I forget what the general rule is, but it's something like for every turn an intake manifold makes beyond 20 degrees something like 15% flow and velocity is lost. You always want a path to the intake valve as straight as possible. This is why those hot rod 911 engines can make just crazy power relatively easily.
The 355 stacks are turned probably 90 degrees, I would have to take the plenum off to look (I will) but looking through the throttle body hole they are really cranked like a hairpin turn for packaging reasons but the length is there. The length is probably more critical than a bend and tilting them a bit wont matter imo other than not looking good.
The only reason I considered angling the manifolds inward was to allow for putting a window on the intake covers. By far, my preference is to run the stacks perpendicular – similar in configuration to the BBLM (stubby manifold, throttle body, trumpet). Injectors would be part of the throttle body (not the trumpets like they are on the BBLM), and I'd be using a fuel rail – but you get the idea. If I run the injectors on the inside (like the BBLM), then I'd even have a similar manifold flange bolt pattern (lower flange is top-left / bottom-right, top flange is top-right, bottom-left). Still working through details, but leaning towards the Jenvey throttle body and trumpets mentioned above, as well as using a vacuum bar(s) to allow for IACV and a MAP sensor (even though primary tuning would be based on throttle position). For me, this would check all the boxes (performance, aesthetics, sound, and street drivability). Image Unavailable, Please Login
The carb cars had what could be used as vacuum bars. Initially on the 365 they were plumbed to the breather pipe for emissions then the 512 used the existing intake holes and modified tubes for cold start enrichment. Just saying this because that part already exists rather than you making them from scratch.
For reference, and I know this is a V engine soi a cant maybe more natural Image Unavailable, Please Login
Ah good idea. Are you referring to these? I would need to collect all of these to a central spot where I can then feed it additional air (IACV) as well as pull vacuum (MAP). Most ITB setups I've seen use soft vacuum lines, but I like the idea of these these hard lines instead (more pro with a nod to the BB). Image Unavailable, Please Login
Eye candy, forget about the windows and complexity of changing the rear lid. the question is where to get the koning intakes.
My car is apart so these are just sitting on the shelf. Not that anything would directly translate but if you want any measurements let me know. Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login
Measure the total length from the tip of the stack to the valve if you don't mind. Ferrari wouldn't have angled them to fit if length didn't matter.
FWIW, Jenvey actually has a blurb on this topic in their FAQ: Curious what that remaining length is from the bottom of the manifold flange to the center of the valve head. This value + 9.25" would be the total length of the CAD image shown above. Even if not the "ideal" length (Jenvey's 350mm), I doubt I'd be "disappointed".
350 mm is for a 9k rpm motor. A 7k rpm motor would have an ideal length of 272 mm, ie 10.7 inches. All of these are at max rpm/hp, I assume shorter would help lower rpm? so its all compromise. As they said airbox design and feed has a big effect too. Those Koning intake boxes fise higher out the decklid, so theres some room there. Your mockup is 9.2 not counting the intake manifold to valve. Im guessing its darn close to optimal, plus one wants a motor that works down low not necessarily just mox max hp. Im guessing cam choice and overlap is critical. Suppose one could just use what koning did. Newman Koning motor once it caught its breath was a peach, I drove that car in the between 5-7k+ rpm and it felt like a superbike with superb sound to match, added a whole dimension to the BB experience, as did those skinny 215 fronts to the steering. I kept thinking Newmans car had shorter gear ratios, but it was probably the way the car ate through the gears at high revs and the sheer joy of shifting at revs right into the meat of the powerband. Good way to get arrested too, so one would need to keep some good midrange cvility. The difference in woken up BB motor is like the difference between a mid 70s chev 350 and the earlier solid lifter 327 and 350 from late 60S. theyre similar up to 4k rpm after that one flattens and the other keeps getting stronger and howling. Love this project. Its at least half the equation, the other being cams and pistons. Eye candy, sound, power that builds to a crescendo.
