Smaller engine Emission DHLA40s - Jetting

[Redroller]

This be my first post, and i hope i'm not too much of a pain...

 

My current project, which in its current state has been on and off for a year, is a 1983 mk1 Golf with a 1272cc hydraulic lifter engine. I couldn't afford a gti at the time, and being a student i can't afford the insurance.

 

I was offered at the beginning of this year a pair of DHLA40-N emission carbs, plus the manifold, pump, regulator and air filters for a sum of £300.... They were from another failed project with the same engine size as mine, and no wonder they were jetted suitably for the alfa they came from i believe.

 

i have taken time to do a lot of reading, not rush things and try to get as much information as i can so i don't end up with the bitter taste of failed sidedraughts! i managed to calculate or deduce a number jet sizes to work with and subsequently rebuilt the carbs with them.

 

I have also fitted a later fuel injection cam from a 'GT' polo with a slightly long duration, but still keeping a smooth idle.

 

I have re-curved my distributor to give a more aggressive advance....

 

i currently have the following jets/chokes etc:

 

50mm rampipes

.3 venturis

28mm chokes

33 pump jets

60 idle jets - fixed air bleeds

.11 emulsion tubes

128 mains

210 air correctors

 

I know the 128 mains are on the large size, and was hoping to work down from there. in testing the plugs seem to remain quite black and the performance down. the air correctors are also large, i do have some 180's but i left them out due to the larger main.

 

I believe near enough spot on with the idles as the length the of the progression phase requires a larger jet to cover this, particularly in a smaller engine?

 

Not at all sure on the emulsion tubes, eurocarb advised me that the .11 were the only type for those carbs, but after reading a few posts here the fitment of .8 and .10 seem possible?

 

Sorry for the long post but i just wanted to get all the information in! Any ideas on my current approach or suitable changes?

 

thanks

 

chris

 

 

 

 

 

 

[DaveNotSoSideways]

Please check the float levels, well actually fuel levels and set them up as per my post below.

 

http://www.sideways-technologies.co.uk/forum/Blah.pl?m-1201970113/

 

You'd be better on the 10 tube I think.

 

Some 1300 Alfa's had these carbs on (H-N) model.

 

They were jetted:

 

58idle

115main

9 tube

200 corrector

40 pump

USING 7848.1 AUX VENT (NON EMISSION) < usual emission is 7848.3.

28mm chokes.

 

No idea how that would run.

 

128 main is ok the 10-11 tubes.

 

Maybe see if you can lean out the progression/idle jet slightly...Try 57, if it doesn't stumble/spit or pulse your fine on that.

 

First step is the fuel levels, basics, check those report findings, if they are off then reset them and try the engine again. You can lower the fuel level to 28mm to help lean things out, jets can be tuned/fudged on the fuel level, but it's better to just set the level correctly and work from there.

 

You haven't fitted "cold" plugs? Suggest NGK equivelent of the original spec...BP or BPR prefix, no irdium or fancy plugs till it's tuned right. Also make sure the ignition system is good.

 

Yes stay on the stock fixed hole idle holders.

 

If the plugs and ignition are sound then it's a bit rich.

 

Maybe also increase the plug gaps to 0.8mm if they are less.

 

 

 

 

[Redroller]

Thanks for the quick reply dave, it looks as if i'm on the right track.

 

I did try to set the fuel float levels, but after a quick browse through your article it was no where near as thorough as that, so i will definitely get the verniers out and start with that.

 

i have a set of 58 idle jets that i took out so maybe they could be used instead of the 57s

 

you suggested the use of .10 emulsion tubes, i assume this is slightly richer in comparison to the .11 and i would see the best benefit when dropping main size to the suggested 115 or so....

 

i have the 7848.3 vents which if i read correctly require a stronger pulse from the block, could you see the benefit of fitting the .1's? i didn't go down that route purely from the fact that they weren't for the carb model

 

plugs wise i have the standard NGK specced for the engine gapped to 0.7mm. i will try increasing the gap to sse if that helps. apart from that the ignition system is strong and advancing well.

 

airs wise i'll stick to the 210s i think

 

 

[webermaniac]

A little note, try to set fuel level in both carbs as identical as possible. You'll be able to sync them easier if levels are the same. Absolute value of the level is as important as that it is exactly the same in both float chambers.

 

Glad to see a fellow dubber here. Welcome to the forum!

[Broke4speed]

What an opportune topic!  I'm hoping that a 1272cc Golf engine shows up on my doorstep in the spring (we didn't get them over here in Canada, and I have an urge to put one in my Mk1), and a set of DHLA40Hs that I currently run on my 1.8.  I'll be keeping an eye on this one .

 

[DaveNotSoSideways]

1 vents would open up different main jet, air and tube possiblities. I've seen the 9 tube used.

 

Theory is one thing, actual use is another.

 

You want the best from this stuff then you must experiment. I tested about 200 combo's on my Triumph 1300

 

10 tube is used often on smaller engines 1600cc Alfa.

 

11 is 1800/2000cc. Before that they used an 8 but with a small idle jet, 55, so that says the progression was shorter and the main more active.

 

Make of this what you will.

 

There is no textbook proceedure really.

 

Best bet is a wideband AFR probe and actually see what happens properly, all else is pure spectulation.

 

If you had some proper non-emissions, well thats a doddle.

 

48-50idle, 7850.1 holder.

 

110-112main

 

7 tube

 

150-160 corrector

 

33pump

 

1 vent

 

28mm choke.

 

Emission will require more fiddling, to be honest I never sell or fit emissions to anything under 1600cc cause they don't work that well, alteast not without alot of a jet testing.

