So, the more I look at this engine that has been sitting on my stand since March, the more I realize I want more power anyways, so why put back an engine if I know it isn't going to be enough? The old motor ran respectively, and was decent power wise, but I want more!

Alright, so what does it take to squeeze a solid 200 horse (and up to 1hp/ci) out of these motors?

Dart270's recipe in the matrix is a good one, and I think what I have in mind will end up pretty close to this. I just have a few concerns...

I have a 23-2500 rated torque converter, and plan on using 3.23 gears with a 25.5 tall tire. Do I have to worry about the OCG346 sacrificing too much bottom end torque and moving the power band too high for this to work?

The spreadsheet lists the 346 with a 106 LSA?! Aren't I going to want a little wider than that? This will be a 3 season weekend/part time daily, and I'm looking for as wide of a powerband as possible. As most torque as low as possible while not sacrificing the ability to rev to 5500 and make nice power (I've got 200hp as a mental goal)

That recipe was created four years ago or so, have any cams been designed since then that would work better?

I've got a set of Sealed Power VS-510 valve springs, any reason these wouldn't work in this build? I plan on setting a redline of 5500, definitely not past 6k.

And I've got Dual Dutra manifolds. Does that make much of a difference here, vs headers? I've got crush bend 2" duals from a local mom and pop shop right now, would mandrel bends make much of an improvement?

Also open to other suggestions of recipes that have or should make ballpark 200 horse, I'm sure there are more ways than one to get there, as different people like to build engines differently. Thanks!

I've been playing with Dyno2000 and (now, take this with a grain of salt) the way the torque curve looks, along with others reviews, I don't think the tc/gears will be a problem.

For a LSA on the 346 cam, would 106 be ideal for the longest and flattest torque curve? or would a 110-112 be better? I was benchracing with a v8 feller, and he mentioned turning the RDP into a standard dual pattern. Dyno2000 likes it, and says 'More torque!', but I don't think I believe it for a bit. I know that v8s tend to like this sort of cam though. Is this because their intake/exhaust flow ratio favors the intake more, but the slant doesn't? I know RDPs work well for slants, but can someone explain to me why?

I've seen mentioned in times past a certain amount of overlap for the H-Pak motors, would that be a concern with my Hurricane? I've got an Offy with a 500AFB that I will most likely use, but I love the looks of the long runners, all downfalls accepted. I've tossed around the idea of either playing with an autolite 2100 1.33 or Holley 500 (2300 series flange only ) or putting it on the shelf for a later MPFI project. Regardless, I'd like to build this motor to where if I want to use the long intake it won't give me any grief.

The valve springs I have are talked about here: http://slantsix.org/forum/viewtopic.php ... 510#423271
I think I'll be pushing it somewhat close lift-wise at .479 valve lift, but the factory rockers are known to be not quite 1.5... Is this too close? Should I look into having my machinist machine down the guides? I dunno a thing about poundage ratings and such, would these springs be too 'light'? I plan on spinning this thing to 6k eventually...

And I recon I'll keep the 2" crush bend duals I have for now. Later on down the road I may go dual 2-2.5 single, and I'll worry bout mandrels then...

Thanks to all that put up with reading this!

Take it with a grain of sugar...Dyno 2000 without some mods will consider your engine to model after a V-8...

Make sure that you use a known set of flow values from the board (just above stock...not Jeffries ported numbers, and make sure the valve size is right...), intake manifold types will skew some of the values...the hyperpak is supposed to use the TPI style but the values fall way short of what real track and driving data hold to be true for the builds...
For the long ram intakes the narrower overlap is very required to keep reversion up the manifold and goofing up the 'signal' to the carb and fuel delivery...it also can have an adverse effect on your ram tuning making it non-existent if the designers designed around a certain benefit at a particular rpm...The Hurricane being slightly shorter than the hpak manifold will realize a little less low rpm torque (but more than a shortie 4 barrel manifold), and will ram tune at a higher rpm (your gears are set for 5K right?)... The 106 gives good torque but the overlap will bleed the cylinder pressure down greatly and it will "lope" and give lower vacuum readings at idle, requiring more SCR to make up for the losses, and the reversion will hurt things all around...typically the hpak wants a very narrow overlap and bigger LSA, the hurricane is a little bit of a compromise so you may be able to fudge the overlap a bit and go with something more akin to a 109 (my last hpak motor utilized a 110-111 overlap)...

