Jump to content

Zaspen

Stumbling 240Z with Arizona Z car intake and Holly 390

Recommended Posts

I just picked up my first 240Z in 20 years and this one has a Arizona Z Car intake with the Holley 390 CFM 4 barrel carb.  The car has a noticeable stumble off idle and a lack of low end.  It seems to do OK at higher RPMs but it seems sluggish compared to what I remember my old Z to be.  I've read a lot on this site about the AZ/Holley combo and it seems that some love it and some hate it.  Are there any tuning tips for this set up?  I have no experience with the holley carb so I don't know where to start.  Previous owner said it has been performing that way since install.  I would like to put SUs back on but its financially not in the cards now.  Thanks for any help!

Share this post


Link to post
Share on other sites

Not really enough to go on.  Unknown engine, Holley 390, AZC manifold.  Is it the stock L24 engine?  Is the cam stock?  Cam timing,  ignition timing, etc. all can affect performance.  Get as much technical info together about your parts as you can, and check the settings against the specifications.  It might just need a thorough tune-up.

Here's a link to some service manuals.  Links are on the right - https://www.classiczcars.com/files/

Welcome.

 

Share this post


Link to post
Share on other sites

Stock L24 engine.  Per the service records / previous owner it had plugs/cap/wires and a valve adjust in the last 5K miles and it has an electronic ignition installed.  I still need to verify the timing and also compression.

Edited by Zaspen

Share this post


Link to post
Share on other sites

 IMO, the first thing to check is the accelerator pump in the Holley. With the engine off and the air filter removed look down into the carb. and operate the throttle linkage. There should be a visible squirt of fuel. I'd also verify the float level is correct. 

Share this post


Link to post
Share on other sites

The receipt says its the 8007 Holley that is recommended by Arizona Z Car.  The accelerator pump looks to be spraying fuel fine.  I did pull the plugs to take a look and found some odd stuff.  The cylinder 1 plug looks fine, 2 and 3 are extremely carbon covered and 4, 5 and 6 have moderate carbon.  Not sure what this is telling me quite yet.  

Share this post


Link to post
Share on other sites
12 hours ago, Zaspen said:

The receipt says its the 8007 Holley that is recommended by Arizona Z Car.  The accelerator pump looks to be spraying fuel fine.  I did pull the plugs to take a look and found some odd stuff.  The cylinder 1 plug looks fine, 2 and 3 are extremely carbon covered and 4, 5 and 6 have moderate carbon.  Not sure what this is telling me quite yet.  

 The fact that #1 looks good and others are carboned up makes me think the problem is electrical. Probably somewhere in the cap, rotor, plug wires, plug wire connections. New plugs, resistance check on the plug wires, double check the plug wire connections and a good quality cap and rotor should clear it up.

 Jalex in Panama had a problem similar to this. #4 plug was always a little darker than the rest. He had good NGK plug wires, at the time. He replaced the plugs, and bought a Bosch cap and rotor. His #4 gremlin disappeared with those changes.

  • Like 1

Share this post


Link to post
Share on other sites

I was thinking something similar so I plan to replace the cap/rotor, plugs and wires with good stuff.  In addition I found the air mixture screws on the carb were not set equally- one at a 0.5 turns and the other at 2.5 turns so it makes me think I need to make sure the carb is set up ok.  Thanks to everyone for all the help!

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

  • Recently Browsing   0 members

    No registered users viewing this page.

  • Who's Online   8 Members, 0 Anonymous, 78 Guests (See full list)

  • Search Engine Meta Tags:
    classic, z, datsun, 240z, 260z, 280z, zcar, zed, s30, classiczcars.com, 240z.org, fairlady, 240, 260, 280, nissan, 240 z, 260 z, 280 z, zx, turbo, classic z, 280z cars, cars 240z, car forums, datsun, nissan, cars datsun, car club, 280zx, car, nissan zcar, classic z car,performance,300zx, car years, car raced, texas 350z, 300z, 350z, nissan racing , clubs car, zcca, club datsun
×

Important Information

By using this site, you agree to our Terms of Use.