tobymack
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| posted on 9/9/08 at 11:07 AM |
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any carb experts?
I've a single DHLA40 carb on my 1600 xflow and I am coming to the conclusion that the chokes are too small. lots of torque but no top end.
Currently the chokes are 34mm. Which (according to what I have read) is correct IF I had twin carbs. But I don't, I have a single carb so each
barrel is driving two cylinders.
Anyone know how to work out the required choke size for my setup? I tried just doubling the choke area on the basis that two cylinders will need twice
the airflow but that gets 45 to 50mm for the choke so the carbs would have to be massive!
Any ideas? (apart from fitting a more normal twin carb setup or converting to injection!)
Toby
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Mr Whippy
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| posted on 9/9/08 at 11:20 AM |
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mind that fitting carbs with huge chokes will not only give you little torque but also the car may become very difficult to start due to low airflow
in the venturi not pulling the fuel out.
I had a cortina with a flowed 1.6 and for a laugh I fitted the carb from a 2.8 v6, was a right sod to get it going sometimes needing fuel poured down
the carb, zero torque but once going was at the limits of the engine, think it did about 14mpg too! 
Fame is when your old car is plastered all over the internet
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tobymack
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| posted on 9/9/08 at 11:52 AM |
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agreed. which is why I don't trust my calculated figures. A 50mm choke is bigger than single throttle bodies on most injection systems and they
feed all 4 cylinders.
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pewe
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| posted on 9/9/08 at 12:09 PM |
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Contact Eurocarb in Tilehurst, Reading. They are the official Dell'orto importer and normally pretty helpful.
Cheers, Pewe
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Dingz
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| posted on 9/9/08 at 12:40 PM |
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I think your choke sizes will be plenty big enough for a 1600, how much other stuff have you done to the engine? Remember only 1 cylinder needs fuel
at a time, I suspect its more of a jetting issue. Look Herefor lots of useful info.
Btw. the usual 38 DGAS has only got 27mm chokes.
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tobymack
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| posted on 9/9/08 at 01:05 PM |
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thanks guys. I've been to eurocarbs before - agreed they are very helpful.
Ok, I have to come clean. The "lots of torque and not top end" comment is from my old engine. Of unknown spec.
I have just fitted a replacement I have rebuilt - 234 cam, GT sized valves, ported (but no idea how much), standard compression. This is not yet run
in but isn't running right so I started looking at the carb. Having read Dave Andrews info I jumped to the conclusion that the carb choke might
be too small. Sounds like the wrong conclusions!
I reckon I need to rebuild and sort out the existing carb and see how it goes before I start changing things. 
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MikeRJ
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| posted on 9/9/08 at 04:39 PM |
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The jetting will certainly need looking at on your new engine, assuming it was fairly close on the standard one. Chances are it's running weak
at higher RPM, which will be strangling the power.
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