Tuning problem HUGE

[Guest sball]

The motor is totally new (L26) with 85mm flat tops, 240Z Su's.

The car ran fine for the first 500kms, so I decided to reset valve clearances, timing, and put new float needles and gaskets in carbs.

Well now it's f$^&^^% ! I cannot get the thing to run smoothly at idle or get it to a drivable state, it spits, farts like a rocket taking off.

I've spent 2 days checking float levels, air leaks, balancing carbs, the list is endless and it just gets worse The spark is good the mixtures should be right I just don't know. The only thing that has me curious is that when I pulled of the plugs to check valve timing I found that they had heavy black soot on them and the new pistons also have it, so Icleaned the plugs ran it for 5 min while I tried fiddling with the carbs and checked the plugs again and they were coverd in soot again.

[Lockjaw]

What needles did you run?

 

You are way to rich by the sounds of things. Are you seeing black smoke coming out of the exhaust?

 

I am assuming you know what you are doing since you did all this work. You can modify things a little by dropping the needle from the piston. Also you should probably check your fuel pressure and make sure you don't have to much.

 

I would adjust the mixture on the underside of the car to make it as lean as possible and still run and let it warm up and then start adjusting the mixture. One carb at a time, and get adjusting the direction that gives you the fastest idle. It you run out of leaness adjustment, you will have to drop the needles down a few mm or get a stock set.

 

I have sm needles, and they run a little rich, and I thought they might be to fat, so I put some stock one's back in, and it may idle better, but it doesn't run better going down the road.

[Guest sball]

It is definately too rich, that goes without saying. I have a 7 psi electric pump on the rear and the standard mechanical pump, would that be too much ? Appart from that I don't think even if I get the mixture right I can tune it perfectly without getting rid of the carbon first, anyone got an idea of how to get rid of it without pulling off the head ? I'm convinced the carbon is burning on and causing multiple firing HEY V12 power

[Lockjaw]

Well you could take the plugs out and spray some brake clean or carb cleaner in each cylinder and then turn the engine over and blow it out the spark plug hole.

 

If you get it leaned out, the carbon should take car of itself.

 

I would drop your needles slightly from the piston, and you also need to get the fuel pressure set. 3.5 is the max psi you can run. You are probably overpowering your needle and seat, which is why you are having such difficulty getting the mixture set.

[Guest sball]

Thanks I took off the 7 PSI pump, and instantly the idle went to normal, but till backfiring under load, I had the 7psi pump with different carbs and suddenly realised tonight that 240Z's didn't have a primary pump, now I'm cofused about float level the car will run OK with the float level too low and run out of fuel at 5500 rpm but set to the manual specs (14.26mm from the inside face of the float cover) it will not run without major backfiring. These carbs have the two different length float jets and float pivot point I'm sure from what I've read the float level is 14.26mm from the inner face of the float cover ??????????? apart from that I'm lost.

[Guest sball]

Problem solved, the problem was dwell angle, it was set at 37 deg, and found it runs like a dream at 28 deg.