Have a fresh banger short block, and a Graham supercharger. Has anybody adapted the Graham to the banger? Need some parts for the supercharger as well. Sources? Thanks Ken
We've been thru this before. A Ford banger truck engine with Graham supercharger that ran in the race of gentlemen. He reported that it performed very well even though it was the smallest motor there. Did not seem to have a definite top speed, just kept accelerating as long as he kept his foot in it. Impressive for a flathead 4, 1941 tractor motor.
The original thread - https://www.jalopyjournal.com/forum/threads/supercharged-banger-modified-now-has-a-v8.850340/ Follow up on the finished car, after TROG - https://www.jalopyjournal.com/forum/threads/super-charged-banged.1000469/#post-11280644
My original reply to the original thread. Everything I wrote then still stands. Should work great. A flathead is especially suited to supercharging because you can't raise the compression very high without choking off breathing, and low compression engines love superchargers. The supercharger, by over filling the cylinder, raises the compression pressure while also overcoming the restricted breathing old engines have. The Graham supercharger is a long living, reliable unit. Basically one moving part (the impeller) and a gear drive. It uses plain bearings so you must see to oiling. No doubt you will take it apart and rebuild it, usually all they need is bearings but you can check with the Graham collectors. The Graham six was 217 cu in and the supercharger gave it about a 4 pound boost. So, if your engine is smaller in displacement it should give a higher pressure in proportion. They provide little pressure at low speed but boost climbs rapidly at higher speed. This works well with the old flathead type engines, that were tuned for smooth low and medium speed power but ran out of breath at high speeds. They had no blowoff valve so they were geared not to overboost at higher speed. You can get more pressure by speeding up the pulley ratio. I would try it stock first, and be satisfied with 4 or 5 pounds of boost. This will give you about 1/3 more HP. About compression ratios and pressure. Your compression ratio should look like your fuel octane. Your engine was probably made to run on straight run, unleaded tractor gas that is the next thing to lamp oil. About 50 octane and maybe 5:1 or 4.5:1 compression. On modern unleaded regular, 87 octane, you could go to 8.7:1 only, it would be practically impossible to go that high on your engine. But, if you had a 6:1 static ratio and your supercharger over filled your cylinders by 1/3 then you would have 8:1 which is more like it. Since atmospheric pressure is 14.7 PSI, then a boost of 5 pounds would do it. Naturally these are not exact figures, just an illustration. There are other factors involved. For example a modern OHV engine has thermodynamic advantages the flathead can only dream of, and can run higher compression ratios safely. This is why I think your engine would do really well on 4 - 5 pounds of boost, with minimal modifications. No doubt you could go higher but you would be pushing it into a high stress, short life situation. Short answer, the Graham supercharger will look cool, and give a genuine performance improvement without killing reliability and engine life.
Thanks all for the responses. I did look through previous threads. I am missing the drive gears for the blower, although I can fab up new drives, possibly changing the internal ratio as well, originally 4:1. I have the unit disassembled currently, will bushings survive if I can provide pressure oiling. I’m planning to use oil-lite bushings. My plan is too mount this unit on the drivers side, with a belt drive off the crank. Not going crazy, just a mild street engine. Header, 97, etc. Ken
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