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Discussion Starter · #1 ·
Having trouble setting my Dells, getting a lot of popping and backfiring. Think they might be setup a bit lean.

They are set-up with 28 venturis,main jets at 115 , 57 idle jets,9164.2 emulsion tubes.

Have been recomended to go with the below. What do you think?

60 idle jets, 120-125 main jets and 30 venturi's?

I am running a 1600 on a 009 dizzy.

I followed the super performance book pre install list. I have checked the balancing and they are spot on. The linkage is working in sync.

Have checked the inlet connections and it is bolted down all the way round. Have sprayed wd40 and no change of engine.

I have set the mixture, twisted fully in, then out until the engine started to run, then out another 1/2 turn. Might check the mixture again. I heard that if I change the idle jets to 60s then it might be easier to get the mixture right

One question is that if I connect a tachometer my idle speed jumps around a bit, could this be something wrong?

Is there anything else I should check?
 

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fido said this

popping on overrun can be slightly weak idle mixture (turn all screws out an extra half turn and see if it helps), usually points to carbs which arent quite balanced, or I have had it because the dissy advance mechanism was sticky, and the idle timing was jumping up and down.
 

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also this

What size venturi's have you got? You want 28 or maybe 30's at most. If bigger, then you will have problems with low-rev acceleration too.
this was for a 2 litre..........
 

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also the consensus is 4 times or 4.1 times the vent for the mains

this 4 x 28= 112 which I got
or 4.1x 28 =115 which is what you got.

key I believe is in the idles as this is where you do most of the driving - couple with a vac dizzy - think u can't go wrong.

Prob is another petronix for the vac -unless some smart arse knows how to convert them?

anyway I'll bugger off and let someone else get a word in edgeways.............;)
 

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I'll only say that main jets should be 4.1X vent size for economy rising to 4.3X for power. Every engine is different, and you'll need to experiment- but start rich then move down. A friend with a lathe, soldering equipment and a set of micro drills makes this far cheaper.
Also, having burned two pistons sorting out carbs myself (a single 44IDF on an 1192cc- what a bitch!) I had the good sense to fork out for an air/fuel meter when I scooped it out to a 1.4 (83mm p&c's, 64mm stroke) and I now have many happy miles behind me in a far shorter time than before. And no burned pistons.
Oh, and small venturis- power off the line and restricted top end, big vents, soggier starts but great on the motorway. Are you driving around town in a 30 limit, or drag racing and nothing else? Think carefully, as things can soon get expensive.
Keep a very close eye on your idle jets- as someone pointed out, unless you're at full throttle, these fellas are what you are doing most of your driving on.
 

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Discussion Starter · #9 ·
Cheers guys, I will have another go tomorrow. Have been helping sett up DubDubs today and they sounded sweet as I left. He has 60 jets that seemed easier to setup.

Will let you know tomorrow
 

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helping out ? ;)

you did most of it !

sounded real nice - smoother engine difference was quite astonishing really

thanks for your help/time/parts let me know what I owe you......
 

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Discussion Starter · #11 ·
Cheers for your help everybody.

Bugger61 - where did you get your air / fuel meter from? How does it work, do you adjust the mixture screws individually?
 

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I got a stand alone A/F meter by Autometer (C2), courtesy of VW Speedshop. Meter cost about fifty, sensor about sixty. It was a small price to pay, I reckon. Paul did say that broader band meters were available.
All you need to do is to weld a boss into your header for the sensor and to wire the thing in- there's nothing to it- and I reckon I'm a bit of a duffer with electrics- if I could get one "plugged in" anyone can. It doesn't monitor each idle screw individualy, but if the carb/ carbs have been properly flowed to start with, it'll tell you all you need to know anyway.
Having blown pistons trying to get carbs tuned in the past, I really wouldn't want to be without one now. It's a great insurance.
It could have saved me pulling my engine twice, and saved me the cost of two sets of pistons, if only I'd have bought it to start with.
 

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why only one? surely dells need one on each exhaust to be absolutly[sp] correct?

any wideband lambda should do - you can get the plugs/mounts from here

http://mocomracing.com/product_details.asp?id=116&cat=15&sub=36

and get a selction from a scrap yard of lambda's - they all measure the 02 being at the 1:14 or whatever it is...........0.45v I seem to remember is spot on.

