Running problems with a 365 GTC 4 - Ferrari Life
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post #1 of 5 Old 12-23-2012, 09:13 AM Thread Starter
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Running problems with a 365 GTC 4

I am relatively new to the forum, but not so new to he Ferraris themselves. Some time ago I bought a wonderful 365 GTC 4 in dark blu. It had a complete motor revision from Modena Motorsport in Langenfeld. The only problem I am facing, is, that in low revs (2500 to 3500) the acceleration is not good at all. In particular when starting off from standstill there is a real hole. This means that the car is spitting before returning to normal power. Carbs are adjusted, motor as said brand new. It is a US car, so one idea was that the exhaust system has to be changed to the wider European version as the US emission control units had been taken away.

Does anybody have an idea? Your response is very much appreciated!

Merry christmas
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post #2 of 5 Old 12-23-2012, 10:13 AM
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Andreas- A couple of things to look into would be the accelerator pumps, oft ignored during rebuilds, and advance on the distributor or distributors.

Terry Phillips

Present: 575M 135171
Past: Dino 246 GT 02984, 365 GTB/4 14009, 308 GTS 25125

Every day I look around, and if nobody is shooting at me, it is a pretty good day.
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post #3 of 5 Old 06-01-2013, 07:52 AM
Join Date: Feb 2013
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dont forget there might be the cam timing wrong by 1 tooth or so....
same problem on any Alfa V6 / V8 and Fiat Dino V6 DOHC,
it might be possible that there happened a mistake during engine
assembly. I have seen Maserati V8s and V6 with exactly the same Problems
the intake cam on one cylinder bank was offset for 1 tooth.

Sounds that you are driving lean during the so called "transition phase"
(between idle jet and main jet operation typically at 2600 RPM) ....there might be one or more clogged idle
jets or your idle jet screws are generally turned in too wide (by 1/4 turn) = slightly too lean....
but dont play around with those screws,
your valuable engine needs a full mixture check under load on a rolling road Dynometer
dont trust your backyard garage in this case better go to "IOZ" the only good
German located Weber carb service station: There is a lady Mrs Anette Hue she is
Germanys best expert regarding the old Weber, Solex and Dellorto carbs, you can trust her
she´s an ex race DTM mechanic mastress from Hockenheim / Nuerburgring. (No joke!)

Also VGS Cologne is a good carb specialist, but much more expensive and not (!) better than IOZ:

Check float bowl level settings on those DCOE carbs...the float valves need to be
replaced any 60.000 KM especially when using the modern dry eco fuel with ethanol.

Please watch this link, it shows the DCOE float inlet needles from scrap to new condition:

Just prevent needle and carb throttle bearing wear

In Germany almost any vintage car driver adds 1% smokefree two stroke oil API TC / JASO FC
to the fuel as top lubricant, carb protection and anti corrosion additive also prevents tank rust
during winter sleep period. Its a great carb cleaner too, (works as good as seafoam)
so just add 1% two stroke oil to your fuel (its transforms todays bad dry fuel to a good classic car petrol)
as recommended by Bosch and Mercedes classic. Also works great on fuel injected K Jetronic cars.
This might clean your carb jets and valves as well
remove ash deposits between your piston rings. Most Ducati motor bike race drivers also do so.
You can get this oil very cheaply at your Kaufland supermarket for 5 Euro / one liter.
K-Classic brand yellow little plastic bottle. You wont believe how good that works.

More you can read here:

Check your intake manifold for air leaks between carb and socket.
Maybe the carb base screws are just loose.

Check the carb jets, often there are some jets mixed...I have seen cars with 1.50 main jets and
one wrong 1,25 (!) jet someone bastardized into the carbs....such jet mismatching can happen quite easily...
Dont trust the words of a garage saying anything is new, often nothing was done.
Sure that your ignition settings and ignition coils are okay?
Sometimes wrong spark plugs are used....only use the plug heat range Ferrari suggested for the
365 that were 12x NGK BP7ES if my mind serves me. Maybe they recommended Golden Lodge or
Marelli plugs...but heat range should be BP7ES.
Another hint, start your engine tonight in the absolute darkness and open the hood, watch the whole ignition wiring
for electric leaks you might see lots of blue little sparks flying from the old wires to ground of the
block, often this is overlooked and the problem are shorts between cabling and ground.
Those Ferrari coils generate 40.000 Volts so wiring has to be very toughly insulated.

p.S. Never start your engine in a locked dark garage you might suffer badly under the Carbon monoxide exhaust gas

Best regards

Last edited by Yorck; 06-01-2013 at 02:20 PM.
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post #4 of 5 Old 06-01-2013, 03:25 PM
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It does sound like it might be an issue with the jets.
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post #5 of 5 Old 06-02-2013, 02:30 AM
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Yeah idle jets too small or clogged, (Idle jets feed the engine up to 2600/2800 RPM)
but wrong air can cause the same, check your carb base nuts and the gaskets between the manifold and the block, ohh I forgot in the case your brake vacuum reservoir has a pipe or hose connected to the intake manifold
this hose can be cracked or the seal ring between hose connector pipe and vacuum reservoir is leaky or even missing than your engine runs much too lean due to wrong air, dont drive around because you might burn your headgasket or even the piston tops.

A wrong float bowl setting (defective float valve needles) can cause the same...than your spark plugs
foul because carbs flood.

You can try the two stroke oil (1:100) in your fuel thats a good opportunitiy to clean the whole engine
induction tract including valves and piston rings. Maybe your clogged jets also become clean.
You engine will perform better with a good top ashless top lubricant (in the past the italian race drivers added
BARDAHL TOP OIL, today you can use modern smokefree ashless JASO FC / API TC two stroke oil.

So let IOZ check all that out that will save you lot of money and an expensive engine defect.
Mrs. Annette Hue is the best carb mechanic I have ever seen.
She´s always on Techno-Classica vintage car trade fair / Essen.

Best regards

Last edited by Yorck; 06-02-2013 at 02:43 AM.
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