LS3 Chimaera

[stefan1200]

Hi all,

if everything goes as planned, I'll be going LS3 with TKO600 within the next few month. Loved these engines for a long time so I chose this way over upgrading the RV8. I know it has already been done by a few people on here who also might be able to answer some basic questions. I've also seen that Sportmotive and other specialists offer LS3 conversion up to 480hp, also for Chim and Griff.

Brake upgrade has already been done and Intrax 1K2 coilovers will be fitted after the engine conversion is finished.

So, considering spirited road driving and the occasional high speed blast on the autobahn, I'd like to know your opinion with these power levels on

a) chassis strength
b) diff (40k miles)
c) driveshafts (newish, about 6k miles.

Any thoughts highly appreciated.

Cheers,
Stefan

[stefan1200]

Brummmie said:

Driveshafts snap like carrots, even the Raceprooved items.

But the Dave mac props ones i have fitted have lasted so far.
The Cerbera diff is different to the Chim one?
But i have gone for a 3.08 ratio change, i have broke one Crown wheel and pinion so far.
Chassis as far as its not rotten should be fine, although i thought my Chim was very nervous at high speed compared to the Cerbera, but i never had it set up.

HTH

Paul,

from your profile your car puts out much more than to be expected with a 480 hp out of the box, given all the necessary compromises on intake and exhaust of LS in a Chim.

Will try with the stock driveshafts first and keep the Dave mac props in mind.

Chim/Cerb diff seem to be the same. For me it will be 3,45 and the long 5th on the TKO for quieter cruising. (normal road car, no track). Maybe 3,08 (than with the short 5th of course) at a later stage.


@scotty and flyingdutchie:

even with the standard suspension the car doesn't feel too nervous up to it's top speed of 160 mph. Standard splitter and closing the gap between rad and bodywork seem to do the trick with my car. This also effectively prevents any bonnet flapping or lifting, which I had experienced before.

Cheers,
Stefan

[stefan1200]

After some more calculation I very much agree that short 5th and 3,08 diff is the best solution ratio-wise.

Who to turn to for a 3,08 in excellent condition? Or should I have the present one converted to 3,08? Still reluctant to have a my good 3,45 diff opened for conversion though.

Stefan

[stefan1200]

Thanks to everyone for pointing me in the right direction!

@7 TVR:
Christian, have already been watching pics and posts of yours and brummmies car very closely. Excellent reading on these conversions, do hope to be able to join the club soon! Must look into the rollcage thing; makes sense to me. And yes, I'm trying to cover as much as possible before really diving into it. Yours seems to be the only cars I came across so far which has the manifolds run downward. Is there enough space down there to place small cats or is it dual pipes from front to back? Would be interested in any pics if available.

Cheers,
Stefan

[stefan1200]

Wow, did not imagine it is that close to the chassis! Needs some stiff engine mounts then to stay clear, but IMO looks so much better than running the manifolds forward. Definitely worth a try!

Many thanks,
Stefan

[stefan1200]

Good point.

Right now in the planning phase I'm gathering as much information as possible. If there's not enough space for cats with downrunning manifolds than it's ruled out for legal reasons anyway. And getting the engine as far back and down as possible is certainly a vital point for me too.

To my eye it looks very neat; but of course everything else must also be taken into account.

Cheers,
Stefan

[stefan1200]

jellison said:

Why any sane person would "Butcher" a TVR in this way is Beyond me.

Hi jellison,

well, you know, there once was this purple thing...;) Has been rather tempting when you put it up for sale, but I wanted to stay with LHD.

Thanks for the reassuring words concerning the drivetrain. It will be staying standard (except going 3.08 diff) initially and I'll see how things work out. Maybe stronger driveshafts at a later stage, time will tell.

Stefan

[stefan1200]

First of all I would like to thank all you guys for sharing your experience!

Very very helpful in order to try to get most of it right from the beginning, as 7 TVR has pointed out!

Taking into account the different opinions regarding the diff ratio the plan is now to purchase another diff with 3.08 but keep the 3.45, so that I can swap and find out what I like best.

Right now I tend to go with the 3.08 for being able to use first better and have an ideal gearing for a topspeed of around 180 mph at 6200 rpm. I know this might sound a bit daring in a Chim and I do not intend to make much use of it. But being in germany and having the opportunity, there sometimes is the temptation to just "go for it", even if it's only for a short period of time. I'm sure you know what I mean!

On the other hand the 3.45 per jellys recommendation would mean instant acceleration without even bothering to change down...

All good stuff for thinking...


@jellison:

Jon, I very much appreciate your offer on advice and pictures! As soon as the real work begins (Feb/Mar) I'm sure I'm going to need it!

Stefan

[stefan1200]

Jon,

love those pics!

Never heard of a Rainer with LS Engine over here though.

LS3 redline is 6500, giving 169 mph on the 3.45 diff. Definitely fast, no doubt, but not (apart from acceleration) that much faster than the 160 (on GPS) in does now with the stock 5 ltr.

So topspeed-wise, the 3.08 would be just perfect and, to be honest, it's difficult for me to imagine the acceleration with this setup being slow, considering the amount of power available from the LS3.

As already said, I might end up testing both in order to find out the best for me. Very sad that the T56 6-speed doesn't seem to fit in the Chim chassis, which of course would be the perfect solution.

