Crankshaft Question

Balvar24 · Post by **Balvar24** » Sat Jun 25, 2011 8:16 pm

Did the L and F head use the same crankshaft?

Post by **wesk** » Sat Jun 25, 2011 8:22 pm

The L134 block castings 641087 (gear driven cam) and on and the F134 used the same 646316 crank.

Balvar24 · Post by **Balvar24** » Sat Jun 25, 2011 8:24 pm

Earlier L heads used a different Crank? Any way to visually tell the difference? I've got a line on a bargain, but need to be sure.

Post by **wesk** » Sun Jun 26, 2011 7:46 am

Earlier L134's had chain drive cams and the crank was different.

The MA/MB 638121 timing chain crank had counter weights that were very narrow when compared to later bolted counterweight cranks. .This crank is easy to spot.

The second timing chain crank 641128 had bolt on counter weights introduced on the CJ2A and was often a service spare for the MB/GPW.

Then came the 646316 gear drive cam crank with bolt on counterweights.. The bold underlined area was edited to correct crank data.

The obvious difference on the cranks will be at the front. Photograph and measure you crank snout area and use it to confirm compatibility.

Another thing to watch for is the use of two tapered dowel bolts or two straight shouldered dowel bolts at the rear flange. Your choice will depend on what you currently have in your flywheel.

AeroE · Post by **AeroE** » Mon Jun 27, 2011 8:12 pm

Wes: your comment on crankshaft evolution intrigued me in that I have what I believe is an NOS M38 crankshaft, still in cosmoline. It looks right, the bearing dimensions are correct for standard bearings, the cam drive gear (NOS) seems to fit nicely, and it looks just like the crank in TM9-1804A page 53. Except it definitely has bolt on counterweights, with a single allen head bolt each. ORD 9 lists the part as ‘Crankshaft, with counterweights’ implying that are an added part. Page 53 also shows the bolts clearly.

If I understood you said only early MA/MB crankshafts have bolt-on counterweights, what do I have?

Balvar24 · Post by **Balvar24** » Mon Jun 27, 2011 8:22 pm

The later F heads had bolt on weights as well. Mine were bolted on and tack welded in place. I think that only the later chain drive cam engines had integral weights while later gear driven cam engines had bolt on.

Would you be interested in parting with your crank? If so, feel free to send me a PM.

AeroE · Post by **AeroE** » Mon Jun 27, 2011 8:48 pm

I thought I may have misinterpreted what Wes said.

I still would like to confirm. Since the manuals only list the crankshaft bearing journal dimensions, it would help if someone posted the length x diameter of the cam gear portion of the shaft. A photo of the correct snout would be great!

Post by **wesk** » Mon Jun 27, 2011 10:32 pm

Nope! Balvar's mostly correct. I wrote it backwards again. You know what that's a sign of!!!

MA/MB chain drive cranks had fixed counterweights and they were very small slender ones compared to the later cranks. All gear cam drive cranks have bolt on counter weights.

Balvar24 · Post by **Balvar24** » Tue Jun 28, 2011 7:09 am

Thanks. That's an immense help.