Carbs!

[1602bmw]

Not the food type, the fuel type!

 

Recently bought a 1973 1602, and thinking about modding it sympathetically. Can you recommend a nice carb upgrade for some extra oomph? I

Edited August 17, 2020 by Chris Brewerton

[AustrianVespaGuy]

Sorta depends on what 'other' work/mods you plan to do with it, but I'd suggest if it has a stock carb then the first step you'd want to take is changing to a Weber 32/36 for a bolt-on upgrade to a stock car.  There's plenty *more* options out there, but really you'd want to couple them with *other* things as well, so either start there or let us know your budget!

[1602bmw]

Grüß gott  AustrianVespaGuy 

 

Not many changes otherwise, unless otherwise recommended. The Weber upgrade sounds good, and it would be nice to couple any upgrades that compliment each other. I'm not sure on budget, as I don't know what upgrades cost. Happy to spend around £1k I guess...

[Hans]

Keeping in mind that there's only so much oomph in a 1600. How about a Pertronix ignition, the carb, new plugs and wires, and go for a drive. After that I'd focus on good tires and maybe larger wheels to improve handling, not power.

[AustrianVespaGuy]

Ha, du auch Chris, servus!  And I would agree with Hans that ignition, tires, and then suspension are probably the next areas of attention.  With ignition, in today's world if you have any qualms about the condition of your distributor, I'd even suggest going straight for a 123Ignition setup over the traditional pertronix/crane/etc. if your budget allows.  Allows you to tune the spark curve to really make the most of what your little engine can offer, plus they're a Dutch company, which I consider a good thing.

https://123ignition.com/products/?filter_brand=bmw&filter_cylinders=4&query_type_cylinders=or

On the more budget end, just new points, condenser, and proper timing with a timing light would still be a great start!

But yeah, a properly jetted 32/36 and good spark will get you a LOOONG ways on stock motor internals, so I'd start there for the powertrain!

[Slavs]

I've tried various carbs on my stock 1600, but the stock Solex 38PDSI in good working condition works best. The original Solex is a great carb, but it eventually wears out; the throttle shaft wears out the housing resulting in an air leak and a carb which cannot be properly adjusted and set. The throttle shaft assembly was at one time available from BMW and aftermarket manufacturers, but it's been a long time since I've seen one. A competent carb / machine shop can install bushings. There are other parts that wear out such as the vaccuum plunger in the lid which eventually works its way through the lid resulting in a hole in the carb cover lid. There are plenty of lids out there and used carbs to scavenge. And, the rods wear out, but they are available from a parts supplier in Italy.

 

The Weber 34ICH replacement for the original Solex is too small resulting in a very noticeable drop in power. But, it is advertised as a replacement carb by many parts vendors. Stay away from this thing which is better suited for a 1,100cc - 1,300cc motor.

 

The Weber 32/36 is not a good fit either. There are few properly fitting manifolds that mate to the smaller ports on the 1600. The only manifold which properly fits is the BMW 316 e21 manifold which was never imported to the US. I obtained one from Australia. When I installed the 32/36 out of the box my car just fell flat on its face and bogged because it was too lean. I had to increase the size of the main fuel jets and decrease the size of the air correction jets to get rid of the stumbling. In other words I had to enrich the fuel air mixture. But, I believe I was running a little too rich. The car ran smoothly and had more "Umph" at full throttle, but The Single barrel Solex yielded more torque at the bottom. Furthermore, my mileage sank from 22mpg in the city to 17mpg city with the 32/36. I just eventually removed it in favor of the stock set-up. If I had more carb parts to play with such as smaller chokes for the 32/36, I may have tried installing them as I believe they would have helped.

 

You will notice a slight improvement in torque and performance if you install the pre-smog exhaust manifold as used on the US 66-67 1600s and most Euro spec 1600s. I highly rccommed this.

 

The Weber DCOE 40 carbs properly jetted for the stock motor work well, but you will need to spend a lot of $$ on jets and order small chokes or venturis (27mm) for the carbs. The mileage is awful with these things.

