Weber 32/36DGV verses the Weber 38DGES

(stranger)
Wed Mar 02 2005
08:21 PM
Gnarly4X
(carpal tunnel)
Thu Mar 03 2005
02:15 AM
Sarge
(carpal tunnel)
Thu Mar 03 2005
02:17 AM
Gnarly4X
(carpal tunnel)
Thu Mar 03 2005
08:18 AM
Can you, if at all possible, run the rpm numbers up to 6000 rpm or so? I know this is a little high for you truck guys, but my car
may see that high every so often. With the weber 32/36 and the electronic ignition my car pulls good up to past 5000 rpm (very
rarely done).
Re: Weber 32/36DGV verses the Weber 38DGES
Quote:
Yes I can.
Gnarls.
Can you, if at all possible, run the rpm numbers up to 6000 rpm or so? I know this is a little high for you truck guys,
but my car may see that high every so often. With the weber 32/36 and the electronic ignition my car pulls good up
to past 5000 rpm (very rarely done).
Re: Weber 32/36DGV verses the Weber 38DGES
6,000 rpm's is high ? Wow, that's just getting started with our sewing machines . The later model 1600cc engines really wind out
good to over 6500, sometimes higher if balanced right . I finally blew a cast piston in half at over 9k on the last 1.3L I built .
Missed a shift with the 38DGAS, no limit to those dual valve springs, either.
Ok, a few points. Overcarburetion . Yep, it can be done. Mostly, any carbureted engine is overdone if you can step down on the
carb with no real engine response. The Weber's design is basically a demand type, as in the way the air velocity moves through
them is the amount of volume in fuel drawn. 32/36's on average pull 300cfm. 38DGAS's run around 380-400 for a good smooth
one. The 40DFAV should be rated at 425cfm or so if the casting is nice. I shot for the middle, the 38DCNF is rated at 400cfm,
right at what the head was flowed for. Here's the trick, though. Intakes have reversions, no way around it. Pulses from the intake
valves opening and closing in a way are bad , but in another way they are good. Here is where technical dyno info is worthless.
At higher rpm's , velocities take over. The a/f mix coming in is traveling at some pretty good speed. My reason for using a fairly
small bore intake is just that , keeping the velocity high and flow rates where they need to be for even larger engines. Same near
theory to using sidedraft carbs, hence the reason they usually are so big. The incoming charge since it's speed is high allows the
extra volume to be rammed into the cylinder. This is why intake bowl port work is so important on high performance motors. Take
a look at any newer model engine, foreign or domestic. The builders finally took the time to make proper use of the castings and
did the work so many hotrodders have been doing for years. Biggest reason they are downsizing engines now, just better
efficiency. This ram effect is very evident at low revs when there is a lack of throttle response. Hence using larger idle jets on
small engines like our Suzuki's. The big carbs are just that, a 38DGAS on a 1324cc engine is huge and in some areas will show
no response in throttle changes. It really does not overfuel the engine since the velocity in the venturi's will not allow the
increased fuel draw. Sort of takes care of itself. But, at high revs where these little engines can really breathe and surprise the
heck out of you, the bigger carb really comes into play and will work right to it's demand limits. Very hard to do with an EFI
system unless it's fully mapped , much like OEM late model units. Look at newer model cars and their plenum systems, huge and
very efficient in air flow , way more than they used to be .
Think about this . Years ago, back in the 60's Ferrari figured out that 4 44mm downdraft carbs would feed their V8's more
efficiently and produced some huge horsepower numbers from very small displacements. The V12's they built with 6 sidedrafts
did even better. I'm just aiming to make more use of what this engine is capable of flowing if forced to do so . Also looking into a
supercharger, as soon as they get re-released, lol .
All I'm wanting to do is set up two 32/36 DGV's onto this twin sidedraft manifold. This will allow better cruise blends with the two
32mm primaries since they are metered for economy . This would provide a better torque curve over a single 32/36 but not as
radical metering as the 38DGAS. Then, there is the added bonus of the 36mm secondaries. The fun part would be setting up the
linkage, although not much of a challenge since I've done much worse things on engines lately. Just getting the two primaries
balanced and having to adjust the secondaries to open exactly the same to keep all four cylinders balanced would be the hardest.
The pulse delay you speak of would be taken care of since the small plenum area below the DGV in that adapter will cover that
aspect.
Sarge
Re: Weber 32/36DGV verses the Weber 38DGES
Quote:
6,000 rpm's is high ? Wow, that's just getting started with our sewing machines . The later model 1600cc engines
really wind out good to over 6500, sometimes higher if balanced right
... RPMs yes, getting useful powerful at high RPMs is the issue.
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The Weber's design is basically a demand type, as in the way the air velocity moves through them is the amount of
volume in fuel drawn.
...all carbs are "demand" type.
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