888 heads marked M

gina

Hello to everyone,

I have an sp4 with a strange engine. The carter is G9. The heads are marked M with 91.
I know sp5 have G heads but not sp4 engine.
Unfortunally I don't know the correct marker for the sp4 heads.

gina

Here pictures

MarkT

gina wroteHello to everyone, I have an sp4 with a strange engine. The carter is G9. The heads are marked M with 91. I know sp5 have G heads but not sp4 engine. Unfortunally I don't know the correct marker for the sp4 heads.

Gina-

I have seen the letter D and M stamped on straight 888 heads. I have also seen G stamped on '91 factory race motors. Most of the factory Corse heads I have seen '92 on up have no stamped letters- and all of the early Strada black heads have had no stamped letters.

But I have only worked on less then 20 motors. Forum members like Brad have seen hundreds and perhaps will have the answer.

BABA

Dudlington asked me a question too, yesterday, about M head.

Here is what I have found with ducati docs, pics of ads, etc...

A1 : head for 851 kit or strada 88 (32/28 valves).
B, C and C1 : 851 strada heads with 32/28 valves.
C2 : heads with 33/29 valves (probably 851 SP 89)
C, C1, and C2 heads are mentionned in a factory document explaining how to modify a 851 in a race bike.

D : 851 strada (probably 90-91 version), with 32/28 valves. I have a pair from a 851 strada 90 engine.
M : 851 '92 and 888 strada with 33/29 valves, same heads on SP4. But I don't know for SP2 or SP3. They have 33/29 heads too, but I 'm not sure the combustion chamber is the same (same difference between D and M head's combustion chamber).

D heads I have (cleaned from their black paint as the rest of the engine) :

M heads combustion chamber

-> Dudlington answered me that the SP3 heads he has, are stamped A2.

G : heads for 34/30 valves, used on R90-91-92, SPS and SP5, and still on 916 SP.
S: heads for Racing 93 with 36/31 valves.
S1 : heads for 926 Racing 94, with 37/31 valves.

Knowing that heads could be or could already have had been modified.

Here are my "M" heads now

And my "D" heads will received (one day...) 36/31 titanium valves

Mr.R

Baba,

The 916SP heads on my 851/916cc motor are stamped B ??? They're also dated as '94.
Whilst the combustion chamber and valve sizes 34/30 are the same as G heads, the exhaust ports have a larger radius on the bottom of the ports and they're slightly smaller in diameter than the G heads.
...and of course the castings are different as they have a shallower exhaust side with a smaller valve cover, this is to clear the front wheel under heavy braking.

I'd always thought that they were the same as the G heads, until a UK dealer sold me a pair of NOS heads claiming that they were 916SP items...
Oh how disappointed I was when they turned up and were G heads. 😏

Because of the lack of almost any radius on the bottom of the G exhaust ports and the huge diameter of them,
I've modified my NOS G heads to take 37/32 valves in an attempt to gain at least some radius on the bottom of the exhaust ports.
I'll be running them on my almost finished 955cc ST4 cased motor.

Steve R

BABA

In attachment a pic from a new front 916 SP head, for sale in France (NOS) with a big G.

Here a discussion about heads.

There is a B "916" front head (but moulded in 92), and a standard G-SP version.
Ajcorse had seen 916 SP G heads without mark too for 916 SP.

Someone bought recently a 916 SP 94 and was affraid to discover a rear head with Desmo 4V DOHC marks (he tought the rear was the same as the front, without marks).
I asked if he had well a G stamped on it, and it was (so he could be reassured that he had well the good heads).

I don't know who's right, it 's the 90's Ducati's production 😁

Mr.R

Baba,

How very Italian of them...😏
My 916SP heads* have only Ducati cast over the inlet side, '94 cast into them with some strange sign also cast and B stamped into them.
My G heads have almost nothing cast into them, no Ducati or Desomquatro DOHC but have a number 1 cast into to denote the year of casting and are (obviously) stamped with a big G.

*I bought the complete top end from a 916SP inc' heads, barrels, pistons and twin injector set for almost pennies, when compared with todays asking prices.
I swapped the pistons (that had 21mm pins) for a NOS Tricolore Kit barrel, piston and gasket set then sold the 888 Kit piston to an owner in Germany.
The 888 Kit barrel now lives on the front of my 851/916 motor.
The 94mm 916 SP barrels with the OD of 102mm, I had bored out and plated to 96mm, then had the outside (102mm) sleaves turned down to 101mm. The ST4 cases are being bored out to suit the 101mm barrels early this week.
The reason for turning them down to 101mm is to leave some extra strength in the C/cases, this comes from the lessons learnt when racing the 916/955cc Corse motors.

Steve R