gemellocattivo.com

Right there with you, designed for 11 but not sure if I have the fortitude for letting it sing that high... we'll see. Maybe on the engine dyno, which reminds me that I need to have a scatter shield made or get a blanket for the bellhousing.

The exact length depends on the taper and diameter. The more taper the longer it needs to be to "tune" to the same RPM as a straight stack. Also the more taper the more volume and lower energy the wave pulse.....but that generates higher flow losses so there is also a sweet spot on taper.

Now try this exercise. If you are at 10.5k you header primaries are....19-20? Put on headers that are about like mine, 32"(you might want 33") long, 1.65" starting, 1.875 ending, collector is 5" long, 2.8inlet, 2.25 exit. That will tune the header to the 2nd harmonic and the collector to the 6th. Then go 17" or 17.5" on the intake length, staring area 3.4sqin so it's tuned for about 6000rpm and see what happens. I'm guessing around 575hp at 8500-9000 rpm with more torque making a better driver and probably faster without the high rpm wear rates and risks.

The exhaust is 22" w/ 8.5" collector & 3" exit. Intake area is 4.34" yeah BIG ITB's right now that results in 585Hp @ 9k

The suggested setup chokes the peak and limits it to 10k, picks up 9k to 588. The rest of the curve is close, bumps around a bit but the top end is cut off. Most notable though is that with the shorter headers 4.5k is 286tq vs 255tq with 33" primaries. i.e. the 22" primaries have no dip between 4 & 5k instead it's between 2.5~3.5k giving the 33" a lead of 8 lb/ft.

I'm a little surprised it wants headers that long.....you may want to add an inch or 2 to all my primary numbers.

choking it and cutting off the top while boost everything below that is the point I think with a little optimizing time you can shift the curve down 1500 rpm from where it is now and pick up 5+% more torque from 5k-8k.

With that HUGE 4.34 inlet area you're going to need about 1 more inch of length so 18.5"ish. Don't worry about the torque dip at 4500...that should go away with a tri-y hearder, use about 26" 1.65" in/out primary, 13" collect 3.0 in/2.25out for the low rpm model....just a hair longer primaries than mine.

Also on my engine optimal power (11200 rpm)was with the cams at 11/115, for a 9k peak the cams moved to 102/110. Its a pretty big bump below 9000. No idea how it all works out with your setup though at I suspect I have more flow and shorter duration cams....but I'd pay with the intake in the 102-106 range and exhasut in the 108-112 range to pull the peak down.

I'd have to go back and check my notes, the cam timing setup for the engine that is in the 308 for sale at the moment was geared towards peak HP, it's what the owner wanted. I can dial it back and pick a lot more bottom mid range as you're well aware.

duration.... yeah lots, like over 280 degrees! but lift is limited to shy of 9mm by a hair. I was going after 'dynamic flow' vs steady state.

A very close cam in terms of lift and duration would be the 275 GTB/4, timing is different but not by much. Look at the timing on the 275/364 4 cam engines. I can dig up the data if you don't have it. I was fortunate to acquire docs and books from a engine shop when they closed up a couple yrs ago on the old 60's vintage Ferrari stuff.

Everybody wants a big number....even if it make them go slower.

280 at .050 or .006? I'm at 243/247@.050 with 11.5/10.5 lift....I was going after open the damn valves and do it NOW! so the lift above about 9mm adds no flow really but is there to get the valve to 9mm as fast as possible.

lets see...

STS = 285/274
0.050 = 248/246

The profile is aggressive and has a fair amount of duration on the nose.

I got my first Ferrari ride in a 275GTB/4,the power justs builds and builds and is very linear,,and just straight up.its like the motor gets bigger as the revs climb,all Ferrari like that.
Im coming up for a ride,if you shoud be so kind.

I'm very close to that....and I lied a bit
@.050 its 241/246
STS = 273/285....funny we're equal but opposite here

@9mm = 115/95........slam to the peak flow point then start slowing down and turning around so it stays at peak a very long time

But that's not what's in Nick's engine is it? I thought he was maore like 240/235@.050....or did you change his cams?