Lotus Elan

Camshaft identification

PostPost by: S4ever » Tue Jul 01, 2008 11:42 am

I found the following numbers stamped on my camchafts.
I have searced in Miles Wilkins twin-cam engine book but cannot find any specifications.
Any ideas what the numbers means? Type / specifications for the cams?

The numbers are stamped in line with Cyl 1 , 2 , 3

Inlet camshaft : MC23929 , C , B26E351
Exhaust camshaft : MC23929 , A , B26E351

Thank you

/Erik
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PostPost by: ppnelan » Tue Jul 01, 2008 1:51 pm

I believe all Lotus-manufactured camshafts have these numbers (mine have the same/similar, from memory)... :?:
The MC one is probably a casting number, and the B26 one is probably a part number (26=Elan).
It is the groove(s) machined on the outside of the sprocket flange that tell you what specification they are. Unless they've been re-profiled... :?

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PostPost by: rgh0 » Wed Jul 02, 2008 1:40 am

Lotus had 3 production cams

B cam - standard - no grooves
C cam - SE - 1 groove
D cam - Sprint - 2 grooves

Yours looks like the B cam from the part number and if it has no grooves. Hoever by now many cams have been reground so check if base circle is standard.

Based on Lotus part numbering methods there should have been an A cam and a no letter cam. Potentially the no letter cam was the Lotsu part number for the raw casting and the A cam was the early cams used in the protoype heads that lacked the rear 5th half width cam bearing.

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PostPost by: EdHolly » Wed Apr 25, 2018 12:15 am

The post above mentions a stamping of A for Exhaust and C for Inlet.

I have a pair of camshafts and I need to use the inlet one but can't identify which of the two it is. They have a single groove and the lift agrees that they are S/E cams.

The pair have the same ancillary numbers but instead of A and C have B and D - does anyone definitively know which is which please.
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PostPost by: rgh0 » Wed Apr 25, 2018 12:36 am

Hi Ed
The inlet and exhaust cams are identical, The timing setup difference is managed by the drive sprocket which is drilled differently for the dowel for inlet versus exhaust. Typically Lotus only stamped the Exhaust sprocket with "EX" but I have also seen inlet sprockets stamped "IN" whether this was done at the factory sometimes or afterwards hard to tell.

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PostPost by: EdHolly » Wed Apr 25, 2018 12:43 am

Rohan,

thanks mate ... I couldn't pick a difference but didn't know they were the same. Will you be going to Winton?
Rod and I are planning to be there Saturday in the 2 Elans.
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PostPost by: EdHolly » Wed Apr 25, 2018 1:02 am

Rohan -

this is the No.4 inlet lobe - looks like a repaired one now breaking up ...

Ed
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PostPost by: 1owner69Elan » Wed Apr 25, 2018 1:14 am

I would add an historical note. Below is correspondence from 1970 regarding the camshafts in my 69 S4 SE DHC.

In the process of setting valve clearances in 1970, I noticed the difference in letters on the cams as well as the "B" reference on the cams. Just as the original post above noted, but only 48 years earlier.

I became concerned that perhaps I did not have SE (Type C) cams for both intake and exhaust. Perhaps "B" cams or an "A" and "C". Thus, I sent an inquiry to Lotus to please explain the apparent mismatch.

The letter below is from Roy Badcock, Customer Liaison Supervisor at the time - though I believe he held a number of positions at Lotus during his career.

As he notes, " We hope that we have been able to clear up the mystery".

lotus-cams-correspondence-1.jpeg and
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PostPost by: rgh0 » Wed Apr 25, 2018 2:33 am

EdHolly wrote:Rohan,

thanks mate ... I couldn't pick a difference but didn't know they were the same. Will you be going to Winton?
Rod and I are planning to be there Saturday in the 2 Elans.


yes i will be running at Winton
see you there, hope the weather is good

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PostPost by: rgh0 » Wed Apr 25, 2018 2:40 am

EdHolly wrote:Rohan -

this is the No.4 inlet lobe - looks like a repaired one now breaking up ...

Ed


Certainly needs to be replaced.

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