Page 1 of 1

LSX camshaft questions

Posted: Tue Nov 07, 2017 10:02 pm
by JodyB
Given a stock based 6.0 ls with stock based rectangle port heads and hydraulic roller lifters. Valvetrain geometry and stock rocker arms limit valve lift to about 625 lift, and open pressure to about 400lbs. Most aggressive aftermarket cams lose valve control about 72-7300. If a camshaft with the same 0.200 duration and net lift, with milder ramps are used, say adding more duration to the 0.50 and advertised to enable more rpm. Will the enormous addition of low lift overlap affect the engine's preferred intake to exhaust centerline, or will it just be nasty at low revs and who cares?

Re: LSX camshaft questions

Posted: Tue Nov 07, 2017 10:10 pm
by JodyB
More on the combo. 6.0ls, 11.5cr, holley hi-ram (tunnel ram) with w 2 600 carbs. L92/ls3 rectangle port heads.

Re: LSX camshaft questions

Posted: Tue Nov 07, 2017 10:16 pm
by JodyB
I see lots of internet heros picking perfect IVO,IVC,EVO,EVC events, however, my motor needs rpm and cylinder filling:)

Re: LSX camshaft questions

Posted: Wed Nov 08, 2017 6:12 am
by In-Tech
That intake is nothing like a long runner stock or FAST intake

These GM lifters(88958689) and cam it similar to a small port SB2, talk to Mike Jones.

Re: LSX camshaft questions

Posted: Wed Nov 08, 2017 6:48 pm
by RAS
YES. Lobe Center angle will effect overlap and it will have a big effect. Note GM uses a wide L/C to keep overlap at a minimum. They have good reasons for this.

Re: LSX camshaft questions

Posted: Wed Nov 08, 2017 11:02 pm
by JodyB
Given prior valvespring limitations. Intake 297advertised, 247@50, 169@0.200, 624 lift. Exhaust 311advertised, 258@50, 172@200, 595 lift. Engine seems to like 110 lobe seperation angle. Valvetrain loses control about 7300. Theoretical cam profile... Intake 321 advertised, 260@50, 169@200, and 604 lift. Exhaust 325 advertised, 264@50, 173@200, and 604 lift. Will the excessive low lift overlap of the new "rpm cam" affect what the engine seems to have preferred for an intake to exhaust seperation angle for max output? Will the engine prefer the same lobe centerlines, and just deal with the sub 3000rpm nasty behavior? Will output improve by spreading lobe centerlines to achieve an overlap "area" closer to the original cam spec?

Re: LSX camshaft questions

Posted: Thu Nov 09, 2017 1:02 pm
by A_VAS
$800 will give some insight...buy 2 new grinds, one at 110 and one at 116 LSA

then more questions will arise...if the 116 is better, then do you try a 121 LSA ?

Re: LSX camshaft questions

Posted: Thu Nov 09, 2017 1:30 pm
by prairiehotrodder
FYI - i just built a 6.0L with a stock LQ9 (Flat top piston) short block and a set of the L92 heads. Piston to valve clearance was not good. Had to notch the pistons with a Lindy tool. I get my cam specs if you care to know.
Brian

Re: LSX camshaft questions

Posted: Thu Nov 09, 2017 3:53 pm
by CamKing
JodyB wrote:
Tue Nov 07, 2017 10:02 pm
Given a stock based 6.0 ls with stock based rectangle port heads and hydraulic roller lifters. Valvetrain geometry and stock rocker arms limit valve lift to about 625 lift, and open pressure to about 400lbs. Most aggressive aftermarket cams lose valve control about 72-7300. If a camshaft with the same 0.200 duration and net lift, with milder ramps are used, say adding more duration to the 0.50 and advertised to enable more rpm. Will the enormous addition of low lift overlap affect the engine's preferred intake to exhaust centerline, or will it just be nasty at low revs and who cares?
Have you tried using a less aggressive profile, to see if the added valvetrain stability increases RPM ?

Maybe something like this ?
Cam# LS1, HR75375-78360-116
298/306 @.006"
244/253 @.050"
161/166 @.200"
.375"/.360" Lobe Lift
.637"/.612" Valve Lift
116 LSA