In cam theory, tight overlap or 104-109-ish LSA = more torque, 110-116 overlap tend to = more top end HP (power band and torque band shifted to higher rpm)....but the long ram intake shifts the torque band a bit lower so the narrow overlap at 110-111 tend to equal out the higer rpm power band and lack of low end torque, but also provides ram tuning at a certain higher rpm as a benefit not realized by the shorty manifolds...

Intake event is very "lazy" and the slant with the small bore and long stroke needs a longer intake event to "suck" as much A/F mix in as it can get...most engines are very efficient in exhausting spent mix... a higher exhaust duration typically works better with headers so the exhaust is held open a little longer so the "suction" from the header can start pulling more mix into the cylinder during the overlap event (you can go too far and suck enough charge out the tailpipe and lean out the engine and start a nice fire and blow up your muffler...)

Let the V-8 guy dream all he wants, there are things that work great on the 90 degrees cycle and big bore short stroke engine...that will not work so good on the 120 degree cycle and small bore long stroke engine.

Yes it can.
The AFB or an AVS would be a fine start...Holley 500 = not best for street use or mileage...Either way you will have some test driving and tuning to do to get the best mileage and "driveability" out of it (note fun factory is high in the "driveability" equation). It took me a while to sort out the street driving and tuning, you will be paving a path as well and writing your own tuning manual for your build and car.

.480 lift is actually very mild as a performance cam goes, but is fine for the street...not too long back most guys would have gone with the MP 268 cam with .500+ lift...with 340 springs.

If you get everything machined correctly and get the custom puch rods sized up there will be no problem with the cam (it will take a mock up with the cam, lifters and an adjustable push rod to determine if everything is good).

Since the duals only have to put up with 3 cylinders each, they don't need to be any bigger than 1 7/8" or 2" ID to keep the velocity up in the pipe, anything bigger is a waste...even clifford long tube duals headers are a 1 7/8" ID outlet at the collector...so those will work just fine until they rot out and need replacing or you decide that something else should suffice.
Good luck, this is a long road that is not as rewarding to start as you sort it out, but once you do, it pays dividends...don't forget that timing plays a big part of the whole picture so you may have to do a few recurves before it all is as good as it gets.


-D.Idiot

Yeah, I've learned that Dyno 2000 is really just some neat gizmo program that can be pretty off sometimes. My 'Flow I may be able to achieve with a home port job' head flows 176 and 134@.500 (intake and exhaust, respectively) I had a hard time finding flow numbers for a home port, so I averaged one of Dutra's 1.7/1.44 heads and a stock head. Now whether that is accurate...

It never woulda crossed my mind about reversion being a problem, too bad that the tight lsa for torque and long runners for torque don't play well together. It makes me wonder if the Hurricane w/109lsa and the Offy w/106lsa would even out?

Oh, and you weren't kidding about 5k ram tuning! If my measurements and Bowling and Grippo are correct, 4" of intake runner in the head, 11-12.5" in the intake, it says ram tuning will start (4th harmonic, 4% pulse strength) somewheres in the neighborhood of 42-4600. Wasn't it Lou's studies with an aussiespeed that says they start to run out of breath around 5500? (2v version)
See, this is another place where I run into decision making problems. The Aussie is big 2v only. I'd like to use the Carter, but I'd like to use the Hurricane, and as of current it'll be one or the other... Anyone got a 4 barrel Hurricane they'd like to wheel 'n' deal for and Offy AND a 2v Hurricane? (*This offer is completely serious, Hurricane must be newer generation with bungs, some exclusions may apply, PM for more details)

If I can't find me a 4v hurricane, I may just run the 350 for a little bit... can you say throttle response and fuel economy? or I may chop it up...

Speakin' of carbs; DI, on your 280/270 build, did you run the 390 on it? Or had you ditched it already for the 450 project/600? And what was the final verdict on your 450 experiment? I've got a Holley 450 lying on the bench in the garage, sorry I cant remember the list # off the top of my head. I think I'll probably use the 500, smaller primaries/bigger secondaries would seem like a good first step to me.

Thanks for being a help! There isn't much out there on these Aussie intakes, so when I want advice that would apply to them, I end up reading your series 'D.I.'s street H-Pak tales and adventures'.