 

Obviously it's difficult to test much with 1 set of vents and tubes.

 

See what works best, move from there.

[Redroller]

I knew when purchased the carbs there was going to be a lot experimentation going on, where there's a will there's a way.

 

I can't drive at the mo as i recently had a knee op, but testing will begin in earnest prob around feb time. Thanks for the helps so far.

 

In the meantime i'll try and source a few more components to test.

[DaveNotSoSideways]

You'll get the best results by fiddling...also you'll learn alot! Knowledge is power!

[Guest]

hi all

i got a dellorto dhla40f

and a lynx manifold for a 1.3 crossflow so i will only running the one 40

any setup main jet help will be greatfully recieved as i have never had a 40 before

cheers

colin

[DaveNotSoSideways]

Colin.

 

F is emission.

 

Not ideal, it's a totally out of it's design window!

 

Try this:

 

32mm Choke

165main jet

7772.11 Emusion Tube

200 Air corrector

68-70 idle jet

48 pump

150/170 needle valve.

 

If you get stuck I have 1x spare DHLA40E body here I could built into a carb that would be ideal.

 

Cheers.

[Guest]

cheers dave

if it dont work

how much will we be talking to build one mate

cheers

colin

 

 

[DaveNotSoSideways]

I can wack something nice together for about £125....I've got stacks of spares that owe me nothing.

[Redroller]

just thought i'd speculate a bit till i have the chance to do the car again..

 

i've had a good read of some of the other stuff on here and now realised that the 'start' of the e-tubes varies

 

so i assume earliest emission 'starter' is .8, then .10, then .11.....and so on, however atomisation of air/fuel increases with no.... a smaller engine would want an earlier starter, i.e an .8, but main jet is kept fairly small?

 

Air correctors have two effects on the e-tubes, can control the urgency at the start of main and then control the leannes at end of rev range.

 

The 9 tube is not an emission e-tube correct? but used in the alfas with the .1 vent and larger aircorrectors to delay it slightly?

 

the .1 venturi design activates the mains at lower air speed, hence why alfa would have experimented with this type in the F carbs in the 1300 blocks...?

 

I would like to try some .1 venturis, but the new price is pretty shocking for 4!!

[DaveNotSoSideways]

9 tube is an "un-used" emission tube. Barely used.

 

You are correct in all you say.

 

F carbs were the first emission, Alfa Romeo were probably testing many things and came to a solution based on dyno testing. This is the was first emission carb, I imagine they were experimenting with it alot, trying odd stuff.

 

1300 is really TOO small for an emission, best on 1500-2000c, so maybe they used the 1 vent to make the emission carb operate more actively...than it would on a 3 vent. Maybe this 1300 had a funny airbox, camshaft etc...I don't know.

 

Also bare in mind they might have done it for other reasons, like costing, they had a load of F's left over or too many, so they just wanged them on the cars for cost reasons, who knows.

 

[Redroller]

very true.

 

some of those alfas were 16v too, which would change things..

 

Its the decision now whether to invest in some experimentation, which will prove costly if i have to source the parts new. what with vents, mains, e-tubes etc.....

 

or

 

cut my losses and invest in a more proven approach with non-emissions (no guesses on recommendation!) and move the H's on.

 

hmmmmmm...

 

 

 

 

 

[DaveNotSoSideways]

I'd get rid.

 

Good time to buy up some carbs.

 

Buy the best you can, no worn out, bead blasted tatt, factor on some "proper" rebuild kits £45 or so with viton valves.

 

If you see any tempting ones for sale, just post the URL I will tell you what they are and speculate on the condition.

[Redroller]

I was beginning to think that way anyways

 

the non-emission ones were no suffix, C and E?

 

[DaveNotSoSideways]

Correct.

 

Watch out, cause E models OFTEN come with No2 venturi. Not No.1.

 

Bar if they are Lotus Elan +2 carbs. Alfa "E"s all have 2 vents (slightly LATER on than the 1).

[Redroller]

Hi dave,

 

I was pointed in the direction of this seller on another VW forum. he's got these what look like non-emissions up for £120, unused by him.

 

Obviously unsure on the condition of the spindles and action of the butterflies. Condition doesn't look too bad, but i can't see them myself unless make the trip.

 

http://www.clubpolo.co.uk/forum/index.php?showtopic=134694&pid=1264976&st=0entry1264976

 

Can you get any opinions from these pics?

 

thanks

 

update - they have no letter and are running .1 vents. he says he's got a spare set of either .6 or .5 e-tubes that he'll let go with them too. he's gonna get back to me though on that.

[DaveNotSoSideways]

I have to register to see them...I might have a look later.

 

If they are non emission you can't go too far wrong for the price. factor in some "quality rebuild kits" (eurocarb OE)

[Redroller]

Ok well i'll see if i can get the pics some other way, they look as if they'll clean up ok.

 

I can get a hold of .5 or .6 e-tubes thrown in with them as well, i guess .5s would be best as they are the closest to .7s?

 

 

[DaveNotSoSideways]

Yes 5's, the 6 will be useless, really bad unless you use 27mm chokes!

[DaveNotSoSideways]

BTW on a lathe you can skim down the 5's to become 7's...

 

Just remove about 0.010" from the lower section...Can explain if needed

[Redroller]

I'd love a lathe to do it on! I'm not sure what a local machine shop would charge, then there's the option of getting some new or second hand.

 

I'm glad i asked some questions about these carbs, turns out the pump rod assembly clamp on the spindle has been borrowed, but the good think is they are replaceable (£20 cough!).

 

i'll make him an offer

[DaveNotSoSideways]

I have a LOADS of spares...ask me first!

 

Lathe it's a 15min job.