Weber 32/36 vs 38/38...how's the gas mileage on a

[Mike Self]

38/38 vs the smaller carb? I realize the performance difference, but I'm interested in the mileage difference...

TIA

mike

[yeewiz]

I get 15 mpg on my 38/38, mostly city driving.

[jrhone]

I am closer to 20...but 15-20 is about right. It really depends on how you drive it....I am sure my spirited runs to the redline dont help mileage at all. If I drove it like a Kia then maybe I'd get more like 25....If fuel economy is what you are after the 32/36 is better. The design allows it to run on JUST the 32 side then when you step on it it opens up both the 32 and 36 side. The 38 is a dual sync carb...so its always got 2 38 sides working. So it eats more gas.

[TobyB]

When I ran one, I could get into the mid 20's by jetting

down and not driving like a maniac.

But never above about 27 on a trip.

If I lean a 32 out, we've seen 35...

and yes, the valves survive!

hee

t

[rover1]

Mine gets anywhere from 12-20 mpg. I got better fuel economy when i had my dual 40mm weber dcoe's witch is a pretty crazy statement.

[robsanab]

When I ran one, I could get into the mid 20's by jetting

down and not driving like a maniac.

But never above about 27 on a trip.

If I lean a 32 out, we've seen 35...

and yes, the valves survive!

hee

t

Toby... would you mind emailing me? I don't want to hijack this thread. I'd like to get your 32/36 jetting setup if you recorded that. I believe it was on a mostly stock M10 wasn't it?

long story short... I bought a new 32/36 with CD's prescription years ago and although it runs great, it's not THAT much better performance wise than the stock carb I had (which was leaking a little air around throttle shaft is all)... but I get horrible gas mileage compared the old carb. These guys with 38's are getting much better than I. And yes, everything is either new or checked out and timed by an '02 pro... I just haven't gotten around having him play with the jets for improving MPG. Plus the car was just restored with engine out and everything was replaced and gone through once again... and still no change in MPG. The odd thing is that there are no symptoms of it running horribly rich... plugs last quite a while... no over the top gas smell... starts good cold and hot... actually if nose is pointing up hill it does tend to act a bit flooded upon warm start... but not like i have to floor it to get it started.

Anyway (sorry, that wasn't so short after all)... I was just thinking that maybe you have a good base line to start from other than stock jetting... I can at least get it close so he's not swapping jets and tweaking for hours ($$$)... or I may do it myself.

[Guest Anonymous]

I just did a highway mileage check (95% Interstates), down and back to the CN Valley Show 'N Shine near Hartford; 273.5 miles on 10.505 gallons. which of course is 26.0 MPG. The set up is: 38-38 carb on top of a 2.2 liter MM engine with a Stall header and BMW '02 turbo exhaust, 5-speed OD and 3.91 LSD running from 65 to 75 mph (average touch on the pedal).

____________________________

Roger

'72 Malaga

RBenson685@aol.com

[ceylove]

TobyB-Just put on a brand new 38 Weber with stock jetting. Had tons of trouble with the electric choke staying on too long, but got that fixed.

I know I need different jets, idle, mains and air correctors but can't seem to find the "right" recipie on searches on FAQ.

Any magic numbers for me to try? I've got fresh motor I just rebuilt, Schrick 292 cam, stock pistons (unfortunately!)

[c.d.iesel]

. . . . . Weber 32/36 vs 38/38...how's the gas mileage ?

it suchs - really . And besides - done properly,

you need to machine the intake manifold for

'matching' mounting ports

[BarryA]

Swap and Show and back on one tank the last two years in a row - 115 freeway miles each way (plus a few miles of surface streets on both ends), needle on the gas gauge just above empty when I get back.

Trip down both years has been with a group running between 65 & 70, trip back solo at 75+. Works out to about 25 mpg at an average of 70 mph or a bit better - Weber 38/38, Schrick 284, 9.1 compression, tii dist, OD 5 speed, 3.64 diff, 185/70x13 tires.

[calicolorado]

I've switched from the stock 1bbl Solex to a Weber 38 and have put 75 or so on it so far. I asked the guys @ Ireland Engineering about a good jetting prescription for my overall setup, which is this:

stock pistons and cam

All smog devices pulled out

Tii distributor w/ new cap/rotor/points/condenser

new NGK plugs

Ireland Engineering Shorty header bolted to the stock downpipe and stock exhaust

stock air cleaner modified to fit 2bbl Weber, flowing through the "Summerbox" and intake bellows

The jets that came with the carb were the standard issue Weber package, far too much for my stockish setup. Jeremy @ Ireland gave me this:

125-130 mains, 180-185 air corr. jet, 55 idle jet. 4.0 venturis

I went w/ 125 main, 185 air corr, 55 idle. It might be a bit rich still, but that's okay with me. It really pulls nice especially from 3500-5000. There is zero backfiring and no flat-spots through the range. I am exceedingly happy with this and I'd guess the fuel economy is maybe 3-4 mpg worse than with the Solex. It's damn near perfect for this car (though DCOE's sound magnificent) and I'd recommend it to anyone as an effective performance upgrade.

We first ran it with the cheapo chrome aftermarket air cleaner, then with the stock air cleaner. It's much more driveable with the BMW intake and it's pulling slightly cleaner, cooler air from the front of the car.

Hope that helps...

[TobyB]

Like I know any of this...

I spent a lot of time fussing with the 38, and seem to remember that

a 135 main, (?) air, and a 50- ish progression jet got me about the

best economy I could muster without too much of a hole between

the progressions and mains. But it's been a while, and I took

the carb off when I broke the nice motor that was underneath it...

as to 32/36, I don't remember a thing! No, not true, I DO remember

being able to lean out from CD's numbers for better economy and

still decent performance, especially on the primary bore. Then I left

the secondary richer, and that seemed to do a decent job of

'light foot, good mileage, heavy foot, go fast'

I usually see low 20's in town/mixed with the 32.

but that's just my recollection...

fwiw,

t

[Tom_Columbus_OH]

Mike, compared to the vast experience on this board, I am a newbie at this, so please consider these remarks with a giant FWIW:

Our 72 had the original Solex, and ran ok, but just ok. It was difficult hot starting, idled rough and fast, and routinely fouled the plugs.

Mike Pugh (saving me some search time) sent me a copy of "the prescription," which I followed to the letter. I installed a 32/36 I bought new on Ebay, re-jetted precisely as indicated in the prescription, and plugged the secondary enrichment tube with epoxy.

Night and day difference: car starts readily and idles smoothly, plugs have a nice brown/gray color, no black tailpipe smoke, big grin ensues when I floor it.

Mileage this week during 800 miles of very spirited Virginia mountain driving was a touch over 26; I expect more during more rational driving stints.

Hope this helps, and thanks for your notes on the OEM air cleaner conversion, worked like a charm.

As always, YMMV

[nesky45]

Tom,

I have a 32/36 and would like to make the conversion to the OEM air cleaner. Could you send me the notes? cdhealy@comcast.net.

Thanks,

Craig

[esty]

Tom,

I have a 32/36 and would like to make the conversion to the OEM air cleaner. Could you send me the notes? cdhealy@comcast.net.

Thanks,

Craig

all that you need to run the original air cleaner is an adapter plate....advertise for one in "want to buy"

or cut out the base of the original cleaner to fit the weber

be careful the 1st time you start it...they have a tendency of bumping the hood and making a nice little dent