Finally started engine but it runs way too high paced...Please help!

[Clomolina24]

Hello, I have a 260z with the original engine. When i bought the car it wasn't running and so after changing the fuel pump, ignition system, and carbs (from flat tops to su carbs) I FINALLY got it to start up!! Only problem is that it is running at a very high pace, and releasing a lot of smoke through the exhaust now I'm no car expert as this is my first car project so i have an idea on what may be wrong but am not sure, so I wanted to see if any one could identify the symptoms on the video below (in link) and provide a solution to help me solve the issue before I dive in and try to figure it out myself. That way I can move on quickly and go on to the other problems the car has so that I may get her on the road.

 

I want to go ahead and thank you for taking the time to read this, hopefully someone knows just how to fix my issue and any suggestions will be greatly appreciated!

 

(The reason for the smoke coming out of the engine is that the air pump is being eliminated and the hoses have not yet been plugged up...)

 

 

 

Edited September 3, 2015 by Clomolina24

[zKars]

oh boy....

Well you can start by turning the idle speed adjust screws out to reduce idle speed. Each carb has a screw that touches the linkage, (left side of front carb, right side of back carb), and there the high speed idle screw up on top by the throttle rod top ball that you might have inadvertantly used to set the idle. Back it off so it does not touch the

Crazy idle speeds can also be a large vacuum leak (carb to manifold or manifold to head, or some hole left open on the balance tube or intake...

The way it suddenly when "bang" then started to smoke makes me a bit nervous....

[Clomolina24]

oh boy....

Well you can start by turning the idle speed adjust screws out to reduce idle speed. Each carb has a screw that touches the linkage, (left side of front carb, right side of back carb), and there the high speed idle screw up on top by the throttle rod top ball that you might have inadvertantly used to set the idle. Back it off so it does not touch the

Crazy idle speeds can also be a large vacuum leak (carb to manifold or manifold to head, or some hole left open on the balance tube or intake...

The way it suddenly when "bang" then started to smoke makes me a bit nervous....

Yeah, thats what my theory was, I literally was just getting done installing the SU Carbs and tried starting it so I figured I was going to have to play with the carbs to get that to calm down but I hadn't thought about there being a vacuum leak...thats something I will make sure to address!, I can't seem to hear the bang, I know he revved it right before it started to smoke and thats why it let out that big cloud but I think what it needs is just a lot of fine tuning....either way I want to get all possible symptoms everyone on this site may know so that I can make sure to address everything, so thank you very much for your comment! I will make sure to test your suggestion out hopefully tonight!

[siteunseen]

Read through this too, http://www.classiczcars.com/topic/39221-quick-and-dirty-su-tuning/

 

Post #5 & 6 have some good diagrams showing where the adjustments are.  Good luck.

[Clomolina24]

Read through this too, http://www.classiczcars.com/topic/39221-quick-and-dirty-su-tuning/

 

Post #5 & 6 have some good diagrams showing where the adjustments are.  Good luck.

 

Thank you very much for that information!!!

[SteveJ]

The smoke is probably from the PCV. Did anybody notice the sparks that accompanied the smoke? The stock PCV hoses had flame arrestors.

 

Download the FSM from http://www.xenonZcar.com and read through the engine, engine fuel and emissions sections. The flat top carburetors are tuned differently from the older SUs.

[beermanpete]

To add to Steve's comment; you will need to use a combination of manuals to properly tube your car. The 72 manual will have the correct procedures and settings for setting up the carbs. The 74 manual will have the correct procedures and settings for everything else (assuming "everything else" is original).

[Stanley]

Is the hose from crankcase breather tube to pcv valve hooked up? Is pcv valve hooked up? If not, big vacuum leak, but that might not be the main problem. Looked to me like smoke was coming out of breather tube. Maybe try compression test?

[Kurbycar32]

When putting SU carbs on my early 260 i found that the throttle linkage between the main shaft that connects to the shaft between the carbs was too long and caused high revving for me.  Try disconnecting the linkage between the carbs and main shaft.  After i discovered this i took the worst looking linkage i had and then bent it to fit, everything works now.  For the long term im going to cut one of those guys in half, trim and thread both sides, then join it with a hex standoff.  That should give me an adjustable linkage