Lotus Europa Community
Lotus Europa Forums => Garage => Topic started by: Sparkrite on Friday,February 04, 2022, 03:07:09 AM
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I am trying to get my engine to run and am having some trouble. My first question is what is the ignition points gap. My manual only covers the Renault engine. Ive set the strobe light timing ok,Ive checked the brass float gaps on the webers and they are close to 8mm. The 2 issues I have are the engine cannot handle any load ie a slight hill, and after a very short time the revs wont go below 2,000.
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Sounds like a fuel / air issue. check for carb. air leak. According to the manual points gap is 14 to 16 thousands for a twin cam.
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Thanks sandyman. I put new o rings for the carb mountings, but the float bowls were only 1/3 full so I thought maybe the float settings or maybe the fuel pump diafram.
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Point gap is 0.015"
We need more information. It is not easy to diagnose running issues over-the-phone, so to speak.
What is the history of the car? Had it a long time? Bought it yesterday? Ran fine for years? Etc.
What is the state of tune of the engine? Stock? Hopped up? Don't know?
What EXACTLY have you done so far?
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Workshop manuals can be found here:
http://www.lotus-europa.com/manuals/index.htm
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the car was standing 30 years, Ive owned it a year,having done the brakes, fixed wiring, flushed the radiator,and lots of small issues Im trying to get it on the road. Its a big valve,5 speed,weber head,freeflow manifold engine. Ive put new engine and gearbox oil,checked valve gaps, cleaned and set distributor, cleaned carbs,fushed fuel tanks and put new hoses,cleaned fuel pump.
Ive run it total about 45mins
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Excellent you checked the valve clearances. Did you do a compression test? If so, what readings?
What is your ignition timing set to? What is it at idle? 2500 rpm and 4000 rpm?
Check your carbs specs against what is listed in the manual. Specs are here:
http://www.lotus-europa.com/manuals/tcwork/tech/index.htm#c
The carb mounts are meant to be flexible. Overtightening can cause issues. Here's the manual section on carb mounting:
http://www.lotus-europa.com/manuals/tcwork/l/index.htm#8
I notice yousay you have Webers. Are you sure? It should have Dellorto carbs. If it really has Webers, can you list:
carb size
model number DCOExx-xx
Choke size
Emulsion tubes
main jets
idle jets
pump nozzles
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The compression results were quite even and over 160psi. The timing was zero at idle and about 22 at 2,000 rpm. These aren't super accurate as it was difficult to do single handed plus there was some scatter. The webers are 40 dcoe type 18. I did not note down any of the jet sizes etc.
I took a resistance reading of the coil ar 2.9 and 7.84 but my meter could not do the condenser.
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Sounds like 3 ohms on the primary and 7.8 kilo ohms on the secondary. That's fine.
Zero at idle is low and may lead to running issues. However, it's the full advance setting that is critical. You'll have to fire it up and measure it. It may not have resistor ignition wires or resistor spark plugs and that can put out a fair amount of RFI giving modern timing lights a hard time. Ideally you want 4° to 6° BTDC static/idle timing and 28° to 30° BTDC all in.
After we know the ignition is OK, we can tackle the carbs and fuel supply.
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Thank you for all your helpfull advice and links which I will use. I will update my progress when I can.
I need to get it sorted as Ive booked to take it on the classic le mans this summer.
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You could also check the resistance of the leads, old resistor leads can often have very high resistance leading to a poor spark
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Just a quick update, had the previous damage to the lower distributor body machined off,then a new ring heated then pressed on for a permanent solid fix. I went over the distributor and set it up to my best, reset the timing and took it out for a very quick spin. Its better than before but not great, remember these are the first drives for 30 years of standing still. The main issue now is the idle will not go down below about 2,000 rpm. Its not the cable as no change when disconnected. The idle screws are fully out.
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Still would like to hear what the actual timing figures are, especially total advance.
Now to the carbs.
There are 3 screws that control idle speed (air into engine). One on each carb that provides an stop for the arm on the throttle shaft, and one on the linkage between the two carbs. If this last one is not correctly set, one carb will not be able to close it's throttle plates and you would get a (crappy) high idle.
Can you post photos of the throttle linkage setup on your carbs? It has Webers so it's not stock. Photos will help us give you better advice.
Also, what kind of insulators are between the carbs and cylinder head? Photos of those and the carb to manifold would be great.
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The timing was about 20 degrees at 2000 rpm and about 30 degrees at 3000 rpm. It has 8 new o rings either side of the spacers and I did not overtighten the Thackeray washers.
I looked at the plugs and the rear two were black and wet ,the front two were not wet and would have got a better colour after a good run. So after trying to adjust the rear carb with no success I've pulled both carbs out for a better inspection. Ive never done a set of webers but cant imagine its hard, I just need to do a bit of reading up first.
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. The 2 issues I have are the engine cannot handle any load ie a slight hill, and after a very short time the revs wont go below 2,000.
Idle hanging sounds like carb. Will it idle before it's warm then hang at 2000? I don't know these carbs but Weber DGV carbs have a secondary that if plugged or partially plugged a car will run good until it's opened under load.
Did the car ever run with these carbs?
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Nothing particularly special about Webers. What is the part number on them? XXDCOE-XX? What size of: choke/aux venturii/main jet/air corrector/emulsion tube/idle jet/accel pump nozzle?
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When tightening up the carbs, the spacing of the thackeray washer needs to be as in the manual but the gaps between the carb/isolator/head need to be even top to bottom as well. I don't like the insulators with multiple o-rings. I prefer these better:
http://www.rdent.com/pages/carbmount.html
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I have stripped the carbs and insides look all good with the following.
