A friend of mine has a 70's Maserati Merak. It's really a beautiful car, looks like a cross between a Ferarri 308 GTB and a Lamborghini Miura. The only problem is that the car is heavy for the engine they put in it. It's a 3200 pound car, so it's about the same weight as a Corvette, except with only a V6 engine.

He was looking for power adders, since he had some engine repair to do anyway. Initially, I had advised a Nitrous system, used modestly since the motor has cast pistons, but the triple Webers would make for a very tricky installation unless he went with nitrous injection.

Then he came up with turbocharging, and I really took to the idea. I advised two smaller turbos for quicker spool-up, and an aluminum box for the carburetors with a tempered glass top- so those great-looking webers would still be visible.

My question is, anyone with turbo experience know how much boost he can safely run intercooled on cast pistons? Despite the inherent weakness of cast pistons, most of the turbocharged Dodges of the 80's ran cast pistons with up to 9 pounds of boost non-intercooled and I've never heard of a burned piston in those things. I intercooled my old Shelby and ran 15 psi of boost on cast pistons for almost 150,000 miles without a problem. But I don't know what the rule of thumb is here.

 

The answer is trickier than it might appear.

Or it might be as simple as "you can run as much as you want until detonation happens". The other issue is that as you go up in boost it is generally adviseable to have larger piston ring end gaps.

Here's the deal: Manifold boost is merely a measure of what is backed up behind the intake valves - it is not a measure of the actual pressure output of the turbos. So for instance you could have two engines with the same exact turbo, one with a "large" cam and one with a "modest" cam. The one with the "large" cam will show less manifold boost psi, but will easily overpower the "modest" cam engine that shows higher boost psi - but at the same time the large cam low boost engine will be closer to detonation than the modest cam high boost engine. I'm guessing that your Shelby had a modest cam.

Thomas

 

Didn't the Maserati Biturbo run the same basic engine as the Merak? It would probably have forged parts where the n/a engine has cast, but if he is doing a bunch of engine work, what is he doing? If an overhaul, build to Biturbo specs.

 

No. It'll fit though. The Meraks had a Citroen V6.

 

I think the Citroen v6 was the same engine originally designed by Maserati.