The sound of webers

[pope]

I'm in the process of tuning the 40IDA Webers on my car.
I'm following the instructions in:
Weber rebuild
(post 13 onwards)

For those that might know what's going on right off the bat, here's a set of sound clips of what's going on:
http://popester.homeip.net:8080/soundclips/

It contains extracts of about 30mins of full recording during which I went through steps 3, 4, 5 and 6 successfully (startup, vacuum adjustment, side-side balance @ idle, side-side balance @ 3k). Every time it dies it is for no apparent reason. Until it dies, the engine is running apparently smoothly with an even idle. Last two clips are with car running at 1200 for Step #7 which I did not finish due to my frustration.




If you need more information here it is:
- Valves adjusted a week ago, with new gaskets, nuts washers, turbo covers.
- New cap, rotor and points.
- Points gap set by feeler at 0.3mm
- Ignition timing checked to be between 30-35 BTDC @ 6k (leaning towards 35) --- should be 30 BTDC
- Dwell measured to be about 30 degrees --- should be 38
- Left timing and dwell as they were believing they are good enough for the first tuning attempt.
- bench test of Silver Permatune results:
A to D: 3270 Ohms,
D to Flange: ~0,
B to C: initially all over the place (10k up to 2M). Even tried two different meters. I kept testing it while I was cleaning the console connections. After about half an hour, it stabilized at 100 Ohms
D to B: ~50uF, don't think I'm getting a proper reading there. I might be doing something wrong.
- Bench test of coil:
Primary coil: 0.9 Ohms
Secondary coil: 670 Ohms

- Took out electrical console and cleaned all connections with vinegar and steel brush. Cleaned all coil connections as well.
- Performed ground tests all around these circuits with good results.
- Performed telegraph key test with success.

- Weber tuning steps:

I skipped the first step till I find a vial that fits in there.
I gauged the 1st float with the PMO gauge but ran into problems. The measurement of the first float bowl (above cylinders 1 and 2) was just below the line + a couple of drops that leaked. I thus decided to leave the 2nd step for later because of the delay of ordering new needle valve plugs. I did not want to remove the other float bowl plugs because of the fact that you need to replace the washer after.
I then moved to step 3 where my problems of the engine dying started as in the sound clip.

- Weber tuning is being done with the fuel tank almost empty (at one point the engine DID die because of no fuel). The reason I'm leaving it low is that I want to check the fuel screen and replace a couple of the fuel hoses under there right after I'm done with the tuning.
- The rest of the fuel hoses are all new. Fuel pressure after filter is nice and constant at 3-4 psi - except when out of fuel

So, WTH is going on?!?

[Mo_Gearhead]

You do not mention if have you have had the carbs apart/rebuilt?

If NOT, I am (guessing) some of the carb. circuits are dirty and if that is indeed the case you will be 'chasing your tail' trying to properly tune them until they are clean and you are assured of a 'clean' flow of gasoline at proper pressure.

[pope]

No, I have not rebuilt them.

I have a rebuild kit standing by though. I first wanted to attempt to tune them before cleaning them.

[Mo_Gearhead]

Then you are approaching the problem backwards. Rebuild the carbs. FIRST.

A CLEAN fuel supply and knowing the carb. circuits are clean is step ONE.

[pope]

Agreed.

My excuse is that I was going to be doing the FIRST step after the SECOND so I can do the SECOND after the FIRST. Heheh.

What I mean to say is that, since this is the first time I have ever touched a Weber, I want to get a feeling of what's going on a step at a time. I thought that by doing a 'tuning run' first, I'd get a better feeling of what a carburetor is. THEN, and regardless of how well they are tuned and running, I was thinking of doing the rebuild. That's why I have the kit handy in the garage .

I've been known to make mistakes though. And if you guys suggest that the best way forward is to just pull the damn things out and clean them because this is what's causing my problems, then I'll get to it.

Thanks for the quick input.

[Mo_Gearhead]

The problem with your approach is that; while trying to 'learn' how to adjust your webers, you will be getting faulty reactions (dirty circuits, wrong float level, etc.) from your tuning attempts.

So turning certain screws (idle/air/mixture) will give you bad results and confuse you even more? "Tail Chasing"

Clean the gas tank and filter, fuel lines and rebuild those carbs!

[pope]

I pulled one off. Looks cool. Got lots of issues and an album of pix. I'll post some questions later on tonight.

This is going to be fun!

[911pcars]

Since you have a PMO float gauge, monitor the fuel level when the engine dies. Does the fuel level remain constant as adjusted? If so, you have enough fuel to maintain idle. Repeat on the other carb.

The second area I'd like is the ignition box. If possible, temporarily remove from the system and revert back to the factory system and retest.

Sherwood

[pope]

Sherwood,

it's too late to do the test with the fuel gauge unless I will still have the problem when I put the carbs back on.

When you say factory system box, which one do you mean? The silver permatune looks very very old. And I only got the car 10 months ago.

[pope]

So, I took out the whole thing:



smart or stupid? What's the thing on the bottom called? Manifold?



Between it and the engine there were the two top gaskets:



The fat black one feels like plastic, the other one is probably silicone. I have replacement gaskets like the one on the bottom. It has two metal sides with paper (or something) in between. When I put the 'manifold' back on, should I put the black 'plastic' one and then the new gasket on top? Or just the new one?

One of the floats looks a bit beaten up:



Should I replace it?

What part is the bushing here?