Stefan

[stefan1200]

Christian,

though I hoped to have the conversion finished by now, we needed much more time than expected to make sure the conversion is street legal with the TUV here in Germany.

However, the engine is now ordered through an engine builder living nearby, who has specialized in providing stand alone LS engines for Cobra replicas and the like. Final specification is now a brand-new 6.0 ltr LS2 with the 28x reluctor, aftermarket cam and an output of around 450 hp, though I'm afraid we will lose a bit due to the limited room for the headers in the Chim. Transmission, as already mentioned, will be the TKO600 with the short 5th. As I still couldn't make up my mind on the final drive ratio, I'm going to keep the 3.45 initially to see how things work out.

One good thing was that I could use the waiting time for further planning on the conversion, having received valuable advice from jellison and having read "The complete swap manual" by Joseph Potak, which also clarified a lot of things I was able to adress before the work starts.

So, as the delivery of my new engine is planned in 3 weeks from now, I hope to be back with an update in the second half of May.

Cheers,
Stefan

[stefan1200]

Gentlemen,

as my new engine is going to be delivered next week, I would like to pick your brains on the layout of the exhaust system. As I learned a few days ago, my LS2 engine will be delivered with LS3 heads and a comp cam, with around 450+ bhp.

The options I'm considering right now are

1. Forward running headers followed by two cats each followed by two pipes which run down in front of the engine and then separately to the end, with a X-pipe (or H-pipe) somewhere in between
2. same as 1., but with the pipes joining soon after the cats and a split to dual pipes again at around the middle of the car
3. Downrunning modified LS7 manifolds like Christian (7TVR) in his Griffith, but I'm not sure if there is enough room for cats between the manifolds and the ACT cherry bombs which I like to keep

What would be your suggestions?

I'm sorry if all this sound a bit complicated, I'm just trying to get it as good as possible from the beginning.

Cheers,
Stefan

[stefan1200]

@eff eff
This seems to be the configuration used for several conversions. Is the Y-piece and single pipe to the mufflers layout just for convenience or does it make no big difference power-wise in comparison to dual pipe layout? I was under the impression that dual pipes from front to end with X-pipe in between is the preferred setup for minimum power loss.

What are the experiences on here?

Cheers,
Stefan

Edited by stefan1200 on Tuesday 15th May 11:57

[stefan1200]

Brummmie said:

Having done a bit of research into this, 32" primaries and 4 into 1 is what i found to be desired.
1 3/4" the best diameter, until you want big power, 600+ bhp.
Loss of torque might result in bigger than this before those power levels.

Almost exactly what I arrived at. Still weighing pros and cons for routing headers forward or directy down between engine and chassis (more difficult than in the Cerbera).

A lot of stuff for thinking.

[stefan1200]

Finally...

....and after having to wait much too long, I got my car back from the workshop last week with the conversion finished after 1,5(!) years. On the engine cover it says LS2, but, as mentioned before, it's an australien L98, so basically an LS3 less 200 ccm. The silver inlay covering the "Corvette" lettering were just for trying how that looks. I'm still not sure which covers to use. Please excuse the dirt on the cars, of course it was hissing down during my 100 miles journey home. Interesting experience, but managable! ;-)

I hope to be on the rollers soon to get the car properly tuned, right now it's running way too rich with some shunting at lower revs.

As you can see in the pictures, the exhaust is routed downward between the engine and chassis. I've seen this first on Christians (7 TVR) car and was very happy that the workshop did this too. For me it gives the engine bay a tidy look and the LS sits there as if it belongs there in the first place.

How does it feel? Of course, very very powerful! The lower part of the rev band still needs some tuning, but upon passing 4000 rpm it comes on the cam and is unbelievably fast!

It's weighing in at 1123 kg with a full tank after the conversion.

The TKO 600 gear change still feels rather stiff in first and second gear, but I hope with time and another oil change to the recommended GM fluid this will be getting better. I'm glad I chose the 0,82 fifth with the gearbox (thank you Brummmie!), 0,64 would definitely take the edge out of it. Still thinking about the 3,08 diff at a later stage. For now the 3,45 is fine with me.

Now one question for you guys with experience: The engine tends to stall when pressing the clutch pedal and coming to stop. Right now, I don't use any VSS signal from the gearbox, which is supposed to help. Are there any other options, or would the tune take care of it? I'm using a Holley 90 mm mechanical throttle with my LS1 PCM.

Thanks again for all your valuable input 2 years ago!

Stefan

[stefan1200]

Ok, folks, I promise to be back with pictures later, after having found out how to upload more than one! ;-)

@flyingdutchie
Thanks for the info with the damper. Might be an easy solution for the problem. A quick lookup showed that throttledampers were also used on Volkswagen VR6 engines at some time, so they should be easy to obtain.


@eff eff:
I use a QuickTime scattershield made out of steel, but weighing not more than maybe 20 lbs, IIRC. It meets some kind of SFI safety standard (might be a bonus in a GRP-body car!) and they claim that no further "dial indicating" is necessary.

Stefan

[stefan1200]

Ok, here we go... though the chassis looks old on some pictures, it has no rust at all.

[stefan1200]

Pete,

I've seen that you also wrapped part of the exhaust on your car. Mine is wrapped a little bit beyond the sump, you think it will still heat up too much?