mk e wrote:
On my bench at 10" h2o the stock QV/328 heads are 92-94 cfm.
The 360 head was 138. Much larger port, too big if you ask me.
I have not flowed a 348 head, but they are the same basic casting as the qv, but bigger valves (30.4mm intake) from the factory so I'm certain they flow more. I was thinking a 32 would fit, but super performance sells 32.5 so that must be the winner......that should get you to about 140cfm (at 10") but with a much smaller port cross-section than the 5V heads have which adds a bit of hp everywhere.
Epoxy can fix a port that's too big
The Bridgeport in the background of one (maybe more) of my garage pics has a CNC conversion with power quill feed. Add a motorized rotary head with a table and dead center and it's a 4 axis contraption that can do most of a CNC port job... That's my eventual goal. Once the program is developed, it might be time efficient just to pour the whole port full of epoxy and then mill the new port out.
Of course the big question of a 5V head is "what's the discharge coefficient of the center valve?" It's (probably?) going to be less efficient (and certainly going to be different) than the side valves, but by how much? I guess Ferrari over-estimated that if they cast the port that much too big.
Appreciate the offer on the practice head. It'll be a while before I might need to take you up on that, but I assume it's already been around a while, too.
Edit: If the port's too big, I can also fix that by bolting the head down to a 4L... then the valves will be too small
mk e wrote:
The 5V cam issue is there is something about the middle lobe that most cam machines can't grind....never looked into exactly what.
There are a few sources for 4v cams and places like web can weld up your cores to give you whatever you want. The problem I had was the firing order of my cores didn't match the crank and they weren't comfortable making the entire lobe of weld...so billets it was.
Generally there isn't much to port on a TB...just match it to the manifold nice unless you're fitting larger throttle plates or something like that. I'm a big believes in big TBs...funny knowing how much I hate big CSA ports but you can taper the port from the TB to accelerate the air and end up with very little restriction at the TB. Mine at ducati and have a 52mm plate I think it is....they're big.
The port entry and taper to the throttle plate, affecting plate diameter, is what I was referring to above.
VW/Audi made 5V engines for a decade or more... I'm pretty sure there are cams available in that community. However, the V8's at least have tiny tiny 91mm bore centers, to the lobes may package better into grinding equipment than the Ferrari's slightly larger bore center.