71 240z, new rebuild. will not idle.

[ciavola]

I have a 71 240 I am restoring. Engine was reringed, new bearings, etc. I bought the carbs from Ztherepy. The issue I am having is the car will only start and run with the choke on. At about 1300 rpm. if I try to bring the choke down even after the car warms up, it will die. I sent the carbs back to Ztherepy, Steve said he ran them and they were Ok. I am stuck at this point. any help would be greatly appreciated.

 

Thanks

Chris

[rejracer]

Did you check the basics?  Cam timing, Valve lash, Ignition timing, vacuum leaks.  Do you have the coolant pipes connected to the manifold?  What are your compression numbers?

Edited March 3, 2013 by rejracer

[ciavola]

I have tripple checked the cam timing, set and rechecked the valve lash, Timing is at 17 deg per book, checked for Vacuum leaks, still need to check compression.

[ciavola]

no on the manifold coolant, strange compression numbers?, 1=90, 2= 113, 3=120, 4=140, 5=100, 6=118.

[ciavola]

cam has a mild grind, if it matters.

[rejracer]

Sounds like a vacuum leak to me.  I would not be terribly concerned about the compression numbers until it's broken in, although they are lower than expected.  Cam grind should not matter assuming it's timed correctly. 

 

Plug wires installed correct?  153624 is firing order. 

What is your fuel pressure? 

Have you checked the float levels? 

What is your vacuum at 1300rpm?

What does happens to vacuum at lower RPM? 

What happens to vacuum when you pull the choke off? 

Edited March 4, 2013 by rejracer

[ciavola]

First thing i checked was pulling the choke off while running,When I turned the choke off, vacuume would go to zero. and engine would die. in messing with the carbs it runs without the choke now. also confirmed the firing order is correct. at 1300 rpm there is about 10 inches of vacuum.if I turn the Idle screw down  the vacuum will drop and the car will die. to check the fuel pressure, is that at crank or running? have not checked the float levels yet.

[rejracer]

If Ztherapy said the carbs are good, then I would trust that, so i'd hold off on checking the float levels.  Check fuel pressure running, as I recall it should be between 2.5 and 3.5 psi.  Confirm that number in your FSM. 

 

What you are describing with the choke indicates a vacuum leak.  What you are describing with the idle screws indicates a vacuum leak. 

 

If it were me, I'd look very close for a vacuum leak.  Use starting fluid to help track it down, cap things off like the brake booster, pcv and any other port.  Check around the head to manifold, balance bar, manifold to carb spacer, carb spacer to carb. 

 

I would also do a basic tune up. Adjust the valves, gap the plugs, re-check the timing/dwell, and plumb the manifold with coolant, these carbs run like garbage without heat. 

I've never worked on one of these cars and not been able to get it to run the best of it's ability without about 2 hrs when I follow what is written above.   

[Zinpieces]

It does sound like a vacuum leak. Try spraying some brake clean at the intake manifold to block and carb to manifold joints. Also spray any fittings and hose connections. A small leak will suck in the brake clean and the engine rpm's will rise. it's an old school way to do things , but it works! you're not running power brakes are you? a bad booster or check valve even a bad PCV valve will give you what you got.