FAQ |
Members List |
Social Groups |
Calendar |
Search |
Today's Posts |
#1
|
||||
|
||||
Split vs. Straight Duration Camshafts in a Race Car?
I know that a split duration camshaft is the better choice for our Pontiacs, especially stock and mild performance street applications that are running a full exhaust/cat converters etc. No doubt the Pontiac engineers knew what they were doing and restricted dog leg exhaust motors like ours certainly benefit more from the split duration than other class of motors do.
My question is: For a aftermarket head open exhaust racecar, is that still the case? For example, I'm about to start building a new 428 to replace my long in use 463. I will transfer over my 74cc 292cfm KRE heads and will be running around 11.0:1 compression with my Hooker Super Comp headers. I have a 290B6 on the shelf (.540 lift .255/.266 @ .050 duration) but would that cam be any better or worse than say a Comp 306S solid cam that is a straight profile (.555 lift .260 @ .050 duration)? Again, open headers with 18" 3" extensions for the crankcase exac.
__________________
Johnny US Army Retired 1978 T/A 463 Pontiac, KRE 74cc 292CFM D-ports, Lunati VooDoo, V-max lifters, TKII, ATM 850 E85 carb, TCI TH-350 race tranny, 3600 converter 3.73 12 bolt 11.63@116.68mph 1981 T/A 4-speed 406 Pontiac, Merrick ported 6X heads, Comp 270S cam, Crosswind intake 750 Street Demon, 3.42 30 spline Eaton posi street car. 1980 Formula 350 Pontiac back burner project 1972 LeMans 350 Pontiac |
#2
|
||||
|
||||
Cant beat the 290B
__________________
Jack Ferris RestoRacing LLC www.restoracing.com Sandy, UT --------------------------------------------------- |
#3
|
||||
|
||||
290B,
then swap rocker ratios around to see what it likes. 1.5 Int/1.5 Exh 1.65 Int/ 1.5 Exh 1.65 Int/1.65 Exh 1.5 Int/1.65 Exh That will tell you if the engine wants more on intake or exhaust side. Changes can also be made in the valve lash as well. Better the exhaust port flows less cam in needs. I just swapped from a 1.65 rocker to a 1.6 on the exhaust side only on a Comp .440 lobe cam and the car picked up a tenth in the 1/4.
__________________
66 GTO Nostalgia Super Stock/Street Legal Car 421 CID, stock block, Wenzler Intake, 2- Carter 750 AFB's, 3.90 Gears, Full Factory Interior, Full Exhaust, Stock Suspension 3750LBS 9.77@136.99 Multiple NSCA/NMCA World Champion 66 GTO 389 3x2, 4 speed, 4.33 gear, Montero Red 33K original Miles 67 GTO 2dr Post, 428, Tri Power, 3.55 Gears 80 Trans Am Black SE Y84 W72 WS6 |
#4
|
||||
|
||||
Some theory depends on airflow exhaust/intake ratio on what split to use.
__________________
Skip Fix 1978 Trans Am original owner 10.99 @ 124 pump gas 455 E heads, NO Bird ever! 1981 Black SE Trans Am stockish 6X 400ci, turbo 301 on a stand 1965 GTO 4 barrel 3 speed project 2004 GTO Pulse Red stock motor computer tune 13.43@103.4 1964 Impala SS 409/470ci 600 HP stroker project 1979 Camaro IAII Edelbrock head 500" 695 HP 10.33@132 3595lbs |
#5
|
||||
|
||||
Quote:
What intake will you run? |
Reply |
|
|