Carburetor Help

[lip277]

Not that I have a ton of history on my car (Tony's - Velocewest's)
But - In the couple of times I have taken it for extended drives - I obtained right at 20mpg - this is with the stock 4 speed and Zenith's.
I an only presume a 5sp OD transmission would improve it.

FWIW - I have put right at 2,000 miles on it (as of today) since I picked it up from Tony last October.

 

[CincinnatiE9]

Well today I decided I want this project done by NEXT summer. So if I can find the right donor car over the next couple months I will swap. I really only want to do it if I can find a sub $500 donor car. Don't want to spend months and thousands of dollars assembling a kit.

I am just used to Fieros where the Muncie 4speed gets like 17mpg and the getrag 282 gets like 29.

Is my Getrag 3.0 4speed worth anything? I have two, was considering selling the one and buying a 5speed.

jhjacobs, that shifter is sweet! My car does not have knob, so I may have to find a cool knob, it HAS to be solid wood.

 

[gwittman]

I have never had a problem getting 25 mpg on long trips running around 75 mph. That is with the JAM Engineering Weber setup and the stock 4 spd. I think even running at 80 to 90 mph I could still get 20 mpg. City driving is 16 to 17 mpg but I like to accelerate quickly.

 

[Honolulu]

The 4-speed has a 4th gear ratio of 1:1, thus direct drive.

The 5-speed OD trans final gear ratio is 0.81:1, or 19% taller.

The OD is essentially just tacked onto a 4-speed trans, using an extra casing at the rear of the trans. This makes them longer, and since no one else has mentioned it, you'll need a shorter driveshaft. The unit from a automatic trans will do just fine. Know that you should not take the two halves of the DS apart unless you can put them back together in the same orientation they were in. Balance....

Carl Nelson can likely supply an auto driveshaft.

Stock coupes need to be going at least 50 mph to make any use of fifth gear. Below that speed/rpm combination, the motor doesn't have the torque to use fifth. This will depend slightly on your differential ratio, of which several were available, and a 25% limited slip version too.

Depending on the driving you do, fifth gear may be a frequent occasion, or not. On days I drive my coupe to work, I use it once on my six mile commute, for about two minutes. But, I'd do it again, 'cuz it bragging rights... "I gotta five speed OD trans, woot"

Veneering, which originally started this thread, can be done at home if you're a handy guy. I'd use a vacuum bag process, but know that a vacuum cleaner will burn out if no air flows through it.

 

[Bill Riblett]

Looking at local u-pull-its inventory:

Bmw 3 series 1985
Bmw 3 series 1987 325
Bmw 5 series 1982 528e
Bmw 5 series 1991 525i
Bmw 7 series 1985 735i
Bmw 7 series 1989 735i

Any of those do it? I don't have the money as of present. Is a Getrag 4speed 3.0CS trans worth much? I have 2, wanted to sell one to fund the 5 speed swap.

The only one of these that might have a Getrag 265 5 speed is the 82 528e. You would have to convert the speedo drive parts on it and find a bellhousing/clutch cover for an M30 engine since it has an M20.

Do a search on 5 speed conversions.

Gas mileage? I have a highly modified 3.0 with triple sidedrafts, 5 speed overdrive and 3.45 diff and get 20-22 mpg on trips.

Best thing about the overdrive, at least for me, is the noise reduction at lower engine speeds.

 

[cdk2921]

Is that a German Wiredhaired Pointer in the background of the last photo?

 

[CincinnatiE9]

It's my buddies dog, Pepper. I can ask him if you'd like to know.

 

[CincinnatiE9]

That is the same Weber 32/36 DGAV setup that I have on my 3.0CS. It came from JAM Engineering. http://www.jameng.com $895.00 new. I probably have the installation manual.

Be really careful about adjusting the throttle linkage. It is easy to get it adjusted so that it will go overcenter and lock wide open. The secondary throttles are mechanical and require a really heavy push to get them open.

Could you look and see? I wouldn't mind a couple scans if its not a thousand pages.

 

[coupeking]

Notes on a couple of points brought up...

First, the carbs are indeed scruffy Webers. Maybe serviceable, and maybe not from the looks of things.

Second, 'back in the day', a lot of cars with Zeniths were switched to Webers because the Zeniths are a tricky carb to adjust and lots of mechanics didn't know their secrets. Primary secret is NOT to overtighten the vertical screw that goes at the very top of the carb and into the air cleaner assembly. Overtightening the nut holding the aircleaner in place can separate the middle layers ofthe carb and create internal air leaks which are difficult to trace. Much gnashing of teeth over bad running 'rebuilt' Zeniths, and a new set of Webers installed. Nice paycheck for the mechanic, cars ran well, all OK. For awhile.
Problem is that those 32/36 Webers--basically a non-rebuildable and throwaway carb, not nearly as good for performance or smoothness as the 32/40 Zeniths--are now all worn out and junk. And expensive to replace. Hence the interest in returning to the Zeniths, which are a much better mechanical device.

