David Jenkins
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| posted on 14/5/12 at 09:54 AM |
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Bike carbs v. Weber 32/36 DGV?
A while ago I swapped my Weber 32/36 DGV for a set of bike carbs - a fun project that improved the performance... but only in some ways, not all.
The old carb was getting a bit old and tired, I was having some problems in getting decent power at low revs, and my fuel consumption was lousy.
However, if I put my foot down hard the engine would give a tremendous kick in the back. I could squeak the tyres in 1st, 2nd and 3rd gears in the
right conditions! I think that this was mostly due to the accelerator pump that squirted fuel straight into the engine when the pedal was pushed
sharply.
The bike carbs now give me good power from just over tick-over revs up to maximum, but I no longer get the kick in the back when I put my foot down.
Fuel economy is a bit better, but not as good as it could be. This may well be because the car hasn't been to a tuner, although I have put an
AFR meter on it and it's pretty much OK. The down-side of bike carbs is that tuning them costs more than 4 times as much as a single down-draft
carb, due to the amount of dismantling and rebuilding the tuner has to do when adjusting and trying out new settings. A session would be upwards of
£200 in the local reputable tuning shops, which is a bit steep for my taste. I'm not even sure I'd get that kick in the back if the bike
carbs were properly tuned, as the WOT AFR is just about spot-on...
So - I'm wondering about going back to a Weber 32/36 DGV, but maybe a brand new one (or new-ish refurb anyway). It would take me just a couple
of hours to swap back. Am I nuts to even consider this?
BTW: The engine is a modestly tuned 1660cc x-flow. Fast road cam, bigger GT valves, basic porting, decent exhaust system.
P.S. Before anyone says it... I can't afford to install fuel injection (and I'm not sure I want to invest that sort of money on this old
engine) and I don't want to change the engine (I like the x-flow, and I don't want to start another big engine-changing project).
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D Beddows
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| posted on 14/5/12 at 10:22 AM |
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Go for whatever makes you happiest! two things I will say though are that 1. a new DGAV wont leave you much if any change from £200 and 2. the
'kick in the back' you speak of usually means your carb is set up wrong!
However there is absolutely nothing wrong with a using a DGAV on a mildy tuned crossflow - in fact I would go so far as to say that in terms of
performance you wont get much (if any) more power out of any other type of carb setup 
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Not Anumber
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| posted on 14/5/12 at 11:12 AM |
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If you want to stick with downdraight carbs that are solid and easy to tune you could always go to a 38 gdav Weber (3 litre Capri carb). It's
synchronous, both barrels open at the same time, so theres no kick in the back when the second choke comes in like with the standard 1.6/ 2.0 Sierra
32/36 progressive Weber but theres solid performance through the rev range.
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ditchlewis
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| posted on 14/5/12 at 12:22 PM |
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I've got a pair of webber 40's in my garage doing nothing. they have no linkage, tumpets or manifold and in need of a service. When i
bought them i was told they were jetted for a 1600 crossflow. My plans changed and i have twin 45's on a 2.1 pinto.
If you want them let me know and you can pop over and collect them.
ditch
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mark chandler
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| posted on 14/5/12 at 04:16 PM |
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Kick in the back is usually due to a flat spot milliseconds before the power kicks in, this makes it a feeling thing not a power/speed thing.
If the carb is fully optimised you should not get this so would not notice on bike carbs with diaphams aka SU carbs.
With a weber you stamp down, butterflies jump open, flat spot, fuel squirt away you go, with SU/bike carbs stamp down, diapham opens slowly
(relatively) fuel is always correct ratio so no bump.
Regards Mark
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David Jenkins
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| posted on 14/5/12 at 06:21 PM |
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So what you're saying is - spend the money and get the bike carbs professionally tuned! 
Maybe this feeling is due to me being pee'd off with the weather - I haven't managed to get the car out for almost a month, what with the
rotten weather and family stuff... 
[Edited on 14/5/12 by David Jenkins]
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rusty nuts
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| posted on 14/5/12 at 06:39 PM |
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David, my car is in a similar state of tune apart from being injected , have a ride in mine , you may change your mind?
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