Mcculloch superchargers

I have picked up a Mcculloch blower to put on my sbc. Do I need to do any modifications to the engine or can I just bolt it on and run it?

The engine is a 1969 350 that runs good. Don't plan to run it hard, just cruise around with and use a few extra horses out on the highway.

How much boost can I run before I have to go with forged pistons?

I think back to where the early Mcculloch's for the flatheads were designed as bolt-ons for trucks. No modifications done to them.

If metalshapes and others that are running these would like to chime in on the subject, great. Thanks. Neal

 

These are unanswerable questions to a certain degree. I'll assume you're using a VS57.

First off, what is the compression of the 350 you're going to bolt the blower on. VS57 were designed to not put much more than 6 psi of boost into a relatively small discplacement V8, ie a Ford 292/312, Stude 289, Chevy 283. a 350 is probably a bit big in displacement for a VS57. Not to say you can't use it or enjoy a nice amount of horsepower and look cool too, just don't expect to go picking fights with Cobra Mustangs or a Corvette. VS57 will not sustain much more than 350 hp. Their maximum safe impellar speed is about 29000 rpm, which is about 6 psi. Ideally your motor whould be about 8:1 or 8.5:1 compression for a blown application. However, since you're using a 350, you may be able to get away with 9:1.

As with any supercharger application, you'll probably want to use a fuel pressure regulator and step up a carb size for the added air. The VS57 are pretty cool in that they are internally overdriven at low engine speeds to build boost, but limit boost on the high end as a precaution against over revving the impellar. This provide a long, flat touque curve, so you way want to swap in a cam to compliment these manners. The VS57 will not put out enough boost to make a forged piston necessary. Save a few bucks and run a good cast piston or a hypereutectic , since they are so cheap for 350 sbc's. I'd say a bottom end rebuild will be the most important. New rod and main bearings and off you go.

Check out www.vs57.com for some more info.

 

I have a DO-59. I also have a SN-60 in pieces.

After reading at the www.vs57.com site and the other McCulloch thread, should I rebuild the SN-60 and use it instead of the DO-59? I suppose the bracket will have the wrong set-back for the SN-60. Neal

 

I'd just use what you have. Neither one will make a 350 a hellraiser. If you feel your DO-59 is in good enough condition to use, do it. It is possible to make a lot of power with the old paxtons, as evidenced by those guys swapping internals and running big boost on drag cars. But I take it this application i for a driver, something cool to cruise and impress people with when you pop the hood. Take care of the important stuff, fuel pressure regulator, carb and ignition (you may need to retard ignition timing or if you're using elctronic ignition, use a boost retard). Rebuilds are in the neighborhood of $800 for these things.