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Discussion Starter · #1 ·
Hi,my dad is building a supercharged 383 sbc in his 1985 2wd long bed truck,it is a 100% daily driver,we are needing some help with the camshaft for it,here are the specs of the combination:

383 sbc(4.030" bore/3.750" stroke/5.70" rod)
4340 forged 3.750" crank,dual keyed
4340 forged Scat H-Beam rods
JE Extreme Duty -31cc dish,Total Seal conventional rings
"0" decked block
8.50-1 compression
Brodix Iron Killer 180cc aluminum heads,2.02/1.60 valves 64cc chambers
Magnuson MP122 supercharger 7 lbs. boost
Quick Fuel Tech. 750 double pumper, 74/84 jets,M.R. Powervalve
1 5/8" headers,dual 2 1/2" exhaust,3" Borla XS mufflers dumped
700-R4 transmission,PTC 12" 2400 stall converter,3.42 gears

We were going to run the NX274H hydrailic flat tappet camshaft in this,here are the specs:

274/292 adv. duration 230/244 [email protected]" .488"/.501" lift
108* intake centerline 113* lobe seperation
Valve Events:
IVO- 29* BTDC IVC- 65* ABDC
EVO- 84* BBDC EVC- 28* ATDC

We are concerned with the NX274 camshaft having that much duration and wide lobe seperation combined with the low 8.50-1 compression,we are thinking it might kill to much low end cylinder pressure,and cause it to feel sluggish at Part Throttle low speed driving,it really needs to be excellent with this combo,since it is 100% daily driven. In fact we are more concerned with having low end torque,and having a snappy part throttle than high end horsepower,because it needs have good drivability.

I have been playing with my Desktop Dyno,and found another cam that seems to work well. It is a one of Comp Cams Extreme Marine grinds,the XM270H hydraulic flat tappet,but I changed the 110* Intake Centerline to 108*,and looks like a good camshaft,here are the specs is for it:

270/286 Adv. Dur. 226/236 dur. @.050"
.480"/.489" lift 108* Intake Centerline 112* lobe seperation

Here are the Valve Events:
IVO- 26.5* BTDC IVC- 62.5* ABDC
EVO- 78.5* BBDC EVC- 26.5* ATDC

This cam shows to better the NX274H in the lower operating range,it has over 500 lbs. tq at 3000rpm,with tq. peak around 4000rpm,and peak hp at around 5600rpm with 485hp.

What do you guys think? What camshaft would you run? Feel free to list other cams also,if you have another choice.

Thanks,Brian
 

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I dont think sluggishness will be an issue -
lean towards the smaller one, if its a genuine streeter.
Psi is your friend here.
You need to start somewhere ;)
 

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Discussion Starter · #6 ·
Thanks for all the replys guys,is there a reason all you guys are picking the NX274 over the other camshaft? I am just curious why it is better?

Steve,do you do custom Hydarulic Flat Tappet camshafts for Prochargers? I know you do hydraulic roller and solid roller,but didn't know about the flat tappet stuff,if so how much?. We may want to put a different cam in my dads D1SC Procharged car one day,and was wondering if you did those.

Thanks
 

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Thanks for all the replys guys,is there a reason all you guys are picking the NX274 over the other camshaft? I am just curious why it is better?

Steve,do you do custom Hydarulic Flat Tappet camshafts for Prochargers? I know you do hydraulic roller and solid roller,but didn't know about the flat tappet stuff,if so how much?. We may want to put a different cam in my dads D1SC Procharged car one day,and was wondering if you did those.

Thanks
For me, it's the over all cam "size". The 274H also has a bit better bias on exhaust lift.

Don't think of this like you do a N/A motor. If there's not enough snap, you toss a smaller pulley up top, especially with that low of compression.

I've run 9.5:1 with 7PSI before on 93 pump gas with iron heads without issue. You having a full point less compression and aluminum heads....you will almost certainly tolerate more boost.

Depending on cost/budget, I'd also be asking Magnusson if they offer that blower with the Eaton 4-lobe rotors, like in the MP1900 and MP2300. The 4-lobe rotors are a 160 degree helix.
 

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Discussion Starter · #8 ·
Ok, we have decided to go ahead and use the NX274H,should we advance it or anything,or just put it in "straight up" at it's 108* intake centerline? We will be degreeing the camshaft.
 

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Degree it per the cam card. It'll do fine for what you're wanting. If it feels sluggish, don't hesitate to up that boost a bit. 10-12 PSI should make it a screamer. I do, however, think you're exhaust is going to choke the power. Particularly the primary pipes.
 

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Discussion Starter · #10 ·
Thanks for the info,we know the primarys is on the small side for a 383,but we figured since this is a street deal,that is going to be driven everyday,we figured would just run the 1 5/8" headers thats on it,as I have read that the smaller tube header will produce more torque than the bigger tube,but does kill horsepower,but we are more concerned with torque and part throttle drivability with this deal.

I appreciate the info alot,

Brian
 
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