Jetting help for Side Draft Carbs

[Betta Carotene]

I was looking at some post from the past had an idea. Maybe we should make a thread with jet sizes and motor combo. Could be used as a quick reffrence of some sort, or even some starter jets used to begin fine tuning.

(example)
Motor Combo:
Jet Sizes:
Misc. stuff like how it ran before and after.

It's just a thought that might save some people time

[MICAH1]

I think this would be a great reference tool for the users of this site. The questions of what jets to install or use had been asked so many times. But don't forget to indicate the carb type too. Great suggestion Betta Carotene!!

[baz]

Originally Posted by Betta Carotene I was looking at some post from the past had an idea. Maybe we should make a thread with jet sizes and motor combo. Could be used as a quick reffrence of some sort, or even some starter jets used to begin fine tuning. (example) Motor Combo: Jet Sizes: Misc. stuff like how it ran before and after. It's just a thought that might save some people time

well i must agree it would be easyer for folks
when are you going to troll through all the archives to compile it

[RallyBob]

It's a good idea, and years ago I had my own database, but be warned it needs to be very precisely documented. At a minimum, you need the following info:

>engine size including overbore
>compression ratio
>head type and valve sizes
>if porting work has been done
>cam specs, especially lobe separation angle
>if cam has been advanced or retarded (very important!)
>ignition timing specs, including modified curves
>intake type, porting work done?
>carburetor type, (venturi size and air horn length if side drafts)
>manifold or header type, diameter, length
>exhaust pipe diameter, even muffler brand/type
>altitude the car is normally run at
>if your local fuel is oxygenated or not, and has methanol in it

If any one of these factors is different, it will alter the tuning outcome and can change the jetting. You can see why there is no 'easy' jetting guidelines to be followed.

Bob

[nobody]

The problem you would get into is all the variables like altitude, electronic ignition, cams, compression, motor new or tired. Then of course the driving style of the owner, weekend warrior or daily driver.

[MICAH1]

I would yield to the fact that most of you guys are much deeper in the Opel and Weber than I, but isn't there a base or ground zero we can advise from for the carb type with jets for the base engine. Tweaking can be done by the individual. The problem for us Opel owners is the Weber may not be set up with our modified engines (ported intake) and such in mind???

[baz]

Originally Posted by MICAH1 I would yield to the fact that most of you guys are much deeper in the Opel and Weber than I, but isn't there a base or ground zero we can advise from for the carb type with jets for the base engine. Tweaking can be done by the individual. The problem for us Opel owners is the Weber may not be set up with our modified engines (ported intake) and such in mind???

there is no base line because of so many things in the states not only the gas that seems to differ from state to state but things like altitude (bring them all over here we only drive between sea level and 1600 feet or so )
there is only 1 way to jet a car right (any car) it has to be done on a rolling road, so there is no base line, as bob says every time you change 1 bit in the system it changes settings through the rest of it and the cost of an hour or so on a rolling road that knows webers will do it the quickest and right for any hight or state of tuning
there are a boat load of threads about how folks have had success with this set up or that but they relate to the engine they are on
the hard part in the states is to find a tuning house that knows the weber and has a stock of jets and tubes for them

[Betta Carotene]

Does anyone want to start? Maybe we could kick it off with a stock hi/low comp weber jetting.

[Crusher]

OK....I guess I'll start
But I only have a Sidedraft DCOE..I think alot of people are having jetting questions on both types of carbs.

2L high compression, DCOE 40 sidedraft carb, Ported head, Perfomance Cam & exhaust.

Jets are as follows:
Mains 175
Air Correction 200
Emultion Tube F2
Idle Jets F9/55
Acc Pump 60
Choke Tube 33

This setup is finally getting real close to opimum and has good low end torque but seems to loose some torque on the high end around 5-6k rpm. Going to be changing the choke tubes to #34 due to the restriction of air flow the #33 has at higher rpm's....maybe even a #36, but that may cause my low end torque to go away...

Steve

[supertiga]

yes!lets list those jets
advance curves will affect mixture
from memory at moment--will correct as nessary.
weber aux venturi chart--can use up to 38mm

1.9(.030 over bore)
reg gas
9to1 comp
1.75 intake valve
1.5 exaust valve
very mild cam(will tick over at 400-500rpm)
ported head
lightweight flywheel.

headers/2inch exaust out the side infront of rear wheel(muffler2incx2inch turbo(bull dung)cost me 10-20hp over glass pack!