Weber 40 dcoe type 18, number 9m
Emulsion tube f16,main jet 135
Idle jet 45f9
Starter jet 100 f5
Choke tube 35
Pump jet 40
Inlet valve with exhaust 40
Float needle valve 175.
Clifton,the engine idles when cold,then as it warms up wont go below 2000rpm but will go more.
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Take the carbs off, hold them up to the light, and see if you can see daylight around the brass butterflies.
If there is daylight, carefully loosen the screws holding them to the shaft, ease the butterflies to reposition to close off daylight, then tighten the screws carefully.
Been there, done that.
135 is big for the main jet. I would expect 125. What sort of power is the engine tuned to produce?
What is the diameter of the main venturi tube? I would expect 32/33. Is that what you say is choke 35? Huge.
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The Lotus TC engine had 40DCOEs in various states with of tune. I’m away from my books until Monday. As Mr 4129R mentions, first impressions that things seem to be on the large size. This might indicate your engine has been hotted up quite a bit.
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There is no daylight around the brass butterflies on both carbs and I cant detect any play either. There were some spare jets with the car. 4 main jets at 130 and about 12 idle jets f3,f8 & f9, as well as the old float needle valves and a carb air balancer device. So someone has given the attention before.
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If all the throttle plates close tight then look at the syncing mech. It may not be allowing one carb to fully close.
Are the brake boosters still hooked up?
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It has to be an air leak on the inlet manifold side somewhere.
Either the air is getting in through the carbs, or the inlet manifold itself.
You will just have to go methodically through all the potential areas where air can get in, one by one, and it only has to be a small leak.
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Jcb brake,the boosters were removed by PO. 4129r I haven't investigated the air leak as the mounting O rings are new replacements .
Still regarding the jets, I found some sizes for an elan sprint which I believe is similar to my engine. Weber 40 dcoe 31, mine weber 40 dcoe 18, choke 33, mine 35, main jets 120, mine135, air corrector 155, mine160, idle jets 50 f8, mine 45 f9, acccellerator pump jet 35, mine 40. The only mod I am aware of is the exhaust manifold which has been changed from cast iron to tubular steel free flow. So to a novice like myself it seems the carb settings are for an engine with more requirements than mine but might they still be within reasonable parameters.
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if you spray some brake cleaner on all of the joints, etc and the engine note changes you will find your air leak if you have one
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You can spray WD-40 as well. Anything flammable works: snuffed propane torch, gasoline in spray pump bottle, etc.
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The latest update on my engine issues is after checking the carbs again and re installing them the engine ran much better and I could now get it to idle.
Top marks to Jbc who nailed it in post 12
"There are 3 screws that control idle speed (air into engine). One on each carb that provides an stop for the arm on the throttle shaft, and one on the linkage between the two carbs. If this last one is not correctly set, one carb will not be able to close it's throttle plates and you would get a (crappy) high idle"
It was that last screw which was not set right and I didn't know better.
I managed to go for a 5 mile drive and whilst much better, its still not fully there.
I think maybe because I have the lucas 25d vacume distributor and the weber carbs do not have a port for this vacume pipe. Without this how can It run the right advance curve.
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The distributor for the TC engine only came with a distributor vacuum unit on the federal spec, emissions engines. The vacuum unit gave vacuum retard, not advance. It is best left disconnected.
Now, all this assumes you have a distributor from a TC engine installed. It could be from something else and it sounds like it well might be. In that case, you have to check the distributor advance curve against what is listed in the service manual.
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My UK Special with Dell'Ortos has vacuum to the distributor from the rear carburetter back throat(? Not sure of term)
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From the Service manual:
Distributor
Type 23 D.4
Direction of rotation (from above) Anti-clockwise
Drive Gear on jackshaft
Contact breaker gap .35/.40 mm. (.014/.016 in.)
Contact lever spring tension .51/.68 kg. (18/24 oz.)
Firing angles 0°, 90°, 180°, 270° ± l0
Cam dwell angle 0° * 3°
Dispatch no. - Dellorto carbs. 41189
- Zenith-Stromberg carbs. 41225 when suction retard capsule
fitted
Centrifugal advance (All distributors)
Crankshaft r.p.m. Crankshaft degrees B.T.D.C. (Add static setting)
Below 1,000 No advance
1,250 2.4
1,500 4.6
1,750 6.8
2,000 9.2
2,250 11.6
2,500 14.0 Maximum advance
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I believe my distributor is the original federal lucas, model 25d number 41225e. Whilst it may be ok to eliminate the vacume, the cam,weights and springs could do with changing to suit my webers. I found this which seems to detail what I should do.
https://lotuselan.net/forums/viewtopic.php?f=38&t=31358&start=
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There are a number of options out there.
The first is to figure out what you have. These cars are 50 years old. Good lord knows what has been changed/modified over the years. You need a way to measure your degrees of advance versus rpm. You can invest in a timing light that measures degrees of advance, or, you can mark your flywheel. It is easy to mark the flywheel using a simple set of steel dividers and a punch. Measure the existing distance between TDC and 10° using the dividers. Now you can mark off 10° increments, half way is 5°. Next use a piston stop to check that your TDC mark is accurate. Last, get an accurate tachometer (not the one in the dash). Now, use the tach and timing light to plot out your advance curve. Minor adjustments can be made by tweaking spring tensions, filing slots and stops.
Way off? You can:
- send it to distributor specialist to set up properly
- replace it with a new distributor (still need to check it's advance curve)
- replace it with a programmable distributor (this is the route I went)