Optimum carb jet choice

[720inOlyWa]

With a freshly re-built engine and brand new plugs, should‘t I be able to get a pretty good idea of my rich / lean mixture by reading the plugs? I suspect that I am running too rich and I will be watching this as I break in my engine. If it carbons up early in the game, isn‘t that a good indicator to reduce the jet size?

 

Do I reduce jet size until the plugs read right (tannish). Is that the best wy to get in the ball park of rich / lean?

 

 

 

[Draker]

What carb, what engine?

[datzenmike]

Rebuilding the engine does not change the air fuel mixture. If you have the original carb that's what you run. Its the same jets that were in it when the engine was first started in the Yokohama plant in Japan 32 years ago.

 

A new rebuild may burn a little oil before fully broken in and sealed tight.

[720inOlyWa]

Geese, Im sorry for the confusion. I did‘t supply enough information.

 

It is a Z24 with a Weber 32/36. When I took it apart there were these little leaves of carbon resting on the top of piston number 3 and 4 and the plugs were all sooted up. The carbon flakes blew my mind.  This was an engine that was running okay when I bought it and had never blown a head gasket, making it a decent rebuild choice. But it had 149k on the odometer and it was plenty tired. Now it is completely rebuilt. I sooted up the plugs myself in the process of learning to set the timing correctly. So I just put in another set of fresh plugs and intended to monitor them closely.

 

I figured it had been running rich for some time and/or showed its age, so I wasn‘t using the previous condition as a baseline, other than to note that it looked like it had been running pretty rich.

[Draker]

You cannot replace the venturis on a Weber 32/36, they are cast in place. This means you can't fit larger venturis for the 2.4 liter. But the 32/36 flows nearly as much air as the stocker Z24 carburetor, so no worries.

 

Here is what Weber recommends as a baseline for the Z24:

Main Venturi: 26/27

Aux Venturi: 3.5/3.5

Main Jet: 140/135

Em Tube: F50/F6

Air Corr Jet: 165/160

Idle Jet: 55/50

Pump Jet: 50

Needle Valve: 2.00

[Lockleaf]

I'm assuming those numbers are at sea level?

 

Edelbrock recommends 2% more lean on jetting etc for every 1000 ft of altitude. Am I safe to assume the same will apply to these settings? Seems like it, since air density didn't change between carb brands.

[Draker]

Not sure on that one but Olympia is like.. at sea level. 

 

For you, you might have to fiddle with it a bit. Or just lean it out with the adjustment? Not sure. 
 

[datzenmike]

If it was running rich before it will be rich now, lean before then lean now.

 

Causes of running rich....

 

Jetted wrong or adjusted wrong.... most likely, as the Weber isn't made for a specific engine and is used on many engines. Chances of it being jetted for a 2.4 liter engine is unlikely.

 

Fuel pressure too high over loads the float needle and carb floods. Webers are 2 1/2 to 3 PSI? someone know? the Z24 electric pump is 2.7 to 3.4 PSI.

 

Choke on, stuck on or not fully shutting off.

 

Air filter dirty..... never in my life seen a filter that dirty but could be oil soaked from blow by.

 

 

 

 

Very common for the plugs and pistons to become carboned up. Choke is on at every cold start and it takes more than a short trip to work to burn it all of, so it accumulates. If checking plugs go for a good long cruise on the highway and carefully pull over and shut the engine off. 

[720inOlyWa]

Oh man, this is exactly what I needed to know!

Now I will assimilate and put it into practice. I am positive, judging from meeting the PO, that this carb was simply purchased and stuck on, period. Air filter is fairly cleanish. Choke is working smoothy and has been adjusted. I drove this set of plugs around town today, but not out on the highway. I will try that tomorrow. When I pulled two exhaust plugs this afternoon, they were actually a tich leanish looking (light, light tan).

 

So I will do the highway test, check it out, and then pour over- and then apply- the info above. I bought a jetting kit some time ago so I probably already have what I need.

 

Thanks!.

[datzenmike]

Light tan is perfect. WHITE like porcelain white is lean. The plug gets so hot it burns off everything and only the white shows.

[720inOlyWa]

I ran 30 miles out of town and back. Will check the plugs tomorrow morning.

[84720FourWheel]

About the only thing a Haynes manual is good for is the plug chart. Shows you, in color, what is what.

[datzenmike]

I ran 30 miles out of town and back. Will check the plugs tomorrow morning.

 

Just remember that driving around may soot them up again.

 

Weber tuning and trouble shooting guide.... http://www.webercarbsdirect.com/v/vspfiles/images/Weber%20Trouble%20Shooting%20Guide.pdf

 

 

 

Try the 32/36 section.... http://community.ratsun.net/topic/6117-weber-tuning-guide/

[720inOlyWa]

Well I drove a half an hour out and back on the freeway last night, parked it, then checked the plugs this morning. Hard to complain about how they look- nice and light tan. Number three looks like it is running a tich fatter, but it is hardly worth noting, the difference is so small. As a matter of learning, I am going to pour over those Weber guides again to see if there is anything I should do further, or bethinking about.

 

In the mean time, it‘s time to begin my second Z24 tear down, getting it ready for the machine shop to do its magic. Hopefully, I will have the 4x4 all done by this time next year...

[banzai510(hainz)]

I think your over reacting to nothing.

 

I just got a new 32/36 o a L16 and its fine. maybe little rich but fine.

 

I have never changed a main jet in any weber carb in 28 years of ownership. all run fine. Except a 38/38 where it was obvious it was too rich as the intake manifold was even getting black and valves cacked with oily black soot.(run some water throw the carb will steam clean that off)

 

only thing I swapped on the is the idle jet.