GeneralDisorder

iTrader: (1)

I've been playing with Comp's Camquest software... probably dangerous to believe what it says....

Anyway I want to try something a little different. I figure the TPI is good for somewhere around 300 HP N/A. Give or take. 250 if you prefer. I don't want to debate it's merits per-se. I'm going to force air through it at 15 psi so theoretically it should close to double the N/A rating.

To the point - I've always run turbocharged in the 9:1 range. The Camquest software is giving me the option of a 292XFI, and I'm also not seeing a wide availability of dished SBC pistons to attain around 8.5 to 9.0 compression.... what should I be running static compression with this cam to get a good dynamic compression for 15 psi forced induction on my 383 build?

Thanks!
GD

cardo0

Your really asking several questions here GD, or at least need help with several issues of the build. First is the 292XFI cam. Even with the wider LSA I'm seeing 70 degrees of overlap. Meaning that 15 psi is gonna push a whole lot'a air/fuel mix right out the exhaust valves and into the headers. Talk about headers turning colors.

Now compression ratio for 15 psi not a known number but for sure you want it a full point below NA ratio. For aluminum heads that means 8.5 to 9.5 range. It's the heat that compressing the air/fuel that causes the detonation. And realistically can a motor have much for performance below 8.5 c.r.? Even with 15psi boost? At low RPM and low boost it gonna be wheezer.

I'll try and share something with you on supercharging here. You want to use open chamber heads to put as much of the static volume above the piston as possible. This allows the positive pressure to fill the entire chamber much better and lessons the recirculation of combustion gases. Yes 76cc chamber heads allows for smaller piston dish. Next you want to maximize exhaust flow rather than intake as the forced induction fills the cylinder better than it can let exhaust gas out. Big exhaust valves and low restriction exh sys is better than too much can overlap.

Hope this helps. Take it or leave it.

Orr89RocZ

iTrader: (20)

You need to list more information.

I dont like comp cams camquest thing.

What heads and bottom end parts are in the motor. 383 with tpi? Thats a giant cam for a 383 let alone tpi. I ran a cam a bit bigger than the 292 in my 400" 7200 rpm 1400 hp setup

I would strongly consider the 280 xfi as biggest cam i would run in a 383 tpi with boost. However depending on the hp goal and if the tpi system is ported and large tubes or not, could even go smaller 268xfi. That is ofcourse you want to stick with an xfi lobe, which are pretty aggressive. If valvetrain is light and good stiff double springs it can work.

With tpi and low rpm i want to see bit lower compression. It will give you a wider tuning window. Tpi makes high ve cylinder fill at low rpms. This makes it timing sensitive. Combine that with boost and high comp you can have issues. Gotta really sneak up on timing.

If its aluminum head, ok chambers, 9.5:1 is good. Fast burn head like a afr or vortec, 9:1.

Cam will help bleed off some cylinder pressure. If you can slowly ramp boost in to avoid hitting high boost in the 2800-3500 rpm ranges, you could get away with 10:1 comp if well intercooled. Size the turbo large enough to not come on like a light switch and watch the timing it will live great

GeneralDisorder

iTrader: (1)

Sounds like the 280xfi and 9:1 might be the way to go. That's about what I'm used to. Last EVO I built was 9:1 and had 272 cams. It runs pretty hard for a 2 liter.

So open chamber heads? Any suggestions? I was thinking AFR aluminium heads and getting the full cam kit from Comp.

I've got a 93 roller block. 4 bolt main. Likely go with forged Scat crank, Arias pistons, etc.

Shooting for 500-600 HP. Either with a turbo or procharger.

Trying to put together my shopping list.

GD

Orr89RocZ

iTrader: (20)

I assume this is 500-600 whp?

10 psi will do it. Afr 195 heads are awesome. But any decent head will work, just make sure it has a proper valve job, with the right springs for the cam, if using xfi lobes.

If thats all you want for power, you really dont need much over 224 deg duration. With a tpi intake that is

GeneralDisorder

iTrader: (1)

Yes just a paltry 600 WHP should do it. maybe more later.

It's just a daily driver. The trans and rear end.... might hold that much. I don't want to turn it up till I blow it up.

My plan is to get the Comp cam K kit.... K08-467-8.... I acknowledge I don't need this much cam to make the power I'm looking for but I rather like the sound of the 280 or the 292. They have a preferable exhaust note and I want to insure I can just add more boost and more fuel later.

AFR 195 heads. Largest head volume they make?

Now I just need to figure out if someone makes a shelf piston kit with appropriate dish volume. Or if I have to order custom.

GD

cardo0

Spend $20 on a book for supercharging. Not likely to have your exact build but a good book should give you the big picture to choosing parts. Many supercharger books are kinda dated so see if you can find something on the shelf that describes your type of supercharger. Heck you'd be surprised what the library has or can get you if you're in a large town.

Good luck.

GeneralDisorder

iTrader: (1)

More than likely I'm going to go with a Procharger....

The 280/292xfi falls right in line with their recommendations on duration and LSA.

With a 3000 stall converter I won't be overly concerned with low RPM performance and most people with TPI are trying to shed low end torque which these cams may help with?

GD

Orr89RocZ

iTrader: (20)

383 tpi with as&m runners and big mouth base
Afr 195 heads. Xfi 224/230 custom cam
5 spd manual
Procharger d1sc on 8 psi

521 whp 583 wtq.

If you go blower no more than the 280 xfi will do it. Turbo i like alittle smaller
Could try the comp 12-415-8 nitrous/blower cam too. 224/236

86LG4Bird

iTrader: (1)

As I was reading through this thread, I was thinking exactly what Orr just suggested: something along the lines of that 12-415-8 cam with the XE lobes. My preference would be to keep life easier on the valvetrain and avoid the XFI lobes. IMO, their merits in a FI application don't justify the extra expense & maintenance on the valvetrain.
GD, is your motor flat or roller tappet? That 12-415-8 is a retro roller. Either way, Comp will make you an OE roller cam with the same profile too.
Or...here's my go-to for a custom cam for just a few bucks over Comp's catalog price:
www.elliottsportworks.com
Lloyd has more experience with a wide array of setups than any of us here.

GeneralDisorder

iTrader: (1)

The block I have is a 93, 4 bolt main truck block with roller provisions.

Procharger does say 10 degrees and .010" more exhaust lobe than intake lobe.

Better valve train life is a plus. Ok I'll look into the XE blower cams.

GD

cardo0

Yes the 12-415-8 cam is a much better choice with 56 degrees of overlap - which is the max amount of overlap I would use on the street. Now if you want the next step down the comp 268XFI HR13 (08-466-8) has only 46 degrees overlap and should idle stock smooth but twist your head off midrange - you do give up some top RPM power though. If you run the 268XFI HR13 (08-466-8) cam try it with 1.6 rockers on the exhaust vlvs if the heads have good enough exhaust flow to support that much lift.

Good luck GD and hope this helps.

cardo0

AFR 195cc SBC Street Cylinder Head
with 75cc chambers. They have big chambers and great exhaust flow. The AFR 195cc Race heads do flow better but are 30% more expensive.

Try calling this guy for great pricing on AFR heads:Jim Barth
801-953-6391. I never seen AFR heads that cheap. No i'm not a salesman as i'm in Las Vegas and he is in Utah. Just trying to help. But you can drop my name if you talk to him.

Good luck.

GeneralDisorder

iTrader: (1)

So that same grind in a factory roller cam would be: 08-301-8

Correct?

I will check out Jim's pricing. Thanks cardo0!

GD

Orr89RocZ

iTrader: (20)

Yeah