Thirdly, your 4 speed Getrag is worth a core charge at the local Pick Your part yard.

Lastly, the only car on your list that MAY have a tranny is the '82 528e.

Cheers-
Peter
[email protected]

 

[CincinnatiE9]

Well the condition of the carbs concerns me about what I may find when I pick up the engine from the same guy. The carbs on the motor in the car right now are newer rebuilds (between 1973 and the early 90s haha) so we'll see what kind they are.

Bavarian Auto Sport sells rebuild kits for the Zeniths and Webers, so we'll see.

If the Zeniths work better properly tuned, and people can help me properly tune them, then that may be the route to go.

I think I am pretty in over my head with the project as it is, I am not going to do the 5speed, just isn't worth it. Maybe when the car is running driving and perfect, but right now I have soooooo many other fish to fry.

 

[gwittman]

Peter, You may be right about the Weber vs Zenith carburetors but my Webers have been on my 2800CS for about 25 years without any problems. I noticed recently a coolant leak on the front carburetor choke system. I sealed it with some silicone and all seems well for now. I am curious as to why you say they are basically non-rebuildable and are considered a throw away carburetor. Surely there are rebuild kits for them. I don't feel the need to rebuild them but have considered it because of their age.

I may consider rebuilding the original Zeniths if they are truly a better carburetor. I felt the Zeniths vacuum secondaries opened later than they should for optimum performance. Is there a way to adjust this like changing a spring similar to what can be done with Holley carburetors? I have no objections to vacuum secondaries as long as they work effectively. What are the other tricks to adjusting the Zeniths?

 

[CincinnatiE9]

Is that a German Wiredhaired Pointer in the background of the last photo?

Pepper is a mutt, I said is he a "Ger...." at lunch and my friend finished my sentence with "...man wirehaired pointer, no, but everyone thinks he is and he looks damn close."

I'll try to get some pics of the carbs on the car today if I can get over there.

 

[nashvillecat]

Peter, You may be right about the Weber vs Zenith carburetors but my Webers have been on my 2800CS for about 25 years without any problems. I noticed recently a coolant leak on the front carburetor choke system. I sealed it with some silicone and all seems well for now. I am curious as to why you say they are basically non-rebuildable and are considered a throw away carburetor. Surely there are rebuild kits for them. I don't feel the need to rebuild them but have considered it because of their age.

I may consider rebuilding the original Zeniths if they are truly a better carburetor. I felt the Zeniths vacuum secondaries opened later than they should for optimum performance. Is there a way to adjust this like changing a spring similar to what can be done with Holley carburetors? I have no objections to vacuum secondaries as long as they work effectively. What are the other tricks to adjusting the Zeniths?

In practice and on paper, the size of the Zeniths may make them the better choice on a bone stock 3L M10. But availability and cost can alter that equation on any given day. One might ask why BMW selected that carb in the first place and whether, if given the choice (unfettered by costs emissions or fuel economy issues) it would select the same carb today on the same car. Considering a few of the E9's younger siblings (e.g., 1976 E24) even used a 4bbl (Solex 4A1), the answer is not particularly clear.

Corrosion and resultant water leaks are not uncommon and do not necessarily make carburettors "non-rebuildable" any more than cylinder heads, water cooled manifolds, thermostat housings, radiators and heater cores. In my experience, the weak point of the commonly used Weber downdrafts is throttle shaft wear. The fixes have been to replace the carb body, re-bush the carb body, OR install a bushing repair kit. http://www.pegasusautoracing.com/productdetails.asp?RecID=5949.

 

[bill]

linkage

Can Mr. Jacobs be more specific about "Weber linkage?" Only thing different from the Zenith linkage I use with my Webers is the straight shaft between the carbs. Seems to work OK, but it is very hard to open the secondaries, and it is even harder to go over center just by pushing the pedal...

 

[nashvillecat]

Re: linkage

Can Mr. Jacobs be more specific about "Weber linkage?" Only thing different from the Zenith linkage I use with my Webers is the straight shaft between the carbs. Seems to work OK, but it is very hard to open the secondaries, and it is even harder to go over center just by pushing the pedal...

Maybe this will help.

From: http://www.jameng.com/products/index.phtml?section=2

 

[jhjacobs]

Can Mr. Jacobs be more specific about "Weber linkage?" Seems to work OK, but it is very hard to open the secondaries, and it is even harder to go over center just by pushing the pedal...

I am hardly an expert on this, or much of anything else for that matter, but I know that the linkages on my Webers (removed) were not compatible with my Zeniths. In the photo below, the straight linkage was used with my Webers and the bent linkage is from a set of Zeniths. Perhaps the Weber linkage I had was incorrect - it would open the secondaries and then keep going so that it would lock in the open position - a great way to test the rev limited rotor!

The distance between the carb link points is not the same and more importantly, the carb throttle lifting arm is much longer for the Webers.

 

[jhjacobs]

Note: I have no use for my old Weber linkage or Webers for that matter. I think I even have a second set of parts Webers, maybe a pair of rebuild kits, and even a Weber repair manual... PM if interested.