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The Purple Monster - 25/01/2006

Why did I put a Chevy LS6 Z06 Engine in my TVR?

It has a 5.0 320bhp engine after all. Err, well no it doesn't. TVR liked the sound of a number somewhere north of 300bhp for their 5.0 TVR Converted Rover / Oldsmobile / Buick engines.

When these things are dyno'd or rolling roaded with flywheel calculated they generally only come in at 245-275bhp (but do have good torque about 290 ft/lbs from the long stroke engine but 'rubbish' bhp / litre 50-55 bhp/litre). They can be made to make 350+bhp (easier to make big torque than big power) but over this things get very expensive and you are basically totally redesigning a 50 years old. I have heard of up to 400bhp for an Rv8 but also 12-16GBP for the privilege they just were never intended to get any where near these numbers.

A lot of people had been discussing doing this for some while on Pistonheads but no one seemed to want to be the first to bite the bullet. I had been banging on about it for as long as I had had my last Chim 500 (4 years back) as I had used a Chevy Race engine builder for a TR4 race car I have, for years, and seen many a crazy chevy powered cars at his place!

TVR at Snetterton So after the cam went in my next Chim500 after only 3k miles of ownership (27k miles FSH!) my mind was made up. (Last one never missed a beat in 20k miles but was never fast enough). So thought bugger this, if no one else is going to do it, I will. My father and I have a good deal of experience ripping my TR4 and father TR6 racer apart over the years so got a new cam in the otherwise fine 500 engine (Christ it cost a lot and in retrospect we could have done it ourselves for a lot less) and sold it (and gearbox see later).

Planning is everything. We researched this with my father down to the smallest detail it was never going to be easy, but good planning made it a lot easier. Sourced an engine from US from someone that will build up a new engine Z06 LS6 from used block but new heads, cam, crank, rods, rocker etc (a new build) but second hand ancillaries power steering pump, Alternator, Coil Pack, etc. Winged LS6 sump will not fit so sold this and went for a really cool alternative. My engine is a new 02-04 spec LS6 with 85mm maf (405bhp) not the earlier pre 02 (375bhp) 75mm one.Chevy Engine in TVR

Bit of detail here the LS engines are the latest in a long line from Chevy and in 97 a totally new engine came out in all alloy, still pushrod, but ultra modern in all other respects, separate individual coil packs (no distributors here!), and a very advanced totally programmable ECU (a million miles from the Rover Efi). There were two specs of engine available for the corvette (more for other chevy vehicles), the std LS 1 320-345bhp (depending on year) and the top models Z06 405bhp version. Of course I had to have this one!

The gearbox was always going to be the weak link with the std Tremec T5 only being rated to 300ft/lbs (even though TVR run them with more than this in the Cerbera). But TVR do not have a car with anything like 370 - 400+ft/lbs of torque and I wanted this conversion to be totally trouble free.

So the T5 gearbox was sold and the Tremec TKO600 purchased (and the parts needed to fit it to an LS engine). The gear position can be moved to one of 4 positions on the tko and we had to get a new kit to move to one of the forward positions. This does away with any remote linkages as on the t5 and put the stick into the box right into your hand.

We engineered a hydraulic clutch release system into the box as we got supplied' some' bits to make it run with a slave-but it all looked a bit Mickey Mouse so now we have no slave and can bleed system without jacking car as per most modern cars!

Engine and box are a good but Tight' fit (T56 from Vette would not fit without cutting chassis and did not want 6 speeder in any case they are Huge too). Needed a custom prop shaft TKO has a larger output shaft as it is expected to be bolted to car with a lot more torque. TVR diff is fine as a BTR used in lot of Ausy V8 cars.

One off exhaust system had to be made to replace the TVR mild steel one which was poor in that the pipe sizes rapidly changed from the head to the large intermediates to a huge main cat this was very poor for a gas flow perspective, then these then went into one 3 inch single bore an back to a twin bore again - mad. I have smaller primary header pipes than on a Z06 (supposed to be better for gas speed) in order to package it but I only have two very small pre cats in each side to keep it all MOT legal so should end up much the same for each installation. These were the only bit left from the original system parts sold, some in scrip.

