Four or six bolt crankshaft

[chrishewett]

When did the crankshaft change from four to six bolt? Did any sprint engines have a four bolt crank?
Thanks,
Chris

[tower of strength]

I think I'm right in saying that only S1 and possibly early S2 elans had the four bolt crank.All Sprints and S/E Engines had 6 bolt cranks and stronger con rods.
If you want definate information I can look it up for you.

Mark

[bill308]

My late model S2 Elan had a 4-bolt crank.

Bill

[1964 S1]

I think the rope seal determined the difference and that S2's were the "end of the line" on that design. But I'll bet a Trumer Pilsner there are S2's with six bolt cranks. What about Cortina models?

[prloz]

Hi,
I understand the crankshaft changed from 4 bolt to 6 bolt with the introduction of the Mk2 engine at engine number LP7800; part way through S3 production.
Therefore, many S3's have 4 bolt cranks, including S3 S/E's.
Regards,
Peter.

[chrishewett]

Thanks for the replies.
I was interested as there is a " sprint" engine on ebay at the moment with a four bolt crank. It is claimed to produce 141bhp.
Chris

[rgh0]

Hi Chris
I saw that engine and its a strange combination. Its a late model block but with a 4 bolt crank, what the heads off is anyones guess.

What they have done with the sump is an interesting question as they will have had to used a 4 bolt sump to match the crnak but with the pickup for the later block and I will bet they have not changed the baffling to suit !

cheers
Rohan

[Early67DHC]

<historical trivia> As was mentioned, the 4-bolt crank engine was the Mk1 and the 6-bolt the Mk2. The official full-up Mk2 introduction was designated LP7800, midway through 1967 production per my and other's experience, although stated (perhaps erroneously) as introduced in autumn 1966 in Robinshaw/Ross. Robinshaw/Ross did get it right that some late Mk1 engines had some Mk2 bits. As was typical of Lotus manufacture, one design sort of morphed into another as parts availability dictated. My engine is LP7464, fitted to my Elan in February 1967 and is the Mk1 engine with rope seal and 4-bolt crank. However, my engine rebuilder (hole burned in piston - keep those Webers tuned properly!) told me of his surprise to find the Mk2 125 rods in this engine, rather than the 116s. This was subsequently explained when I found my specific engine LP7464 referenced in Robinshaw (pg 69) as the first Mk1 engine to use the Mk2 push-fit oil pickup and thus to have a hybrid Mk1/Mk2 pan. So maybe it was also the first to use the Mk2 rods. Don't know if this was because it was fitted to an S/E, or if all subsequent S3 Mk1 engines used 125 rods as well. Other data points welcomed. On page 71 of Robinshaw, he reiterates a hybrid sump was available briefly, but here he lists the starting engine as 7764 rather than 7464. My experience is that LP7464 is correct. Robinshaw doesn't state which Mk1 engine first used the 125 rods, except to say it was very-late in Mk1 production. My guess is that it might have been LP7464 as well.
<end trivia>

[1964 S1]

Elans are not Porches. The hair splitting doesn't apply to Lotus. Lotus built their cars with what was on the shelf, not with what corresponded numerically. And I'll add that forty years have passed and just maybe did a previous owner change the connecting rods? Was your oil pan gasket original?

[garyeanderson]

Hi Ian

Weldon bought the Elan New, the DPO was Lotus...

http://www.unibrain.org/motorsports/ela ... &fm=60&sfn[0]=-6&sfn[1]=2&sfn[2]=4&sfn[3]=5&sfn[4]=1&operation=View&rec=159

Gary

[1964 S1]

Who's Ian?