I have been playing with a supercharger on my engine for most of the year. I have learned a few things that I thought I would p*** along just because it was interesting. The starting point was a recently rebuilt original engine with a Specialty Cams 340 cam, a Lion III cast iron head, electronic ignition, the Weber carb adapter manifold, a Snyders' cast iron exhaust header, electric radiator fan and electric water pump. The supercharger produced 4 psi of boost with peaks of 5 or 6 psi on occ***ion. The fan and pump were installed to free up the fan belt to run the supercharger. I live north of Denver so the al***ude was around 5000 feet. 1- I had a problem with my front pulley coming loose before I put the supercharger on. This only got worse with the additional load of the supercharger. I even added a second 1/4" key to drive the pulley. I think the longer heavy 5/8" v-belt may have been the problem? 2- Tuning the carburetor required adding a fuel/air ration meter since the supercharger hid issues from the tried and true old methods. I tried the Weber, an Autolite 2100 and finally ran a Stromberg 97. The Stromberg performed better before adding the supercharger as well. 3- The supercharger pressurized the crankcase causing me to think more about why. My conclusion is that the pressurized intake ports pushed air past the valve guides and into the crankcase. Remember, flatheads engines do not have valve guide seals in stock configuration. 4- The compression test at the end of my little experiment showed 100 psi across all 4 cylinders cold so I don't think piston ring blowby was a problem. 5- The supercharged engine produced considerably more heat than the un-supercharged engine did. Although this engine ran hot before adding the supercharger. 6- Wow! The supercharger added at least 20% and probably closer to 30% to the horsepower output of the engine. Now that I have returned to normally aspirated, the engine runs smooth but I am disappointed with the performance. If I return to supercharged, or if anyone is considering it, I will make some changes to the engine. I am looking into what it would take to add valve guide seals and how to run a serpentine belt instead of the heavy V-belt. Possibly changing the attachment of the front pulley to the crankshaft. If anyone else has experience with running a supercharger, I would be interested in their lessons as well. Have fun!
How about some pics of your blown banger. What blower did you use? Here's a video of another one using a modern Eaton blower: And another using a SCOT blower;
Yes, a serpentine belt uses less/makes more power. No, valve stem seals are not the solution to your problem. They are there to stop oil from being ****ed up by vacuum. They will not hold against 5 PSI of pressure. Verify the valve guides are straight and round, .001" clearance on the intakes, .002" clearance on the exhausts. jack vines
I love seeing what you're doing. We have added superchargers to a number of cl***ic British cars and our experience mimics yours with the Model A. The power increase is significantly noticeable and makes even a sluggish little Brit car feel way faster. 0-60 times usually indicative of 25-30% increase in power with a stock cam. A couple of things we always watch out for: Oil pressure and volume have to be good. We won't put a blower on a worn out engine. The cooling system is going to have to handle more heat so we usually put in a bigger, better radiator. Finally, we are very mindful of the advance curves on the distributor. Detonation can kill an engine in a hurry. Some of the blowers use serpentines, others use V-belts, but we've never had and issue with either at the low boost pressures we build, 5-8 psi typically. We normally use an SU carb and those are really easy to tune. Also, being a constant velocity carb, you have a lot of la***ude with sizing.
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