Hi guys,
My Name is Robin and i'm from The Netherlands
I drive a white '75 260z 2+2
I have completely rebuild the car except the engine. Because of futureplans.
For now the Original l26 engine is in and is het 53k Kilometers on it. In Miles i gues something between 25k and 30k.
It has a Janspeed 6-2-1 header and a full freeflow 2,5 inch stainless steel exhaust.
My distributor is from a '81 280zx and has the E12-8 module.
It has been set on the original L26 advised degrees.
The engine has had a complete tune up with new spark plugs etc.
The carburators are 3screw Hitachi SU's from a 240z with a N42 intake, velocity stacks en open air filters.
The carbs are synchronised and run well in low rpms.
I need to choke to start and let the choke on for a few miles and then it runs fine.
When the car is at worktemperature the engine will stutter as soon as i come aboven 3500- 4000 rpms and stops at 6000 rpm. At these high rpms you can feel the loss of power.
I have tuned the carbs a dozen time and try a few adjustments to find out why it is running bad at high rpm's.
What i've tried and discoverd:
-The carbs have been adjusted very lean. the screws are almost completely turned in. But the car drives good at low rpms.
-The mechanic fuel pump is still Original but gives good pressure at idle
-Idle is around 900-1000 rpm
-The vaccuum pipe on the left carb is blocked of.
-One vaccuum pipe on the intake is blocked of and the other one is connected with the distributor
-When tuning the carburators and lifting the needles up doesn't give difference on the left carburator. The engine has to raise and fall back to normal idle when the mixture is correct. leaner or richer doesn't make any differen when lifting the needle
-the right carb has more or less the same. But i can hear difference on it but it is not very clear.
I am thinking myself to replace the mechanial pump for a new one, same type although electric is better
I want to rebuild both carbs and give them a good clean.
I hope these discoveries could help you guys to think with me about what could be the problem.
Please scream everything you think. maybe it will help others with argueing
Thank you!