I've been running the middle sized Comp Thumpr in a 273. With 1.75 headers 3in collectors with street tunnel ram and pair of 450 cfm Holly's. My car is around 2600lbs with a 4speed with 4.56 gears and currently 29in tall tires.
That Comp Thumpr has been a good cam for my only 9:1 tween. Car idles awesome, right at 700rpm, sounds great, and pulls to 6000rpm quickly. Motor is only 9:1 and heads have minor porting.
I choose the Thumpr because I didn't want to machine the heads for more than .500 lift. I wanted a more radical cam that would work with my only 9:1 compression. I have 155psi cranking compression with this cam.
Specs for the Comp Thumpr is a
Operating range 2,200-6100
Adv duration (IN 287) (EX 304)
Duration @ .05 (IN 235) (EXH 249)
Valve lift (IN .497) (EXH .483) with 106 LSA
I'm now building a 318 with 10:1 compression and ported 360 heads and was considering running my old cam but felt I'd be leaving to much on the table. I've been looking at the
Comp XE 285HL Hyd flat tappet or the
Comp XS 282S Solid flat tappet.
I'd be curious AJ with your math if it would show which would be better cam for a small cube manual trans combo like mine. Im doing oiling mods and prep to get this motor to rev to 7 to 7500 for peak power. Been trying to read up on adv or retarding cam timing to shift the power band up.
The XE285HL specs are 2500-6500
Adv dur (IN 285) (EX 297)
Dur @ .05 (IN 241) (EX 247) with (IN.545/EX.544 lift) on a 110 LSa
The XS282S 2500-6500
ADV Dur (IN 282) (EX 290)
Dur @ .050 (IN 244) (EX 252) (IN.520/EX.540 lift)
on a 110 LSA
I'm not sure on the intake center line of those 2 cams. Not sure how much to retard cam for the RPM range I want. The motor may be small enough that peak power will move up to the 7000rpm range with the larger cam without needing to retard cam. Either way I plan to call call luntai and comp and see what they recommend. I may go custom grind but would appreciate any further cam info. This isn't a daily driver but does need to run on pump 93.