How can I tell if it's worn?

I have problems taking out the needle plugs and the float screws. I've left them with WD40 over night and hope tomorrow things will be easier.

[911pcars]

I think you took some suggestions to heart and went too far w/o diagnosing it further. Not every "no engine run" issue requires rebuilding the carbs.

If it idles fine for awhile, then it doesn't, that doesn't necessarily suggest there's something wrong with the carbs.

BTW, the extra "gaskets" you discovered were aftermarket parts. The thick gasket is an insulator block to reduce heat transfer from engine to carb. and reduce heat/soak/fuel expansion in the float bowls. The gaskets seal the top and bottom of those blocks.

The collapsed float should be replaced. Reassemble to reduce introducing other "repair" factors, reinstall, then retest. As you have found out, removing the carbs is a relatively easy task. Next time, separate the carbs from the manifolds. That'll save a few replacement gaskets (12).

Check fuel level in each float bowl; check fuel pressure and volume.

At some point, a PO installed the aftermarket Permatune ignition box (a Bosch is factory). As with all things mechanical and electrical, nothing lasts forever and could be the source of the engine symptom.

Sherwood

[pope]

I imagine I wouldn't have been so quick to rebuild if I wasn't already planning on doing so.

When you say extra gaskets, which ones are you referring to? It's clear I have to put back the insulator block. The 12 gaskets I should get and put over and under the block are like the notched green ones?

[RoninLB]

I always keep a spare ignition around.

The sound of the abruptness of the engine dieing with carbs lead me to guess there is an ignition problem.

[lateapex911]

I'm inclined to agree, Ron, but it is indeed a guess. I do see a couple red flags, though....but the symptoms don't point to the red flags as the issues, in my limited experience.

Nevertheless, I'd want to look at the carbs for the typical old Weber issues. Rebuilding them won't do anything for the throttle shafts...check those for play. If air is entering the engine through the throttle shaft/carb body interface, it makes things tricky to tune.

Also, this looks like an E motor, and it appears that the heads were merely pugged in the conversion form the factory mechanical fuel Injection (MFI) to the Webers. (I wonder if it's still running the stock cam?) I would check the plugs in the heads for tightness. Again, air leaking into the engine through these will lead to tuning issues.

(It's too bad the PO didn't give you the removed parts..like the stock CDI ignition box and the MFI parts...)

Perhaps there is a Pelican local to you who can loan you spare ignition components. I would also spend some time checking and cleaning related electrical connections, checking grounds, battery connections and proper voltages, just to be sure.

[pope]

Sherwood (or anyone else),

could you please explain how the gaskets work there?

thx

[911pcars]

Originally Posted by pope

Sherwood (or anyone else),

could you please explain how the gaskets work there?

thx

Nothing complex. The insulator block reduces heat transfer from cylinder head to carbs, but the insulator requires gaskets on both sides to prevent air from bypassing the carburetor.

One or more gaskets appear torn. Replace them.

The fat black one feels like plastic, the other one is probably silicone. I have replacement gaskets like the one on the bottom. It has two metal sides with paper (or something) in between. When I put the 'manifold' back on, should I put the black 'plastic' one and then the new gasket on top? Or just the new one?

The replacement gasket (the bottom black one) doesn't look correct. It even looks like the ID is larger than the intake port and existing gaskets - could be a muffler gasket. The proper gaskets are single layer, stiff gasket material like the middle one above.

Sherwood

[pope]

OK. Got the idea. Actually, I just discovered the SECOND gasket stuck on the bottom of the insulator but it was black and I had not initially noticed it
thx.

[pope]

Sooooo, after a long period during which I had to replace various parts on the carbs like the float bowl plugs:






...which were cracked when I took them out - I presume by an over-zealous PO.

I finally started the car again this morning. I had a feeling it was running better than before. Unfortunately, I didn't get a chance to confirm this as the engine started dieing on me again as soon as it warmed up. It died a couple times and then I couldn't start it so I quickly tried to do a 'telegraph test' to see if my problem is my silver permatune CDI box. In my hurry though, as I was pulling on one of the spark plug wires, it slipped and I pulled it from the wire rather than the connector so:



Yet another delay............

[911quest]

Pull the other half of the plug wire connector off the cap and screw it back into the wire.You will see on the connector there is a a little screw inside that the wire just threads onto you might want to cut about 10-13mm off the wire so that you get a better connection.

[pope]

Learn something new every day .

So, I've started it up and it seems that the stalling for no apparent reason has stopped. I'm certain it will happen again at the worst possible moment but I'll have to wait and see.

In these last couple of days I've gone about tuning the carbs as per the methodology in the link in the first post. I'm quite happy with the results except for three things.

Here's what I've done:
- Accelerator pump volume
- Float levels
- Vacuum adjustment
- Side to side balance at idle and 3k
quite successfully I think.

Here's what I found: In general, all barrels were pulling approximately the same. The two banks had a bit of a difference at idle but a significant difference at 3000rpm. I corrected this by adjusting the throttle shaft rods. Now I'm pretty sure this difference was there before I rebuilt the carbs because I was very very careful with not modifying the initial throttle shaft settings.

Here's what I'm not happy with:
+ I did the Mixture adjustment once but am not very happy with the results. I understand that you need to play around with this to get used to it and do it well.

+ My cold idle is 150rpm lower than my warm idle. What is the reason for this? Is it normal?

+ I get lots of black exhaust at high rpm. Why?