Lotus Elan

Advice on jet sizes please

PostPost by: chrishewett » Thu Feb 11, 2010 9:58 am

I have just bought a 1968 +2. The engine was rebuilt some years ago with a big valve head and L2 cams. Weber carbs.
I havn't started it yet as there is a problem with the ignition barrel but have been told that it requires choke, a bit unusual for webers.
The carbs are 40dcoe31 with 32mm chokes, 115 main jets, 200 air corrector jets and 50.F8 slow running jets.
Any advice would be much appreciated.
Chris
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PostPost by: elans3 » Thu Feb 11, 2010 7:59 pm

Chris, the jets you have are more than good enough to get the car started and it should run and idle reasonably well., but by the fact that you have L2 camshafts fitted, you really need to have a session on a rolling road to optimise choke and jet settings. My advice is to get some miles on the engine, (around 1000), and then take it to a reputable rolling road for final set up. You should not need to use the choke. on a cold day, 4 pumps on the throttle should start it ok. I've been around T/C's for 30+ years now and never even had a choke cable connected,
Hope that helps,
Steve
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PostPost by: Bill » Fri Feb 12, 2010 5:21 am

Chris.

I have my 1964 shop manual in front of me.

At that time Lotus offered a "stage 2" upgrade from 105 h.p. to 115 h.p. This comprised of a change of camshafts "L2?" and jet changes for the webbers.

I will assume that your '66 cams are the same as the '64 stage 2 cams are (sprint grind now ?)

Anyway I changed them out 45 years ago for my street and competition use -still unfailling! Except for my deminishing reaction time.

Here are the stage 2 upgrade carb specs from the Elan manual which likely apply to youl:

choke 32 mm.
Main jet 120mm.
Air corrector jet 180 mm.
Pump jet 40 mm.
Idling jet 45F9
Emulsion tube F11

If you are close to that you are good to go!!

NOW if anybody out there can give me a benchmark starting point for jetting DCOE40's for use on the 2.2 liter TR4 engine (in my street rodded Tr3)
I would reallyappreciate it.

Please watch the Olypics, when you see the mountainscapes outside of Vancouver - remember- the roads in there are Lotus Land roads.

Keep your stick on the ice boys!!

Bill 26/0538
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PostPost by: Bill » Fri Feb 12, 2010 5:33 am

Chris

PS

The Main jets @ 115mm and the air corretors @ 200mm are the origional jet sizes for the stage one tune Elan S1 / S2 105 hp version - so says my manual (and my spare carbs).

I suspect '66 twinks are not far off that benchmark


I would pursue it!


Wild Bill
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PostPost by: chrishewett » Fri Feb 12, 2010 9:11 am

Thanks for that useful information.
I managed to start the engine yesterday after cleaning the points and a liberal spray of brake cleaner! It ran poorly. When I looked in the float chambers I was surprised it ran at all. Fuel is obviously old and dirty. I am now heading to the garage to drain the tank and remove the carbs for a clean. The car has obviously not been started for some time.
Chris
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PostPost by: elj221c » Fri Feb 12, 2010 11:16 am

Bill,
I think that the SE cams are CPL2 (26-66). According to the Wilkins book also the same as C and D Sprint cams.
According to Miles, the L2 cams are 46-70.
I ran a 1700 with L2s, normal valves, on 34 chokes and 135 mains, purely because that was what I had from running BRM phase 3 cams in the previous 1600 motor. It worked well after a trip to the rollers.
Chris, it's definitely one for the rolling road to get the best from the cams but you might need to check their timing first. Miles says they should be timed at 102 degrees, not the 110 of the standard and Sprint cams.

Roy
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PostPost by: elans3 » Fri Feb 12, 2010 4:22 pm

NOW if anybody out there can give me a benchmark starting point for jetting DCOE40's for use on the 2.2 liter TR4 engine (in my street rodded Tr3)
I would reallyappreciate it. (Bill)



Bill, your TR4 motor.

Picked straight from my Weber book, as follows:-

Chokes 32mm
Mains 140
Air Corr 150
Idle 50F2
Pump 50
Em. Tube F15
Aux Vent 4.5

This presumes an otherwise standard motor, and should make a great starting point.

Original Conversion for the TR4 utilised 40DCOE 2's, but I guess any more modern DCOE (with the exception of 34 & 35's) will work ok.
Hope that helps
Steve
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PostPost by: Bill » Sat Feb 13, 2010 8:25 pm

Steve

Thanks for carb info; I will start this car up on its stock SU's and when I am satisfied that all else mechanical is well I will then install the webbers and tune. (A year or two mehaps!)

can you recommend a supplier of rebuild kits and bits on this side of the pond that I can go to when the time comes?

Chris

Hope this all helped!

To All

In your Olympic viewing, check out the British Columbia mountain panoramics - the mountains you see are laced with Lotus roads with min. traffic.

From Lotus Land.

Bill

Go Canada Go!!
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