Don't mind at all. Easier as I bought a junk head to cut apart and measure. So it's- Cylinder head intake port- Short side- 3.25" Long side- 3.95" Throttle body- Pretty much straight and squared from flange to flange at 4.6" Inlet bells- Short side- 4.65" Long side- 6.15" I eyeballed the side/middle centerline and that measured 5.45" which makes sense as it's about the average of the long/short sides. Also note that the longer inlet bell side matches the short side of the cylinder head port. And the inlet bell has a bit of a complex shape, bulged in the middle. So then actual overall is- - At short side of inlet bell (matching to long side of cyl head) 13.2" - At long side of inlet bell (matching to short side of cyl head) 14" Overall length averaged- 13.6" or 345.5mm Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login Image Unavailable, Please Login
Oh and you would want a longer length to make it ideal for less rpm so would think you would be shooting for longer than what I measured.
Thanks for that. The long runners plus the plenums would be a great combo. Less eye-appeal but more functional. I knew they were at least a foot long which goes with the general rule of thumb for stack length. I wonder how long the 360 setup is.
Did some reading, longer narrow runners tq shorter fatter runners ho. So there is a correlation between cc’s intake velocity etc etc. in the old hot rod mag days they’d test different cams carbs etc on a dyno. I’m assuming here the cams will have rinhave beem decoded before, on question then how to test different stack with and height. I guess once again one could look at what they did ona bblm and what koning did in terms of stack width and length to valve in the end once can only go so long, that really leaves width ? In guessing we’re looking at not less than 440 hp so the question then is engine charteristics at various revs. More than the last ultimate 10 or 20 hp. if I remember well Carobu did a 475 ho carbed BB. Wonder what they did there in terms of cams pistons and intake.
yes piston moments are a 180 degree v12 But physically it’s flat so canted intakes may look a bit off astheticaly
Some koning pics I found for reference. He def made an airbox out of the intakes Image Unavailable, Please Login
I agree. I highly appreciate aesthetics but I don't prioritize it. For me I think, what will work the best- that's what I'm doing. Then, how can I build what works the best in the nicest looking way possible. Seems no matter how you built an ITB setup on this car it would be shortening the intake. That would usually result in trading low/mid rpm power for high rpm power. A few things to consider. Can you raise the rev limiter? May need to rev it higher to take advantage. Also, are you ok with the power being softer, probably up to 5500+ or so (just a guess). Usually if you are making a change like this (ITB, shorter runners) that maximizes efficiency at a higher rpm, you would change other things to match. Such as cams, header length and then maybe compression ratio, gearing/etc. Other than throttle response, one of the great advantages of ITB's is their ability to tame aggressive camshafts, for example. Just my opinion but I think the original intake runners and plenums look very nice. Aesthetically and functionally. (doesn't mean they are in fact, just saying they look pretty good to me) If it was mine I would try to determine how well they work before deciding to switch to ITB's. For that, don't look at your VE table, as that will roughly follow your torque curve (peak VE at or slightly later than peak measured torque on a dyno but should be pretty close). So of course then you will find the VE table peak around max torque and taper down from there the higher you spin it. To get an idea if it's inlet restricted (by throttle bodies/induction leading to them), note key on manifold pressure or if you have it, baro, or simply, low rpm wide open throttle manifold pressure vs manifold pressure at redline. So for example, if your key on map or baro is 100kpa and it is 98-100kpa at redline, it's not inlet restricted by anything at/before the point you're measuring. If key on map/baro is 100kpa and say 88 or lower at redline, it has some degree of inlet restriction.
For a visual on that. Here is the chassis dyno and VE table from my 69 Charger. You'll see the dip on both at 4300 or so then peak VE at just under 6000rpm. Peak measured torque 5800+ but still carries 7200-7500 peak horsepower. Image Unavailable, Please Login Image Unavailable, Please Login
There's two styles of of rear scoops. Those ones that use the stock air cleaner housings have the sealing lip recessed up into the clamshell opening. Mine had the flat base plates with further reaching scoops. Not sure if sealing the stacks to the scoops was a consideration yet? Also inside the opening of the scoops about 6" dow there's a wire screen to support a foam panel which is your air filter. You can go uni-filter but seeing the stacks open looks great. Mine had tea strainers on them.
