Supercharging

[Faron]

Chad is right , and I do love to share , BUT , I also hate typing , LOL the info I would give to 65r would be more specific to a combo, than general , but AS for general info , I will say this, a 671 is NOT low , it can easily spin past 6500 , and if put together with the realization it will ( have yet to figure this one out ) cause the car to run about 20 degrees hotter than a comparable normally aspirated combo , so OVERKILL on the cooling system is a Must , I run a Crank tiggerd Ignition ( because Pa has a Obstruction of vision requirement in the Vehicle Code ) so My combo is as low as any FE 671 with carbs can be , but its still high enough that a big scoop or hole in the hood is needed on almost any car , for Carb's , you need to be honest and say I will race this ( full 1/4 mile bursts ) or its a fairground / street only cruiser,  racing dictates Holley Double Pumpers , or 660's , Holley Vac Secondary's can be made to work , but with the right mods , Stay away from Eld's or Carters , unless you like ash trays that resemble pistons , also ALL, brands of Headers will Crack given enough  time , No coating short of top fuel stuff will stay on , Stainless might last ,( just my pockets are not deep enough to try them ) unless you have a crossbolted block , stay away from strokes over 3.78 ( 390 )  use Head and Main Studs , Good machine work is critical ( as is any engine making 500+ hp ) I run stock 390 3/8 bolt rods with good bolts and have never had a falure , BUT my last combo was put together in 96 , lots of aftermarket stuff now , My engine is apart , it started pushing water ( after 8 full seasons and 3 partial seasons 0 plus 11 years of street miles between ) turns out #7 cyl wall cracked , its a garden variety 390 block .030 so no big loss , also , if you like the whine of a Blower ( who doesn't ) use the 1/2 pitch drive , the round tooth millimeter stuff is stronger , but doesn't sound as cool , if yo run 10% over or less 1/2 is fine , JUST BE SURE to use as big of pulleys ( teeth count ) as possible to get the ratio , in other words 31 crank and 31 top is 1-1 , BUT , you get poor belt wrap , and that can cause problems of belt skipping , ( rips off the belt teeth ) and at about 100.00 a pop aint cheap , I don't like under 37 for tooth count , also belt tension is critical , it needs to be almost TOO loose when cold , those pulley really expand , get it wrong and off comes the crank snout ( SBC and BBC have the most problems ) , also I run JUST a Hub , no Dampener , ok enough for now , have questions shoot away

[lovehamr]

I'm actually surprised that no one has mentioned it, so I might be missing some new info here.  But I personally wouldn't use hypereutectic pistons on anything that I was going to flog, especially a blown application.  Just because they have a higher silicon content than other cast pistons doesn't mean that they are equal to forged and there are way too many off-the-shelf forged pistons for our application these days to consider a cast piston for a performance FE.

JMHO, Steve

[fe66comet]

His proposed engine was a low boost application. Say 7 lbs or boost and no Moore than 5500 rpm. There ate advantages of the hyperutectic over forged, Wear resistance is one the other is lower expansion. They outlast a forged piston in a non race environment about twice as long. As far as breaking cranks off and such that is simply a case of harmonics, if harmonics are not controlled in any machine bearing failure will occur, shafts and gears break simple engineering fact 101. As far as belt wrap and tension this is maintained by an idler on the pull side and adjuster on the slack depending on therm an expansion is a uncontrollable factor it starts loose and once warmed ends up still loose, belts are engineered with expansion figured in regardless of the style, if it has teeth it shears, if it is v or ribbed it burns. A lot of good info on basic belt function can found on the Gates site. I an engine when breakage occurs and you started off with good parts engineered for an application then you are going beyond the expectations of the part, superchargers are no more than a pump. If you spin the pump to fast it overheats and raises the incoming air charge to the extent you are getting no volume and burning everything up making it completely inefficient, at this point a larger pump is needed to keep up with demand or part failure will occur. If pressures exceed the capacity of the vessel containing it a rupture will occur along with the excess heat of the over spun inefficient pump. In the case or a supercharger that is spun over designated modified design, over 6500 and the drive system is improperly engineered, harmonics at not controlled and boost exceeds the capacity of the block it is a ticking time Bond. A prime example of a properly or even over engineered engine would be the Buick 3800 supercharged engine, the rum for over 200,000 miles with not an issue. My beater Park Ave Has over 260,000 on it and still runs like new. The rest of the car is junk but the engine uses no oil and has cast pistons.

[lovehamr]

John, while I claim to be no expert, I purport that an FE with a huffer and a pair of Holleys has very little to do with the tightly controlled fuel/air/spark of your high mileage Buick.  The advantage of forged pistons lies in the ductility of the aluminum after the forging process.  This ability to absorb damage without shattering has the potential to save an engine where a hypereutectic piston's harder makeup would shatter rather than deform.  To assume that the spark and A/F ratios are going to be controlled such that there'll be no detonation in a supercharged FE would be ambitious in the least and that is the reason that I'd go with forged in any non-computer controlled performance engine.

[fe66comet]

I myself went forged due to I needed the extra strength for high compression and higher than normal engine speeds. I I had built it to run 8-9:1 I and ran gas at 5500 red line it would have been different.

[Faron]

I would NEVER suggest anything but Forged Pistons in a Boosted app , just one of the things I had eluded to before I relented and typed a bigger reply