I worked on the heat shield/ cable bracket some more today.

Here is the current pattern

An earlier template on a piece of coil metal

I glued it to piece of 16ga I had laying around

A little cutting

We will have to clearance it around some of the header pipes. Since it's an equal length header, they intrude on the carb area more than some

We will use some stainless exhaust tube to deal with the clearanced areas. Once I finalize a design I will have sendcutsend fabricate it for me

Current test mule

Cable installed. There is some excessive flex but we will deal with that on the finished product

So Lily is too lean and Cody's car is too rich...

I have lower the fuel level 3 times. It is way lower than Steve at Ztherapy recommends. The nozzles are only threaded down 1 1/2 turns. Fuel pressure is 3 psi and the AFR is 10:1. Black sooty smoke out of the exhaust. Ignition is about 10d before TDC at idle speeds.

My only ideas at this point is the wrong jets and nozzles or bad float needle valves. Even though they seem to seal when bench testing them. Any other ideas??

On 2/15/2026 at 5:09 PM, Patcon said:

Current test mule

Cable installed. There is some excessive flex but we will deal with that on the finished product

Maybe it's just me, but I always enjoy seeing an owner make a part rather than buying a new one.

5 hours ago, Patcon said:

I have lower the fuel level 3 times. It is way lower than Steve at Ztherapy recommends. The nozzles are only threaded down 1 1/2 turns. Fuel pressure is 3 psi and the AFR is 10:1. Black sooty smoke out of the exhaust. Ignition is about 10d before TDC at idle speeds.

My only ideas at this point is the wrong jets and nozzles or bad float needle valves. Even though they seem to seal when bench testing them. Any other ideas??

You should be able to check the float needle valves by looking at the bowl level. Really easy if you have the drain plugs on the bowls. Not as easy, but possible without those drain plugs. That said, I suspect the problem is elsewhere.

So, a couple questions to start:

Are those carbs supposed to use a 0.100 nozzle, or a 0.090 nozzle?
And have you verified that you have appropriate needles installed?

Maybe if you ran the two cars into each other real hard, things would even out? 🤐

The nozzle must be a 0.090". A 0.092" drill bit won't fit but an 0.087" will

We don't have drain plugs

OK, so 0.090 nozzles. Do you know what needles are in there (and what needles are supposed to be in there)?

And even if they are appropriate needles and nozzles, it could still be a problem there. They might have worn from rubbing due to incorrect alignment. Or corrosion over the years eating away at the brass. Those kinds of issues would be most pronounced at idle since the gaps are (supposed to be) so small.

The needle appears to say M66

Well I have no idea if the M66 is the correct needle for your application, but I did a few minutes of web searching and came up with a couple hits:

https://ratsun.net/topic/57757-needle-modification-for-l20b-sus/
http://www.team.net/html/datsun-roadsters/2000-07/msg00225.html
https://ratsun.net/topic/52225-hitachi-side-draft-su-needles/

There was some mention that the M66 run rich at idle, but then go lean at higher throttle positions. So yours sound like they are following that pattern... At least the idle part.

So we replaced the needles and nozzles. That helped some, we can get it to idle around 11.2:1 on the AFR

We are really lean on acceleration. So we went 10w-30 in the dashpots, better, 10w-40 better still but still on the lean side of 14.7 on acceraltion.

Codys is going to get some 10w-50 and we'll try that and see if we can get on the rich side for acceleration

Also, are coils supposed to get this hot? This is after about 30 minutes consisting of three testing runs

Any thoughts on coil temp?

We put 50w in the carbs. It did not make it rich enough. Very little change. We may try a really heavy oil to verify that that is all the enrichment heavier oil is going to get us.

We also have a problem with "running on" when shutting down. May actually be running in reverse. What causes that?

I don't think the coil is too hot. They have to be able to withstand all of the rapid flux changes involved with generating a spark. That's a lot of energy flowing through it.