Ferrari 365/400/412 Cylinder Head Port & Polishing

Just fix what is needed and leave the rest as they are. Let's not go looking for problems. The path to hell is paved with good intentions..

 

The intake runners, intake and exhaust ports, and the header lengths are all designed as a system. The final configuration is determined usually after many dyno runs. You could run into problems if you just alter one without changing the others. Stick with the old saying, If it's not broken don't fix it.

 

Do not try to mess with the exhaust port under any circumstances : these ports are less than 2mm thick. As soon your guy is going to grind the port he will plunge directly into the water jackets... The inlet are not as problematic (they do not sustain the exhaust gases), but still way to thin.



(abstract from https://www.ferrarichat.com/forum/threads/compression-and-leakdown-tests.635769/#post-147695453)

In stock form the head has already a serious tendency to crack: this head is nicely designed, with better inflow than the Testarossa, but unlike the Daytona, the carbs/injection is not inside the valley, but on the side of the engine, which implied to re-route the exhaust further down, so the exhaust port has a tight turn (see red highlight in the drawing) that has to sustain lots of heat. This makes matters even worse. Keep as much material as you can...

 

The best thing you can do is improve the valve seats. The placement of the contact between seat and valve is always pretty bad in those older heads. I have done flow testing on my flow bench and a slightly larger valve allows for a seat profile change that will improve flow. I agree the ports are well done for what is there. No need chasing that. If you are interested in flow number for your heads, contact me and I can arrange to flow test them for you. If you are not planning to change anything, this is actually not helpful. Just numbers. 770-845-8335 text me.

 

Good advise, I have had similar experiences. Depending on the seat geometry it can make a significant difference.

Cheers Jim

 

You could also use thinner vavle seats, as the difference between the inner and outer diameter is quite significant compared to standard seats. During the first rebuild of my cylinder head we decided to use the same inner diameter and smaller outer diameter, which allowed to add more material on the outside of the seat, and hence strengthen the head were it usually crack.

You could do the opposite: keep the same outside diameter and increase the inside diameter (i.e bigger port).

I had to drop the left head 4 times on my car, the three heads I bought all had to be fixed, and only one could be finally made to work: when you mess with these, be ready for some painful mistakes.