ive got 2.0 pinto running on twin dhla 40's it ticks over ok but when i accelerate it bogs down or hesitates quite a bit then picks up again and accelerates well. from what ive read it seems to be a problem with the progression stage, the carbs are 'H' models which means they are emission type. Anyone any suggestions

try advancing the ignition a bit

Check the pump jets are squirting -- no unknown for the plungers to stick or the jets to clog or the roll pin that attaches throttle spindle to the bell crank that operates the plungers to break.

Also standard DCOE advice applies check all the jests are clear and tight.

Thanks for the replies.....ive opened the idle mixture screws 1/2 turn and that seems to have improved things but think thats gonna do the mpg nogood at all, Ive heard about the pump jet set up seizing up because water gets in and does what only water can in a carb....!! British Trident can you tell me how to check that the pump jets are squirting

Is this a new setup?

I've been experimenting in the garage today with my DHLA's and 2.0 Pinto. I had the same thing at one point. It seems to be because the idle jets are too small.

General consensus, reading around on the net today, is that between 57 and 60 idles are the jets to use.

I had 57's in and all was reasonably OK, with OK progression, reduced to 55 and had the same problems as you (engine stalled when I opened the throttle quickly). I didn't change the timing or any other mixture screws.

I increased to 60 and the progression was even better

I'm no expert but hope that helps .

Rob

[Edited on 16/5/10 by RobBrown]

Rob yes it does help thanks... , i have just bought some 55 idle jets (cos i read somewhere that they are the size to use)and i tried them in my pinto....no good, i put my 58's back in and opened the idle mixture screws 1/2 turn and definately better....i'm thinking trial and error, might try going a bit bigger on the idles....is there a difference between a smaller idle jet and more turns out on the idle mixture screw or a larger idle jet and less turns out.........

Quoting the infamous Des Hammill guide "How to Build and Power Tune Weber and Dellorto DCOE and DHLA Carbs":

"The idle mixture adjusting screw controls the amount of air-fuel mixture to the engine, but the idle jet combination controls the overall ratio of that air-fuel mixture"

Interestingly in the back it has some examples and it suggests that for your H type DHLA on a standard 2000cc pinto the following is the setup to use :
34mm chokes
140 Mains
180 Air correctors
10 Emulsion Tubes
55 idles (but 55-57 quoted later)
4 turns out of the mixture screw.

This setup didn't work for me, but my carbs are Type N, maybe that's the difference?

It also tends to make a difference as to how warm the engine is as well. I found I could get the engine idling well, then come back the following day and struggle to get it started, until I'd just about flattened the battery.

My suggestion would be to get it runninging reasonably OK and get it along to a Rolling Road who knows what they are doing with Dellorto's. I've lost numerous weekends trying to work out what I need to do next to make it run better.

Good Luck
Rob

Rob, ive got Des Hammills book as well, thats why i bought 55 idles, 140 mains 180 air correctors, the only things ive used are the 180 air correctors (it did have 210's in before), the 140 mains and 55 idles make it pop and spit worse than ever....ive currently got the idle screws 3 1/4 turns out, i'm gonna experiment with a bit more adjustment on them and if that dont work try 60 idles. Its running ok but just could be that bit better....but i suppose that feeling never go's away. Thanks for your input and interest, much appreciated.
Ian

Get the throttle pedal to where you feel the hesitation and get someone to mark the spindle on the carb against the carb body. Take out one of the bolts covering the progression holes out and move the throttle spindle to the marked position. You need to see if the butterfly is covering one of the holes at this point, if it is you probably have a progression problem and a new hole needs to be drilled.

that sounds a bit technical but something else for me to look at, thanks

Personally I would not drill any holes in the progression circuit. If you get this wrong you will end up with a scrap carb.
I have tuned hundreds of Webers and Dellortos and to date I have never drilled progression holes to correct a fault. This method should only be used as a last resort when all other areas have been explored.
Find your nearest rolling road and get them to sort it out it could work out cheaper in the long run.
Hope this helps, Alan

The mixture screw only have any effect at idle speed --- that have little effect on fuel consumption.

Not wanting to upset anyone on here that is trying to help someone out and I would never bad mouth anyone that tries to help, but the idle jet performs more than just idle. It makes up the wide open throttle (WOT) mixture as would the pump jets, also on a light car you could be doing 60MPH and still be on the idle jet at very small throttle openings that a light kit car could be on, so an incorrect idle mixture could also make for poor cruise and poor fuel consumption and progression onto the main system.
Hope my ramblings havnt offended anyone and only helps you gain valuable information.


[Edited on 19/5/10 by atspeed racing]

quote:

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Originally posted by Barksavon
Thanks for the replies.....ive opened the idle mixture screws 1/2 turn and that seems to have improved things but think thats gonna do the mpg nogood at all, Ive heard about the pump jet set up seizing up because water gets in and does what only water can in a carb....!! British Trident can you tell me how to check that the pump jets are squirting

---

quote:

---

Originally posted by atspeed racing
Not wanting to upset anyone on here that is trying to help someone out and I would never bad mouth anyone that tries to help, but the idle jet performs more than just idle. It makes up the wide open throttle (WOT) mixture as would the pump jets, also on a light car you could be doing 60MPH and still be on the idle jet at very small throttle openings that a light kit car could be on, so an incorrect idle mixture could also make for poor cruise and poor fuel consumption and progression onto the main system.
Hope my ramblings havnt offended anyone and only helps you gain valuable information.


[Edited on 19/5/10 by atspeed racing]

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An idea just occurred to me ---

Has the car got an old fashion mechanical centrifugal advance distributor --- if so the problem could be cause by sticking bob weights in the dizzie. This happens quite often if solvents have been used to clean the dizzie washing all the lubrication out of the mechanism.

A tiny ammount of lubrication would cure that