Weber 45 DCOE jet settings 3.1 stroker stage 3 cam

[zedhed]

Hi Guys,

I've a new 3.0L L28 with stage 3 cam

I've got factory settings for now, except for Air

Venturi 36
Main jets 145
Air 185 (was 155)
Emulsion F16
Idle jets 55F8
Acceleration pump 45

I will end up doing a rolling road session when the engine is broken in, but I'm just curious

What setups are working best for you guys?

Cheers, Nick

 

[jonbills]

Looks a reasonable starting point, but I'd expect to end up with bigger on several things for a 3.1

 

[atomman]

I have a sheet some where with recommended setting for Datsun as a starting point,

I will try and dig it out, Im sure Alan T posted it on a thread a while ago,

 

[zedhed]

Hey thanks Guys, I thought I'd experiment a bit while breaking it in to get a feel for these Weber things. They're a totally different beast from the 2" Jag SU's I had on the old engine

Jon that's interesting, what would you expect to get bigger?

I would like to try get the smoothest progression between closed or part throttle / acceleration I can.

Having read up on open/closed throttle progression, I was wondering if trying some pump jets would make sense but then I read that the adjustment of the idle jets determine when the mains come on.

Just tightened the banjo bolts this morning after another outing - fuel was leaking out of them onto the exhaust. Oops. Might need to check everything from ground up.

Nick

 

[morbias]

The idle jets do affect the progression phase but the most important thing for transitioning to the mains is the fuel level in the float bowls. If you've set your floats using the distance of the float to the lid method then they are almost definitely wrong, and everything will be effected, including the size of the idle jet.

This is how to set the fuel level properly, the fuel levels in all three float bowls should be the same and within 1 to 2 mm of the feed hole in the emulsion tube shaft:
http://www.apexspeed.com/forums/showthread.php?t=64306

Edit: you should probably aim for 2 mm below the hole otherwise you run the risk of excess fuel being drawn through at idle.

Edit 2: this diagram better explains what you're trying to achieve: http://www.classiczcars.com/topic/44512-setting-weber-dcoe-fuel-level-with-caliper/

The fuel level in the float bowls is the first thing you want to do as if it's wrong then you'll spend a long time changing parts to solve issues which are all down to the fuel level, but have symptoms that make you think it's something else.

 

[Albrecht]

What series 45DCOEs are they? And are they proper old die cast Italian ones, more modern emissions type or the latest Spanish ones with the occasionally iffy reputation?

Cam lift and duration, cam timing and compression will have a great bearing on what way you go with your carb tuning. Another big factor is your choice of main venturi size. Obviously a bigger main venturi will give more power high up the rev range, but can lead to inlet air speeds coming close to stalling lower down the rev range, so you might want to choose a compromise size to give more 'driveability'.

I have personally found that accelerator pump rod stroke makes a big difference with these engines. They seem to like a really short pump rod stroke. What pump rods have you got?

 

[zedhed]

Here's a picture of the carb setup at the moment below - I bought them in the USA with the engine. No idea where they were made - not sure if they're "iffy" or not

OK so check fuel levels first step. Hopefully get that done this weekend... Then we'll see what happens next. Also I made a mistake - my engine is a 3.0 not a 3.1. I have 3.1 on the brain for some reason due to long discussions about it. Will try correct post title...

OK pasted from build sheet Cam specs are:

(Compression ratio: 11.8 : 1 )
Schneider Camshaft: Stage III
Duration 290
Max Valve lift: .495 (12.6mm)
Lobe Center: Exhaust 106 (IN: 104)
Valve Timing @ 0.50” lift:
IN: 18 BTDC, 46 ABDT (I think this should probably say ABDC),
50 Before Bottom DC, EX: 14 ATDC.
(Inlet should be fully open @ 104 deg after TDC, Exhaust fully opens 108 deg BTDC)

 

[zedhed]

Albrecht if you tell me exactly what to measure I can let you know the size?
N

 

[240carsten]

This thread is of interest of me too, I am sorting out parts to get a 3.1 buildt so a baseline weber 45 setup would be nice as then I dont have to throw money at buying alot of jets/venturis/expensive trinkets to sort the engine out.
So I appreciate any input for Zedhed!

