new owner '74 TCS misc ?

[Kendo]

I have a Mikuni carb conversion kit on order, hope it arrives soon.  Looking forward to swapping out my Strombergs.  Any tips you guys have would be appreciated.

LotusBob74, I'm very interested in that Mikuni conversion. Please give us all of the details. I know at least one other lister has done that, and several have been interested over the years.

[Lumbes]

Looking into replacing the original Lucas 25D distributor.  Feeling like more can be gained with a better ignition curve.  I've tuned the Mikunis to operate around the 12.5 afr throughout the rev range but power seems to drop off after the midrange.  Any suggestions?

[jbcollier]

Ignition 123+ tune allows you to adjust the advance curve with a phone or tablet through bluetooth.

[Lumbes]

Thank you JB.  I like the idea of a custom advance curve.  Going through the Miles Wilkins book I was curious on which distributor would be ideal for a Big Valve with a Stromberg head and Mikuni carburetors.  Domestic Strombergs run with a maxium advance of 33 degrees to overcome the deficiencies of the carburetor so was assuming less advance than that would be desired on my setup.  Current distributor max advance of 19 degrees at 5k rpms.  Can only see compromises being made with adjusting and should be replaced rather than tweaked.  Custom advance curve should be between a distributor 41189 Big Valve and 40953 Stromberg? (looking at page 169 in the book)  I'm still uncertain of which advance curve to mimic and adjust from but will continue to dig into it.     

[jbcollier]

Mikunis breath very well.  Strombergs? Not so much.  I would start with the 41189 curve.

[Lumbes]

That makes sense.  It should be similar to the weber big valve only difference is I have the C cam instead of the D cam and the Fed exhaust manifold.
https://123ignitionusa.com/kent-engine-naturally-aspirated-bluetooth-programmable-w-angled-cap/ - is this the right fit?

Not able to view the installation link on the site that pertains to that specific distributor but the wire diagram that is shown looks straightforward.
I've never done any distributor work but reading up on it I think it won't be a problem.  Been doing tappet clearances on my bike so finding tdc and compression stroke I'm familiar enough with.  The rest will be a new territory.
Will the original tachometer be "plug and play" or will I be needing to do a tach conversion to electric?  That would be sad as I like the original tach and have been surprised at the smoothness and response in relation to engine revs.  Sure it's not perfect and modern vehicles are smoother in comparison but it's not bad at all.  Can't say how accurate it is other than it idles around 800 rpms and ive reached 7k a few times. I try to shift no later than 6500rpms to keep it whole. 
I dream of an engine rebuild in the near future and want to find a great lotus twin cam shop to do the work.  Not sure how far out from local I will have to go or if I'll need to ship the engine.  That's a bridge to be crossed at a later date though.  Second summer of ownership is approaching and one year since I took over the entirety of the maintenance it has proven to be very reliable and was excellent on a little 200 mile road trip 2 weeks ago.

[Lumbes]

lower compression 9.5 rather than 10.3 is another difference.  That is why a custom ignition curve could be good or at least that is how I am looking at it.  Lastly if engine work is done then yeah I will need a new ignition curve. 

[Lumbes]

Took out the old distributor last night and in place installed the 123 ignition plus.  Programmable with my phone it all connects and I created a ignition curve then loaded it onto the dizzy...it wont run.  I know I'm making a beginner's mistake(s) just not sure what they are.
First I put the engine in static timing.  Found the compression stroke by putting the car in 5th gear and pushing it in my garage.  Felt and heard air on spark plug hole #1 (closest to the firewall) with a finger as a plug then watched for TDC mark in the small cutout on the crank case then backed off 10 degrees.  Popped off the dizzy's cap and the rotor arm was pointing to the number 1 spark plug lead.  Labeled distributor leads and looked up firing order and everything seemed to make sense.  Rotor on dizzy rotates counter clockwise starting at 1-3-4-2.  The new dizzy looked like the same layout so lubed the o-ring with a little oil and pushed it into place.  Next wired 2 of the 3 wires.  Blue to chassis ground and red to positive side of coil (Lucas Sport dlb105) then the instructions state to rotate the dizzy until the led under the rotor arm lights up through 1 of 4 holes.  Did that and locked it down.  Rotor arm was lined up with number 1 spark on the cap.  The cap needed to be wrestled into place after the leads were installed.  Tight fit and initially was thinking the cap's lead nipples might need shortened/sanded down but it squeezed in.  Hooked up the last wire from dizzy which was a black and went to the negative side of the coil.  Plugged in coil lead and spark plug leads so wiring and physical installation was complete just time to create and load a map.  I did that and the car does not start.  Heard it backfire twice but did not come close to starting or holding idle.

