Sidedraft Weber 40 dcoe help

[SRSANDS]

Any carb guys out here that can help me diagnose my problem. I have a Weber 40 dcoe on a cannon mani. The car starts up and idles great when warmed up....blows smoke though. After its warmed up and I take it out on the road it doesnt quite pull as hard as my old weber 32/36. When I get to the higher RPM range it just flattens out like im at a rev limiter. It doesnt surge or sputter its just flat. Its a stock L16 and the Weber has base line guts. Someone told me they think its getting too much fuel in th higher RPM and Ive read that a stock L16 should use a 50mm pump Jet??? but I just dont know.....suppose I could take it to Carb Unlimited but Id rather fix it myself and learn.

 

This is what it has:

 

Primary Venturi 30mm

Primary Aux Venturi 4.5

Primary Maint Jet 115mm

Primary Corrector Jet 200mm

Primary Emmulsion Tube F11

Idle Jet 45 F9

Needle Valve 1.75mm

Pump Jet 40mm

[Cuts metal like mad]

check your spark plugs... bet they're fouled.

[Jesse C.]

Too much fuel. The base setup for that is based on the L20B.

 

Time to re-jet!

[b210in]

have you checked the fuel pressure at the rpm? do you have a fuel pressure regulator?

[kiznook]

This is what it has:

 

Primary Venturi 30mm

Primary Aux Venturi 4.5

Primary Maint Jet 115mm

Primary Corrector Jet 200mm

Primary Emmulsion Tube F11

Idle Jet 45 F9

Needle Valve 1.75mm

Pump Jet 40mm

 

First of all the jet sizes are not in millimeters, they are arbitrary weber identification numbers (as far as I know)

 

check your spark plugs... bet they're fouled.

of course they're probably fouled if he's been tuning..this doesn't really tell us much right now, or solve the problem

 

Too much fuel. The base setup for that is based on the L20B.

 

Time to re-jet!

How do you figure. 115 main is very small, especially for a single.

 

have you checked the fuel pressure at the rpm? do you have a fuel pressure regulator?

Doesn't really matter as the stock mechanical fuel pump should be able to keep up just fine and not over-load it.

 

Sounds to me like the mains are too small and the air correctors might be big. Of course, I can't tell much right now as I have loaned out my book and have yet to get it back.

 

Or you might need some more timing advance. I would try bigger mains (a couple sizes) and see what it does.

[MAG58]

200mm main jet... That's over double the bore of the piston in each engine. IIRC they're not arbitrary (except the Emulsion tubes, and even those have basis on sizes and shapes, just how rich or lean they make it came out arbitrary). Though they are some weird number series to bring it into scale, something like 200 is a .200in hole which is about 1mm, though I don't think that's quite right. I'll have to look this up.

 

If you've got it, Go a size or two smaller on the AC jet. That should help the top end and not mess with the bottom end as much as running a larger main. You may also want to run a leaner E-tube. That should also balance the bottom end. I don't think you should need a larger pump jet though, unless it stumbles when you put your foot in it.

[SRSANDS]

Thanks guys I will have to pick up smaller and larger of each to try it out since theres two different opinions but its a good start. Ilso one more question two venturis two sets of every jet right? A set for each side....do I change them both to the same size when I rejet?

[MAG58]

Yes

Two venturies

Two E tubes

Two mains

Two AC's

Two Idles.

 

Each throat Individually controls two cylinders in your case and as such you want the same jets in both. (Not like the DGV's where you save the fun big one's for the 36mm throat ;) ) Otherwise it'll run really bad. You also may want to pick up a synchronizer since even though it's only one carb, the throats can be metered individually by the set screw between the flanges so you can change air flow to each. You should be able to rent one from your favorite auto parts store, though you may not need one if it's running smooth as it is. Also I'd wait to pick up E tubes as a last resort because changing Etubes can get expensive in a hurry. Just my .02

[SRSANDS]

Thanks I will mess with the Air and Main first and see how it goes

[Cuts metal like mad]

of course they're probably fouled if he's been tuning..this doesn't really tell us much right now, or solve the problem

 

Your pretty smart! :fu: Ok not really... "Of course, they're PROBABLY fouled..." yeah, NO. If he was running lean they wouldn't be fouled at ALL. It DOES tell something, it tells him hes running rich and needs go the other way, its a good baseline, lean it out till you can't, if you're still fouling plugs, different jets are in order.

 

Wow, wrong twice in one post, try again after you've rested. :lol:

 

Oh, as far as jets go. I am pretty sure the fuel jet sizing works similar to the 32/36, and in that carb a 160 main jet is 1.6mm, 180 is 1.8mm, 175 is 1.75mm, and so on...

Edited September 11, 2009 by zuum510

[Cuts metal like mad]

Heres some jets.

 

http://www.cbperformance.com/catalog.asp?ProductID=1157

[kiznook]

Your pretty smart! :fu: Ok not really... "Of course, they're PROBABLY fouled..." yeah, NO. If he was running lean they wouldn't be fouled at ALL. It DOES tell something, it tells him hes running rich and needs go the other way, its a good baseline, lean it out till you can't, if you're still fouling plugs, different jets are in order.

