Dual Weber 40 jetting for 2.0 Opel Kadett (284H cam fitted)

[peinsa]

I'm runnig 2x 40 side-draft webers on my 2.0 Opel Kadett 8Valve. After fitting the 284H cam I could hear a major difference in how the webers sounds (loader), but not such a major increase in power and performance. My guess is that I dont get the cams full potential because of the jetting on the webers.
My jetting on the webers is as follows:
32 Venturi's (chokes)
128 mains
190 airs
F16 Emulsion tubes
55F8 idling jets.
I was thinking of changing the jets and chokes to:
34 Venturi's
135 mains
190 airs
Does this seems to be a more accurate figure for a 2.0 with a 284 cam. I dont want to push the Venturi's up to 36" as I think I will then loose on bottom end torque. By changing the chokes and jets as planned, can I expect a major performance increase, or should I rather go for 36 Venturi's with say..145 mains and 195 airjets. I'm a bit worried about the "bigger is not always better" fact.
Any suggestions will be appreciated.

[baz]

the best way to get the power right is to have the car set up on a rolling road/chassis dyno

this will get the carbs working right without guess work as all set ups differ

your car is a little new for us here as we are for pre 1975 opels sold in the USA

you may get a better answer @

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vauxhalls of that age being opels with a badge change

[peinsa]

Even though the car is not pre 1975, the side-draft issue stays the same. My question is not about the later model opel but standard 40 DCOE Weber side-drafts

[tekenaar]

Originally Posted by peinsa I'm runnig 2x 40 side-draft webers on my 2.0 Opel Kadett 8Valve. After fitting the 284H cam I could hear a major difference in how the webers sounds (loader), but not such a major increase in power and performance. My guess is that I dont get the cams full potential because of the jetting on the webers. My jetting on the webers is as follows: 32 Venturi's (chokes) 128 mains 190 airs F16 Emulsion tubes 55F8 idling jets. I was thinking of changing the jets and chokes to: 34 Venturi's 135 mains 190 airs Does this seems to be a more accurate figure for a 2.0 with a 284 cam. I dont want to push the Venturi's up to 36" as I think I will then loose on bottom end torque. By changing the chokes and jets as planned, can I expect a major performance increase, or should I rather go for 36 Venturi's with say..145 mains and 195 airjets. I'm a bit worried about the "bigger is not always better" fact. Any suggestions will be appreciated.

34 chokes
150 mains
190 airs
F16 E-tubes
40 pump jets
5.0 aux venturi
50F8 idles
1¼ turn out idle screw
7.5mm float shut-off
15mm float full drop

Disconnect vacuum advance, 10 deg BTDC initial, 35 deg total all in at ~3500RPM . . .

. . . ran this setup on similar cammed (292), 8-valve & port, slightly ported, larger valve (non-Opel) engine . . . never dyno-ed, but ran very strong 3000-6800RPM (7000 redline) . . .

. . . should be close with a bit of final further "road" tuning . . .

[peinsa]

Thx Tekenaar. Was that jetting at sea-level? If not, how will jetting change at sea-level compared to inland....larger mains vs airs, or smaller.

[baz]

Originally Posted by peinsa Even though the car is not pre 1975, the side-draft issue stays the same. My question is not about the later model opel but standard 40 DCOE Weber side-drafts

i appreciate that the issues are the same but all engines are different and all are at there best when set up on a rolling road/ chassis dyno (name dependent on where you come from )

i have ran a 1971 gt with a jag 6 cylinder engine in it and 3 48 dcoe weber side drafts

the jets in it when i got them were a set that the carb vendor had used in other jags and were supposed to be spot on for the engine
when i had it on his rolling road for set up they all needed changing as sooooooo many things were out

it felt good and strong when i drove it to be set up but was a whole world different and better when i drove it back

i dont have the read out now or the jetting's after a fire in my garage a few years ago but i do remember there was 43 bhp more from the first set up run to the last


the link is to a site that covers the newer opels and they would be able to give you a much better idea of jets to start with as they use the engine you have and some one there will have the same ( piper i think ) cam and carbs

altitude throws all out the window and unless some one knows the hight you are above sea level and has numbers to match from a set up at that hight every thing will be pure guess work

[peinsa]

I'm almost always advised to go back to Fuel Injection...told that I will get much more pwr and performance from FI. I'm almost sure I will get the same pwr from dual sidies as from FI, if not a little more if correctly jetted.
One of the guys here in my area have the same car, same cam, same branches, etc than me...with one difference, he run with FI and I dual side-drafts. He's giving me time to jet my sidies for best performance before we take each other on at a quatermile to see which is best....FI, or dual DCOE's.
For ages Webers are used in racing conversions, so I cant see hoe this guy can kick my behind if my carbs are jetted correctly?

[baz]

electronic injection will make its best power in every load and throttle position right through the rev range until the injectors run out of volume (they all have a max value in cc ) so can out run a side draft carb engine where all else is equal as posted in the other thread you have going injection has so much input to help it work perfect all the time