This is the map I loaded.  Thought it would be close enough to run so any insight or tips would be great.

[BDA]

I don't know anything about the 123 dizzy but here are some things you can check.

First, the TC static timing spec is 5° BTDC not 10 but that's not likely your problem.

Take all the plugs out and one at a time put a plug in the wire that you expect to be the next to fire given your firing order and with the ignition on, roll the car through the place in the engine rotation where the plug should fire. I think you know what I'm saying here even though I'm doing a poor job explaining. Your plugs should confirm that your plug wires are in the correct place in the cap so your firing order is correct or that you made a mistake. Of course you'll also be confirming that the plugs are actually firing. A side note here is that way back when I learned to statically time an engine I used a test light between the + terminal on the coil and ground. Using a spark plug give you more direct feedback so if you were using a test light and it's lighting when you time it, it might possibly be that the electronics in the dizzy are not firing your plug. (remember, I don't know anything about the 123 dizzy).

If your plugs are firing when you expect them to, you have gas, air, and your timing is at least close, you ought to get something going with the engine.

One thing you want to be aware off is if the 123 is protected from leaving your ignition on for an extended period of time so if you have to, you can keep your ignition on for a minimum amount of time.

[Lumbes]

Thank you BDA I am following your explanation and will be using your steps to confirm the installation.  Expecting a long night but if I can make a few confirmations that will be progress.

[jbcollier]

Pull the coil wire from the distributor cap.  Hold it a 1/2” from the valve cover.  Crank the engine.  Got spark?  Since you are back firing a bit, the answer is probably yes.

Then remove #1 plug and put the car in fourth gear.  Hold a finger on the open spark plug hole as you nudge the car forward.  Stop when it builds pressure.  Watch the timing marks and slowly continue nudging it until it is at TDC.  Remove the distributor cap.  Is the rotor pointing at the wire going to cylinder #1?

Nudge the car forward again and note the direction the rotor moves.  Now check that your wires are properly ordered in the cap (rotor rotation is noted incorrectly in the manual).

[Lumbes]

Success.  Engine is running well and holding idle.  I let it warm up for a bit a revved to 3k in neutral (big wind gusts tonight going to have to wait till tomorrow for a test drive) no popping or apparent missing.  I believe I made a couple mistakes successively during my first attempt.  The distributor body orientation was forcing the cap to sit unevenly.  Confirmed that when I pulled the cap and saw gouge marks from the rotor arm contact.  Nothing but superficial damage to the interior of the cap.  Had to pull the distributor multiple times and reinsert with the rotor arm in various positions to find the right orientation for given clearances.  Found a position that will let me advance and retard the body so many degrees before jamming up on the intake ports.  Once that was squared up I was able to check for the spark sequence all looked okay then tried the key.  Engine was much closer to wanting to start and idle. Rotated the dizzy's body a little bit and it started right up. 

[Lumbes]

It's past 4am so calling it an evening and will see what progress can be had tomorrow with finer tunings.  Really liking the bluetooth features.  Nice program with a couple bells attached to make for a great kit so far.  Thank you jb and BDA for imparting highly useful troubleshooting techniques.  My Lotus relationship could not survive without the members of this forum so I am highly grateful to every person who frequents and chimes in. 

[SilverBeast]

  😴

[TurboFource]

Awesome perseverance!