 

And then there is the twin Solex 40PHH set-up from the 1600Ti. It works, but the 1600Ti specific carbs are rare. The ones used on the 2002ti differ in jetting and venturi / choke size. You got to have some good resources and be prepared to spend some $$, if you go this route. In most cases these carbs need to be rebuilt.

 

A tight suspension with a properly tuned and stock 1600cc works best for these cars.

 

Slavs

 

 

Edited August 18, 2020 by Slavs

[uai]

a 2 liter engine would be my choice....

[TobyB]

Quote

The Weber 34ICH replacement for the original Solex is too small resulting in a very noticeable drop in power. But, it is advertised as a replacement carb by many parts vendors. Stay away from this thing which is better suited for a 1,100cc - 1,300cc motor.

 

It works great on my dad's combine.  I wouldn't put it on a CAR.  I have 2 now- I was thinking about making a manifold to 

put duallys onto an M10.  And SU's, since I have a pair of those, too.  And...  well, you get the idea.

 

There are smaller 2- bbl Webers that are usually put on 1600 VW's-  28/32?  

 

There was also a 1600 ti- I had a pair of those manifolds at one point, but sold them on to another 1600er.  Very noticeably

different ports, the 1600 head.  

 

Good luck (and I don't disagree with uai, either)

 

t

 

 

 

[1602bmw]

Gosh, lots of info there guys, many thanks! 

 

Sorry, going to rule out the 2 litre engine - sounds like a too 'easy' and sensible an option ?

 

Need to get my head around your feedback and spend some time on Google checking out parts over the next few days ?

 

 

[Slavs]

On 8/18/2020 at 1:29 PM, uai said:

a 2 liter engine would be my choice....

That's what happened to many 1600s. But, if you install a 2 liter motor you got to also replace the 4.11 diff with a 3.64, otherwise you will end up with a car that is less comfortable at highway speeds than the 1600 whose short stroke is much better able to cope with high rpms. The alternative to the diff swap would be to leave the 4.11 in place and install a 5 speed overdrive from a 320i. It's really a must with the 2 liter and 4.11 combination and a highway speed improvement for an otherwise stock 1600. All of this is expensive, though. And, with the bigger motor, the smaller 1600 drum brakes should be swapped for the larger 2002 drums. It's a snowball chain reaction.

 

With you existing block you can build either of these two motors:

 

You could build an 1800 or 1800 ti by maintaining the existing 84mm bore and using 9.5 :1 high compression 1800ti pistons and a crank from the 2002. In this scenario you would leave the 118 head from the 1600 along with your flywheel, pressure plate and clutch disk (The 1800ti shared the same valves as the 1600, interchangeable head with 1600, same clutch and flywheel as 1600). You can also use your existing connecting rods. Make sure your flywheel bolt pattern mates to the crank. Post 69 2002s and 1600s have an 8 bolt flywheel vs. the earlier 6 bolt. To take advantage of the increased compression a set of Weber DCOE 40 or stock 1800ti Solex PHH 40 side drafts would do the trick. I'm sure the 32/36 would also work well. The 1800ti is good for 124hp SAE or 110bhp.

 

Another scenario would be to get a hold of 1600ti 9.5:1 high compression pistons. And, like the 1800ti, you would need the Weber DCOE 40 side drafts or Solex PHH 40 sidedrafts as used on the stock 1600ti. Lacking side drafts a 32/36 would probably be a cheaper alternative. The 1600ti is good for 118hp SAE or 105hp bhp.

[alexis]

not me, I am not mechanical guy, but just want to share with 2002 fans that my original 5 speed and dual solex carbs, adjusted every 18 months of course, is incredible, it is worth, as a driving classic car......

[alexis]

Thank you, by the way, I am from Uruguay, only country made a deal with BMW to build 500 2002 in 1970. We have a great 2002 fan club. Sometimes we go out in 2002 events and we are 60-80 cars, 2002 of course. Thank you guys.

 

[alexis]

And there are still several excellent mechanic people that work on these solex as well as weber...their routine I should say.....

[alexis]