No response to idle mix DCOE 40s - what would you try next?

[man_mark_7]

37 minutes ago, m5bb said:

This is my M30 motor in my 3.0 CS. 

I built this in 2014. 

10.5:1 pistons.

Custom cam. 

Headers 

Larger valves. 

B35 head, the best one for this motor. 

Dual valve springs with titanium retainers. 

All custom balanced. 

Lightened flywheel 

45 DCOE Webers

123 ignition 

 

Stunning. Is the M30 basically an m10 block extended by 2 cylinders?

[man_mark_7]

45 minutes ago, m5bb said:

Like I said if you're going bigger get a drill set from Pierce or another. It's easy and it's done in a few minutes, no waiting a week for a delivery. 

If I was positive going bigger was what I needed, I'd be all over this idea. I like to have the ability to go back down and compare AFR and how the car runs.

 

In the grand scheme of things 2 days is not a big deal. I've got new front rotors, calipers, pads, and H&R springs waiting to go into the front end. I'll probably get started on this while waiting.

[Son of Marty]

I'm in the no drill camp, Weber after all says 150 main jet doesn't mean it has a 150 hole in it, it is tested and flows like a 150 jet, the actual hole maybe larger or smaller and the tapper leading to the jet or at jet exit maybe off, but it flows a set amount of fuel. 

[man_mark_7]

Found this info from Top End Performance very interesting:

https://www.racetep.com/manufacturer/carbs-and-injection/weber/electric-fuel-pumps.html

 

Notable points they claim:

• Some old books "incorrectly" state that Weber DCOEs only want ~2psi fuel pressure. TEP says they want 3-4psi
• DO NOT hook up the distributor vacuum advance to the intake Manifold. That does not work and is a common mistake we see. If you do that you will pull full advance at idle then as soon as you open the throttle it loose vacuum and the timing will retard quickly causing a big stumble or flat spot and very bad throttle response.

The second point makes a lot of sense. Right now I've got the 123 dizzy set to not use vac advance at all, but I guess I might as well pull the vacuum port I set up on the intake to clean things up a bit and just cap the 123.

[man_mark_7]

11 hours ago, m5bb said:

This is my M30 motor in my 3.0 CS. 

I built this in 2014. 

10.5:1 pistons.

Custom cam. 

Headers 

Larger valves. 

B35 head, the best one for this motor. 

Dual valve springs with titanium retainers. 

All custom balanced. 

Lightened flywheel 

45 DCOE Webers

123 ignition 

 

 

 

@m5bb Based on my link to the TEP article above, I have to ask. Are you running any vacuum advance with the 123 dizzy? If so, where are you tapping in to get vacuum?

[Golfcar]

7 minutes ago, man_mark_7 said:

 

@m5bb Based on my link to the TEP article above, I have to ask. Are you running any vacuum advance with the 123 dizzy? If so, where are you tapping in to get vacuum?

I am not running any vacuum advance as my motor is heavily modified. 

A friend in NOL with Webers has run vacuum with success. 

My manifolds have a hole in them near the head that can be used for vacuum advance for a vacuum brake booster. Which I don't have. 

I would have to build a manifold to connect all three manifolds together to have any chance of it working. I don't need it. 

[man_mark_7]

Update - While waiting for jets I went in and adjusted the valves. I also thought, hmmm the fact that I dropped the 123 dizzy in place with the vac port and wiring pointing out into the engine bay has always annoyed me so why don't I pull it and drop it back in 180 out. Got everything back together and was plagued with nasty popping through the carbs. After much hair pulling I realized that the dizzy rotates clockwise! Thankfully if you have the firing order backwards the 1 and the 4 cylinder still fire at the right time...  The sad thing is that I did this exact thing when I originally installed the 123. I think now maybe I've learned my lesson.

 

I also pulled both the carbs and found that one of the butterfly plates was cocked about 10deg. The throttle worked nearly perfectly, but I could see the tiniest hint of light around the butterfly and it very, very slightly dragged as the throttle fully closed. I re-oriented the butterfly and now it closes fully and seats with a very positive stop.

 

Anyway, I am now able to tune out all the popping and get the car around the block so the real tinkering with jets and AFR can begin! I did find that part of the butterfly linkage was hitting the throttle speed screw boss not allowing the idle RPM to drop below 1300 originally so many thanks to @Son of Marty for pointing out this potential issue!