Lotus Elan

crank rods and pistons

PostPost by: Davidb » Sat Jul 11, 2009 5:46 pm

Thanks, I have dealt with DB many times. :)
I wondered what the group thinking is on different crank/rod manufacturers?
Are forged cranks available?
Is QED SOL?

edit:
OK, QED's site must have been down for a day or so.
'65 S2 4844
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PostPost by: CBUEB1771 » Sun Jul 26, 2009 5:37 pm

Davidb wrote:Does anybody do a forged, narrow throw crank for the TC?


You could try Marine Crankshaft in Santa Ana, California: http://www.marinecrankshaftinc.com/bill ... hafts.html They machine from round stock, so not forged. Moldex cranks are also machined from round stock and don't break in NASCAR engines. I have recently seen a Marine Crankshaft unit going into a two liter, turbocharged Twin Cam being built here in the Boston area. This crankshaft is to Cosworth BDD dimensions with twelve flywheel bolts and narrow journals. The crank nose is machined for the Twin Cam cam chain sprocket.
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PostPost by: Davidb » Sun Jul 26, 2009 7:22 pm

Many thanks for that-I was not aware of that company.
I may be moot because I hear tonight if my offer has been accepted on an Elan that already has a billet crank :wink:
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PostPost by: pauljones » Sat Sep 19, 2009 6:44 pm

Since posting this a while ago,i still havent got round to the engine,work comitments. however,is there anything wrong with putting the 1600 xflow crank in the L block,with standard twink rods and pistons(no idea which..!!).i know its a long shot but any ideas on bhp and torque that i should be seeing on basicaly a standard engine with electronic ignition?
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PostPost by: msd1107 » Sat Sep 19, 2009 6:56 pm

Paul,

You are going to need different pistons with the piston pin located up to compensate for the longer stroke.

See Dave Bean's catalog on page E21, PN 560E0754

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PostPost by: rgh0 » Sun Sep 20, 2009 12:28 am

An otherwise standard big valve sprint specification engine with a long stroke 1600 crank and suitable pistons to maintain the compression ratio should deliver around 130 hp to 135 hp.

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PostPost by: elancoupe » Sun Sep 20, 2009 1:15 am

pauljones915 wrote:Since posting this a while ago,i still havent got round to the engine,work comitments. however,is there anything wrong with putting the 1600 xflow crank in the L block,with standard twink rods and pistons(no idea which..!!).i know its a long shot but any ideas on bhp and torque that i should be seeing on basicaly a standard engine with electronic ignition?



As noted by the others, Dave Bean has Omega short height pistons for just what you described. I have been using this combo in my car for some time, and it has worked very well.

I purchased a brand new xflow crank from my Ford dealership, and had my 125E rods checked and prepared for peace of mind.
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PostPost by: msd1107 » Sun Sep 20, 2009 1:56 am

Paul,

If you are going to a different piston, consider boring the block 40 over for 83.5mm and 1700 cc.

Rohan's guesstimate on horsepower brought out a spreadsheet. The original Elan engine had a BMEP at peak hp in the 150 psi region, good for the period, and an intake air velocity based on valve size of almost 200 fps, also in accordance with normal industry practice.

The big valve Sprint increased the intake air velocity to 224 fps, normal considering the increased cam duration. The BMEP increased slightly to 162 psi.

In theory, increasing displacement with no other intake changes will result in virtually the same horsepower, developed at a lower rpm. However, different engines respond differently to displacement increases, with some acting as above, and others maintaining the same rpm. In the first case, peak power comes in at 5,900 rpm. In the second case, power increases to 138 hp. According to Rohan's guestimate, you might come somewhere in the middle of the range.

Depending on the size of your budget, a 1700 cc engine should get 1 5/8" intake valves (the largest that the TC cylinder head can easily accommodate) and a more modern high lift camshaft profile. You are starting to wander off into a swamp here, but there are many who have done this. Depending on the details of your engine builder, you can get a torquey street engine with 145-160 hp. There have been some posters here who claim 180 hp.

