Lotus Elan

Crank swap

PostPost by: pauljones » Fri Jan 21, 2011 4:45 pm

Hi all,
Just a quick question,is it possible to do a bolt in swap to the 1600 xflow crank without changing the rods or pistons. My plus 2 will soon have its MOT and I am thinking of doing this at the same time as a box swap so the engine will have to come out anyway latter in the summer.

Many thanks.

Paul
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PostPost by: garyeanderson » Fri Jan 21, 2011 5:16 pm

pauljones915 wrote:Hi all,
Just a quick question,is it possible to do a bolt in swap to the 1600 xflow crank without changing the rods or pistons. My plus 2 will soon have its MOT and I am thinking of doing this at the same time as a box swap so the engine will have to come out anyway latter in the summer.

Many thanks.

Paul


Nope, needs new pistons. Time for a bit of reading...

elan-archive-f16/1700cc-stock-twin-cam-block-t11169.html

http://www.lotuselan.net/cgi-bin/search ... oom_sort=0

OR

http://www.lotuselan.net/cgi-bin/search ... oom_sort=0

OR

http://www.lotuselan.net/cgi-bin/search ... oom_sort=0
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PostPost by: pauljones » Fri Jan 21, 2011 6:18 pm

Gary,
I once got told at the 1st lotus show I went to that the way forward was a xflow crank and rods and it would bolt "straight in with no worries,a cheep way to torque and hp" So as soon as I could find one I done the deal.Looking at but a few of the posts it seems I was very niave.
I now have a 1600 block with caps,crank and rods.At least with 84mm pistons(not 85),I can build a tall block that will give a bit more torque and hp,keeping a good thickness around the bores.All I need to do is get the pistons,how hard can that be??What I would like to know is the pin height of the pistons.Do I have to build a dry engine and take some measurement to get this(using standard pistons) and give these to a piston company to make some that will suit? If so,what measurements?

Paul
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PostPost by: garyeanderson » Fri Jan 21, 2011 7:05 pm

The first question is different then the second.

A 1600 block, 1600 crank, 1600 rods, with Stock compression height twin cam pistons will work but you must trial assemble and determine the amount that the cylinder block face must be machined to achive the correct clearance. That amount is usually around 5.5mm (.215 inch) and then you need a spacer on the top of the front cover along with a long cam chain and a modified timing chain tensioner. None of it is a weekend job unless you have done it a few times and even then I am sure it takes a bit more then what I am writing. Talk with Brian
(bcmc33), I think he has done a few...

Gary
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PostPost by: pauljones » Fri Jan 21, 2011 7:14 pm

Gary,

Your right,the questions are different.I was told that it went in the lotus block easily.the only way I could get all the parts I now have, was to buy them together.seller wouldnt split,even came with the xflow covers.Having read some more of the links you sent,and thanks for them,the question I was going to ask is to do with what you mention about cutting of the top of the block.Why not have it flatened true,and just have longer con rods?

Paul
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PostPost by: garyeanderson » Fri Jan 21, 2011 7:59 pm

More money! Cosworth has 5.23 inch long rods as do others.

1600 block is 8.21 inch from center of crank to top of block face

8.21 - 5.23 = 2.98 inch

1/2 the 1600 stoke is 1.53 inch

2.98 - 1.53 = 1.45 compression pin height in the piston.

How much money do you want to spend?

Finish reading the other hundred or so posts, spring is just arond the corner.

We are talking about an average increase for the 100 cc of extra displacement (for the crank swap) of about 10 hp and 15 lb/ft of torque.

Just get your MOT and drive it, It's more fun. Dreaming is great, I done both and I like both, I used to spend the money but its gone now so I just drive...
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