Tuning Delimma

[Bob Slayden]

I'm preparing my '62 roadster for the Mountain Mille in October.
I am having serious difficulty establishing a stable hot idle. In all other respects the car runs superbly. Pulls strong all the way to 5,500+. No detonation, can cruise at 75-80 mph, not overheating.
Engine is 912 with 6 VOLT system
big bore kit,
mild to moderate cam possibly 912 but not sure.
Solid shaft Solexes rebuilt by Bieker years (but only a few thousand miles ago.) Floats set with P78 to 2 mm below original low line
New Bosch WR7BP plugs gapped @ .0025"
6V Coil with 2.5 ohm internal resistance (also tried new high energy coil also 2.5 ohm, no change)
123\VW (no vacuum) distributor installed in 2013 set to max advance of 28'. Idle advance is hard to read hot but warm I can get engine to idle at 700-800 rpms. The idle advance varies from a few degrees BTDC to a few degrees ATDC depending on curve selected once max advance set to 28'. Any more advance over 30' gives a little detonation in 4th gear pulling a hill.

The problem occurs hot regardless of which distributor curve setting I use (C,D or E) each timed to max of 28'. Engine will start and idle well when warm but hot it will idle for a short while at 1250 to 1500 and then when it drops off the last bit of advance it idles down until engine dies at 350-450 rpm or so.

Before I lowered the floats (last night) engine would be very, very difficult to restart when at full temp (middle of gauge.) Car will now can restart hot with considerably less cranking.

I am convinced that the engine doesn't like to settle down to a normal idle hot. Fuel or timing??? Do I dare lower the floats any more? Any other ideas?

[Ron LaDow]

Not sure what you mean "warm" vs "hot", but things move around on aircooled engines with temp rises. You might try popping the down-links off the throttle levers to see if there's any sort of heat-related changes in the linkage and/or carb 'location'.

[Bob Slayden]

Warm = start run 10 mins to warm up. Temp gauge just off dead cold.
Hot drive 15 miles @ 75-80 mph temp gauge to mid range.
Tried wit down links off, still stalls out when "hot". No amount of balancing carbs stops rapid slow down to dying. if throttle speed screws set to hold idle has to run above 1250-1500 depending on Dist curve.

[David Jones]

28 degrees at full advance sounds retarded to me and retarded timing will cause an engine to run hot. I have a very similar engine set up but I may have less CR than you as I am able to run 35 degrees of max advance and 87 octane with no detonation. I also run my plugs at 35 thou but I am also running a Permatune.
What is the actual oil temp. Use an IR gun at the temp sensor or on the sump. The gauges are really only an indication unless you have had it calibrated. My "A" runs in the middle of the heavy green portion on the left of the gauge and the oil is at 170 *F after a run using 5K rpm in 3rd and 3500 in 4th on some very twisty roads over 30 miles.

[Ron LaDow]

Agreed with David that 28* all in is a VERY small lead for a single plug.
But at this stage, I'm gonna wear out my welcome and suggest a full, in-sequence tune. You may have a couple of issues causing the problem.

[Dick Weiss]

Bob,

I'm unfamilier w/a VW123 distributor--having a proper -022 (or -BR 18) w/it's proper advance, the idle should return to 800/900 RPM when the carbs are tuned after the engine is warmed up to running temperature.

Proper balancing is definately required @ 2800/3000 RPM, then the idle. (You may do this more than once)
The float levels should be @ the low line on the gage, the injections aimed, and squirts around .50cc/2-strokes for all-around driving; no need to get .65cc unless you drive in cold weather? The Bosch platinum plug are OK, but not @ .0028".
Pump output shouldn't exceed 2.8 PSI (you'll need an accurate low-reading gage if possible).

Finally, make sure the carbs are not held open by not having a slight amount of 'slack' @ idle--the engine and trans. will expand which tend to hold them open and not touching the idle stop screws! Same thing w/the clutch adjustment.

Dick

[DonCichocki]

Bob,
What advance curve are you running with the 123 distributor? I have a '65C with a 1720 kit, 8.5 CR, the rest is stock, so probably close to yours. I'm using the "D" curve on the VW123 distributor with max advance set at 34 degrees. Runs great and when warm always returns to idle at 800/900 rpm. Rather than spending the money on rebuilding the Bosch 022 I decided to try the 123 and am very happy with it as my car is a driver.
My $.02 would be something in the carb settings or linkage.

[Bruce Smith]

It sounds like your distributor advance is on the rise at or near idle. The BR18/022 begin to advance at about 450RPM at the distributor (900RPM at the crank). Regardless of your static, if mechanical advance occurs in your idle range, you're on the slope of the curve and idle can become unsteady. The 031 was designed for an advance onset above 500RPM (1000RPM at the crank), which eliminates this problem. This might be your problem if your 123 is advancing too early. Changing static won't fix it. Curve selection might or your distributor may need to be serviced.