The Loom was a hugely important part of the conversion and custom one was created and then fitted by a person we know from racing (he does looms for race and rally cars).TVR Exhaust

The build went a lot easier than you would imagine with such a huge swap but I put a lot of that down to my father being absolutely meticulous in all things he does (can be annoying at times as I have the patience of a fly!).

The engine and gearbox mounts all had to be altered dramatically or fabricated from new, but right from the start I did not want to cut any parts of the chassis this would make it harder from an insurance perspective so every thing was done to get back to the original twin hole mounts on the TVR.

There are a multitude of other things to do to make it all run, re plumbing in new larger fuel lines, moving electric underneath, larger fuel pumps, placement of air filters, a big list.

Anyway the aim once we had all the parts in one place (a lot of the initial time was doing this wasting some time trying things finding out they would not work or fit and changing them etc), was 8 weeks out from Le mans to go with the Berkshire mob and with it all run in. I did have a week to 10 days when I could not do anything so took the body off 8-8 inches (seem silly not to) and gave the chassis a once over with the wire brush and loads of hamerite it lives in a garage all year now so should be fine for many a year now. Got it all done 2 weeks out and put 1000k miles on it in 2 weeks.

The car felt mentally fast, but we did not know we were only scratching the surface. Le man's and a few more k miles out of the way and it was about time for the rollers (Surrey RR which is know to be accurate or if anything read slightly low)-but when we ran it up it only made 320bhp and 365 ft/lbs. Not a good day I did think I had been sold a duff engine or and LS1. But Charlie of SRR said he had never seen a car running so rich since he had the rollers. The ECU basically had a supposedly Z06 and then some programme. This was later found to be rubbish after Wortec the Holden Tuning people took it away for a few days tuning-all done in the car driving it around with a lap top plugged in. Back to the rollers and after few runs and a bit more tweaking we got 380ft/lbs and 390bhp (Paul Wortec says that it was really making more like 400 as we were dropping 2 deg of advance on the last run when it was starting to get hot running fuel advance on the road with the pc monitoring it-these engines are very temperature dependant and 1 deg of advance at top revs is 4-5 bhp.) So basically we were getting what a std Z06 was on the same rollers (with slight smaller headers) and with the promise of a good bit more-my exhaust not being as it should be in one area-Paul thinks there is another 25bhp to come easy with a few minor tweeks and ecu time. If I cammed it (rockers, cam and valve spring set) I could add another easy 40-50bhp! (maybe in a year or two!)

Luckily I had put Tuscan / Cerb AP CP6600 calipers and 300mm disc on it pre-chevy as I ways thought the std stuff was pants, will be getting larger rears at some point and will be getting a custom cage much like the New Tuscan 2 but with side bars for safety in the new year.

TVR Chimaera with Rover 5.0 engine
Power to weight before 270bhp in 1080kg = 250bhp per ton
Torque to weight before 290ft/lbs in 1080kg = 269 ft/lbs per ton

TVR Chimaera post swap LS6 / Z06 (based on base 405bhp / 400ft/lb figures)
Power to weight before 405bhp in 1110kg = 365bhp per ton
Torque to weight before 400ft/lbs in 1110kg = 360 ft/lbs per ton

It was not cheap but a lot cheaper than getting a New Tuscan or a C6 and a good bit faster than both. Had to put on full Leda suspension and stiffer springs (spec to my poundages), to get chassis to keep up with speed, allow it really was not that bad unless really pushing or on track-then not great!

Currently over 13k but I did use new gearbox and clutch release, and new LS6 (not second hand or LS1 new or second hand) and full new custom SS exhaust. There is a huge amount of hidden cost that you do not envisage when you do this type of thing-but that always turn up). But then I did sell the engine, gbox, brakes and various smaller bits.

So in reality not THAT much more 2 or 3x a Taraka-and I like being different! It is great when you open the bonnet!

Uprated brakes It is MAD AND BAD. Already working with a TVR Chimera owner in Lichenstein to do a copy of my car!

Chevy's Small block have always been THE engine and now the modern all Alloy LS engine are here it is crazy not to use them!

TVR will no doubt do this at some point-but if anyone want the same contact me via Pistonhead (jellison) or jrellison@lgc.com

Cheers
Jon


Article from Jon Ellison, this article also appeared in Sprint in Feb '06.

You can see and hear Jon's awesome TVR Chimaera here.


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