GM LHU valve timing verification

[Mills21]

Hi,

Recently performed valve timing measurements on a GM LHU are as follows. Can anyone verify ?

CA @ max. lift [Intake=54°BBDC, Exhaust=61.5°ABDC]
Valve opening @1mm lift [Intake=24.5°ATDC, Exhaust=36°BBDC]
Valve closing @1mm lift [Intake=48°ABDC, Exhaust=22°BTDC]
Duration @1mm lift [Intake=203.5, Exhaust=194.0]


Thanks a lot!

[cobaltssoverbooster]

your center-line's are i/e 101.8/97 @ 1 mm lift
normally the CL are around the 106-112 mark intake side

if you don't have a set of cam adjusters that you can tear apart then you will not find the tri-spec for the cams.
Tri-spec= Max mechanical advance/Max mechanical retard/Mechanical Median Specifications.
The factory cams are measured in both positions and then calculated for the median which is what the cam spec card from gm shows. Cam Phaser's are supposed to have the camshafts degree'd for mechanical center so they can be adjusted evenly both for retard and advance.

it sounds like your cams are in the correct spot but your only matching values to a gm cam card would be max lift at valve (by height not at what angle it achieves max height).
Max height angle is null and void because the valve actually spends normally about 5-10 degrees sometimes more for race cams at max lift values. because of this the lobe center-line is used to determine correct positioning of the camshaft. it is found by measuring .050" under max lift before and after the max lift. so if max lift is .400" you take angle readings at .350" before .400" and .350" after .400" lift. the middle between the two angle readings it the mechanical lobe center-line which is mucho importante to blueprinting engines.