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Dual Weber jetting ????


Tim240z

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I've been running a set of dual weber downdrafts on my 240 for several months now after pulling them from a 260 in a JY (20 bucks later :D ).

 

I know that these are not set up right, and haven't even checked to see what jets are currently in there,

 

but can anyone tell me what the correct (at least best fit) jets are for this setup?

I think they are a bit fat right now, but no point pulling everything apart 'til I know what to replace them with.

Thanks,

Tim

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Guest Anonymous

Need Weber jet info ??? Where is all the Weber experts? DAW in Seattle ? Tim I had to butt in here and solicit info for you since I can barely recognize a side draft weber from draft beer. Post a 'pack rat post' and get responses but get serious with weber issues and every one is out to lunch (LOL) Did you "imply" that you paid $20.00 to the JY for these jewels?

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TZ,

No implications made. I DID pay $20 at the local Ecology yard on a 50% off day. That's 10 each!!

And, to top things off, someone had already pulled them and hidden them behind some cinder blocks the day before (obviously to come back and get them on the discount day). Well....I just 'happened' to find them!!!!! So all the work was done for me!!

 

All's fair in love, war and JY hunting, right!

 

Tim

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Guest Anonymous

Where are the weber jet experts? I am shooting in the dark here. The down draft weber carbs that need re jetting are they: 32/34 DGV (?). My old pal Ocbaar has some jetting info on Webers. I could pick up the spec sheets and email them to you after I see him in a few days.I just wondered if they were jetted for L 20 B four cylinders?

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Guest Anonymous

Ocbaar is still looking for the Weber jet spec sheet specsheet. Apparently all the jets are number stamped.I found this page that is similar to info that has all the DGV air corrector jets,idle speed jets and main jets:

web page

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It ain't cheap, but I'd recommend going to the dyno and doing some runs with the A/F sniffer going. See what your mixture is like throughout the rev range at full throttle, then also try gunning it from different rpm to see how the A/F readings respond. If the downdrafts are anything like the sidedraft carbs, they'll have idle mixture screws to control (duh) idle mixture, an accelerator pump that pisses raw fuel into the intake when you open up the throttle, a main fuel jet that controls how much fuel is metered at midrange and up, and an air corrector that prevents the mixture from getting too rich at the top end. I'm new to these types of carbs as well, but my plan is to try to get by with adjusting idle mixture screws and the accelerator pump stroke (volume) without changing the jets associated with idle and accelerator pump. The only jets I plan on changing out are the main fuel and air jets. Main fuel jet controls mixture at midrange rpm and up, while the air corrector largely only affects higher rpm mixture. I'm currently kind of rich in the midrange, and lean up high (dangerous), so I'll first try progressively smaller air jets until the mixture is somewhat the same at the mid and high rpm ranges, then reduce the main fuel jet size to bring the mixture to ~12.5:1.

 

But I am definitely NOT an expert on these carbs, so take the above with a grain of salt.

 

Go here for info on the DGVs from a 510 website:

http://dimequarterly.tierranet.com/articles/tech_weber_tuning.html

 

Good luck!

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Dan,

Thanks for the response. I really am not after perfect tuning. After all, this is just my daily beater, which I spend as little as possible on so that I can focus on the LT1 conversion in the project car (only reason I put these on was because I got them for $20 bucks at the YD). I have tuned it as best as I can by ear (which is pretty close). I would like to see if the jets that are in there are at least close. I assumed that the jetting info would just be floating around as this is a fairly common carb swap....I guess I was very very mistaken.

The car just doesn't pull like I think it should and has a stumble off idle. So I'm thinking either idle jets are off or pump jets are off....just don't know and to trouble shoot from scratch would be a PITA.

 

I'll keep hunting.

 

Thanks guys....I'll keep my questions V8 related from now on! malebitchslap.gif

 

Tim

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Guest Anonymous

Been searching for this same info for a while as well. I was wondering if we could use the jet sizes they list in the 510 article as a estimate for determining jet sizes for an L28. If the 510 has a single carb feeding a 1.8 liter engine and our Z's have 2 carbs, each one one feeding 1.4 liters of the engine (assuming you have a 2.8 liter), then would dropping the main and secondary jets down a size or two (from what the recommend for a 510) get us pretty close to the best jetting sizes?

I know this thread is pretty old, but hopefully someone will see it in the active threads.

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Guest Anonymous

No one solved the dualWeber downdraft "jetting " problem posted By Tim 240 Z for his daily driver until recently when he bought a Turbo ZX to replace the Webers.Now that is a hard core renegade Hybrid solution to a mechanical problem.Now you put the 500 ci caddy in the ZX,drop the turbo L6 in the daily driver and put experimental quad turbos on the LS1/LT1xxx combo for the project Z.

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Guest Anonymous

Mudge -

Definitly let me know what those books say on jetting the DGV carb for our cars.

I read that the DGVs were orignially fitted for a 2.0 liter.

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