I want to do some minor work on my 396 that is currently apart. 1st im going to polish the connecting rods. Does anyone have any tips, tricks out there for that? It looks straight forward enough...

I would also like to knife edge the crank. I think this means that a smooth out the out parts of the throws so the oil is thrown off better??? Im planning on just smoothing the edges and any rough spots. Is there any risk of removing too much and having to add heavy metal to the crank? I have to have the crank turned and balenced so I figured know would be the time to do it right. Im looking for every last HP because I run a stock class and all the tricks add up to wins.

Thanks, Mike

PS. Any other tricks to make the 396 bottom end lighter,and faster are greatly appreciated!!!

Knife edging the crank is for reduced rotational drag, the sharper edge supposedly cuts through the windage better. The best thing you could do for your rods if it hasn't been done yet is to install good ARP bolts and have them resized by a good machine shop, after that removing the forging line and polishing then bead blasting would add extra strength. It would be a good idea to have them magnafluxed before doing anything. Or you can do like I did and sell off the factory rods if they are 3/8" bolt versions and buy some good aftermaket H beam rods. JMO Bob

Knife edging is a great idea. A lot of work to do right. The sharp edge should be on the rod side so any oil is thrown toward the mains. I guess you checked if knife edging is legal in your stock class.

Another thing to consider, any weight alterations to the crank, pistons or rods will require rebalancing the assembly.

Pat can you expand on the "do right" statement. What should it look like?? When you say rod side what do you mean. The crank rotates clockwise so I would want the leading of each counterweight to be sharp????

I think I might be in too deep....

That's knife edging. The leading edge of the counterweights are sharpened. Not razor sharp smile.gif . The sharp edge is next to the rod journals and the taper is toward the mains. That way the oil is directed toward the mains and not the rods. I suggest going to a book store and looking in David Vizard's book "Building a Max Performance SBC on a Budget". SB, I know, but the theory is the same. There are pictures of a correctly done crank.

You could detail the crank and that is a lot less work. That entails clean up any rough spots and chamfering any sharp edges (like the weight removal holes). That's what I did to my crank. You can do this after the crank is balanced. When doing this I suggest putting tape around the journals to protect them.

Buy a whole bunch of grinding wheels. That's some of the hardest steel you'll ever try to work with. Look at a Lunati crank - they're pretty much cutting edge as far as windage goes. HTH

The Lunita cranks look very nice... So I want a sharp edge on the side of the counterweight that is towards the rod bearing. On the other side a want a gentle slop...

Does anyone have any "tells" on how to learn if a BBC crank is forged or cast. You know on a SBC you can tell the difference is it the same on a BBC?


My crank has a 45 degree camferred end on the rod side of the counter weight. How could I make that sharp??? Lunita's cranks are much thinner than mine but I get the basic idea. I want the oil to leave the rod side and go to the mains where it can eliminated into the pan. This doesnt harm camshaft lobes does it???

How many people here have Knife Edged their own Crankshafts ? I'm not talking about those that do it for a living. How many would do it ?

Monte,
Verification of forged crank is the same for BBC as any other engine. Forged crank will generally have wide parting lines. To further test or validate your findings, set the crank upright on the floor and tap it with a hammer. Forged crank will have a distict ring when whacked (unless it is cracked). Cast crank will have very narrow and straight parting lines and will have more of a "thud" sound when tapped with a hammer. A billet crank will have no parting lines and will (usually) have very slight machining marks on the counterweights.

As far as knife-edging a crank goes, it is a huge anount of work and probably will not result in measurable hp gain in a street or street/strip application. Best method is to use a large industrial type angle grinder with a rigid disc to do the rough grinding, then finish with a die grinder and a large supply of stones. The journals must be protected, especially when using the angle grinder. I would recommend putting old bearings into place and secure them with duct tape before starting.

I think i'd forget the whole idea like one fellow said it will create balancing difficulties. Why not just fabricate a crank scraper and not mess with the crankshaft itself? If horsepower increases are your goal then a deeper pan and pickup would be more beneficial than taking on a knife edging project. You would probably end up destroying the crank and having to buy a replacement. Run this one by Wolfplace or the east coast engine guy whose name i can't recall.