Datsun 240z engine issues

[Valentin]

Hello everyone,

I recently bought a 1972 Datsun 240z. The car have a L24 engine with emission control.

I am currently trying to make the engine run great before completely dismantling the car to work on the body but I'm experiencing some issues.

In fact the the engine start very well but when I try to accelerate the engine make a weird noise (like if it was backfiring in the admission) and sometimes smoke is coming from the carburetor axis.

The spark plugs are brand new, I've done the valves clearance ajustements, it was pretty tight.

I've set my static ignition timing to 5° BTDC.

I made a video so you can hear the noise :

 

I would really appreciate your help to fix this problem.

Sorry for my bad English

Thank you in advance

Valentin

 

[Mark Maras]

 Welcome. I'd look into the SU's. Pull the plugs and check the color. Verify that plugs 1 - 3 are the same color as 4 - 6. It sounds like the engine is running too lean. Check the float height on both carbs, oil level and check the balance. 

[jonbill]

If the colour of the plugs is OK, and it really is backfiring through the inlet, I'd suspect the ignition timing.

[zspert]

I agree with Mark, sounds like one carb is lean. Also, sounds like you may also have a leaking exhaust manifold or manifold to cylinder head leak. 

[Valentin]

Thank you very much for your fast replies.

I will check and come back to you as soon as I can.

[240260280]

Heads-up @Lazeum   A new 240z owner in your patch ?

bonne année!!!

[7tooZ]

I agree with Mark, sounds like one carb is lean. Also, sounds like you may also have a leaking exhaust manifold or manifold to cylinder head leak. 

P


72 body and block, everything else 71, Tokico springs, Illumina, R180 CLSD, 83 close ratio, 3.90 gears, Ztherapy SUs, BRE 15X7 Libre wheels and BRE front spoiler.