formula_novice

iTrader: (1)

Hi Guys,

I'm taking my 383 out of the Firebird and putting it into a Camaro soon. I'm wanting to switch to carb, an Edelbrock RPM intake and a manual transmission. Here is my current setup:

383
~11:1
AFR 195cc w/60cc chambers
XFI-280 cam
Doug's 1 3/4" LT Headers
CC 1.6 Ultra-Pro Magnum Roller Rockers
Cloyes Double-Roller Timing Chain
Aluminum Underdrive pulleys
Edelbrock Water Pump
Powerstarter mini-starter
aluminum driveshaft
3:73 rearend

Being a car guy, I was wondering if there is anything I can do to squeeze a bit more power out while the engine is easily accessible? I am hoping for 500-550 FWHP if possible but need to retain my power brakes.

My first thought was upgrading cams to either...

08-433-8 XR288HR 288/294 236/242 .555/.576 w/1.6

08-433-8 XR294HR 294/300 242/248 .540/.562 w/1.5

Any thoughts? Car is mostly a weekend driver for sunny days & car shows.

Thanks guys!

skinny z

Are you certain about the 11:1 CR?
Are you looking for the most peak horsepower and torque or something that might limit the peak numbers but tend to flatten out the curve somewhat?
A 383 to make 500-550 hp would need in excess of 6000 RPM to produce. Your cam overlap will be part of what determines where that RPM is (among other factors). For best peak numbers, work with something on a 108 LSA. With the AFR heads, you have what it takes in terms of air flow. You'll be on the cusp regarding RPM and a dual plane intake although the RPM Air Gap arguably will support you up to 6500.
You'll probably find that the 288 you've listed, with the 110 LSA and 71° of overlap will produce enough idle vacuum to run your power brakes. If the ignition timing is right and your compression ratio is as you say, you could expect 10-12".
Tighten up the LSA to something more along the lines of what a 383 requires for best peak power and if you're keeping the same duration values as the Comp 288, expect peak values to move up the RPM scale by a few hundred RPM. That said, with the tighter LSA and same duration, overlap increases to 75°. Expect your idle vacuum to drop a couple of inches. Power brakes would be suspect.
All of that said, the best advice is to contact Jones, Walters , Speiers etc and get a proper specification.

As a follow up, with 11:1 and the 288 installed on it's spec'd 106 ICL, your dynamic compression will be in excess of 8.4:1. Experience says that it'll be difficult to keep out of detonation with a full and proper timing curve. Not impossible though.
That's why the first question asked was the certainty of the 11:1.

formula_novice

iTrader: (1)

Thanks for the info skinny. When I built the short block, I calculated about an 11:1 compression ratio... but keep in mind, I'm a novice engine builder

To lower the dynamic compression and stay away from detonation, could I simply use a thicker head gasket? Or will that not be a large enough drop (i.e. I would need new pistons)?

GOTCHEVY

iTrader: (1)

Has the car ever been on the dyno? If so, what did it put down?

Orr89RocZ

iTrader: (20)

Yeah whats it run now? Track or dyno time?

280 xfi is a great cam and makes power with them heads

I would move it to a 108 or so icl but that cam should run fine at that compression and those heads.

A new xfi cam on a tight 108-109 lsa vs the stock 113 would help alot, beef the midrange and you can add 2-4 deg intake duration
Get it in a billet core and run the afr 8019 springs. Vic jr single plane and turn 6800 all day

You could also try my custom cam i got for my 383 back in the day. Same heads and compression just about. I had flattops and 64cc chambers. Comp magnum high lift lobes. 230/245 .603/.613 lift on 1.6 rockers and 109 lsa in on a 108. Shift that at 6800-7000. Trapped 119 in summer heat all motor

formula_novice

iTrader: (1)

Sorry no track/dyno numbers yet.

Thanks for all the info Orr! Would the tighter 108-109 lsa effect my power brakes?

Orr89RocZ

iTrader: (20)

It will lose vacuum but should still have enough. You can idle higher if needed or run a canister

skinny z

That's a double edged sword. A tight quench helps reduce the tendency to knock. Increasing the piston to head clearance leaves more room for end gases to remain. So it's kind of back of forth.
What do you have for: piston dish volume, piston below deck distance, rod length? Is it overbored?

Orr89RocZ

iTrader: (20)

I wouldnt do anything until you dyno or get a decent track pass in to see what it actuall does for power