Lotus Elan

Twin-cam Crankshaft Replacement:original Or En 19?

PostPost by: BenMcCarthy » Thu Apr 29, 2004 9:32 am

I am based in the UK. My engine is being rebuilt at present and needs a new crankshaft. I use the car everyday and want it to last although I have no intention of using it for the track. Any ideas?

The crank has had a -40 grind on it and I am faced with the stark reality of choosing between:

1. A EN 19 Crankshaft (Supply either by QED at ?750 or possibly Dave Bean in the US) or

2. Obtaining a standard or -10 grind crankshaft.

3. I also have the option of getting a 711M QED short engine (tall block 1700cc) attached and saving myself some money but this may affect the value of the car and insurance.

As a plus I have renewed friendship with my bank manager.

Regards

Ben
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PostPost by: steveww » Thu Apr 29, 2004 9:53 am

I would go for a new steel EN19 crank. OK so it is more money but the steel crank is very strong, old cast iron cranks can develop cracks. If the crank breaks it will be very exspensive :o

I would think by the time you have found a second hand iron crank, had it crack tested and reground the cost will not be that much less than a new steel crank?

QED are the Lotus Twinc engine people. Having a 1700 QED short block in your Lotus will not devalue the car, it might put up the insurance a bit though. If you don't want to go to 1700 you can get a new 1500 block from Burton as they are casting new ones again.
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PostPost by: charles jackson » Thu Apr 29, 2004 10:47 am

I have a spare crank, if you get stuck give me a call on 07763831545 to discuss.

regards - Charles :)
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PostPost by: gjz30075 » Thu Apr 29, 2004 11:35 am

Ben, I don't know if #3 will save you money as you still have to get a spacer for the timing chest, a longer timing chain, longer block breather and if its a true, unshaved 711 block, it may not clear the bonnet. Also, if the pistons are the dished type, you'll loose tons of compression. If the block has been shaved down, all of the above is still true but now you're looking at a different set of pistons with a corrected wrist pin location.

For your purposes, I think another standard or -10 crank will be fine.

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PostPost by: rgh0 » Thu Apr 29, 2004 12:05 pm

Ben

Another option is to fit the Datsun L16 crank machined to suit and a new flywheel to suit the 5 bolt pattern on this crank. Cost in Australia is about A$1300 equivalent to around 400 pounds sterling. Just as good and much cheaper than a new steel crank for a competition vehicle. I dont know if anyone does this conversion in the UK though it is common in Australia.

For a road car a standard second hand cast iron crank should be fine assuming you can find a good one.

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PostPost by: types26/36 » Thu Apr 29, 2004 7:08 pm

Ben,
I fitted a 1600 (711 crank) into a 1500 block and just cut the standard Lotus pistons down to suit the block......... O.K. its getting close to the top ring.
Only just got it together so it has'nt done many miles yet so dont know if it will last but so far so good. Had to do a bit of grinding on the block & crank to get clearance and then a balance on the crank,rods, f/wheel & pistons.
Regards Brian.
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PostPost by: stelz » Sun May 02, 2004 9:38 pm

I might have thought the 711M block and crank option is best for a road car. I am currently getting all my bits together to build my engine and was going down this route. The plan was to use 711M block, crank and rods, t/cam pistons (standard compression height) and deck the block to get the right compression ratio.

Curious about what was meant by the other post re modifying t/cam pistons in the 1500 "L" block. I guess this is about larger gudgen pin and reduced compression height to accomodate long stroke on 125E conrods.

Could others elaborate ?

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PostPost by: types26/36 » Mon May 03, 2004 7:18 pm

Ben,
I have done the conversion you are planing i.e 711 block,rods & crank but you will still need to fit a timing case spacer (unless you get the tall t/case) You will also need a 122 link timing chain, decking the block alone will not work. Using the tall block & longer chain changes the valve timing (as does skiming the head) and you will have to reset the valve timing....off-set dowels or adjustable sprockets etc.

The other modification I refered to (cut down Lotus pistons in a 1500 block) involved fitting the 1600 crank (77.62 stroke) into the pre Xflow block, it will fit but catches inside the block, hence the grinding of both the block and crank untill it clears. Even with 125E rods the pistons pop out the top and the pistons were cut down at the outer circumfrence leaving a "dome" in the centre, valve to piston clearance was checked and a fluid check of the combustion chamber (head installed) gave a C.R. of 11.4 to 1. If this proves to be to high for road use some more modifications will be done.
The only work done on the pistons was to the crown, the gudgeon pins were not touched.
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PostPost by: BenMcCarthy » Mon May 10, 2004 9:23 am

Thank you for all of your suggestions. I think ultimately I am going to take a nice condition original crank. The EN19 crank is good for 8,000 rpm but I don't plan on racing it and don't beleive I'll benefit from the steel crank while I've still got a fairly standard engine with cast pistons etc. I'll just be using it regularly and the cost differential is ?150 (with delivery and testing) versus ?750.

Its almost impossible to get a 2nd hand EN19 crank that's any good but there seem to be a fair number of iron cranks lying around if you phone the usual people in the UK like Sue Miller, Kelvedon and specialist twin cam workshops who spend their time taking perfectly good iron cranks out and replacing them with steel for race engines.

Make sure the crank has been well used and stored properly (to test out any propensity for cracks) although not worn.

Thanks again, folks
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