s57_s2k

is it ok to have 50 kpa vacuum at idle with a -4.8 overlap camshaft ? the ls7 lifter preload was 0.100 , engine is l76 ( 6.0 with l92 head ).

s57_s2k

Some of the lifters have 0.105 preload . I guess I should try 7.375 pushrod so I can get 0.08 preload.

the problem am facing now is low engine power ( or small power increase with a wider power curve ).

went from stock l76 cam to 224/234 117

07NBSChevy

iTrader: (1)

0.080 is ideal for LS7 Lifters. 0.105 preload is definitely on the high side. I know at a certain point that if the lifters pump all the way up it will hold the valves open. Vacuum is on the lower side but still ok. Are you measuring it in gear, well if its an auto?

s57_s2k

will oil pressure ( DOD oil pump ) effect lifter bleed down at high RPM ? I am measuring vacuum in park , yes it is auto 6l80e.

I thought -4.8 overlap is going to be stealth and no one will detect the cam.

pantera_efi

iTrader: (1)

Hi, did you install a "tune" in your ECU ?

I LOVE your cam choice, should Idle well, better than stated.

This IS NOT a "pre-load" problem as the KPA reads would BOUNCE.

Lance

s57_s2k

yes I tuned it today , now it idle just like stock . the preload now is 0.080~0.075 and it feels good, maybe I will try 0.050 preload next week.

JakeFusion

iTrader: (7)

What is your RPM set to? If stock, it'll idle worse. Bump it up to 700.

s57_s2k

RPM is set to 700 and air to fuel ratio is 14/1 to hide the cam sound. It will pull good up to 6500 rpm , the stock cam after 5500 rpm fall on its face.

JakeFusion

iTrader: (7)

14:1 is too rich. Lean it out some more.

What's your timing set to?

s57_s2k

If I lean it to stoichiometric 14.7/1 you will hear the cam , and we need it to be stealth to cheat some people . Base idle timing is 13 deg but it moves up and down a little. I will try to increase the timing next time.