Weber 45 DCOE jet settings 3.1 stroker stage 3 cam

SKiddell

Well-Known Forum User
The velocity stacks (altering the inlet tract length) will have a significant bearing on the distribution of the torque (and consequently bhp), long ones will tend to move the torque down, shorter stacks move the torque up the rpm range and give the better headline BHP figure (if all else is matched correctly) it all depends on what you want from the engine, bottom end torque or top end power.....its a science on its own.

I’m using a set of adjustable ones at the moment so I can vary between the two, oddly when we did some testing (on the rolling road) the length of the stack didnt have a huge bearing on fuelling.

Once again you need to consider the inlet/exhaust/fuelling/cam/ignition as a balanced entity as all parts contribute to the whole.

I think I have a couple of sets of different stack lengths that you are more than welcome to borrow once you have got the fuelling right, but its really all down to time on a rolling road which isn’t cheap
 
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morbias

Well-Known Forum User
Also noticed fuel pressure was around 2.5 too low. Adjusted to 3.0 to see what effects that will have.

3 psi sounds a little high, iirc the pressure should be between 1.5 psi and 2.5 psi depending on revs. I know that when I set my fuel pressure to 3 psi it easily overpowered the float valves at idle and there was petrol pouring out everywhere, but then again I have a near standard L26 and 40 DCOEs so your engine and carb setup might require higher settings. But still, it might be an idea to check if you have any leaking fuel at idle, especially if you have no fuel return setup yet!

I hope you post some videos up when it's all done, I imagine it sounds pretty freaking amazing :)

(sorry to hijack, but if anyone has 2 or 3 67.5mm slide-in stacks for 40 DCOEs that they don't need any more then I'd be interested in buying them, a few of mine have bent rims and I can't find replacements anywhere in this size)
 

Albrecht

Well-Known Forum User
(sorry to hijack, but if anyone has 2 or 3 67.5mm slide-in stacks for 40 DCOEs that they don't need any more then I'd be interested in buying them, a few of mine have bent rims and I can't find replacements anywhere in this size)

I've got two or three you'd be welcome to have, but to be honest they might not be that much better than you've already got...

I'll have to dig them out and see what they look like to you.
 

morbias

Well-Known Forum User
I've got two or three you'd be welcome to have, but to be honest they might not be that much better than you've already got...

I'll have to dig them out and see what they look like to you.

Well that would be most appreciated, thank you very much! :bow:
 

zedhed

Club Member
I think I have a couple of sets of different stack lengths that you are more than welcome to borrow once you have got the fuelling right, but its really all down to time on a rolling road which isn’t cheap

Hi Skiddel, I wouldn't mind taking up you on that offer, thanks very much. I'll wait until the engine is broken in and then take them with me to the rolling road if that's OK. I'm after shorter stacks than the current setup to get more low down torque which I think will be more fun and practical for sure.

At the moment I'm driving the car to and back from work to get things bedded down. I'm only on 250 miles now, and the engine is more or less running well enough to get some miles on it and drive reliably. I've had to make some changes to the timing as advised by the engine builder which helped make the car more drivable - and now the car is way better. I'll post some pics of the timing chain setup when I get a chance.

Then I'll be after an air-box or some kind of filters. At the moment I've got socks on the carbs which I'm sure isn't optimum but OK for break-in. Not much room in there though...
 

zedhed

Club Member
I've got two or three you'd be welcome to have, but to be honest they might not be that much better than you've already got...

I'll have to dig them out and see what they look like to you.

Thanks Albrecht, also much appreciated if you wouldn't mind pinging me some info or pics that would be cool. I guess they all fit DCOE range so I can try a few types before settling on some which work.

I tried asking Dellorto about the pump stroke length and if anything is swappable, but they were swamped today sales on the phone only and no techies available so I'll try them sometime this week.

Best, Nick
 

zedhed

Club Member
3 psi sounds a little high, iirc the pressure should be between 1.5 psi and 2.5 psi depending on revs. I know that when I set my fuel pressure to 3 psi it easily overpowered the float valves at idle and there was petrol pouring out everywhere, but then again I have a near standard L26 and 40 DCOEs so your engine and carb setup might require higher settings. But still, it might be an idea to check if you have any leaking fuel at idle, especially if you have no fuel return setup yet!

