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Early vs late A65 crank dimensions #767227 03/05/19 2:34 am
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MarcB Offline OP
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I'm looking to fit a late crank into an early set of cases and, although I've searched this forum for information on the differences between the early (narrow) and late (wide) crankshafts, all I've been able to find are vague references to what fits and doesn't fit together, but no concrete specs.

Comparing pre-65 cases to a later set, all measurements appear to be the same except for where the timing side bush sits, and even that is pretty close. The early bush is about .040" thicker at its flange while the later one-piece bronze bush is thinner, and the case is machined slightly to hold the thrust washer in place. It's not a huge difference.

From the research I've done, it appears that the early cranks were about .070" narrower than the later units. Looking at the crank itself, it would appear that the narrower section would have to be on the right-side counter-weight (not sure that's the correct name, the right "shoulder" maybe), otherwise the crank (and rods/pistons) shift to the left against the bearing as well.

I had expected to find the left and right counter-weights to be about the same size but, on my late crank, there's .060" difference with the timing side being the smallest. If my assumption above is correct, then the early cranks would be even narrower on that side. Does anyone have easy access to an pre-65 crank that could take a quick measurement of the two sides for me?

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Re: Early vs late A65 crank dimensions [Re: MarcB] #767232 03/05/19 3:01 am
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drunkenmonkz Offline
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Interested to hear what people say. Ive been curious what exactly the difference is myself as im rebuilding a 64 motor and want to make sure i do not mistakenly order the wrong parts..

Re: Early vs late A65 crank dimensions [Re: MarcB] #767243 03/05/19 10:25 am
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Rich B Offline
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Marc,

I had measured and posted some of that years ago......

I do have some early cranks.....but they are a bit buried. It will be this weekend before I can get to them.

But, as I remember, the major difference was the shoulder that meets the timing side bush. The dimension I had was from the shoulder on the drive side where the shim cup abuts the crank to the shoulder on the timing side that abuts the timing side bearing. I didn’t measure the rest of the crank like you did.


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Re: Early vs late A65 crank dimensions [Re: MarcB] #767245 03/05/19 12:40 pm
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Ola Offline
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I have gone the other way, early crank in late cases, and it is, as you say, not a big difference. I had to add a thin spacer to the shim cup. I guess you may have to remove the cup, and do with just the shims, as on A10.


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Re: Early vs late A65 crank dimensions [Re: Rich B] #767257 03/05/19 3:58 pm
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MarcB Offline OP
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Originally Posted by Rich B
Marc,

I had measured and posted some of that years ago......

I do have some early cranks.....but they are a bit buried. It will be this weekend before I can get to them.

But, as I remember, the major difference was the shoulder that meets the timing side bush. The dimension I had was from the shoulder on the drive side where the shim cup abuts the crank to the shoulder on the timing side that abuts the timing side bearing. I didn’t measure the rest of the crank like you did.


Any info helps; thanks. I went through your old posts and didn't find specifics on width. I think my options are these:

  • Narrow the crank (not likely)
  • Install the later TS bush, with the shallower shoulder (is this a valid option?)
  • Pick up a 66-and-over right-side crankcase
  • Pick up a 65-and-under crank


My main concern with the last two options is that I have a known good crank and a known good set of cases already rather than taking a chance on picking up someone else problems. I'm going with a ball bearing on the DS. Can anyone speak to the second option above? I would imagine that it would be the same as using a later bush with a ball bearing on later cases but maybe I'm missing something else.

Re: Early vs late A65 crank dimensions [Re: NickL] #767429 03/07/19 2:18 am
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MarcB Offline OP
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Originally Posted by NickL
The cranks are interchangeable but you need to use the appropriate timing side bearing and driveside shimming.

If you are using a late crank in early cases with a ball race you will probably need the late thinner flange timing side bush,
but as the thrust is done on the drive side with this arrangement you will need to measure and centre the crank and
may not be able to use the standard timing side thrust washer, so a thinner one may be required. It is advisable to have a thrust
washer that side as the drive side bearing can move inwards in the case due to the natural thrust of the engine being biased to
the timing side by the oil pump.
BTW. The beezer timing side bushes were all lined steel types, only aftermarket bushes were one piece bronze ones.


Thanks for the info. I guess my next step is to drop in a new TS bush with the thinner flange and see how close that gets me. The case isn't machined for a thrust washer but I'll see what I can do.

Re: Early vs late A65 crank dimensions [Re: MarcB] #768022 03/13/19 7:07 pm
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MarcB Offline OP
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One more tidbit of information:

The later TS (right) case halves are only machined to accept the newer bush and thrust washer. The flange on this bush is thinner but wider, so the case is machined accordingly. No other difference.

The later DS (left) case halves are machined by about .055" all the way around where the counterweight rides. The later crank is thicker on the left side to shift the rods back to center.

I still don't have measurements of the early crank counterweight but my guess is that the left and right sides are probably closer to each other than the later cranks. Whether they match the right-side of the later crank or are some other size altogether is still unknown.

Re: Early vs late A65 crank dimensions [Re: MarcB] #775695 06/05/19 4:12 pm
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MarcB Offline OP
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Here's a write-up I put together after doing some thorough measurements: https://www.classicbritishspares.com/blogs/news/early-vs-late-cranks


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