Crank serial numbers ?

[acarlson]

Is there a table somewhere which lists the various cranks by serial number which were used in the LM engines ?

Alec

[66vairguy]

AFAIK - there were no "serial numbered" crankshafts. The books describe how to identify them. Basically the short stroke 60-63 and long stroke 64-69 crank. The LM crankshafts for 140HP and 180HP engines are nitrided (very thin surface hardening) to resist wear and have an "&" (ampersand) mark on the end. The nitrided crankshafts usually do not need to by turned down, if they are, then the hardening is removed. The nitrided crankshafts are no stronger, the bearing surfaces just resist wear better under higher loads.

The 140HP PG (automatic) crankshaft has a unique crankshaft gear that retarded the cam shaft timing (long story). The only way to identify the unique 140HP PG crankshaft is to examine the crank gear tooth position - it is not easy as it's only off a few degrees. The books have pictures to indicate how to examine the crank gear.

[bbodie52]

Here are a few images and details to supplement the above post..

The 164 CI crankshaft displaying the number 8409 is found on 164 CI engines.



5607 signifies it from an early 145 CI engine.
7293 signifies it from an early 145 CI turbo engine.
8409 signifies it's from the late 164 CI engines, regardless of HP.

The 140 hp and 180 hp Turbo engines had a heavy-duty nitrided crankshaft — identified with an ampersand (&) stamped on the flywheel end of the crankshaft.


Here is a link to a brief discussion on Corvair nitrided crankshafts on the Corvair Center...


http://corvaircenter.com/phorum/read.ph ... 115,249229

All of the Corvair turbocharged engines had nitrided crankshafts for added strength. They are identified by an ampersand "&" stamped on the flywheel end of the crankshaft. These nitrided cranks were also used in the 4 carb 140 engines...

This ampersand stamp indicating a nitrided crankshaft is also mentioned on page 69 in the book Performance Corvairs: How to Hotrod the Corvair Engine and Chassis by Bill Fisher and Seth Emerson. The book also mentions that GM lab tests showed Spyder model (1962-1963) crankshafts (forged in SAE 5140 chromium alloy steel and surface hardened by nitriding) were five times more resistant to cracking than the plain carbon steel models. In 1964 alloy steel crankshafts were used in place of the previous forged carbon steel in all models as the displacement was increased to 164 cubic inches by raising the stroke from 2.6 inches to 2.94 inches. A harmonic balancer was also used on all engines except the 95 hp unit. As previously mentioned, nitriding was included on the highest horsepower 140 hp and turbocharged engines.

[/i]

[acarlson]

So, it would be safe to say that all LM 164 ci engines used the same crank EXCEPT that the 140 & 180 HP engines had cranks which were nitrided ? I'm asking because my Corsa turbo engine has a LM Monza 110 HP case (not the turbo case) and I just needed to know if there was a crank difference between the two engines (besides nitriding).

Alec

[Scott V]

yes...............all 64-9 cranks are the same except the 140 & 180 hp engines had cranks which were nitrided. some say that after '67 not all 140 hp engines had nitrided cranks.

-Scott V.

[66vairguy]

Brad posted some great information.

If your engine case is a 110HP it's difficult to say what crankshaft was used (BTW in the old days the performance guys would look for low mileage 95HP or 110HP cases because they were generally in better shape vs a H.O. engine case for use to build up an engine). As noted the LM crankshafts were all the better alloy and I would not worry about nitriding since most of our cars are for occasional pleasure and will never see 100K miles where nitriding makes a difference.

[bbodie52]

The presence or absence of a harmonic balancer on a 164 CI crankshaft can also potentially impact the stresses a given crankshaft has to absorb over years of operation. GM engineers were forced to compromise by GM accountants in 1964 when the engineers specified the use of an [expensive] harmonic balancer on the long stroke (164 CI) crankshafts. A compromise was established where a solid cast pulley was permitted only on the low horsepower (95 hp) engines, with 110 hp and 150 hp engines receiving the desired harmonic balancer to prolong the life of the crankshafts that were assuned to be exposed to greater stress factors. In 1965, as engine stresses increased even more, nitrided crankshafts were specified on the 140 hp and 180 hp engines. We must assume that GM engineers concluded that there was potentially some stress weaknesses in the top 164 CI engines that might bring on possible crankshaft failures in these street engines that were not likely to occur in low revving, lightly driven "grocery-getters" fitted in 95 hp Corvairs driven by little old ladies nursing their Powerglides.

Of course GM only expected the average Corvair to see about 10 years of use before it hit the scrapyard. I don't think they anticipated 50+ years of use -- much less these engines migrating into race cars, dune buggies, air boats, aircraft etc.

Over the years some owners substitute inexpensive solid crankshaft pulleys (steel or cast) when their pricey harmonic balancers age out and suffer separation. Doing so could possibly introduce small stress fractures or cracks into aging crankshafts. Any machine shop work on the crankshaft journals on nitrided crankshafts would also remove this nitrided surface. When performing an engine rebuild, it might be wise to consider all of these factors when having the crankshaft inspected -- including a check for cracks.

[acarlson]

Well, my Corsa has 120,000+ miles on it although I don't know how many are on this particular engine. The speedo odometer was dead when I bought the car and I have no way of knowing how long it was broken. The car was built in '65 with a 140 4x1 and the current engine replaced that engine somewhere along the line - back around 2009 as near as I can determine. I believe the guy had the crank turned since he bought +.010 rod bearings from Clarks back then. I'll see what kind of shape the crank is in once I open the case up. Anyway "Thanks" to everyone for your help. I'll let you know what I find.

Alec