TheSamba.com :: View topic

Sat Nov 20, 2004 1:06 pm

It all started when I realized that I wasn't getting very good gas mileage: around 15mpg in my newly acquired 1973 Super Vert with a stock 1600DP. The guy I bought it from had rebuilt some things on the engine (new heads and valves, but didn't split the case).

First, I think it's running too rich. The inside of the tailpipes are black, and the plugs are pretty dark. So I changed the oil, checked the valves (they were perfect), and went to try to time it, which I've never done before.

The distributor is of the 2-hose variety, so apparently it wants to be at 5*ATDC. Now, I have a simple stroboscopic timing light (but no tachometer anywhere), but I am a little confused with these terms: ADVANCED, RETARDED, BEFORE, AFTER. What means what? When I hook up the timing light, at idle, which side of the split in the case should the TDC notch fall? I have the original pulley with no numbering, just the TDC notch. Also, will that notch be accurate forever, or might it be off right now?

I don't know if the timing is off anyway, because it runs really well, it just seems like it's getting pretty hot after 30 minutes of 55mph (although I don't know because there's no temp guage). After it gets hot, and I drive it up a long steep hill, it starts to make an intermittant thumping sound. It's very irregular and sporatic. Is that what a ping is? Should I "retard" the timing? Is that turning the dizzy clockwise or counter?

Anyway, once I get the timing sorted, how should I adjust the carb to lean it out? Don't the idle speed and volume screws meter the gas only at idle? And what about that screw on the throttle cam? Please help. I've been reading and reading on the topic, and only managed to confuse myself. I really need better gas mileage, as it's $2.79 /gallon for the good stuff here in Hawaii. Plus, I want my engine to run right and last long.

Sat Nov 20, 2004 1:53 pm

That "thumping" sound means the timeing is was off, and if it's getting real hot when it's runnign that means your running "advanced" this also wastes gas like a mofo. Basicly you have the notch in the case, and the notch in the pully, the notch in the pully when lined up with the notch in the case is the 5 advanced, not TDC. Advanced is when the spark is firing before the piston hits TDC and retarded is when the spark is firing adfter TDC.

Assuming you know how to use a timing light, it should all work out if you time it notch to notch. Refer to an old post of mine.

http://www.thesamba.com/vw/forum/viewtopic.php?t=82855&highlight=timing

Sat Nov 20, 2004 6:50 pm

Well, I timed it notch to crack in case and it seems to run a little better. How can you lean out the carb, though? Also, what is the best procedure for tuning the carb to its optimum performance?

Sun Nov 21, 2004 5:27 am

Well this is what you are supposed to have...

Bookmark www.type2.com lots of good reading over there which is where I got this stuff.

Beetle 1972-1973 * 1600 Manual Trans

Distributor: VW 113-905-205AN, Bosch 0231 167 070 > 043-905-205C, 0231 176 028
Can Use: VW 113-905-205AJ, Bosch 0231 167 049
Points: 01 011
Points Replacement Plate Assy: VW 311-905-227C, Bosch 1237 110 161
Condensor: 02 054
Rotor: 04 033
Dust Cover: 039-905-241, Bosch 1230 500 139 > 1230 500 147
Cap: 03 010
Distributor Cap Clip: 034-905-265, Bosch 1231 251 033
Parts Kit (Shims, Washers & Hardware): 059-998-211, Bosch 1237 010 007
Coil: 00 015 (Blue Coil: 00 012)
Vacuum Can: 07 102
Ignition Wires: 09 001
Spark Plug: W8AC
Timing Set At:: 5deg ATDC @ 800-950rpm w/strobe, vacuum hose(s) connected
Advance/Retard Range: Vacuum: 5-8deg Adv, 11-13deg Ret; Centrifugal: 6-12deg @ 1500rpm, 22-25deg @ 3800rpm

Here is something to read about the hoses..

Distributor Vacuum Hoses - Where Do They Go?
by Jim Thompson
--------------------------------------------------------------------------------

Over the years, many a 71-74 Beetle and 71 Bus with Dual Diaphragm Distributors have graced my doors and about half the time the vacuum lines are backwards. So here's the poop:

First, take a look at your Vacuum can. On the flat side of the can is a hose fitting - for the larger (4.5mm GREEN) hose. This is the RETARD side.

