SPA Corvair USA Made Billet Crankshaft
DSCN2020Billet Crankshaft Rod Radius Close UPSPA Corvair USA Made Billet Crank Rod Throw Closeup

Corvair USA Made Billet Crankshaft

$2,500.00$3,085.00

This crank is a stock replacement and will work with all current components being used.  It is made of heat treated Timken 4340 Billet, CNC machined and Ion Nitrided.  The crank is threaded for a safety shaft and ready to use.  This will be the finest Corvair crankshaft available, showcasing meticulous attention to detail and surface finish.

We worked hard with the manufacturer on the design and cost.  The cost is more than we strived for but after exploring many manufacturing options this is what we can offer.

For those of you who are starting a new engine we offer a complete kit option.  For those that may have some parts, or those that want to purchase one thing at a time we have the crankshaft only.

Click HERE to look at 5th Bearing Options for your Billet Crankshaft

Corvair Stock Crank Replacement Complete Kit includes

  • Corvair Crankshaft – Timken 4340 heat treated Billet, CNC machined and Ion Nitrided
  • Tapped for the safety shaft

Optional

  • Clevite 77 main and rod bearings
  • New 4340 Billet Connecting Rods

 

 

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Product Description

The Concept

Develop and provide New High quality Corvair crankshaft as a replacement for the GM crankshafts in all applications.

Why?

This is a long list, with many things to consider.

First – any Corvair crankshaft is at least 50 years old and we have no real idea of many factors:

1.  How much time is really on the crank?

2.  How was this engine treated?

3.  What is the metallurgy of the crank?

4.  Was it repaired or reground in the past?

A new crank shaft of known origin would answer these questions.

Second –  Corvair engines were produced in a cost constricted environment.
The Plan:  Our current thoughts, after talking with many people in the industry and several metallurgists:

  • Maximize strength and fatigue resistance while maintaining compatibility with the stock Corvair components.
  • Increase all critical fillet radiuses to maximum possible without causing issues with bearings.
  • Throws will be increased in width to increase section area. Thickness would be better, but that cuts into room for large fillets which are critical!
  • Material will be US sourced 4340 Timken QA steel.
  • The Crank will go through a extensive metallurgical process to include heat treat, stress relief, ion nitriding etc.

Our primary goal is to offer a replacement crank that will require no major changes to the existing setup to install, while maximizing strength and service life.  Second to that goal is to keep the cost down as much as possible.

THE BIG QUESTION “DO I NEED ONE?”

This is what everyone asks, but there isn’t a definitive answer for that question. You have to ask yourself what your guideline of acceptable risk is.  The circumstances listed below should be the guidelines for running a stock crank:

  • If the crank had been Nitrided
  • Crank has been reground with attention to detail and as large a radius as possible
  • If the crank has a 5th bearing installed
  • The engine setup for a front starter
  • Wood prop dynamically balanced
  • Ignition timing set below 30 degrees , use 100 ll only,  and a good known carburetor set up (MA-3, Stromberg  and Possibly Ellison) to eliminate any chance of detonation

*** Any “trauma” to crank like a prop strike (regardless of magnitude), or a balancer issue etc would be cause for replacement.***

With the above guidelines the re-manufactured stock GM crank should perform well and have an acceptable service life for most users. 

All that being said; if a new manufactured, extremely high quality crank as above is available, we will use one.  If the new crank cost $1500 more than a reworked stock unit then it is well worth the money and the Vair would still be an excellent value in the 100 hp engine market!

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