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Shaving Reciprocating Weight

G Guest
Hello Fellow Enthusiasts!!!; In an effort to obtain the lightest engine reciprocating parts. I have researched & found the following. Weight of stock 351 Cleveland crankshaft "56" lbs. A Scat brand "Super Light" 351c crankshaft "48" lbs.
A stock Cleveland flywheel "30" lbs. A Centerforce brand Cleveland Aluminum flywheel "14.7" lbs.
By combining a "Super Light" crankshaft in conjunction with an Aluminum flywheel the combined weight saving would be "23.3" POUNDS!!!.
My question is....The cost of the "Scat" "Super Light" crankshaft is around $1,300.00...Does anyone know of a "Quality" machine shop that can machine a stock Cleveland crankshaft to "Super Light" specifications?...and if so...What would be the cost?...or...am I just better off spending the $1,300.00 for the Scat "Super Light"?...I have already purchased H-Beam rods & Aluminum pistons & 180 headers. I have a 1991 Ferrari Testarossa, & ENJOY hearing that motor rev to 7,200 rpms almost INSTANTLY!!!!....I want the same instant revving capabilities from my Cleveland. Appreciate your input/s....THANKS!!!....Mark
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D danieljonesMember
> What would be the cost?...or...am I just better off spending the
> $1,300.00 for the Scat "Super Light"?...
> I have already purchased H-Beam rods & aluminum pistons & 180 headers.

You have to be careful here. The weight of the rods and pistons
plus the type of balancing (internal or external) will determine what
the bobweight needs to be. When lightening a crank, it is not unusual
to upset the balance to where large amounts of expensive mallory metal
is required to re-balance the crank. I have a friend who had more in
the balance cost than in the cost of the billet crank. I beam rods are
lighter and will balance with less heavy mallory metal (a.k.a. tungsten)
slugs in the crank. A crank manufacturer can tell you the required
bobweight for their cranks. You could contact SCAT and see if they would
machine your 351C crank but it might end up cheaper to buy a Super Light.

Dan Jones
bosswrenchbosswrenchMember
If you REALLY want to get into cutting rotating weight, billet aluminum crank and waterpump pullies will also reduce the package weight. MIne are 5 lbs less. They are not at all difficult to make on a lathe of 6061-T6, or March Industries makes some commercial aluminum pullies for the 351-C. There are others but beware of cheap cast aluminum pullies with Gilmer belt conversions. The wide toothed belts seem to apply a larger load, and some have gotten premature water pump bearing/seal failure, plus actual breakage of the crank pully has happened on a couple of cars.

FWIW, as Dan said, H-beam rods are usually heavier than equivalent strength I-beam rods. Rule of Thumb on rod types: use I-beam rods for torquer engines and H-beam rods for very high rpms and significant power-adders. I would never risk using aluminum rods on the street, either. That's like owning a pet rattlesnake.... you KNOW bad things will happen, you just don't know when.
R 1Rocketship (Guest)
quote:
Originally posted by Daniel_Jones:

You have to be careful here. The weight of the rods and pistons
plus the type of balancing (internal or external) will determine what
the bobweight needs to be. When lightening a crank, it is not unusual
to upset the balance to where large amounts of expensive mallory metal
is required to re-balance the crank. I have a friend who had more in
the balance cost than in the cost of the billet crank. I beam rods are
lighter and will balance with less heavy mallory metal (a.k.a. tungsten)
slugs in the crank. A crank manufacturer can tell you the required
bobweight for their cranks. You could contact SCAT and see if they would
machine your 351C crank but it might end up cheaper to buy a Super Light.

Dan Jones


Hello Daniel; I'm going to be externally balancing the rotating assembly. I going to give the machinist the flywheel, crank, harmonic balancer, clutch & pressure plate, & let him balance as an assembled unit. Is this the correct approach?....Thanks, Mark
Last edited by George P
Views: 338
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