Hey fellas, first post ever and I am grateful to learn all I can. I am in the beginning process of building a blown 230 flathead motor. I have bought a VS-57 McCulloch superchager from a 57 Tbird that I plan to use. In 1957 (the year of my Plymouth motor) the compression was 8:1 so do you think that would be too high for the 4-5 pounds of boost the supercharger would provide? I have not decked the block or milled the head at all. Also the crank has been cross drilled because I know the bottom ends starve on flathead 6's but that's as far as I have gotten other than the hot tank, magnaflux, .030 over, and line honed. Anything else you guys would recommend to make sure the bottom end stays put together? I wish I could find some aluminum slugs for this thing. I am not going to be revving this thing high or racing it but I do want it to last. I plan to get a cam from Edgy and a split exhaust but I haven't decided on an intake/carb set up yet. One thing at a time I suppose.
I don't have any pics of the motor yet because its still in the machine shop. Here is the car it will end up in. I have an s10 tranny to go with it. First pic was taken by my grandfather in the 40's. His father (my great grandfather) bought the car new in 1934. Second pic was taken by me last year. Been in the family 80 years!
I looked into this build a few years ago and discussed it with some Mopar experts. A flathead Mopar is well suited to this for various technical reasons like low compression, needs help with breathing, and has a strong engine. 4 -5 PSI is a very small boost. A stock engine will handle this with no problems. Stock pistons, crank, stock everything. 8:1 compression is on the low side these days. You will have no problems running on pump gas. At worst, you might have to buy high test instead of regular. You can get pistons from Ross that are better than anything they had in the fifties. Your 57 motor has modern type crankshaft seals. You should be able to use moly rings or modern rings and synthetic oil. These are especially good for a long stroke motor. Check with Edgy before you buy the cam and make sure he knows it is for a supercharged engine. One of the big advantages of a supercharger is you DO NOT NEED expensive heads, cams, intakes, carbs etc to make power, the supercharger will give you 30 - 40% more rear wheel HP by itself which is about all you can get out of a typical street hop up anyway. The stock intake is fine. The blower will force the air in. You will need to jet the carb a lot richer to make up for the extra air. Bigger exhaust is a good idea. Headers are best, with the pipes grouped 3 front - 3 rear going back under the car as far as possible then duals. Next best, split exhaust manifold and duals, or simply have and exhaust system made 1/2" bigger than stock, and port the manifold a little (grind out any lumps or roughness). Use a straight through muffler, turbo muffler, or other low restriction exhaust. This is important on a flatty because the exhaust valves and seats are not well cooled, getting the exhaust out is important for power and also for long engine life. Your engine does come with high temp exhaust valve seat inserts. You might want to invest in new high temp exhaust valves. Getting the engine balanced can help a lot for smoothness and reliability, and even a few extra HP. John Erb is the expert on these superchargers. He rebuilds them, and recommends eliminating the variable speed feature, basically converting to later SN specs. This would allow a more modern flat belt drive, and eliminate the jockey pulley as well. Mr. Erb is an engineer for Ross pistons. You will need to pressurize the back of the fuel pump (not hard) and add an electric pump for more volume.
A basically stock engine plus VS57 should work great in a light car like that, and be as smooth, quiet and driveable as a stock engine. No doubt you have heard of the flathead six Kaisers that came stock with the same blower. They only had 4 pounds boost. In an old road test, the tester was a little disappointed that there was NO sign it was not a stock, unsupercharged engine except for the extra power. No noise or temperament at all.
Rusty O'toole I was hoping you would chime in. I have read many of your other posts on flatheads here on HAMB. So you think I should mill the head a bit? I have everything all torn apart and would like to build it correctly the first time. Correctly meaning as much SAFE power as I can get. John Erb will definitely be building my blower, everyone says he is great. What do you think about putting in Chevrolet valves? I have heard pro and cons. I have some money saved and would like to make this the best it can be. One last thing, should I lighten the flywheel or does it need the extra weight?
You might want to use more boost if it doesn't detonate. In an engine with restricted breathing the boost will read higher because the blower can more air than the engine needs.So a few more PSI might be needed to overcome this resistance and make it worth the trouble....Unless it comes apart because I only have blower experience on a different type engine..
The blown Stude V8 runs so much better than the unblown one that I think you will love your six with the added boost. Never had a blown flathead motor but 10 pounds with 9 to 1 compression runs great on the street IMHO.
