Checking advance curve 400GT

Idle advance is somewhat easy, but testing the curve "in situ" is not for the faint of heart.

As a minimum you need a timing light with a very long cable so as to be able to reach the timing marks that are under the car. Maybe you could use a programmable timing light (with timing offset) and raise the rpm, but I doubt you will get any meaningful result. At least this would let you know if the distributors are stuck (this happens quite often as they are hard to access, and as a consequence left without service for extended periods).

On the Workshop Manual you have some guidances on how to set a "base timing".

 

I do have the workshop manual (WSM) for the injected cars (electronic ignition). Checking of ignition advance under load is described in section D8, should not be vastly different for the 400 carb (except the flywheel has two sets of timing marks).

WSM available here : https://www.ferrarichat.com/forum/threads/wire-diagram.564951/#post-145737999

 

You will need a partner to raise the rpm while other person is under car with the timing light. You need to be sure your car is very stable in the raised position as high rpm (up to 5000) is pretty "exciting" when directly under the motor!

I did this several times for my single distributor car. As mentioned, your timing light needs to have long wire from the plug connector, and ability to adjust timing offset. For single distributor you can use spark pickup sensor on #1 or #6, so for your right bank you can use either of these two. I found timing mark for zero degrees for the 1/6 mark rotating motor manually and marked it with a paint pen. I am not sure if you use #7 and #12 for the left bank. Hopefully someone else will chime in. I spent some time to get the low rpm advance CORRECT. I then set the timing light advance to the 3000-rpm advance from the manual; this way you are always looking for the TDC mark as rpm increases. My helper, inside the car now slowly raised rpm to 3000 and held it for a few seconds and then back to idle. If you are lucky, it will be close to spec. Tail pipes will now be quite hot on either side of person below! Now I reset timing light advance to 5000-rpm spec and repeated step as for 3000. The hardest thing was to convince my wife to actually get to 5000 rpm with me under the car and motor roaring!! I think most important is that you get a smooth advance going up through the rpms and you are relatively close at 3000 and 5000 rpm. You will need to do this for each bank separately.

If you are unhappy with the results my recommendation is to send one or both distributors to a professional service to rebuild and set advance curve to spec. If you are in US, I can recommend a very trusted service provider.
Ken

 

Who would you recommend for distributor work?

 

Hi!
Ken has the correct procedure!
Use a 2nd person, and it's quite useful to set up a phone call between both parties using ANC-headphones.

If you're anywhere near Stuttgart in Germany, I'd be more than happy to help.

This is what my curve looked like, orange being the measured and blue the reference.

Cheers

Esben

 

My recommendation for distributor work is David North. In is in NJ, near NYC. He usually runs an ad in the FCA monthly Newsletter. PM me for his email and pictures he sent be of before and after work and the advance data.
Ken

 

As a personnal preference, I set the base timing at 10~12, and recurve the peak.

Low idle timing is better for polution as it generates hotter/cleaner gases, but this is a fragile head that should be spared such stress, and in terms of comfort, the hotter the engine bay, the hotter the cabin.

Ignition timing on the 400i is quite low compared to the others of the serie (including 412). The car idles much better with a bit more timing, with cooler manifold, (but as said gases are less clean).

 

Hi!
I've already installed a programmable MSD ignition, and once I gett round to locking out the distributor, I shall be doing exactly that

Cheers

Esben

 

Hey just a suggestion - why not take the distributors out of the car and send them to a dist shop to have the advance set? Admittedly I do not have great knowledge with dist / advance etc. But might be easier to do it on the bench as opposed to in the car?

 

If it were a 400i with its capacitative ignition and reluctor, a timing light could make it do. Not in your case.

The issue is that this is lots of breakers that have to be aligned against each others, so my guess is that you now have an uneven spark distribution between cylinders (a few too late, others too early, etc...). You definitively have to check the distributors on a proper tester.

Where are you based? With a bit of luck you may have a shop with a tester close to where you live.

Photo taken at the Ferrari Dealership last week, funny to see this old tool (with the proper magneti marelli adaptor) in the middle of this pristine shop.

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Where is that at, Raoul?
I'm inclined to think that the Ferrari dealer here doesn't even know what a distributor is....

Esben

 

Tom Yang is working on my ‘78 400GT right now. This is a video he made a few months ago. Right at 6:40 he starts to go over the distributor and advance etc.

 

That's in Paris, but these are the oldschool type that used to race Ferrari. Where I am it's the Ford dealer that managed to get the dealership, all the other guys that knew how to work on our cars are not approved anymore.

This being said, there is a Sun tester in my area: in my backyard actually... (any 400 owner is welcome to play with it if need be).

Esben, Niedermeier in Regensburg is an excelent mechanic. I think he is retiring, but he still services the my brother's 400gt.

Just for the pleasure here are two cars next to the sun-tester, as you can see, they love Ferraris, regardless of price tag. (The 400 has seen some better days)
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