I hope you post some videos up when it's all done, I imagine it sounds pretty freaking amazing :)

I just took it for a drive and it's a lot better with the floats correctly positioned and the fuel levels at 25mm. Great tip that guys, probably the first thing any tuner should do (!). I was tempted to push it a bit today but I'm going to be patient - don't want to mess anything up so for now maximum 4K revs for short periods is the way to go :) Very different from my previous 2.8 with Jag SU's. Was thinking about trying them too, but they're sold - though still at the Z Farm, with a few other bits left there by mistake I'm hoping Duncan will send me the rest of the bits this week. It certainly sounds the business with that SS exhaust from Sean. You can sure hear pinking easier with SS exhaust too LOL.

I'll plumb the return back in, makes sense, (the carbs came with the dead-end banjo-bolt) but so far no more leaks I can see - does smell a bit though.

One thing I will do is replace the Sytec fuel pressure regulator with a Malpassi one. I tested that with my (accurate) guage I have here with a takeoff placed between the last two carbs. Wasn't impressed to say the least. Inaccurate and while it holds it's level you can't just set the dial and reliably get what you ask for.
 

Nigel Brook

Well-Known Forum User
Thanks Albrecht, also much appreciated if you wouldn't mind pinging me some info or pics that would be cool. I guess they all fit DCOE range so I can try a few types before settling on some which work.

I tried asking Dellorto about the pump stroke length and if anything is swappable, but they were swamped today sales on the phone only and no techies available so I'll try them sometime this week.

Best, Nick

I'm confused. Why are you trying to talk to Dellorto when you've got Webers?
 

zedhed

Club Member
Yep they're the main agents I'm lead to believe. Or at least I thought they'd know - unless you guys know anyone else who has better in depth knowledge?
 

zedhed

Club Member
according to them the accelerator fuel pump rod lengths are interchangeable so you can choose what you want.

Having read up on it, I believe the rod length determines the stroke, and therefore how much fuel is delivered. The spring determines the pressure and therefore speed of delivery, and the orifice diameter determines the amount delivered over time.

Apparently this is a part of the carb which is often left as-is and your average guy doesn't to fiddle with them - probably because the effects are hard to quantify...

I'm running

Main 145
Air 185 (was 155)
Emulsion F16
Idle Jet 55F8
Pump 45

Anyway, seeing the timing is now what I think it should be (or at least drastically improved) I have decided to richen the mixture on the idle jets by moving from 55F8 to 55F9 (hope I've got that the right way round!)

Then (assuming the timing is right!) I would like to try and make the main circuit slightly richer to see if that gets rid of that lack or power and responsiveness higher up the rev range. I think it might involve an F2 Emulsion Jet? I think that's the next step, but if anyone has suggestions to make the main circuit richer or that looks wrong, please comment?

cheers, Nick
 
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morbias

Well-Known Forum User
Don't know if this is any help:

Idle jet F code order:

rich to lean, number in front is the size of the air bleed hole in mm:

0.7__F6
0.9__F12
1.0__F9
1.2__F8-F11-F14
1.3__F13
1.4__F2-F4
1.6__F5
1.7__F7
2.0__F1
2.3__F3

I haven't played around with emulsion tubes yet (I have F16s fitted), but I did read somewhere that the air bleed holes on the F2s are too far up the tube to work efficiently in some cases, or even sit above the fuel level when the fuel in the float bowls is slightly lower than full. Can't remember where I saw that but it might be worth researching that first cos a full set of tubes isn't exactly cheap!
 

zedhed

Club Member
thanks that's good info.

Either way, I'm running lean so I'm lead to believe that either I change the F number, or I change the air jet - which is probably cheaper and easier I think.

So apparently there's this rough formula:
36mm venturi x 4 = air jet size 145
plus 50 = main jet 195

so actually on paper, my setup is close to what this, and my air jet is even slightly undersize @ 185

I wonder if a .5 or .10 change in air jet makes a big difference?

also see here - the guy suggests the F2 emulsion tube for cylinders of around 450 – 575 CC, but then he says "For a 2000 cc Vauxhall/Opel engine each cylinder capacity is 500 cc and a F2 emulsion tube would be appropriate. However, a 2000 cc engine in just on the cusp of change for emulsion tube type between F16 and F2, if you already have F16 tubes, use them it is not worth the expense of change, they will just cause the main circuit to start marginally earlier."

so if the main circuit starts too early (therefore at low revs), I wonder if and how that contributes to flat spots, and if it's possible to (overlap/meet?) the main circuit with idle circuit?

Complicated things these Weber carbs - I guess it probably is rolling road time after all. Hope you don't mind me sharing my thoughts while I get my head around it. You've probably all been there, got the T-Shirt etc.

N
 
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