Tcs engine tune issues

[jbcollier]

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?

[jbcollier]

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

[Sparkrite]

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.

[4129R]

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.

[jbcollier]

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.

[Sparkrite]

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.

[jbcollier]

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?

[4129R]

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.

[Sparkrite]

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.

[MRN I J]

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

[jbcollier]

You can spray WD-40 as well.  Anything flammable works: snuffed propane torch, gasoline in spray pump bottle, etc.

[Sparkrite]

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.

[jbcollier]

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.

[SilverBeast]

My UK Special with Dell'Ortos has vacuum to the distributor from the rear carburetter back throat(? Not sure of term)

[jbcollier]

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