- Bruce

[Wes Bender]

For clarity, edit your spark plug gap to read .025" instead of .0025".

Wes

[David Jones]

The drivers manual calls for a plug gap of between 20 and 28 thou depending on make and range of spark plug. That of course was in the 50's and 60's when we had leaded fuel which was less volatile and much more variable in quality. I think plug technology as also changed a lot. I have used a minimum of 28 thou on VW's and 356 engines for decades. What advantage is there for a smaller gap as I have never had an issue with the larger gaps? The factory manual also calls for spark plugs to be changed every 10K miles. I think on our engines 50K miles may be more realistic because of being carburetor equipped. Platinum plugs apparently go for as much as 100K miles. This applies only to stock Kettering type points ignitions. I use bigger gaps with the Permatune modified ignition.

[Dave Wildrick]

Bob,
Here's what worked for me on my 64C with Weber IDF40s, AA big bore kit, and stock C cam.

With the 123 set at TDC on #1, set the curve on the 123 VW/R to "D".

Adjust the static timing to 5 degrees before TDC, which means the light comes on at about 1/4 inch to the right of the TDC mark on the crank pulley as it is turned clockwise.

When you rotate the distributor to get the green light to shine through a window in the plate beneath the rotor, try to only rotate the distributor body counterclockwise. If you go clockwise, you will have the light shining through an incorrect hole in the plate, and the car may not start.

On my car, when I did the above and checked with an Innova Equus digital timing light, I saw 9 degrees advance at idle (even though static was 5 degrees), and I saw 35 degrees max advance at 3000 rpm and beyond.

[Neil Bardsley]

The correct setting for the Porsche 123 is now 5. The setting for the older VW 123 was D so just be careful to check which one you have before setting.

http://www.123ignition.nl/pdf/123SWITCH4.pdf

I think this because when I got my 123, it was a Porsche unit, I set it up correctly but they garage that did a topend build for me assumed I had got it wrong so changed to D!

[Bruce Smith]

I saw 9 degrees advance at idle (even though static was 5 degrees), and I saw 35 degrees max advance at 3000 rpm and beyond.

Dave - This is interesting. If you have what looks like 4° additional advance at idle, it's either climbing pretty fast or there's additional built-in static in the 123 advance curve. If it is climbing, small changes in idle speed will be joined with changes in advance making it that much more unstable. Do you know what the curve is?

- Bruce

[Neil Bardsley]

It claims to be a 022 curve but it also claims that they advance starts at 1600 (crank speed?) which isn't my understanding of a 022 curve.


D 1600 3100 / 30,0 100 300/9,0 0231.129.022 JFR4[R] Porsche 912

[Dave Wildrick]

The correct setting for the Porsche 123 is now 5. The setting for the older VW 123 was D so just be careful to check which one you have before setting.

http://www.123ignition.nl/pdf/123SWITCH4.pdf

I think this because when I got my 123, it was a Porsche unit, I set it up correctly but they garage that did a topend build for me assumed I had got it wrong so changed to D!

Neil,
The problem here is that there are two different non-vacuum, non-programmable 123 distributors that both work in the 356.
These are the 123/VW and the 123\Porsche-4. They each have different settings on the adjustable curve setting dial.
The 123/VW has letters and the 123\Porsche-4 has numbers.

If you look closely at the PDF file link you put in your message, you will find a different page in the document for each of these distributors.
For the 123/VW the info on the page looks like this, where the curve setting is in the first column:

123\VW (FOR 181,1200,1300,1500,1600,2/1200,2/1500,2/1600,2/1700,3/1500,3/1600)

C 800 3100/35,0 100 300/9,0 VE4BRS383, VJ4BR9 & 18, VJR4BR18 Porsche 356
D 1600 3100/30,0 100 300/9,0 0231.129.022 JFR4[R] Porsche 912

For the 123\Porsche-4, the info looks like this:

123\PORSCHE-4 (FOR PORSCHE 912, 914, 356)

5 800 3100/30,0 100 300/10,0 BOSCH 0 231 129 022 Porsche 912
6 800 3100/30,0 100 300/10,0 VE4BRS383 JV4BR9 VJ4BR18 VJR4BR18 Porsche 356

So, it depends on which model you bought, whether you use curve C or D, or 5 or 6.

This has caused much confusion in this forum in the past, and I suggest that you look at the long discussion about this held previously.
viewtopic.php?f=1&t=38495&hilit=123+ignition#p235046