V12 Engine Balancing

[Rudy van Daalen Wetters]

John,

Do you miss the DB2? I just can't see ever parting with the DB 2/4.
Well, maybe that is why I have too many cars?

Rudy van Daalen Wetters
1963 GTE s/n 4001
1966 330 GT s/n 8705

[Rudy van Daalen Wetters]

Andrew,

I think that is a good point you made. I thought that the chain should be looked at but the motor is quite fresh from rebuild. Who knows if the timing chain may have settled a bit? I will have to check on that.

Hope to see you at the Casa Munras.

Rudy van Daalen Wetters
1963 GTE s/n 4001
1966 330 GT s/n 8705

[mark]

Thanks Jim:

I will have a look at the linkage. I suspect the fittings on the end of the linkage rods. They seem to be a bit worn as I recall.

Mark

[John Vardanian]

John,

Do you miss the DB2? I just can't see ever parting with the DB 2/4.
Well, maybe that is why I have too many cars?

Rudy van Daalen Wetters
1963 GTE s/n 4001
1966 330 GT s/n 8705

Hi Rudy,

I miss the coziness of the car's cabin and the sexy shape of the DB2. Mine was a RHD. But, I never got used to the weird front suspension behavior. The performance was also sort of lack luster.

john

[Melchior]

I have balanced the carburetors of my GTE and the exhaust gas analysis shows that the left bank is running too lean. I suspect that the main jet (number 26 in the attached exploded diagram) is too small. Can anyone share which size of main jets they are using on their GTE with Weber DCS 36?

[Melchior]

My GTE has 6 main jets size 145 - the same jets at both benches. However, the left bench runs with poor mixture. I could not find a reason for this - everything seems clean and o.k.
Does anybody run left and right bench with different sized main jets? Is it appropriate to use different sized jets at the two benches to have the same mixture at both sides?

[tyang]

When is it running poorly, how are you testing? All the jets work in unison throughout the rev range, with the main jets working mainly alone only after about 3000 rpm. Unless you have a gas analyzer testing above those rpms, how do you know it's the main jets? The idle mixture screws allow some adjustment at idle into the transition to the other jets.

Tom

[Melchior]

Hello Tom,

Yes we tested with a gas analyzer at 3.000 rpm where only the main jet works. So far we only tested at the exhaust pipe rear end, but will soon test at the front pipes after the exhaust manifold with Lambda sensors where you have 3 cylinders at one pipe. This will avoid wrong reading due to possible air intake at the final pipe and will allow specifying the problem down to 3 cylinders.

In the meantime I ordered larger main jets with size 150 and 155 so that we can play around a little. Did you ever have a difference in the mixture of the left and right bank? The carburetors are completely new serviced from a well known specialist, I do not think there is a problem at the carburetors itself. Of course a contamination is always possible, however we need to find the reason and if we can’t I intend playing with the size of the main jets to adjust the poor mixture at the left bank.

What is your opinion?

[tyang]

When you say it's running poorly above 3000 rpm, what is happening? Is it missing, stumbling, popping in the exhaust? 3000 rpm is also when the ignition system is reaching full advance. Many times people mistake carburetion issues with ignition problems. Unburnt fuel from poor combustion due to a bad spark event can lead you down the wrong path. Is this engine a fresh engine? Is the compression the same on all cylinders? It sounds like you're on the path to eliminate some of your issues, but don't eliminate something until you can prove it's working properly.

Good Luck.

Tom

[Melchior]

Thank you for the hint. The engine is brand new from complete overhaul. Right now the workshop proceeds the 1.000km service, fastening the heads, checking ignition and valves. I could not say that I felt anything from the poor mixture at the left bank. The engine ran properly the first 850km. We just saw a the exhaust testing that the mixture is too poor.

We will test again after the service will be finished and I will inform about the situation. You are absolutely right, we try to find the reason and eliminate one possible reason after the other.

Have a nice weekend Tom and thank you again for your expertise.

[abrent]

Hi Martin,

Keen to hear the outcome of this, as in O2 sensor tuning.
Back in the day you just rounded up a Tom Meadows like fellow (or Tom Yang, or I'm sure many others here) and watched them adjust/drive/adjust till things were pronounced good.
Did not ever fit differing main jets to 3835, however did change idle jet's twice to get smooth running with good transition.
Same jet's across all carbs.
.65's from .55 (via .60)

Rgs,

Andrew.

[Melchior]

Hi Andrew,

I have my temperature gauge and sensor brought to a workshop in Modena and they are closed until next week. Without the sensor I can’t refill the cooling fluid to start the engine. It will take some weeks, but I will report here as soon as we can do the testing.

Best regards, Martin

[Melchior]

Hi Tom,

after checking the whole system again it seems that there was a little metal chip in the nozzle that caused the difference between the left and the right bench. Although there are 2 fuel filters we found several little metal chips in the chamber which probably come from the new fuel hoses. I have additionally fitted extra filters at the intake of each carburetor now.

I have a problem with the red fiber seals at the connection with the chromed fuel distribution tube. There are different recommendations: using copper or alloy seals, soaking the fiber seals in fuel over night before installation, using black delrin seals, etc. What do you use to prevent the connection from leaking?

[DWR46]

A light coating of Locktite 518 on the copper or fiber washers. No more leaks! Also a drop of oil on the threads so the banjo bolts tighten smoothly.

[Melchior]

Thank you!