Weber Jetting

[atomman]

Hello

Been doing a bit of searching and came up with a few answers but not really anything suitable,

I need a basic set up for my 40 DCOE weber's to start with then I will take it to the rolling road to set it up properly,

I have some jets and emulsion tubes etc etc, just wondering what to start with really

Engine is a L26 with a janspeed manifold and elctronic ignition,

What is everyone running in there cars ?


Thanks

Gary

 

[Alphabettispaghetti]

If you look on the Classic Z forum there's a couple of great topics about it with final settings etc etc.

Should get you in the ballpark.

 

[atomman]

cheers Franky

I've read loads of threads on other forums now and got some idea's thanks,

I know there are a lot of factors to take into account when setting up carbs, exhuast, head porting etc etc , but it seems strange that no one on here knows what they are running in their cars ? perhaps there are only a few running tripples on here

 

[zbloke]

I know what's in my triples, but I run Mikuni PHH44's so not of much use to you?

 

[Albrecht]

I need a basic set up for my 40 DCOE weber's to start with then I will take it to the rolling road to set it up properly,

What series 40DCOEs are they though?

Jetting recommendations differ for the different types of 40DCOE....

 

[atomman]

What series 40DCOEs are they though?

Jetting recommendations differ for the different types of 40DCOE....

Thanks for the reply Albrecht

Im sure they are 151's but I will doulbe check the number's tonight and post them up

 

[Albrecht]

I'm afraid that if they are indeed 40DCOE-151s, then I won't be able to give you any useful basic setting data. Sorry.

They are - essentially - the 'wrong' type of 40DCOEs for your engine. You'll probably even need to change the pump rods to suit the L-series engine's characteristics.

Weber themselves recommended the 40DCOE-18 for the L24 & L26 in period. It's the actual body of the carb ( internal drillings, progression holes etc ) which is a big part of the fine tuning and 'driveability' that they give on any particular engine.

 

[atomman]

I'm afraid that if they are indeed 40DCOE-151s, then I won't be able to give you any useful basic setting data. Sorry.

They are - essentially - the 'wrong' type of 40DCOEs for your engine. You'll probably even need to change the pump rods to suit the L-series engine's characteristics.

Weber themselves recommended the 40DCOE-18 for the L24 & L26 in period. It's the actual body of the carb ( internal drillings, progression holes etc ) which is a big part of the fine tuning and 'driveability' that they give on any particular engine.

Ok thanks for the Info Albrecht,

Im hoping I have the number's wrong then, I could be thinking of the one's I had fitted to my Porsche they were the newer type with plastic float's,

 

[MikeB]

Here's what seems a decent article on Webers and Z engines and explains the differences between the 151 and the 18 models

Weber DCOE triples, L28s, and Datsun Zcars

 

[atomman]

Here's what seems a decent article on Webers and Z engines and explains the differences between the 151 and the 18 models

Weber DCOE triples, L28s, and Datsun Zcars

thanks Mike Ive had a good read of that, Found some other useful info on a alpha site to, shows data for each DCOE model with float level, accelerator pump stroke etc,

Also Checked the numbers on my DCOE's on the weekend and they are 4's not 151's as i had thought,

From what i can tell the float levels are the same as the 18's but the accelerator pump stroke is 4mm longer ,(14mm instread of 10mm), but i cant find any info on the progession holes to see if they have the same amount,

will have another look today if i get chance

 

[Albrecht]

Also Checked the numbers on my DCOE's on the weekend and they are 4's not 151's as i had thought

40DCOE-4 was made specifically for Alfa Romeo, and used on some of the 105-series Giulias. It was never offered as a 'Conversion' model by Weber, as it was adapted to the requirements of the Alfa engine in Sprint GT spec.

40DCOE-2, 40DCOE-31 or - ideally - 40DCOE-18 would have been more suitable.

You can adapt the 40DCOE-4s to your needs ( they DEFINITELY need the correct pump rods ) but they might not give the ultimate 'driveability' that you are no doubt aiming for.

 

[atomman]

Thanks the info Albrecht,

Am I right in thinking they are all the same casting and Weber just changed the pump rod lenght and number/position of progression holes for each application ?

So I could change the pump rod but maybe not have the right progression hole set up on the 4's ?

May be it would be better to stick the #4's on ebay and start with the right ones in the long run,

Gary

 

[Albrecht]

Although they will look like they are the same castings ( outwardly ) there were often subtle differences inside them. When Weber made carbs for specific OEM applications they often played around with internal circuitry, and that's why the 'Conversion' models are a better choice as a starting point. They are more of a known quantity.

But now you've got them ( and hopefully all three are roughly the same vintage? ) you might as well try to use them. You can change the pump rods ( might need to change the discharge valves at the bottom of the fuel bowls too ) and block up the progression holes to start from zero, as it were. No idea what other differences the 4s had that were specific to the Sprint GT, but hopefully they won't give you an untuneable 'gasp' at particular revs / vacuum. You won't know until you try to set them up....

 

[atomman]

hopefully all three are roughly the same vintage?

I checked them last night and had a chat to my friend that gave them to me and he got them from another friend that rallyed alphas in the 80's, so they do seem to be all of the same vintage,

They all have 32mm chokes in them at the moment with some F9 emulsion tube and some F16's and various manis and airs,

I was thinking of leaving the 32mm chokes in and going with 120 mains, 170 air, F11 emulsion, 50F9 idle, 40 pump, 55 exhaust and changing to the correct pump rod legnth as a starting point,

Would it be a good idea to try this before I block up and redrill the progession holes ? so i can get an idea of how rich they run and any flat spots from the idle circuit to the main circuit,

I have drilled extra holes in before but never blocked them up and redrilled them,

Thanks

Gary

 

[Albrecht]

For the L24 engine, Weber themselves recommended the 40DCOE-18 with 30mm chokes ( small, for better response coming off idle ) with 4.5 aux venturis, 130 main jets, 175 air correctors, F2 emulsion tubes, 50F9 idle jets, 45 accel pump jets, 55 accel pump inlet valves and 1.75 need valves.

Going up to 32mm chokes will be no problem as the Weber data is very conservative and 40DCOEs should give you good inlet tract speed anyway. Even 32mm is very conservative.

Emulsion tubes are more influential than many people might suspect, and getting the 'right' ones for your individual engine can make all the difference in driveability. I'd try to go for F2s if you are buying 6 new ones, but if you can get hold of F11s cheaply then maybe try them ( I've used F11s in a set of 40DCOE-2s on an L24 with good results ).

By all means try the carbs as they are, and see what they are like with the current progression drillings. If you get any flat spots or gasps, you can epoxy them up and start again.

Good luck.