ehirst83

iTrader: (5)

I'm ready to choose a cam. There are so many variables that any input would be hepful. My current motor is as follows: '71 455 bored .60 over w/ forged pistons, balanced and blueprinted, stock heads with port and polish, Edelbrock Performer RPM intake, and Edelbrock 825 CFM Quadrajet carb. The cam I am looking at is made by Schneider, 248/258 duration at .050, .525" lift, and 108 LSA. Is this a good choice for street/strip? BTW my Firebird is a '67 so emmissions are N/A

Clair

chief455

iTrader: (21)

Nice combination until you hit the cam.
First question: What cast number on the heads?
If they are '71 455 heads it's got under 9:1 compression, which hurts the overall idea. Around 9.5:1 is ideal.
Anyway, for street/strip with a 455 my best and 12 second street cams were no more than 230-240 duration at .050 and around .470-.490 lift. Also for street use a 110 lca installed at 106 works great.
Call Jim Butler Performance in Tn - or Ultradyne Racing cams.
They will hook you up.
The cam you describe is more for strip with that much duration and narrow lca. Probably designed for a built 400. The split duration, high on the exhaust side is best with factory, even ported factory heads because they tend to have superior flowing intake ports. Thus more duation on the exhaust side to help out. Straight pattern cams like Lunati Bracket masters are not as well mannered or receptive to ignition timing in my experience.
Another thing I've found to work well with Poncho motors is purposely picking slightly less lift and using a higher ratio rocker arm. The factory used 1.65 rockers on some of the performance motors intead of the standard 1.5 ratio.
Of course the springs should be suited for them.
Should check your actual flow number (intake+exhaust) before selecting the cam.
The 455 doesn't need much cam and the one that goes in will be more driveable because of the size of the motor!
My pick if 8.5:1 to 10:1 would be=
.470/.470 lift, 237/242 dur at .050 and 110 lca installed at 106 intake degrees.
Good Luck

ehirst83

iTrader: (5)

Thanks for all the info! I'm not sure of the casting numbers but I could check. The motor was actuallly built by my father and I know the compression is around 9.5:1 with the pistons that are in right now. I guess I am trying to compare lift numbers to an LS1 motor .470 lift just seemed small in comparison. What do you think that set up (around 230 duration and .470 lift) will put down power wise? I want 400rwhp with a 75 or 100 shot of nitrous.

chief455

iTrader: (21)

I'm not to good at the dyno races, but a very similar combination to yours in a 3700lb GTO I had went 12.80 at 109 mph with radial T/A's - not even drag slicks or sticky! My 60' was like 2.2 so you do the math. If your 67 bird is 300lb lighter than mine with the same motor and you hook up it would be very low 12's as driven daily without nos. Maybe even high 11's but that's optimistic.
See looking for rwhp with a 455 is like looking for torque at the crank on an LS1.
You need to utilize the gobs of torque the Poncho puts out to throw you down the track!
Forget rwhp numbers like everyone in here goes by. Make torque. At 5250 rpm torque = horsepower
That is usually the sweet spot for shifting a big cube Pontiac.
Example: my last motor made 610hp at 6400/610lbtq at 4400 max.
The tq was over 500lb from 3000rpm up and never went below 550lb until peak hp!!
A different animal. A .030 455 with ported 9.5:1, that size cam and good headers/ignition/intake/carb can easily make 450hp at the crank.
Try that before you spray it.
Pontiac bottom ends are designed for the low rpm range and unless you built the crank/rods/pistons for nos you will hurt it.
Let me know your exact piston/head specs along with the details of your shortblock and I can pick an intake, carb, cam and ignition to make you pump gas 500hp at the crank that's real street friendly. And will be reliable, never need to fill a bottle.
Torque - it's there when you want it
PONTIAC!