38mm venturi in 2x45mm DCOE(air filter area is to small for max flow)
emulsion tube f-16
main-?
aircorrector-?
slow run(idle but it ain't!)-?
pump jet-?
pump spring-?
pump stroke-?

lets check our mecanical advance curves at mabe
1000rpm
2500
3500-38deg(max)(mine)
4000
vacuum adv at various inches of mercury
(dont remember what vac numbers at moment)
vacuum adv is tremendous milage gain---must dampen pulses so breakerplate dosent wearout.

throw out the carb linkage that came with canon/other dcoeX2s manifold--its hard to set wont hold settings and you will never make it run right!
the type that slaves one carb to the other is best(only one speed screw and a balance screw)it will blow your mind how smooth and perfect things will be!
once mine are set i never have to reset--years without touching the idle settings!and you can use the speed screw to check carb progression to!

will add missing info soon.
lets compleat this project--its a bitch to set one from up from scratch and can take years to even get
close expesily when they come from another ap.
even if our engine specks are diffrent it will help as somekind of starting place.

David

[ConreroGT]

2x45 DCOE

CHOKE: 34
MAIN JET: 145
IDLE JET: 55F8
EMULSION: F2
AIR CORR.: 200
PUMP JET: 45
2 1/2" Velocity Stacks


2.2l bored .040 over
Hot cam
Elec Ignition
75' Exhaust manifold
2" Exhaust w/ single flowmaster muffler
Elec fan
Undersized pulleys

Comments:

Still too rich below 2500 rpm. No mixture adjustment except RICH right now. Need to try different idle jets. May try 36mm choke also and 150 or 155 main jets at some point. Will also try shorter velocity stacks; 1 1/2" - 2"

[supertiga]

edit feature not working
conrero and crusher--are you runing single or twin dcoe?
yes!lets list those jets
advance curves will affect mixture

weber main venturi chart--for 1 barrel per cylinder--1.9can use up to 37mm at 6000rpm and 41mm at 7000rpm. 2.4 can use 46mm venturi at7000rpm
1.9(.030 over bore)
reg gas(87)
9to1 comp
1.75 intake valve
1.5 exaust valve
very mild cam(will tick over at 400-500rpm)
ported head
lightweight flywheel.

headers/2inch exaust out the side infront of rear wheel(muffler2incx2inch turbo(bull dung)cost me 10-20hp over glass pack!(it is quiter but not enough!)


38mm venturi in 2x45mm DCOE(air filter area is to small for max flow)
emulsion tube f-16
main-135
aircorrector-160
slow run 50f9(idle but it ain't!)-?
pump jet-40
pump spring-?
pump stroke-?in mm
v-stack-2.5inch
this works good for milage/drivability(runs like stock until more than 1/4 throttle)it does not give max hp.
after seeing other post i think the f-16 emulsion tubes(these carbs came from lotus formula2 engine) may be a problem as i have to be careful to not have flat spot as mains come in.i have 2 f-2s--anyone got 2 extra?
there is no ryme or reason to webers emulsion tube numbers-yet this and the venturis define how the carbs will act!
f-2 is listed for hot hot mini copers--f-7or f-8 for road
f-16 is listed for mgb 1800racing--f-9 mild engine
in 20years i have never seen sugestions for opel--until now!


lets check our mecanical advance curves at mabe
1000rpm
2500
3500-38deg(max)(mine)
4000
vacuum adv at various inches of mercury
(dont remember what vac numbers at moment)
vacuum adv is tremendous milage gain---must dampen pulses so breakerplate dosent wearout.

throw out the carb linkage that came with canon/other dcoeX2s manifold--its hard to set wont hold settings and you will never make it run right!
the type that slaves one carb to the other is best(only one speed screw and a balance screw)it will blow your mind how smooth and perfect things will be!
once mine are set i never have to reset--years without touching the idle settings!and you can use the speed screw to check carb progression to!

will add missing info soon.
lets compleat this project--its a bitch to set one from up from scratch and can take years to even get
close expesily when they come from another ap.
even if our engine specks are diffrent it will help as somekind of starting place.

David
Last edited by supertiga : 1 Day

[nobody]

Um well for twin OEs I think that if you could get your hands on a pair tuned by Irmsher and then imported would be a good benchmark. Slight changes for altitude and such from there but nothing major. Dean, wanna chime in with some #s?

[opeldean]

weber dcoe 40's dual side drafts
engine 1970 high compression-old
exhaust 2 in
pertronix ignition
sprint exhaust

irmscher shorties dual intake

mains 115
airs 190
f11 emulsion tubes
40 pump jets
30mm choke tubes
4.5 aux venturies
45 f9 idles

car runs dam good with this set up. easy start. no dieseling. no hesitation, no coughing or bog.jets have been tested for 7,000 miles. no problems, other than a filter that caught fire on a 24 degree day, due to a backfire on an old engine that was off on timing that day

dave and I believe this jetting was done in europe at the irmscher shop, but dave advised that i use a smaller choke from 34 to 30 and a change in the airs from 130 to 115 .


this same engine ran very good also on the prior jetting listed by betta carotene,very similar to what is quoted as' tekenaar jetting for the 32/36'

[Betta Carotene]

is there any way to measure jets? Cant think of any way to do it.