 

Wow, wrong twice in one post, try again after you've rested. :lol:

 

Oh, as far as jets go. I am pretty sure the fuel jet sizing works similar to the 32/36, and in that carb a 160 main jet is 1.6mm, 180 is 1.8mm, 175 is 1.75mm, and so on...

 

Unless his idle jets are rich, and/or it idles for a while before shutting down and pulling plugs. Let's not forget about the likely clutch-kill which will foul out the plugs, or the fact that the plugs probably weren't changed right before he tested it.

 

The only way your plan works, is if you start with NEW or at least very clean plugs, leave the carb alone, start it, perform a test pass (0-35 flat out) and shut it off and pull the plugs. How are we supposed to have any idea why the plugs are fouled, or when it happened? Do you know they were replaced when he installed the carb? What about the smoke? That couldn't POSSIBLY indicate burning oil, which could NEVER foul the plugs. No no, the plugs are fouled and that means you need smaller main jets, SWEET a miracle answer!!

 

Don't try to call me out for trying to help. Seems to me that I'm not the one that posted a worthless reply.

 

"I'm having trouble tuning my carburetor"

 

"I'll bet your plugs are fouled"

 

Let's try to help here instead of pounding our fucking chests.

[Cuts metal like mad]

EDIT; removed for the better of the forum...

Edited September 12, 2009 by zuum510

[freaky510]

try

200

140

f2

36 choke

 

thats the set up my chart tells me

 

and get new plugs so you can get a good reading off them

 

let it idle for like 5 10 min take for drive pull then plugs for a reading load reading and idle are to totaly diffrent readings

 

man i have learn more in the laST week than i ever new llol

Edited September 11, 2009 by freaky510

[alex843]

I was running a dcoe 40 on a cannon. What I can remember I was running was

135 main

F11

190 Air

32 choke

 

I was running okay, still needed some tunning this was on a stock l16 with a 210 head. I cant remember the other jet sizes off the top of my head.

[b210in]

Doesn't really matter as the stock mechanical fuel pump should be able to keep up just fine and not over-load it.

 

.

 

 

yes, but it's better to rule this out as possibility and it's cheap to check.

[Jesse C.]

First of all the jet sizes are not in millimeters, they are arbitrary weber identification numbers (as far as I know)

 

 

How do you figure. 115 main is very small, especially for a single.

 

 

I dunno, I have this bad habit of reading books!

 

[SRSANDS]

Just ordered new mains and airs! Gonna try a 135 main and 190 air, researched the internet and didnt find too much for my application (single 40dcoe) on a L16 stocker, so I compared engine size to other cars and took the info given and decided to try that combo. Carbs unlimited was a local shop I looked for my parts but the were 10 bucks more than weber direct. That place has good prices! If it works out Im gonna order the soft mounts next.....I will let you know how it runs :)

[SRSANDS]

Heres some jets.

 

http://www.cbperformance.com/catalog.asp?ProductID=1157

 

Dang it I didnt see this reply until now....they have even better prices! Oh well a couple bucks less :)

[SRSANDS]

try

200

140

f2

36 choke

 

thats the set up my chart tells me

 

and get new plugs so you can get a good reading off them

 

let it idle for like 5 10 min take for drive pull then plugs for a reading load reading and idle are to totaly diffrent readings

 

man i have learn more in the laST week than i ever new llol

 

Financially, since I have like three or so projects going at once on the dime Im gonna try to not get into changing the chokes and emulsion tubes yet......if I have to do that I think it will be cheapr to take it to the pros instead.....I can afford a trial and test for 20 bucks but 70 or so for trial and error prob not :)

 

If the sizes I ordered still arent workin I may change size direction smaller main larger air. All you guys have helped me alot already learning where and how to do it. The arguements are a bit confusing though :) Bigger smaller smaller biger.......huh...ha ha

[banzai510(hainz)]

going by that chart that was posted the carbs come stock with the sizes installed and you figure there will be 2 carbs per application

But since you have one carb, I would think you would go bigger on everything??????

 

to me sound like your running out of gas in the higher RPM range. Ok at idle. At idle thes motor dont need much gas at all.

 

maybe better to ask this question on OZDAT as they are more Weber guys.I have a chart at home on some motors what was installed as a base line but its still trial error and better with a O2 sensor.

 

 

Never was a fan of the singe weber sidedraft set up. By the time you spend tuning it could have bought twin sidedraft set up.

[ggzilla]

After its warmed up and I take it out on the road it doesnt quite pull as hard as my old weber 32/36. When I get to the higher RPM range it just flattens out like im at a rev limiter.

The most simple cause for this is when the linkage is not right, not opening the carb throttles all the way. Check the basics before spending money. If it ran good on stock L20B, it will run fairly well on a stock L16.

[SRSANDS]

The most simple cause for this is when the linkage is not right, not opening the carb throttles all the way. Check the basics before spending money. If it ran good on stock L20B, it will run fairly well on a stock L16.

 

Butterflys opn all th way when pinned already checked that out :)

[SRSANDS]

Just put the new jets and airs in......now it falls on its face when ever the gas is pressed...go figure. Screw it I will have to take it to a carb specialist. My original set up it was good but flattened out in higher rpms....now it wont make it their just blahhhhh woop blahhhhh cough cough gay I hate carbs!

Edited September 18, 2009 by SRSANDS

[RoadRace]

where's the timing at?