Twin Turbos

I’m interested in your opinions on and experiences with equipping a GT40 with twin turbos. I’ve seen pictures of a TT GT40 in the UK that was using a small Rover V8, and I think someone has told me of another TT GT40 in Australia. The appeal of a twin-turbo GT40, other than outright cool factor, would be abundant power on tap without all the lopey idle and poor street manners of a high-strung naturally aspirated small block. The downsides are complexity, fitment, heat management, and the drivetrain durability.

I expect to have an Incon twin turbo kit on my Mustang Cobra by this summer, and I’m familiar with Incon’s offering for the 5.0 Mustang. I believe I could locate a used Incon TT kit for about $3,500, but I’m doubtful that Incon’s cast manifolds and GTBB35 turbos would fit. If not, I’d have to fabricate some custom headers and dump tubes, and fit them to some appropriately sized turbos. Incon’s GTBB25s are nice and small, but can only flow enough to support 500 flywheel hp, which would probably be fine for a GT40. The nice thing about the smaller turbos is they would spool very quickly and would probably achieve maximum boost as low as 1800 rpm. I think the actual limiting factor in a TT application would likely be the transaxle and clutch, as even a 500 hp twin turbo would likely be putting down close to 600 lb-ft of torque.

Has anyone else done this on a small block Ford, or considered this approach?

Thanks in advance for your feedback.

Mark -

Your idea sounds workable. But remember, the GT40 engine compartment is extremely tight. You would have to make custom plumbing, and find a location for the intercooler. This sounds like a project for Gordon.

Keep us posted. The sound of a TT GT40 accelerating would be awesome indeed!!

Bill D

Check here, there are some pics:

Pics of Various GTDs

Mark, The TTGt40 in UK is Rover powered, british Racing green GTD Mark 2 version owned by EX hill climb Champ Tony Marsh. His Son Runs Turbo Technics Here in my town. His car is very rapid, I own A Renault 21turbo, A nissan 200 sx turbo and a Williams V6 turbo and Im a fan of Whistling boost. The Car in Australia is a GTD owned by Cosi Sergiovani (I hope i remembered his name right!) He has A Ford V8 Running twin Turbo's Monster. Our club has photo's I'll See if i can get a copy sent. I have some digitized Photo's of Tony's Car, which i will endeavour to put up on this site. I've had a go already and FLuffed it! If you use a space frame you can get more under the hood as you can run pipework and coolers in the voids. Tony's is a neat installation and the Mark two rear deck does give a little more room. Hope this helps.
Regards
Mark Sibley

HMMMM, a twin turbo, 9000 rpm, 1000+hp small block in a 40. I could do that.

Some quick general notes on my own personal experience with turbocharging engines (not GT40s).

The drivetrain seems to be far more reliable when the horsepower/torque is produced with a turbocharging engine rather than a conventionally aspiration. I have put this down to the always-present turbo-lag “cushioning” the drivetrain. So you can probably add a bit on the horsepower figure and still feel confident.

Similarly, its possible for these engines last longer if they are a loved road car, given that the compression ratio is probably lower and that high turbo boost only exists over a small fraction of its overall lifetime.

The heat produced from my Garrett T4 at 9.5 psi boost was enough to blister the paintwork (I’d hate to think what it might do to fibreglass) and raise the engine-bay temperature to the levels where it created problems, so make sure that you have very good heat barriers and air flow.

Tony Marsh's TT set up utilised a full race Hewland gearbox to cope with his 630 bhp and involved a lot of chassis mods and body chopping to fit it all in. I have only seen pics of Cosi's car in Aus but it looks like one hell of a set up. He is claiming 800 plus bhp but can't find a suitable rolling road to test it on!

Malcolm