 

[zedhed]

I'm just wondering if anyone else in the UK has a 3.0 or 3.1 stroker ?

 

[jonbills]

I think there are probably many, but not with exact same setup as you: you've probably got as good a baseline as you can have, and I don't think there's an alternative to rolling road time to get it right for your engine.
The thing I'd suggest to do first is decide on the choke size - for max top end, you might go upto 38.
If you get it all setup with the 36s, and THEN decide on 38s, you have to start again!

 

[SKiddell]

I'm just wondering if anyone else in the UK has a 3.0 or 3.1 stroker ?

As jon said, there are a few but with different setups such as FI and as such are not apples for apples

BTW you might want to fit a fuel return line and regulate pressure from there

 

[Albrecht]

Albrecht if you tell me exactly what to measure I can let you know the size?
N

It's the accelerator pump rod stroke length I'm interested in. You'd need to take the carbs apart to take them out and measure them, so you'd probably not want to do it.

If you can tell me what series / type the carbs are (it should be stamped into the top covers, just after the bit that says '45 DCOE', on the bit where your fuel lines are covering in the photo) we might be able to pin down just what pump rods you have.

Like I say, after taking advice in the past and trying it for myself, I've personally found that L-gata engines with Weber DCOE carbs like a short accelerator pump stroke.

Most of the generic aftermarket Webers seem to have long pump rods. Weber themselves specifically recommended the 40 DCOE-18 and 45 DCOE-9 for the L24 thru L28 engines, and both had the short pump rod stroke.

 

[zedhed]

45DCOE
152 046015
Made in Spain by LCN (CE)

 

[zedhed]

Can I remove the pump rod by removing the top cover while on the car or are we talking major procedure and hav8ng to reset everything here? I will probably have to remove the cover to adjust the floats anyway...

 

[jonbills]

Pretty sure you have to take the carb off the manifold. There's a Des Hammill book called 'how to build and power tune' that is very useful

 

[zedhed]

Thanks for the advice guys, done the float levels and they were all over the place fuel levels too maybe 4 - 5mm out.

Also noticed fuel pressure was around 2.5 too low. Adjusted to 3.0 to see what effects that will have.

Hopefully get a chance to test today...

Need to add a return.

Will ask Dellorto what the differences are between the older carbs and these ones, they should know what's what..

Then I need to learn how to balance these things and get the idle circuit mixture right. If anyone has a nice tutorial, let me know.

Nick

 

[jonbills]

All the tutorial you need: http://www.amazon.co.uk/Build-Power...F8&qid=1434355140&sr=1-3&keywords=des+hammill

 

[Albrecht]

Will ask Dellorto what the differences are between the older carbs and these ones, they should know what's what..

Compared to old (Italian) Webers they have an extra air bleed and quite different progression drillings. I grew up with the old Italian ones on all sorts of cars (first of all on Dad's cars when I was a kid) so they are my main point of reference. I don't know too much about the 'new' ones.

I had a look for the length of the pump rods in the 45 DCOE-152s and can't find any reliable data. I suspect they are long, as the 152 is a one-size-fits-all conversion carb. You may in fact find that they work just fine on your engine with long pump rods, but I've always gone for short pump rods with good results on L6s. Maybe leave them alone until you have gone through everything else?

If you ever come across them, John Passini wrote some great books about Weber carburettors in the late 1960s. They were published by Speedsport. I've got loads of other books on carbs, but I still think of the Passini books as my 'bible'. The introduction to the 'Theory' book (Book One: 'Theory', Book Two: 'Tuning and Maintenance') is priceless.

 

[zedhed]

I can see that the extra bleed screw would allow fine mixture tuning so that's a major improvement - as for the pump rod that might make a difference but it might not. There are so many factors at play here I think you're right to try setup with what I have, try to get a better transition before rolling road then see. I'm just trying to get the car as drive-able or close as possible before fine tuning.

One thing I did notices is the standard long velocity stacks which my carbs came with in the kit are often replaced with shorter stubby ones on the pictures I've seen on the USA forums - which I assume is for better low-end torque.

So if anyone has experience, insight or general info as to what venturi and trumpet lengths made a big difference from standard, it would be interesting to know.

Talk about a learning curve