Poor throttle response with Dellorto DHLA carbs
Discussion
Hiya,
I'm new here (spend most of my time on MG-related boards). Excellent site, great forums as well! Will be returning a lot I think ;-)
A little info about my car: MGB with B series engine, HRG Derrington crossflow head, bored to 1950cc using aluminium Accralite forged pistons, 11:1 CR, Piper 285 cam, 2 Dell'Orto 40 DHLA carbs, Aldon modified mech. advance only dizzy.
Had it setup by a tuner over here in Belgium, was done quite badly. Went to Peter Burgess this weekend, he got 150 hp out of it(124 at wheels) using other chokes (34mm instead of 30) amongst other tricks.
The car is great at full throttle but stutters rather badly at part throttle. (but that's impossible to see at the rolling road of course)
Can you please help me? I'd really like this prob to be sorted...
Cheers,
Alex in Belgium
I'm new here (spend most of my time on MG-related boards). Excellent site, great forums as well! Will be returning a lot I think ;-)
A little info about my car: MGB with B series engine, HRG Derrington crossflow head, bored to 1950cc using aluminium Accralite forged pistons, 11:1 CR, Piper 285 cam, 2 Dell'Orto 40 DHLA carbs, Aldon modified mech. advance only dizzy.
Had it setup by a tuner over here in Belgium, was done quite badly. Went to Peter Burgess this weekend, he got 150 hp out of it(124 at wheels) using other chokes (34mm instead of 30) amongst other tricks.
The car is great at full throttle but stutters rather badly at part throttle. (but that's impossible to see at the rolling road of course)
Can you please help me? I'd really like this prob to be sorted...
Cheers,
Alex in Belgium
Thanks for the replies!
The problem is when softly accelerating (part throttle), not when suddenly depressing the gas pedal.
Idle jetting should be right, as the idle jets work al the way up to 3000 rpm, so that would be noticable when at full throttle too, right?
No probs when cruising at constant speed.
So my guess is pump jets. I'll install a set with a larger size and see what those do.
(Rob, it's nice to see there are Belgians over here!)
Thanks again,
Alex
The problem is when softly accelerating (part throttle), not when suddenly depressing the gas pedal.
Idle jetting should be right, as the idle jets work al the way up to 3000 rpm, so that would be noticable when at full throttle too, right?
No probs when cruising at constant speed.
So my guess is pump jets. I'll install a set with a larger size and see what those do.
(Rob, it's nice to see there are Belgians over here!)
Thanks again,
Alex
Tim,
I'm with Ian here: thank you very much for the info! Excellent stuff! Your comments are being printed and I'll look into them this afternoon!
The engine was set up at a chassis dyno last week, so I presume idle and main circuit should be set up quite good (Peter Burgess is one of the most respected tuners in the MG world).
Cheers!
Alex
I'm with Ian here: thank you very much for the info! Excellent stuff! Your comments are being printed and I'll look into them this afternoon!
The engine was set up at a chassis dyno last week, so I presume idle and main circuit should be set up quite good (Peter Burgess is one of the most respected tuners in the MG world).
Cheers!
Alex
Tiny update: tried the things you suggested on the road today:
no prob when totally and utterly slowly accelerating, but as soon as I push the pedal a little deeper, the stumble appears.
I also heard from Peter and Chris that the number 50 for pump jets might be necessary, so I'll go and get a set of those and see what happens.
Thanks again for the reactions!
Alex
no prob when totally and utterly slowly accelerating, but as soon as I push the pedal a little deeper, the stumble appears.
I also heard from Peter and Chris that the number 50 for pump jets might be necessary, so I'll go and get a set of those and see what happens.
Thanks again for the reactions!
Alex
Puma,
I don't have quantified data to support Peter's measurements, but experience (on private roads, evidently) shows that my car is significantly faster than other MGs who are modified and rolling roaded independently, one of which a well-developed rally car.
(fwiw, my experiences with Peter were so positive that I bought cylinder heads for my MGB GT V8 from him as well)
I don't have quantified data to support Peter's measurements, but experience (on private roads, evidently) shows that my car is significantly faster than other MGs who are modified and rolling roaded independently, one of which a well-developed rally car.
(fwiw, my experiences with Peter were so positive that I bought cylinder heads for my MGB GT V8 from him as well)
ToniD said:
Hi all, if anybody is interested still, I am, just found this and I am playing with a similar setup, HRG ,Twin DHLA 40 G !!!
as per last comment, its that Suffix "G" These are Emission Carbs and require a different approach apparently,
TD
Looking good!as per last comment, its that Suffix "G" These are Emission Carbs and require a different approach apparently,
TD
And as luck will have it, I just decided to start tinkering with my HRG/Dell'Orto equipped car again as well!
The story about Emission sounds like it might warrant some further looking into.
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