Second, on the cone (or rounded) side of the can is the smaller hose fitting. This uses a 3.5mm hose, usually black. This is the ADVANCE side.

Third, look at your 34PICT Carburetor. The fitting on the LEFT side of the carb is for the ADVANCE side of your Vaccum can. Connect appropriately.

Fourth, look at your 34PICT Carb again. On the rear (RIR) of the carb should be a fitting up towards, but not on the carburetor top. This push-on fitting is just slightly larger than then one on the side. This is for your RETARD side of your Vacuum can. Connect appropriately with the 4.5mm Green Hose.

Fifth, Any other fittings on your 34PICT Carb are for the infamous Throttle Positioner sometimes improperly called a "Decel Valve". The fitting for this jewel is an angled one right at the rear base of the carburetor. Connect the small vacuum hose to it to the Throttle Positioner Diaphragm Fitting. If your Throttle Positioner has two fittings (as original on 71 Buses, 71-74 Beetles), connect another length of 3.5mm vacuum hose from that to the Throttle Positioner Solenoid, usually located in the left side of the engine compartment. If you don't have the Throttle Positioner, cap off all the remaining fittings on your carburetor.

If you're running one of those new replacement H30/31PICT carbs, the procedure above is the same as they come with these fittings like their distant 34PICT cousins. Original 30PICT Series did not have the RETARD fitting, except for Beetle Auto-Suck Models - BUT - this fitting was for the Auto-Suck Solenoid, not the distributor because they were still single vacuum models (Actually, the Auto-Suck use a combined vacuum/mechanical distributor similar to the 76-78 Buses). Buses don't have these, right? So use this fitting for your RETARD side of the Dual Diaphragm Can.

Timing is usually 5 degrees AFTER Top Dead Center when using a Dual Diaphragm Distributor, give or take a degree or two - no two engine setups or running conditions are the same, so you''' have to fool with with of course. One other thing - Strobe Light at idle speed with the hoses CONNECTED. Sorry, no static timing with these, except to initially set the distributor at 0 TDC, start the engine, then strobiscopically time it after it warms up.

For those wanting to put a stock push-pull distributor back on their 71 Dual Port 1600 with a 34PICT (or other Bus with the same arrangement, here's the skinny on interchangeable distributors. All have the same Advance/Retard Curve specifications:

Vacuum: 2-5deg Adv @ 6.7 In. Hg, 11-13deg Ret @ 9.1 In. Hg
Centrifugal Advance: 6-12deg @ 1500rpm, 22-25deg @3800rpm

Distributors:

211-905-205Q * 0231 167 055 (Stock T2 '71)
211-905-205S * 0231 173 001 (Stock T2 '71)
Note: Originally equipped w/Speed Limiting Rotor, but can use a regular 04 033 Bosch Rotor)
113-905-205AH * 0231 167 053 (Beetle Auto-Suck 71-73)
043-905-205D * 0231 176 033 (Beetle Auto-Suck Calif. 1974)

About carb tuning....

34 Pict 3 Carburetor Tuning
by Barb and Eric
--------------------------------------------------------------------------------

Prerequistes:

Spark plugs serviceable
Engine adjusted and tuned
Dwell and timing adjusted

Connect tachometer and oil temp gauge and start engine.
Check oil temp is between 122 -158 F ,and shut down engine.
Check that choke is open fully.
Disconnect the accelerator cable from the carb.
Turn idle screw out until it is no longer touching fast idle cam.
Turn idle screw in till it just touches fast idle cam.
Carefully turn volume control screw in till it stops, then turn out 2 1/2 To 3 turns.
Start engine, make sure that choke is open again and reinstall air cleaner.
Set idle speed at 900RPM by the bypass screw.
Turn out volume screw to highest idle speed and then turn back in till RPM drops by 20-30 RPM.
Turn the bypass screw till the idle is correct at 750-900RPM.
Reconnect the accelerator cable.

And me again..

Also of note is the fact that this distributor is a vacuum retard and advance running off a 2 way vacuum can. With it timed correctly at 5* ATDC, and with your timing light still connected, pull off the retard hose and plug it with a golf tee and the timing should advance to about 7.5* BTDC. If it doesn't, it is possible that the vacuum can is leaking vacuum and the can might need to be replaced. That is a good distributor though and would be worth the money to make it work right.

Reconnect the retard hose and you should be OK.