Has anyone had success with supercharging a 235 with the carter yh sidedraft carburators? I have acquired most of what I need to build a duplicate of the supercharged 235 Mcculloch built when trying to sell chevrolet on the idea of offering a higher performance version of the 1953-54 corvette. I will be using a 261 though, not a 235. I have several of the intakes, an original set of the carbs, the ignition shielding, the proper valve cover, fuel pump, the coolant tank and mount, the McCulloch VS57,and a few other odds and ends. This engine will be going in my 47 business coupe.
Things move slowly for me. I am in the parts acquiring phase right now. Some are one offs and will need to be fabbed up, and some are out there but made of unobtainium. It will come together though. I would love to find a mcculloch ch101 mounting bracket so I can start fabbing the piping to the carbs but they are pretty hard to find, so I will likely be making my own.
You don't need to hop up the engine when you have a supercharger. The McCulloch will give you 4 -5 pounds boost. Normal atmospheric pressure is 14PSI so that means a total of 18 -19 PSI. This will effectively increase your compression by about a third. So your 7:1 compression engine becomes a 9.5:1. The octane of your gas should look like your compression ratio, so 92 octane hi test will probably do. This is why supercharged engines have low static compression. The blower gives them high compression automatically. A high compression engine + supercharger won't work as well as a low compression engine. Hot cams are counter productive. Too much overlap allows pressure to blow right thru the cylinder and out the exhaust valve. You don't need twin carbs, the blower will pump enough air thru a stock carb. A few things you can benefit from are free exhaust (headers or duals) recurved ignition and a lightened flywheel. But, you can get practically all the benefits of a souped up motor with none of the drawbacks, just by adding a supercharger. In your case the stock 261 with Corvette cam intake and exhaust should be fine. You will need to modify the carbs, ignition and fuel pump to cope with the supercharger but that is about it. Did they even make an installation for the Chev six? The McCulloch was only out for a year or so before the Chev V8 was announced. That would take away the incentive to buy a supercharger. If you have seen the mounting brackets for other motors you will have a good idea what you need. When they made a new installation they welded up brackets of steel plate and when they were satisfied that they had it right, used those as prototypes to make cast aluminum ones.
Is there a web site or pictures of the Corvette installation? Have seen pics of several different motors but not that one.
Look up the 53 corvette built for Chevrolet when they were trying to sell Chevrolet on the idea. There were two built initially but only one is left. It currently resides in the Lingenfelter Collection I believe.
If you aren’t aware of him, take a look at http://paradisewheels.biz/power/superchargers/ Craig Conley bought all the old inventory from the Granettelli’s (sp?) when they sold off the ball drive super chargers to concentrate on the gear drive Novi’s. He got tons of stuff, I even saw some patterns marked in grease pencil for Kaiser brackets. He knows those inside out. The other guys that were really helpful to me on my SN series on my y block were Meyers Studebaker. I’d start with them on the carb, and what would work. http://www.myersstudebaker.com/ A local truck shop had a lot of molded elbows, etc. to make up the blow thru ducting. Rusty said pretty much everything else that needs saying.
Thanks, I will reach out to them. I have owned quite a few turboed vehicles, but this is my first foray into supercharging.
Part of this is “vintage supercharging”. Pretty old tech compared to the modern stuff. Lower boost at higher rpm, and those units don’t like overspeed, the races fail.
Latham used the Carter type YH carbs (tag number 3172s) with their aftermarket superchargers. From memory, the Latham was a pull-through, whereas the McCulloch was a blow-through. Totally different carburetor modification necessary for the two different systems. Have never modified a carb with diaphragm pump for use with a blow-through blower. Have modified a number of carbs for use with the early 1960's Paxton blow-through. Typically, throttle bodies and throttle shafts were machined for vacuum shaft seals, accelerator pump stem was sealed, mixture screws were sealed, and the more difficult task of disassembling floats, fabricating an aluminum strengthening baffle to prevent side collapse, and reassembly of the floats. Also a boost reference to allow the fuel inlet valves to function. The pull-through designs only require calibration changes. Have aided in the setup of a number of the Lathams. Jon.
I appreciate all of the input. I am acquiring parts as I go. I have most of what I need now, except some small bits.
That long pipe to the carbs must have really slowed down throttle response. Much better to mount the blower higher, or to the other side if there is room. By the way Slow if the engine is going in a 47 Chev you don't need the ignition shielding that was because of the plastic body of the Vette not shielding ignition static. Or the coolant tank. The closer you can get the blower outlet to the carbs the better.
Minor item, but in the engine mockup above, the front of the unit needs to be “clocked” to set the emblem level, and the dipstick near the 2 o’clock position to read the oil level correctly, and I suspect to oil properly. The cast mounting bracket and tension arm look typical of original McCulloch parts.
I just wanted to throw out a +1 for Craig Conley. He is the guy to see for McCulloch and SN series Paxton's. Knows all the tricks to make them live a long happy life. Also if you are looking for tubing try these guys http://www.woolfaircraft.com/index.html
Yes. I give a big thumbs up to Craig Conley. He is a great guy and very knowledgeable about the early mcculloch Supercharger s.
I am building the engine to look exactly like the engine in the vette. When I open the hood I want people to know that it resembles the engine bay in the mcculloch vette. I love the early vettes, in my opinion they are the purist form of a sports car. I guess I was born in the wrong era.
A different valve grind is also helpful, but on an old motor a valve grind doesn't hurt anyway. Supercharger motors like wide flat valve seat grinds. But not entirely necessary with low boost.
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