Thoughts on Weber 38/38

[Slavs]

I guess it's all relative. What's considered lousy by some of us is great for others. I briefly had a motor built by one of the BMW tuners, and I thought it was junk. With barely 10K miles it was drinking oil, running with a lumpy idle and getting terrible mileage. It had oversize JE forged pistons in the 10.0 / 1 compression range, a reground 292 or something to that extent cam, header and free flow exhaust. It also had a "properly" jetted 38/38 carb. There was nothing fun about this motor as the driveability suffered along with the mileage which was in the 15mpg range. I tried using the 38/38 on a stock motor, where it fared even worse. My conclusion is that the stock motors, including the stock "Ti" and "Tii" motors with the standard 264degree stock cam are much more flexible compared to the higher performance builds. Different strokes for different folks, but that is my assessment based on using the 02 as daily transportation since 1982. The last thing I want is a "Hot" motor with a narrow power band, and that is what you get with high performance builds and long duration cams. Maybe some of you have had better luck, but I've relegated both of my 38/38 carbs to the parts bin. I think the Weber DCOE sidedraft carbs work better with the stock motor, if properly set-up. But, in addition to the carbs, be prepared to spend an additional $500 on jets, venturis and other tuning items to make them work right. Synching the carbs is an art in itself. And, your mileage will really suffer. All of my high performance stuff is sitting in boxes. It just isn't practical for the street. There are people here on the FAQ who claim they get great mileage with all the high performance mods. But, I simply don't believe it.

['76mintgrün'02]

2 minutes ago, Slavs said:

I guess it's all relative. What's considered lousy by some of us is great for others.

 

So true.

 

38-38 vs 32-36

 

Pertronix vs Points

 

Electric fuel pump vs Mechanical

 

Around and around we go.

 

[ray_]

17 minutes ago, '76mintgrün'02 said:

 

So true.

 

38-38 vs 32-36

 

Pertronix vs Points

 

Electric fuel pump vs Mechanical

 

Around and around we go.

 

Two cams vs. one.

 

?

[Simeon]

1 hour ago, ray_ said:

Two cams vs. one.

 

?

 

Aren’t we all agreed on that one?

[VWJake]

15 hours ago, rstclark said:

Ray  Since very few of us drive for MPG or even check it  MPG is basically insignificant  Shoot me if I ever start clogging up the roadway like some Prius driver  ( notice the next time you are on the freeway and somebody is doing 62 MPH in the car pool lane. the odds are its a Prius  but I digress. 

The difference from driving with a 32/36   and starving on the 32 single barrel and driving with a 38/38 synchronized is the low end torque is substantially greater  The car feels like it has a lot more power in normal street driving range.  The 38/38 is a lot of carburetor and can be jetted down especially for a stock motor  I run one on a mild build motor and have run one on a 150 hp build. In each case  I have jetted it smaller and they start well and run smooth.

If anyone is interested I will dig out the jetting sizes  and post them here. 

 

I for one would be interested in hearing your take on jetting. 

-Jake

['76mintgrün'02]

3 hours ago, VWJake said:

I for one would be interested in hearing your take on jetting. 

-Jake

 

I would too... along with the AFR #s, please.

 

(MPG is significant to me)

 

11 hours ago, ray_ said:

Two cams vs. one.

 

How about :

 

Poly vs Rubber

 

5 speed vs 4 speed

 

LED vs Halogen

 

15s vs 13s

 

123 vs Weights and Springs

 

 

The  weights and the springs go round and round...

 

 

[AustrianVespaGuy]

We're starting to get close but I don't think anyone's quite nailed it yet: truly there is no 'wrong' answer and what's best for you is mostly driven by taste.  With the stock bunch o' bananas manifold (hogged out or not), the 32/36 and 38/38 both flow plenty for a stock motor, and both make equal peak torque and HP, but the pedal response is much different.  It's just like the 'comfort' vs. 'sport' mapping on modern drive by wire cars: you need to put your foot further down with the progressive carb than you do with the synced barrels to get the same throttle opening area.  Most people prefer getting to the sweet spot with less throttle input, so the 38er is probably more popular for that reason.  However if you do a lot of around town driving, the gentler tip-in of the 32/36 can mean smoother starts, and the greater mid-range throttle resolution is great for cruising and efficiency.

Once you step up cams and headers somewhat, I think the 38/38 will start to flow a little more peak power, but only like at 6000+ RPM. And frankly, in my opinion anyway, if you're doing that type of head work already it's well worth considering single or dual sidedrafts or fuel injection at that point.

Lastly the 'points' (haha) about properly dialing in the ignition and jetting are correct in that these items make a significantly larger difference in how the car runs compared to which of the two carbs are installed.

All this to say, set stuff up right and then there isn't a wrong choice, just go with what's available and you think suits your personality better.  From the original post, it sounds like you WANT a 38/38, which is just great, go for it!  But don't do it as a quest for something appreciably better than the 32/36, because that's not really what it is.

[rstclark]

Here my jetting for a Motor with 9.5 compression 292 cam header and 123 distributor 

Also used for the same setup with 284 cam

Mains 135

Air 180

Idle 50

E tubes F66

 

No AFR   Just butt dyno It appears to run rich. Tailpipe is black   But as they say “a fat motor is a happy motor

['76mintgrün'02]

2 minutes ago, rstclark said:

No AFR   Just butt dyno It appears to run rich. Tailpipe is black   But as they say “a fat motor is a happy motor

 

...until the oil starts smelling like gasoline.

 

Is your timing set-by-ear?   

 

 

[rstclark]

Should add that this setting leans the carb from stock carb jetting

Timing is set at about 6 degrees and the rest is done by the curves set in the 123 tune distributor  Basically the Tii mechanical curve with some vacuum advance The 123 makes a dramatic improvement but that’s an entirely different subject A search will reveal several pages of posts

['76mintgrün'02]

41 minutes ago, rstclark said:

that’s an entirely different subject

 

yes, and a shitty question on my part.

 

I apologize.

Tom

[rstclark]

Not really Tom

you raise two good points 

Being casual or sloppy about carb settings and timing can have disastrous results and I admit I’m being a little casual about running a little rich

An AFR is great tool to have especially to tune a Tii 

Someday I’ll probably get one and then I can really tune the car

A good deal of credit for the car running so well goes to the 123 distributor  It is probably why the car runs so smoothly 

Some people play with 38/38s and are never happy With 123 on place the 38/38 ran fine from day one

 

Thank you BTW for your contributions to the board