Jump to content
HybridZ

Problem with triple SK carbs...........


Hybrid240z

Recommended Posts

I am having a problem with my triple SK carbs. It idles a little under 1000rpms when I turn the car on but the idle goes up to 2000rpms when the car is warmed up. It stays around there and won't come down. Has anyone had this problem or does anyone know what is causing this. Any info or advise will help.

 

Thanks,

Marcos rockon.gif

Link to comment
Share on other sites

Sounds like too much air. Have you tuned carbs with a uni-syn? I don't know how the SK carbs are adjusted, but start by trying to close the throttle blades further to restrict air, then (this is my plan when my Del'Lortos go on next month) buy the $29 air-fuel ratio gauge from Summit and a $20 02 sensor from your local auto parts store to tune the carbs.

Link to comment
Share on other sites

So you think they are getting too much air after the engine heats up? I am new to carbs, never had a carb motor, but I want to learn so I can tune them myself. I haven't tuned the carbs at all. I was hoping to get this kind of help so I can figure out how to tune them and what tools to buy. I will look into those tools on the Summit website to see if I can figure them out. What about that color-tune tool that I heard about. Would you suggest using that. hail.gif

 

Thanks,

Marcos

Link to comment
Share on other sites

Hey Marcos, I also have SK Racing Carburetors and can attempt to give you some info. First off I am by no means an expert on SK Carburetors, but I have managed to gather some knowledge of the SK’s. With that in mind here is what I know of the SK’s.

 

The SK carburetors are a hybrid between the Mikuni PHH and Weber DCOE, where the best of both designs was taken to create the SK's. Unfortunately, the SK carburetors are no longer imported into the USA. However, TWM Induction was one of the distributors and may still carry some parts for the SK carburetors. You might also be able to get a manual from them, if not I can try to scan mine and email it to you.

 

In order to troubleshoot any problems you will need to find out what size all of your jets are and what size SK carburetors you have, i.e. (40mm or 45mm). You should also invest in a Synchrometer Tool to balance the carburetors. Top End Performance sells a good one.

 

Since you are new to multiple sidedraft carburetors you really need to get several books on tuning and troubleshooting DCOE type sidedraft carburetors. I have listed below some books that will start you off in the right direction.

 

The following SK Carburetor parts are interchangeable with the Weber DCOE carburetors:

Main jets

Air correctors

Idle jets

Emulsion tubes

Pump exhaust valves

Pump rod, spring and piston

Auxiliary venturis (45 DCOE only)

 

The following are interchangeable with Mikuni PHH late model carburetors:

Pump jets (Mikuni calls these pump nozzles)

Floats

Needle Valves

Fuel Union Banjos (I think Mikuni calls these Fuel Pipe Assembly)

 

Some sources for parts:

TWM Induction

325D Rutherford Street

Goleta, CA 93117

(805) 967-9478

Ask for Gary

twmindsb@aol.com

www.twminduction.com

Carry some SK Racing Carburetor jets, gaskets and Manual

 

Rebello Racing

110 Second Ave.

South Unit D-8

Pacheco, CA 94553

(925) 682-0103

www.rebelloracing.com

Carry Mikuni Carburetor Jets

 

Top End Performance

7452 Varna Ave.

North Hollywood, CA 91605

(818) 764-1901

topend@racetep.com

www.racetep.com

Carry Weber Carburetors, jets and the Synchrometer Tool

 

Good books on Weber, SK's and Mikuni's:

Weber Carburetors

By Pat Braden

From HP Books

Try www.amazon.com or www.barnesandnoble.com.

Good information on theory, troubleshooting, tuning and rebuilding Weber Carburetors.

 

How to Modify Your Nissan/Datsun

by Frank Honsowetz

From HP Books

Try www.amazon.com or www.barnesandnoble.com.

Has a good chapter on Weber, Mikuni and SU's.

 

Weber Carburettors (The spelling is weird but that’s the title)

By John Passini

From MRP (Motor Racing Publications)

Try www.amazon.com or www.barnesandnoble.com.

Has a lot of design theory and functionality of various Weber carburetors.

 

As for your specific problem, I think Mike has a good point in that your throttle plates are open too much. You should also check for float level, fuel pressure and any intake manifold leaks. If you go to www.zcar.com and do a search for the user id of ZR8ED you will find some very well written instructions on setting up and balancing Weber carburetors. These will also apply to the SK’s.

 

Hope this helps. Let me know if you have any questions and I’ll try to answer them or direct you to someone who can.

 

Ruben

'72 240Z

Link to comment
Share on other sites

They are getting too much air all of the time at idle I believe. It just acts differently when it is warm, BECAUSE it is warm. You need to see if you can get a tuning book on the SK. I have one for Webers and Del'Lortos but not on the SK. They are similar to Mikunis, correct?

Link to comment
Share on other sites

Thanks for all the info mike and ruben. I've been so busy leaving my old job and starting my new job today that I haven't been keeping up with alot of stuff lately. I hope to get back in the swing of things by this weekend. I will finally get a chance to work on my Z this weekend and I will be at the Motorsports Show this weekend. Looking forward to that. I will try and figure out the carbs soon. I will post up if I find the problem, but let me know if you have anymore ideas.

 

Thanks,

Marcos

Link to comment
Share on other sites

  • 5 weeks later...

One of the other things to consider is the carb syncronization. One carb can cause your idle to go up, so you need to make sure they are properly in sync.

 

The SK's use weber fuel circuit jets, at least according to motorsport, so I could get you in a jetting ballpark with some basic info. Esentially would need engine size, choke size in the carb, and the sizes of the main, idle, Air control, and pump jet.

 

Also double check for vaccuum leaks, and make sure all the bolts that attach the carbs to the manifold and the manifold to the head are tight.

 

Good luck, it is not to tough to handle trust me.

Link to comment
Share on other sites

Thanks for the info Lockjaw. I haven't had a chance to check it yet. I have been really busy trying to sell the ZX I have, with my new job, fixing other cars and going to graduations. I hope to get rid of the ZX within a week so I can start to work on my 240Z. I am not even sure what is causing the high idle now. Might also be an electrical problem. My tach is dead, needle doesn't move. I hope to get a chance to work on it soon.

 

Marcos

Link to comment
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.

×
×
  • Create New...