Hey guys hopefully someone will read this that know allot about building engines........Well here it goes.......I want to build a 383 for my 91 Firebird......I want to be able to drive it on the street with no prob and haul a$$ pretty much ........ maybe go to the track as well........Rear end will have either 3.73s or 4.10s and a 5 or 6 speed tranny.......I think I have it pretty much all planned out........here it goes........Eagle stroker kit 4340 forged crank 6 inch forged rods flat top SRP pistons with 5 cc relifes.......AFR 190 cc heads with the 68 cc chamber.......0 deck a fel pro 1010 head gasket........compression would be like 10.59:1.............TPIS miniram which is basically an LT1 manifold 58 mm Throttle body...........not sure how big of injectors I would need.........and as for the cam I’m debating between 2.......Comp XR 288 Hydraulic roller which has 236 degrees of duration on intake and 242 on exhaust and .555" of lift on intake and .576" on exhaust......the 2nd is the comp XR 264 Hydraulic roller Intake duration is 264 degrees and exhaust is 270 degrees with the lift for the intake being .487" and exhaust .495"..........from what I learned at school in there high performance section I learned a bit about cams but don’t understand too much of it so I played with my desktop dyno and for what its worth both of these cams are night and day the 288 has way more high horsepower and the 264 has a way bunch of low end torque so if the 288 is advanced 8 degrees the torque and HP just about level out and on the 264 you retard the cam 8 degrees and the torque curve levels out but the HP doesn’t go to high.............So I figure with a manual tranny suck as a 6 speed and say a 4.10 rear.......I wouldn’t think id need as much low end torque am I right????.........but with the bigger cam I don’t want to sacrifice derivability either.........Please tell me what you think.

 

Let me know if you need the LT-1 Intake. I have a spare. The top fins have been shaved off as well to give it a smooth look.

$75.00

Mike..

 

I'd go with a 3.90 or 4.10 rear gear, probably the 4.10 if you go with a 6spd. That way your overall First gear would be 12.18, which is super for drag racing, and you'd have no problem on the highway either.
As far as the bottom end, my engine guy (Bob Snyder- the best in SW MI) usually steers folks away from the Eagle cranks but their rods are OK. A Scat crank would probably be fine, and 4340 forged is the way to go. Also, 6" rods would give you a 1.6:1 rod-to-stroke ratio, which is considered a good compromise.
You're right on with the CR, but if you have it decked to 9.020" you'd have about 10.1:1 CR, which is more streetable. The AFR 190 heads have a great rep, but you might consider smoothing them out just a bit since a 383 can use a little more than 190cc (the 210cc ones are probably slightly too big for street use). Just smooth out the casting ridge on the intake port floor with some sanding drums.
As far as the cam, give Comp a call and just be totally honest. You'll be happy with what they recommend. And you're right: a manual trans doesn't need as much low end torque as an auto, and that means you can pick a cam with a wider lobe separation angle (which also means a smoother idle). Also, remember that a hydraulic cam can only spin up to about 6500rpm before lifter pump-up becomes an issue. Good luck, and have fun!