I wouldn't mill the head at this time although I might smooth and polish the combustion chambers a bit, to make sure there are no sharp edges or hot spots. Try it first and see how it runs. If it runs great and does not knock on regular you can consider upping the compression. OHV engines have the advantage over flatheads when it comes to combustion chamber shape, and can run higher compression ratios without knocking. This is why I would go easy on the head milling. Also, you can only mill the head so low before it cuts off the breathing and 8:1 or 8.5:1 is about the limit. Your 57 already has about the best head they made, although the 58 - up might be a touch better. For street use, a TOTALLY STOCK engine with 5 pounds boost will have 30 - 40% more rear wheel HP than stock. McCulloch claimed 40% and this is not out of the question. You do not really need more carbs, hot cam, bigger valves etc. The blower takes care of all that. In fact, too much cam overlap can let the pressure blow through and be lost out the exhaust valve. Bigger exhaust will help power and also get rid of heat before it burns your valves or cracks your block. Lighter flywheel is always a good idea. Quicker shifting and whippier acceleration. Cars of that day had a man hole cover for a flywheel, so granny could make every mistake in the book and not stall the engine. I have no opinion about Chev valves but, if they fit, they would be a cheap way to get aftermarket valves. You don't need oversize valves with a blower.
GrahamPaige used a centrifugal blower on their 218 ci in six. Non blown HP was 95, blown was 124. You might want to research that engine and its specs. If you keep it under 4200 rpm you won't have any worries. The engine has a cooling distribution tube that directs coolant toward the valve seats. As long as it is in good condition you don't need to worry about valves either.
McCulloch advertised 40% more rear wheel HP with 5 PSI boost. This is mild enough boost, to be used on the street with a stock engine, radiator, exhaust, etc. If you build basically a stock engine with a few improvements 50% should be a cinch, without harming the smoothness, reliability or longevity in the least. In other words you should be able to get about 200HP with good fuel economy, stock drivability and engine life of 80,000 to 100,000 miles or more. This is about the power level of a stock small block V8. If you really need more than that, the flathead six is not the place to get it. You have to spend too much money, and sacrifice too much drivability and engine life for too little HP. Beyond a certain point it makes more sense to build a V8. I would suggest basically a stock rebuild with Ross pistons if you can afford them, or NOS stock pistons ($75 a set of 6) if not. Stock cam, or mild cam as recommended by Edgy for a blown motor if you insist. Shim the valve springs if you plan to rev it. 3 angle valve job. Clean up the head of sharp edges. Get reciprocating parts balanced. Light flywheel and possibly a little heavier springs in the pressure plate. Maybe a larger single barrel carb, like one off a Ford 300 cu in six or the like. Definitely a header, duals , or oversize exhaust for more power better economy and cooler running. For the ignition I like a rebuilt stock distributor on 12V with a Ford thick film module and matching coil. Very hot ignition with stock reliability and easy parts availability. Or, Pertronix ignition if you like. The ignition may need to be recurved but this depends on tests after it is running. Remember the VS57 BY ITSELF is equal to the typical hop up of twin carbs, head, cam, etc. and does not need any help. There is such a thing as gilding the lilly.
Graham straight eight supercharged engine had heavy duty rods, bearings, valves etc but the six did not. The supercharged six came along several years after the eight. In their advertising they said the engine was modified but owners who have taken them apart and rebuilt them, say they were the same. They also said they made their own motors but they came from Continental. For the supercharged motor they just took the engine as it came from Continental and bolted on the supercharger. Kaiser also used a Continental flathead six, practically the same engine as Graham. I don't believe they were modified at all, except for adding the blower. By that I mean, no heavy duty internal parts. You don't need them with only 4 pounds boost.
According to this web site, the only changes to the Kaiser supercharged engine, were heavy duty bearings and valve rotators. Other than the supercharger installation of course. http://vs57.y-block.info/kaiser.htm
You say you've cross-drilled the crank already. It's the rear of the crank that needs the help, so make sure all oil holes line up well (shells etc) and make sure the holes are all chamfered nicely. An S10 will give you the shifter in a good location, but some don't like the S10 ratios too much. Search for threads by Flat Ernie, a wealth of info there on swapping in T5 gears to get better ratios.
I would consider looking at using the Kaiser carb and carburetor box, see if you can make them fit..? see what you can do to modify your fuel pump to compensate for the blow through demands, drill a hole above the diaphragm and plumb for air from carb box to overcome relief valve action at boost? or plumb in a separate electric fuel pump that only comes on when boost dictates. like suggested above, I would also keep everything stock but the exhaust, the supercharger will get it in but it will need somewhere to go
These engine commonly used in marine use (ie Chrysler Crown) were in that application indestructible. The only difference bottom end wise was the marine engine had a lot more oil pan volume. It did not seem to me unreasonable that that was all it took to move these engines from iffy to indestructible. My brother used to be Pres of the Antique and Classic Boat Club . He leaned on me for a few motors over the years for the Moskoka style wooden launches. I used to back then get the cams upgraded by Bob someone who worked at Crane Cams in charge of ancient regrinds. They would really smarten up the build. Although as previously mentioned with a blower stock cam will be good. don
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