Crossflow And Twin Dellorto 40 Problems

[Guest elliot tanner]

Hi Everyone,

 

I have a 1700 cross flow, stage 2 head and Dellorto twin 40's. It has a couple of problems:

 

1. Car runs rough at low revs (sub 3000rpm). Bit of a lumpy tick over and takes a while to clear when setting off. Above 3000 she runs very sweet and pulls well. (makes me think idle circuit problem)

 

2. Very hard to start when warm. Engine spins over and does sometime limp into life but generally have to leave to cool down untill it will start. Very embarrising in busy town driving

 

3. Fuel coming back through the carbs and in to the K&N air filters which then drips out and onto the steering shaft.

 

4. Pops and bangs on deceleration.

 

5. Once started from cold the car seems to either run on 3-cylinders or very rough untill taken above 3000 rpm for the first time. Then clears and sits and idles ok-ish.

 

I have recently replaced the leaking exhaust gaskets thinking that this would help the problems but alas not. I then cleaned the jets out, again no difference. Could any body shed some light? I have a carb re-build kit ready to be fitted but thought I'd check if there was a simple fix first as the car has been rolling road tuned in the past and didnt really want to play with too many of the adjustments.

 

The chokes also seem to be disconnected by the way.

 

Thanks for your help.

 

Elliot

[Guest gdc]

hi elliott

check fuel pump pressure and float heights in carbs , depending on cam could be a balls out engine that wont run well at low revs , also have the carbs ballanced this is why i ditched my 1700 x flow cos of unreliability .

 

graham

[Guest elliot tanner]

hi elliott

check fuel pump pressure and float heights in carbs , depending on cam could be a balls out engine that wont run well at low revs , also have the carbs ballanced this is why i ditched my 1700 x flow cos of unreliability .

 

graham

 

There seems to be a regulator type thing with numbers on built into the fuel line, how would I check pump pressure?

[Guest trackerjack]

There seems to be a regulator type thing with numbers on built into the fuel line, how would I check pump pressure?

 

The regulator should have filter king or malpassi written on it.

You need a pressure gauge with a fine range (possibly 0-15 psi) and that needs to go between the reg and carb.

Webers and Dellorto's like 3-4 psi and bike carbs 1-2 psi.

I have such a gauge and if you lived near me you could come and check it.

I live 10m north of Portsmouth.

Cardiff is a long way but hell who knows where you go!

Edited September 14, 2009 by trackerjack

[Guest RichardO]

Sounds like over fueling at low rpm, I have/had a similar problem with twin Weber 40's on a Pinto.

 

I would also suggest fuel pressure (mine is about 3 psi with a fuel return), and float bowl levels. Possibly worn needle valves, or a problem with the progression circuit (idle jets)?

 

Rich...

[Guest whiz]

Hi I can sympathise with you mate just had someone work on my twin 40 dellortos for 8hrs the car was doing simliar to yours its not just about fuel pressure my carbs had to be soldered & re drilled. the jets where all wrong. car was over heating & very flat big difference now though just waiting on delivery of new accelerator pump jets so the little bit of hesitation goes. its no problem getting spares either can get them from dellorto uk. best of luck with them i,m seriously considering changing to a 38 dgas from a 3litre capri, my tuning guy says the difference is unnoticable. Andy