Technical > Matt Shaff's Engine Shop

offset grind crankshaft

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jeff/21:
stroking normally helps there is one class i built motors for and we where allowed to stroke 3.48 to 3.50 it showed on the dyno we spent a lot of time on the dyno trying to get the most from a limited motor.

Van:

--- Quote from: speedbump on September 22, 2016, 01:43:51 PM ---i been in touch with tony. he has been very helpful. but my question is should i go ahead and do the offset grind and whatever goes with that comb. or just bore the shxxx out of it and be done. will i gain that much hp offset grind. over over bore and have 4oo plus ci. getting the parts is not the problem.

--- End quote ---

 I ran the 394 olds on blown gas & had a lot of fun with it. Back then every one off set stroked and used the 57-58 journal size, which is the same as Pontiac & 354-331 Chrysler. Today every one that strokes a big block typically uses Big block Chevy journal & so should you. The 394 is a fun & cheap motor to build, best head is the #23  1964 head. To run big valves you will need to use offset guides to move the valves apart.  use the 64 front cover as its aluminum, unless Tony makes a race cover.  If you want to do this on the cheap  use a 400 SBC stroker piston & do the math on rod length & stroke to go with the piston. All you will need is a flat top or small dome.  I don't know why all this Olds info is still stuck in my head ?

Frontenginedragsters:
Mike:
 It always comes down to being cost effective.
It sounds like a lot of work to do what your asking. Then the added cost of custom pistons.
I agree that cutting it down to BBC size makes the most sense.
You also have to look and see how much mass the crank throws have between the rod journal and main journal. You don't want to weaken it.
I do not have an Olds 394 crankshaft to look at.
Is it a forged steel crankshaft? Most of the older engines used forgings. You would not want to use a casting.
I will guess that between straightening the crank, Magnufluxing, the mains will get cut .010 to establish a perfect centerline. Then off set grind.
Send it out for nitride. Might have $900 or more.
I like the idea of large bore size. Have the cylinder walls sonic tested first.

Matt

George:
The Olds engine with a 4.125 bore and 3.95 stroke is 422 CID. A gain of 28 CI. over the stock 3.688 stroke. Is that worth several thousand dollars? I would look at getting the engine to breath better before spending $$$$ on a stroker crankshaft. Again just my 2 cents. 

Van:

--- Quote from: George on September 23, 2016, 08:38:29 AM ---The Olds engine with a 4.125 bore and 3.95 stroke is 422 CID. A gain of 28 CI. over the stock 3.688 stroke. Is that worth several thousand dollars? I would look at getting the engine to breath better before spending $$$$ on a stroker crankshaft. Again just my 2 cents.

--- End quote ---

  My 2 cents says, He can buy a off the shelf forged 400 SBC piston & a BBC  aftermarket rod & re bush the pin end to SBC size and off set stroke the crank. At .060 over bore & stroking I think 440 is more what can be had.  The stock rebuilder pistons are not cheap and the stock rod is no good for HP use. My local crank shop offsets cranks for me at $250 max, I had him offset a few Cast 460 Ford cranks last year. The Olds crank is Forged, and like I've already said this was the norm back when the Olds was raced. To try and have any success with the Olds using stock rods and rebuilder pistons is not going to work. This is not a SBC  The racing world already has to many of them   

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