[baz]

size is stamped on jets normally , i would not use anything to stick in a jet hole to gauge it as any thing soft enough to not damage the jets would run the risk of snapping off in the jet

[Betta Carotene]

thanks Baz I went and looked at mine.

Jets: 135 Mains
155 Airs
F16 E tubes
45 IdleF8
70 pump jet
34 chokes

Motor: .080 1.9L flat tops (8.4:1 comp)
SSD 40dcoe, Steinmetz manifold
Sprint with 2" exhaust
Stock head with 290H cam (.435 lift, 230 @ .050 110 lobe sep)
Stock ignition
Usually drive around at 400ft above sea level

full throttle this can can pull very hard, but seems at half throttle to bog at around 3000-3500rpms (could be caused by the stock ignition). Any imput on different jets to run would be helpfull.

[supertiga]

this is for pinto 2.0
should be valid info for us?

http://members.aol.com/dvandrews/webers.htm

just noticed that the above link might be for single sidedraft.the weber venturi chart used is for one barrel feeding all cylinders.the chart for 1 barrel per cylinder is diffrent.

crusher--do you run single or twin dcoe?

also found this in weber info(this apears to be official weber settings?)
opel 2.4 rally
50mm dcoe
m-180
a-160
e-f7
i-65f8
p-45
pb-100
choke- 46mm
aux v-5.0
needle/seat-250
float level -12/?


Jetting for modified 2000/2100 Pinto on 45s
this is close to what i have in mine except for main and air

38mm chokes
145 main jets
F16 emulsions
180 air correctors
40 pump jets
50f9 idle jets
4.5 aux vents

with the jets currently in opel i have flat spot at around 3000 to 3500.(135m-160a)lean miss/stumble
am going to try 145m and 180 as this should richen mid and not top(due to larger air corrector)

[supertiga]

JUST NOTICED THAT WE HAVE seperate places for down and side drafts---should some of these post be moved to the side draft area?

from 20+years of tinkering with little info and all alone in lousiana!
this is written quick and dirty!
this is only what i think i know-
hope this info helps someone

LINKAGE
--best is slave one carb to the other--this is the only set up i have found that keeps syncro correct at all positions.this also leves you with one idle speed screw--important when checking progression.

SYNCRO
you must syncro with flow meter--your ears wont work!
also make shure that readings are real close from one barrel to the next on each individual carb-if verry far off check that butterflies are centered or for bent throttle shafts(i run across this often)

IDLE
change in idle jet slightly effects main ect and vice versa as thing(jets overlap in supplying fuel)also at full throttle mains have more say than idle even at low rpms

once jetting is drivable--fully warm engine-drive for 15-20 min
1- at idle set for best idle
2- speed up to 1500rpm check syncro-if out then linkage not right(see above)
3-at 1500rpm lean or richen idle screws-if things improve(runs better)make note of lean or rich.
4 -repeat 2and 3 at 2000rpm
5 -repeat 2 and 3 at 2500 rpm
6 -repeat 2 and 3 at 3000rpm
7 -repeat 2and 3 at 3500rpm(the mains may be well in by now)
this will let you know if idle jet is to small or big and if the air corrector part of idle jet is to big or small.
this gets the normal driving/gas millage real close(all above done with no load and might need one size richer if miss under load happens--so far i have found no nessary jet change here)

one way to tell when mains come in is to leave one main/etube/air out or not screwed in at least and drive car--belive me-you will know when mains start taking over!

i have also set idle screws at 2500rpm or so to cover slight lean spots in idle jeting and then slow idle with speed screw to 900rpm with good results-this also helped cold run.

it is best to never use the starting device(choke)as the valves are known to not seat agin--this will run you nuts!

MAIN CIRCUT
full throttle plug cuts(or o-2 senser or exaust gas temp) should be used for main and air settings at the respective rpm range.

main jets are mainly mid to upper range

air corrector is mainly for extreem upper range

e-tubes have say over when mains come in and some on mixture strengh.?

FLOATS
settings should work with e-tubes-higher setting makes mains come in earlier and make every thing richer and vice versa--so far have not found real diffrence in this.?

