Z Powered Healey painted and back on the road...but stumbles.

[Healey Z]

I found this project car that was kept under tarps in a not so nice part of Oakland CA. It had a Datsun 280ZX drive train with a custom intake with down draft webers. The swap was done 25 years ago. There was very little rust which was repaired and painted a nice BRG. I swapped the tired Z motor with a fresh one and put on some stock SU's. I had the 5speed trans rebuilt. Starts great, idles fine. Has petronix disti module that I had installed on the old motor and ran fine. I replaced the plugs, cap, rotor, checked timing, swapped out the wires, so I really don't think it is ignition related.

The SU's are new to the motor (and me). A great guy that races Datsun and owns a number of them came to my house and adjusted and balanced the SU's. They have 20w oil in them. When it is cruizing, it stumbles. When I just put the pedal to the floor when it is low in the rpm range, it stumbles. When I accelerate smoothly, it does pretty good. Any recommended trouble shooting ideas?

Edited August 24, 2011 by Healey Z

[olzed]

Wow. Thats a nice looking car. Could be running lean.Try screwing the mixture screws OUT quarter turn and try it, then a bit more.

[madkaw]

Float levels? The levels are good enough to maintain cruise, but empty out to quick for acceleration. The car looks fantastic!!!!!!!!

[Montezuma]

That car is simply beautiful.

[Arne]

I can't see the carb inlets - do you have air horns or trumpets on them? SUs depend on smooth airflow for accurate metering. If there is inlet turbulence due to the lack of air horns, it can play all sorts of havoc with the mixture under some conditions.

[Healey Z]

Thank you for the replies. Yes there are air horns on the carbs. I had to replace one of the floats (which didn't float) and I cannot say that I saw the means to change the float level? It has an electric fuel pump and it provides plenty of gas, as evidenced by what came out of the vent tube when my float wasn't working. It is quite possible that it is running lean and I will focus my efforts on learning how to properly tune the SU's.

[tlorber]

Are you sure there are no air leaks between the intake manifolds and the head?

[Healey Z]

tlorber, I had the intake surfaced at a machine shop and torque it down to spec when I assembled it. Worth double checking though, thx.

[CW240Z]

Fuel delivery issue? I would check the floats like madkaw said. I had that issue as well, my car would idle in the driveway for a bit then when I look off down the road it would run out of gas and studder for fuel. Maybe double check the fuel system, I did and my 240z had a cracked outlet tube on the tank. Car looks great though!

[Reverend]

What a beautiful car.

[madkaw]

There is a ton of info on this sites and others for adjusting float levels, but basicaly the lid on the float bowl has to come off and you bend the tab that rides against the needle and seat(like most carbs). Note the level of gas when you take the lis off. The float level is pretty cruical on this carbs for proper running through out the power band.

[5150 will]

I second what everyone else says regarding fuel. I was having some similar issues recently and went back through the mix/balance procedure and now it runs great. Do you have a copy of the Z Therapy video? Not to go off topic, but who did your paint? It's gorgeous!!!