 rpm. BUT, that's with a 4" stroke. Your mileage may vary. What stroke are you running, and what rpm do you want to make peak power?

Re: LT5 race engine
 

Hi Todd
Theoreticaly we could go according the racing rules up to 545 cui. But then we would have to put additional weight into the race car.
Another point is the piston speed. With a 4 inch stroke or bigger it's hardly possible to go up to 9'000 rpm's.

So we think to go with a 4.075 bore and a offset grind stock crank with a 3.85 stroke. The power peak we hope to get somewhere in the 8'500 - 8'800 rpm range.

About mileage and idling we don't care much. What count is the power output with a useful torque band.

At the moment we drive with the 350 cui motor with ported heads and stock cams and 2 manifolds with individual runners. The LT5 like very very much to breath with the runners.

We look for the ideal cam combination and many other components to make the engine turn high.

Sam

Re: LT5 race engine
 

Lotus had the rear engine car that was a flat plane crank engine with a velocity stack type intake that I believe was up over 750 hp and revved to 8500

not sure what the stroke or all the mods to the valve train (likely solid lifters)

Graham,

you out there?? he would know about this setup

Re: LT5 race engine
 

Exactly this engine I mean. I remember about more than 10 years ago race parts were sold in Ebay. I could bite afterwards myself I didn't buy.

Very much I would be interested in this engine specifications.

Sam

PS: Gentlemen, please leave at the end of your posts your name because I do not like much to be inpolite and call you just "hello" or "hi". :-D

Re: LT5 race engine
 

Sam- Here's a 9,200rpm LT5......Listen, and enjoy:

https://www.youtube.com/watch?v=x2T3A14oy5Y

Re: LT5 race engine
 

The engine in the video is a different engine, but similar intake.

The Lotus GT-1 engine was 4.00 bore x 3.64" stroke, flatplane crankshaft. I have the blueprints for that crank, as a matter of fact. Just under the 6L limit of the GT-1 rules of the time (1997).

It ran stock size valves, at least initially. Comp ratio was "more than 12.0:1"

The engine ran in competition through a pair of 34.3mm intake air restrictors, such was the rules at LeMans back then. At Silverstone, running that restrictor size, the engine made peak power at 7300 rpm, 570bhp. Over 600bhp was available if the car ran at the larger restrictor size afforded for 1000kg weight.

LeMans engines were built for endurance, and so peak power speed was in the region of 6600-6800 rpm.

Graham once included an unrestricted Dyno sheet in a presentation at BG. According to that the engine made 620bhp @ 7000 rpm, and ~480 lb-ft @ 5000. LPE assisted Lotus on the project.

I wasn't a part of any of this, but most of the above was written in a Race Tech article from the era.

Todd

Re: LT5 race engine
 

Interesting numbers Todd

Very much I'd like to know the cam specs.

Our current engine has stock cams, stock compression ratio, stock valves and pulls about 550 crank HP at 7'500 rpm and 445 lb-ft of torque.

The new displacement we consider to make about 402 cui and run with a 13,5 : 1 compression ratio and with 97 octan gas.
I do not know yet if it would increase the airflow and VE to go on the inlet side with 1 millimeter bigger valve seats and 40.6 millimeter custom made valves with a 6,5 millimeter valve stem.

Sam