Have fun, and post a dyno sheet.

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PostPost by: pauljones » Sun Sep 20, 2009 5:55 pm

Thanks very much for the reply's lads,much appreciated.

I better start by saying its not a sprint, just a plus 2 s spec with the 118hp. but to be honest if, (when) im going to stick in the xflow crank, then i will get the pistons that give as good as the sprint in compesion ratio terms and give me a larger safe capacity.I didnt really consider puting in valves past the sprint size, maybe i need to rethink that. As for cams i was going to start with what i have then maybe get a set specialy ground for the spec of engine,or if they available,the clossest off the shelf items. i think im right when i say the modern idea is high lift/sort duration.

The idea is to build a torque'y engine as i now have a 3.54 diff,soon to have a quaife ATB in,and a newly rebuilt 5 speed box to replace the 4.

thanks for the help every one.Paul
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PostPost by: bigvalvehead » Sat Jan 09, 2010 11:53 pm

Hi guys
I have built several larger capacity engines over the last 35 years including turbo and supercharged varieties.
It is possible to use the 1600 crank and rods in a st T/C block with 2litre Zetec pistons which are 84.8mm bore and a low compression height. You need to use the Omega forged pistons which have circlips to retain the gudgeon pins as the std piston is a press fit pin. Cutouts for valves also need to be machined into the unfinished crown. This gives around 10.5 to 1 C/R with the std clearnce volume and a 1740cc approx capacity.
Makes a good torquey road engine with no need for spacers etc.

I am currently building a 1953cc all steel turbo injected T/C using a 711m block with an FVC crank and 5.23inch narrow journal rods. Engine will be going in my 26R Shapecraft replica complete with T5 gearbox.
I'll keep you posted on progress
Dave Hughes

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PostPost by: Billmack » Wed Mar 17, 2021 2:48 am

6800 rpm . That's what formula ford used.Best FF engines do 7200 and crankshafts break. Forget 85 mm bore. 95 percent chance it won't end well. Stop at STD bore for an elan maybe .020 past that.
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PostPost by: rgh0 » Wed Mar 17, 2021 3:16 am

Billmack wrote:6800 rpm . That's what formula ford used.Best FF engines do 7200 and crankshafts break. Forget 85 mm bore. 95 percent chance it won't end well. Stop at STD bore for an elan maybe .020 past that.



We seem to be reviving an old post.

Yes I agree with a standard crank I would not use over 6800 rpm. Seen lots beak when used at 7000 rpm for extended periods on the track.

In terms of what bores are possible it depends on the original block bore casting diameter and how centred the original bore is in the casting and then how to offset bore to maintain maximum wall thickness and how thin a wall thickness you are prepared to go with. I prefer a minimum wall thickness of 3mm / 120 thou for race engines but could be talked into 2.5 mm / 100 thou for a road engine depending on the location and extent of the thinnest spots.

Lots of devil in the detail e.g. if the original bore is well off centre versus the casting you can struggle to get it even all around as you end up boring into air on one side !, the amount of offset possible is limited which limits the amount of bore increase in a block with non centred bores which is normally the case as it is rare for the bore to be central in the bore casting due to tolerances on the core locations


In general with careful measurement and offset boring 83.5 mm is safely obtainable in around 70 to 80% of blocks. 85mm is obtainable safely in maybe 5% to10% of blocks. No difference between the various Block versions and or between L and non L blocks of specific casting number versions in terms of these outcomes

The South African AX blocks are supposed to have a thicker bore wall casting but I have never measured any to see what they have and what variation exists. However the gap between the cylinders pretty much precludes walls beyond the upper end of the tolerance range across the standard blocks due to sand casting requirements with non siamesed cylinders so they cant be much better than a standard block at the top end of the tolerance range.

The modern Ford motorsport blocks appear to have tighter tolerances on the bore casting OD and location and you will struggle to go beyond 83.5 mm in any of them from what I have measured but they will all also go to 83.5 mm

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