Temporary Weber 32/36 Conversion, Fuel Pump Questions...

[jakub421]

Hi!
With the quarantine in full effect and lots of weekend time on my hands, I'm looking to convert my K-Jet '78 320i to a Weber 32/36.
My K-Jet is tuned well and running well right now, but I would like to experiment with the carb just for fun and I do plan on converting back to K-Jet some time in the future (before next required CA smog test ).

Already have the correct intake manifold and ready to order the carburetor, but I wasn't able to find a clear explanation for the conversion of the fuel delivery system.
I recently replaced all of the stock K-jet fuel / vent hoses, so there are no leaks in the back.

I read that the recommended fuel pump is the Carter P4070, but what does the hook up for it look like?
Would it just go straight from the outlet of the fuel gauge that is already in the tank -> fuel pump -> fuel filter -> carburetor? What about the current fuel tank return hose?

If someone could lay out a basis schematic for the new fuel system with the 32/36, that would be great!
Thanks alot!

[WantingAfunE21]

I did a similar conversion to a 38/38 on my 77. I removed the internal and external pumps an ran only the carter. I mounted it it the side of the spare tire carrier. Make sure you flush all the fuel from the K-jet stuff after removal or it will turn to varnish and not work properly when you reinstall it.

[jakub421]

It does not have an internal fuel pump, RealOEM P/N 16121114255 calls it out as just a sending unit assembly.
Would I just be able to then hook up the pump to the outlet of the fuel sender so that I don't have to cut holes in the tank?
At that point all I would have to do is run the hose to the carb, make a throttle bracket, and it should be good to go

What driveability differences did you notice with the carb vs original K-jet?

[autox320]

It does not have an internal fuel pump, RealOEM P/N 16121114255 calls it out as just a sending unit assembly.
Would I just be able to then hook up the pump to the outlet of the fuel sender so that I don't have to cut holes in the tank?
At that point all I would have to do is run the hose to the carb, make a throttle bracket, and it should be good to go

What driveability differences did you notice with the carb vs original K-jet?

Using the factory return line is the easy way. Can plug the larger 12mm line fitting just cap it off. Pump from the 5/16 hookup on return tube to tank, filter inline before and pump, line to engine. Yes dead head system and no regulator using a p4070. This is recommended by many even at racetep how they say to do it.

That's it in a nut shell. Carter P4070 user here. Difference? I think a well tuned jetted carb wakes the motor up and can have just as good driveability gas mileage as kjet if using a 32/36 especially. 38 is more for a modded motor with cam and at that point nobody looks at fuel consumption

FYI I don't really like the carter pump knurled post wire hookup. I have a ziptie the goes around the pump to keep the wires seated on the post. Then again our car isn't stock and gets a beating. Had wires pop off and cause running symptoms until noticed one of the pumps(using a dual carter setup with surge tank) wasn't working due to simple contact issue of these wires. Simple fix is zip tie. Long term would be to run a die over the post for a 1/4-20 nut which I feel would be better for track setups.

There's plenty of carb jetting guides on racetep's and redlines websites. Biggest thing is set the factory float level. It's the main thing to make any other jetting or tuning work properly the float must be correct and exact.

[jakub421]

Thanks alot! I was looking at the Redline Weber kit K 8205 that they make for the 2002.
It looks like it's already jetted specifically for the M10 engine, so that seems like the easiest route, just bolt on and do some minor tweaking.

[jakub421]

UPDATE

Carb conversion went great, everything bolted up, fuel pump and necessary fuel lines hooked up no problem. Got it tuned up based on reccomendations from the 2002 forums and runs beautifully

BUT

I did not mess with the timing yet. Right now, I have the dynamic timing set at 2200 with the Z ball showing (25 BTDC).

I was reading on the 2002 forum that they time it to 1500 with the Z ball showing.
Any experience with timing adjustments after switching to a carburetor?
Thanks!

[autox320]

UPDATE

Carb conversion went great, everything bolted up, fuel pump and necessary fuel lines hooked up no problem. Got it tuned up based on reccomendations from the 2002 forums and runs beautifully

BUT

I did not mess with the timing yet. Right now, I have the dynamic timing set at 2200 with the Z ball showing (25 BTDC).

I was reading on the 2002 forum that they time it to 1500 with the Z ball showing.
Any experience with timing adjustments after switching to a carburetor?
Thanks!

Not sure can help on street car setup but remember the Z showing earlier is advanced faster timing. As in the advance is "all in" earlier. If can get away with it using pump fuel yup I'd try it for more zip.

example
Our race setup uses the aftermarket Tii mechanical distributor. Initial timing is 14deg @1050rpm idle, and all in full advance of 36deg @2200rpm.

If to advanced too early you'll notice things like the motor will fail to rev fast to redline. Sometimes it just won't reach redline at all. Also if too advanced it will tend to have bucking under load at slow speeds. A vacuum distributor should help keep bucking to a minimum low speed and cruise due to pulling timing.