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MG MGB GT V8 Factory Originals Technical - Turbocharging primer wanted.

Where can I find a primer on turbocharging a carbureted motor? I am a pretty good amateur mechanic but only on plain-vanilla stuff: I'm utterly ignorant of the science of turbocharging. Among other things, I don't understand how the carburetor works if the manifold is pressurized (???).

Can anyone point me in the right direction?
Bill Withum

Well, lots of places, any info for a Chevy of Ford motor will be applicable for a 215. Albiet at lower measurments...

You might check they make superchargers for Early Ford cars. a supercharger will be a better bet for a V8 B both in term of complexity of install and lower heat in the engine bay...
Larry Embrey

Not to try to throw cold water on your project, but my understanding is that turbocharging a carburated motor for the street is kind of an exercise in futility because you need the fuel control and computer management that goes with fuel injection. Consequently, you run into lots of problems. Just a possible heads up.

Joe Ullman

Joe, I don't know if that's right ... a friend of mine has a '69 Mustang with a turbocharged 302 (the turbo unit was made by a company called Hatch & Kirk in Seattle, whoever they are); it's just carbed with a Holley double-pumper. Runs absolutely perfectly and oh gawd is the thing powerful. In fact there is a lot less turbo lag than on most modern Asian cars.

Harry, Bill,
That's just what I'd heard, and I'm sure there's ways to do it. As usual, there's an airgap in my knowledge base, but I'll throw what I 'know' out there, even if it is 'half-fast' and let each sort the wheat from the chaff.

Joe Ullman

It should be quite easy - the MG Montego Turbo (not sold in USA) is a 2-litre straight 4-pot with a big SU carb and a Garret T3 blowing through it. It has a high pressure fuel pump and a rising-rate fuel pressure regulator controlled by a pipe supplying boost pressure from the turbo. You need a return fuel pipe back to the tank as well. The carb is a special version which is built with various seals to withstand the boost pressure running through it - but I don't know anything else about it. That takes care of the fuelling. The electronic management is simply for ignition control and automatic choke, taking inputs from inlet air temp, water temp, anti-knock sensor, flywheel TDC sensor etc and controlling the timing of the sparks accordingly.

>The carb is a special version which is built with >various seals to withstand the boost pressure running >through it

I realize the carb's pressurized in a supercharged setup, but in that Mustang IIRC the turbo unit is between carb and manifold. Maybe I misunderstand what's going on there. I'll have to go study that setup because I don't think there are any electronics there at all. I do know that it's a sickeningly fast car, and is apparently totally reliable, driven year-round and maintained by the corner gas station ... don't know how much fuel it swills though.

If you look at this link, you'll find some information on turbocharging. The book that is talked about there is "Turbocharging" by Hugh McGueness (sp?)and was written before fuel injection was popular and deals almost exclusivly with carbs. It is old, but physics hasn't changed much and it is well written. You can find this book and other informative stuff at this site-

Most of what I know about turbocharging comes from use on VW engines. There are many 'blow thru' setups that have virtually no turbo lag and double the horsepower. 250 HP from a VW motor is not uncommon. There is a book written especially for the VW engine called "Turbomania", but it has a lot of information that applies to any turbo instalation, not just VW. You can buy a copy from

Hope you find some informative help at these websites

Here are a few books you should read:
ISBN 0-91472-02-4 Super Power, S-A Design
ISBN 0-8376-0160-6 Maximum Boost, Corky Bell
and if you are considering an S-U type carb,
ISBN 0-85696-299-6 S-U Carburettors, Haynes
For Holley, Rochester and others there are plenty of good books out there.

I took the turbo off mine because I wore out the shaft bearing in the turbo, and as it was the original Olds setup (nearly) the parts are no longer obtainable. I used a 2" S-U from a Jaguar motor to feed it and made several new needles for it before I got decent fuel delivery under all conditions. As for power, it was impressive, however boost was limited to 6 psi, and the turbo was sized a bit small. A hood scoop was mandatory as the turbo mounted directly to the intake manifold and the exhaust was routed up to it, in my case with specially built headers (8-4-1 unequal length).

I cannot say that for the amatuer builder the supercharger is an easier option. In either case the difficulty rises exponentially with the sophistication of the system, and with the Roots type a good deal of machine work and special fabrication is needed. In either case a pull through carb is the easiest option. My advice: Take it a step at a time if at all possible and complete each step before starting the next, since you may be biting off more than you realize.
Jim Blackwood

This thread was discussed between 22/08/2001 and 23/08/2001

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