I've got a link somewhere of the cheap way of doing it - only prob is the size of them they are quite long with the wires.
 

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I'm sure that if you wanted to buy four gauges from Autometer they'd sell 'em to you, but if you'd flowed your carbs properly to start with, each eighth turn on the idle jet adjustment screws is the same as any other, in a one choke -one port instalation.

I know what you're saying, Man, and I have no intention of causing offence, but you know what I mean...
 

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The only time you'd really need to check individual cylinders would be at tune up time, so you just need to swap your single sensor from one pipe to another to check that cylinder, and use a long enough extension piece to extend the wiring.

Then put the sensor back in the main collector when you've finished the tune up job, so you can keep a check on everything when driving.

OR ....

Get 4 extra sensors from the scrappy - fit one in each pipe, wire them all back to the dash, then use 5 switches (or one multi position rotary switch) to connect each sensor to the gauge, one at a time, so you can easily check any one you want.

Dave.
 

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Dave your second approach was my exact thinking - but I think I've got it wrong and it's narrow band lambda I'd need - anyone confirm this?

Only snag is how much do scrappy's sell lambda's for? they are a high'ish price item new BUT 2nd hand is a gamble [therefore lots of hassle with returns etc] so I guess if not tested /gteed should be quite cheap.

Any makes that known to be ok? assume for our purposes it's not essential which model they come off ie a 1.4 polo or a 2 litre cavalier??
 

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From what I know, they come in two basic types, heated and non-heated. The heated versions have 3 or 4 wires, the non heated ones have 2.

The heated versions are the best, as they will give a reading while the engine is still warming up.

They output between 0 and 1 volt but you need a very high impedance meter to read it, (more than 1 M Ohm) otherwise the meter just shorts it out.

I did a bit of research a few years back and made my own digital LED readout for one, however I never got round to fitting it in the car.

While the car is in for a mini resto, I'll weld the boss into the collector before I replace the rear valence panel.

I had a few posts on the old Flat 4 forum with John Maher on the subject of A/F meters and he said they were OK for a rough guide, but only use readings obtained at steady full throttle for making any jetting changes (I assume the accelerator pump will cock up the readings otherwise)

So if you want to know what your mixture is like at (say) 2000 rpm, you'll need to find a good steady incline and give it full throttle in a very high gear to get a decent steady reading.

Obvoiusly this dosen't apply to the mixture tickover settings, only to jet changes.

I have seen AF meters for sale on Ebay lately, using the LED system in a dial style layout. They look a bit naff to be honest, but if they do the job then that's the main thing. You're probably not going to be looking at it much once you have used it to get your jetting sorted.

I think you'd be best just moving one sensor between diferent locations, rather than using five sensors of dubious origin, because then you know that the readings will all be comparable, otherwise you could end up adjusting one cylinder just because that one sensor was on it's way out or not calibrated quite the same as the others.

Dave.
 

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Dave that's exactly what I then came up with - weld in 4 bosses and swap between the 4 - only snag is the time thing - as I'm not attempting to pull out a lambda from a hot exhaust!!

so I figured for the benefit of checking readings - I could get 4 and swap in one location and check voltage - and range appears same with a 1/2 turn say each way on the mix screw......

it may seem overkill - but as someone put up ^^^^^ wrong mix can kill engines. And that way I can perhaps get close to what a rolling road would acheive with the idles. And with some careful analysis maybe understand if the mains are working or not.
 

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Well it's right that lean mixtures can kill engines, but when you're adjusting your idle mixtures they only apply at tickover and I'd reckon you'd have to be pretty unlucky to burn out a piston on tickover, plus it would be popping and farting like mad if it was that lean at tickover.

As for the jetting, that's another matter. I set my 1776 up by the book, then a couple of jet changes based on plug colours, engine oil temps and "seat of the pants" readings.

I think if you have your carbs all equally jetted, drive it sensibly until you know you've got it pretty close, listen to the engine (John Muir style), keep an eye on oil temps and read your spark plugs, you won't go far wrong.

A single lambda in the collector should be fine to keep an eye on things and it will certanly make jet selection easier, but there's nothing to stop you puting one in every pipe. (also bear in mind the sensor sticks out into the exhaust flow so it will restrict the exhaust a tiny bit)

Dave.
 
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