ACC PUMP
pump jets-after all else is getting good -1st gear at 1000rpm or so and floor it!
keep trying leaner pump jet until gasp/miss/stumble occours then go back up one size.
pump spring controles how fast or slow the discharge from pump jet is
pump shaft lenght controls how much fuel is stored for pump discharge.

how the acc pump works---cam on throttle shaft(between barrels)moves pump piston to loaded position.it will only be completly full at or close to idle.
when throttle is opened rapidly cam moves out of the way and the spring pushes fuel out through pump jet.stronger spring=faster discharge.longer pump shaft(stroke)=more fuel avalible.
i also think there are diffrent cams avalible but almost impossible to change

also have found plugs missing from carbs in past.these are the plugs that plug the passages after drilling.i make my own plugs(bbs)by melting solder(rosin)into a pan of water with a torch and then finding one the right size to peen into passage.


PLEASE-ANYONE THAT CAN ADD TO THIS DO IT!
Most info i have found is to vague or unclear as well as contradictory.
and some things(or all)of what i think i know might be wrong

i havent played with my jets(or idle settings) in 3 years or so and am going to do some playing soon to try to get rid of lean spot in midrange.either diffrent etubes or higher float setting.

this is the best site for opels ever!
where have yall been my whole (opel)life?

Thanks
David

JUST NOTICED THAT WE HAVE seperate places for down and side drafts---should some of these post be moved to the side draft area?

[kwilford]

Originally Posted by supertiga JUST NOTICED THAT WE HAVE seperate places for down and side drafts---should some of these post be moved to the side draft area?

Done. I made this the "Side Draft Jets" Thread. The Down Draft Thread is at
http://www.opelgt.com/forums/aftermarket-down-draft-carbs/7434-jetting-help-down-draft-carbs.html

[nobody]

A little bit ago I purchased a pair of OEs with irmshers off of a GT tuned by Irmsher themselves. I got them just to know the Jet sizing but found they weren't compatable with my OMs. Dean has the set on Celeste and has posted all the jet and choke sizes around here somewhere. Yes and a good sync tool for them is in the product review section. Seems Dean did a write up on install and rebuild too.

[supertiga]

today I tryed the 145 main jets(did not change air)and this did eliminate the flat spot around 3000rpm.i will drive this awhile and see how milage is and hopefuly get my o2 sensor back up and working before long.

when i had 4spd in car the flat spot was only sometimes noticed.
it ony became a problem after the 5 spd and only in 5th(OD)-not as bad on hot days
the 135 was as lean as i could go with the 4sp(trying for milage)this setting did hurt power

the 145 also boosted response and power in the 2000-4000rpm range

just for fun--the most power this engine has ever had was with 170m and ??air(these were soldered up and redrilled smaller as i had none on hand small enough)about what a size of 100 would be.this was with a 2inch glass pack.
going to turbo muffler knocked what felt like 15hp off and reduction in jets was required.

David

[supertiga]

built new airfilter/airbox set up with about 50% more filter area

jet changes--
f-16 to f-11 as f-16 didnt seem to alow enough fuel flow
currently main-160
air-220
idle-f9-40(was 50--f-11 must flow sooner needing less idle jet supply?)

it still seems that the top end is going lean and i am wondering if float level is to low?
current level is 6mm
i find settings listed for dcoes from a low of 8.5mm to a high of 5mm--none of it was for opel.the only info on opel float setting was for the drop--12mm.
found bmw ti/sa with 45s listed at7.5 with 38 chokes but 5aux vent(all i have is 4.5)and f9 e-tubes.
any ideas or settings would help.

BTW--the f-11 e-tubes seem to do a better job(smother more consistence)
than the f-16 and no flat spots now under any conditons/jets.

Thanks
David

[CDN OpelNut]

I picked up a used DCOE45 on E-Bay to replace the Solex 40DDH on my car.

The Solex is running OK but I can't get the idle down to a reasonable level and the jets are like hen's teeth.

I am hoping to get some help on initial jetting that I can use as a baseline. The basics of the engine are 2.4l, combo cam, header, compufire and short Irmsher SSD manifold. 2.25" exhaust.

Correct choke size would be helpful as well.

Thanks,

[myopels]

Supertiga, I had a wild hair and adapted a set of 4 propane fork lift carbs to my 1900 manta on a sidedraft manifold. I got a unisyn synchronizer to set them up and took for ever. I would go down the row, and when I came back to ceck the first one, it had changed. I got smart and ordered a motorcycle synchro from JC Whitney-4 vac gages on a manifold(they also have a mercury model). All you do is adjust all gages to the same vac reading with the little valves and all vac lines on one source.Then you plug in your carb vac source and do your adjustments. You have a readout from each venturi and the synchro is done way faster and more accurately. My manta ran fantastic after I did that, and it was super easy and FAST! The gauges were pretty cheap, and I'll never use any other method.