Phozzy

okay, so i have been searching the forums but haven't found anything that sounds like my problem. i put a cam in about 2 months ago and since then i hear a loud tapping when a step on it or try speeding up in 6th gear. it almost sounded like a rocker arm tapping however i see no signs of contact under the covers. all are tight and no pushrods are bent. i have also heard loose spark plug but already check and everything is good. getting very frustrated. also car doesnt idle right sometimes. it will drop revs then come up... it will do it several times then level out. also oil pressure drops quite alot as it does this???

Burken01

iTrader: (88)

Did you measure pushrod length and proper preload for the lifter your using.. Too little preload will cause slight tapping.. Ls7 lifters like .060-.080 preload

Phozzy

ya i measured the pushrods and they are exactly the same as stock... but i have not checked the preload

the404man

Did you happen to remove your oil pump or loosen your pickup tube during Cam change ?

If so, might be a O-ring problem.

Or maybe the new Cam lift is too high for the springs and your getting a small bit of coil bind, did you have the car tuned yet for new Cam ?

If not that might be the problem for the not idling right, and the oil drop could be just as simple as, when the rpms go down, pump no pump as much.

Im only throwing out idea's here is all ...

Kinda hard to say with out hearing the tap your trying to explain. (for me anyways)

You should post up a sound clip/video..

Cause it could be and i say could be, a rod knock "under load"

Does it tap on a free rev ?

... hope you get problem fixed soon peace ...

crainholio

iTrader: (2)

You'll want to measure your preload as a next step. Bigger cam means smaller lobe base circle, and if you're running stock-length pushrods you most likely ended up with inadequate lifter preload.

FIVEPOINT7

iTrader: (2)

Also if your cam has extreme ramp rates like mine does (XE-R lobes) the car is going to sound like a sewing machine no matter what you do. I run .075 preload on comp 850-16 lifters and my valvetrain sounds like a taiwanese sweat shop. The idle is in the tune. Mine does the same thing you're talking about, I call it idle walking. Either have the shop spend more time on it, or do what I am doing and go somewhere else.

Phozzy

thanks for all the suggestion guys and actually i did the cam myself with help from some buddies.... i was doing some research and saw the steps for valve adjustment and lash, which i know how to do, but my buddies put the rockers on while i ran to get some oil and other parts. i asked them today (assuming they did at the time) if they set the lash and adjustments but they were clueless... sooooo tomorrow im gonna set them right and hopefully that solves the issues.. not to mention i do still need a tune.

Burken01

iTrader: (88)

whoa what rockers are you using?

Phozzy

just stocks.... but what i am thinking is that they were thrown in and tightened way to much... whats your thoughts on how much to turn after pushrod has stopped moving when tightening them???

Phozzy

not to mention that they probably tightened them without turning the engine.

Burken01

iTrader: (88)

Stock rockers don't need adjustments, you set it to zero lash using an adjustable pushrod.. Then add the preload you desire for the lifter brand your using..

And if you knew how to do it but they ended up doing it without knowing how, why didn't you fix the mistake then?

Lol if they are clueless why on gods earth would they put any hands on your engine...?? This to me makes no sense!


And you tighten the rockers down to 22 ft lbs

Phozzy

ya i see my mistakes now..

so from what you have said and from what ive looked into...

rockers to 22 ft/lbs

"only way to adj preload is with shims at the fulcrum or longer or shorter pr's
and that ls1's have a tendency to sound like sewing machines after camming
( heard that on many different forums)"

personally i dont want that sound but may have to deal with it...

also sorry for being a newbie!! i am more use to a mechanical flat tappet cam like on my 440 and 400

crainholio

iTrader: (2)

There is neither valve lash nor adjustment on an LS engine valvetrain.

There's lifter preload. The only easy way to change it is by swapping in shorter or longer pushrods.

And if they just ran the rocker bolts down without bringing each cylinder to TDC (and the cam's lobes for that cyl to base circle) they probably ran the lifter plungers down into the bodies. If you're lucky they'll pump back up, but on old & tired lifters it can be enough stress to cause failure.

Phozzy

i got everything perfect now!!

no more noise and smoother plus cam sounds much nicer.. even fixed the idle

also just went with a full tune up on the car so all i need now is a computer tune and i am all set... thanks for the input guys.. much appreciated

gagliano7

SO what did you do to fix the problem?

03Sssnake

iTrader: (20)

^^^^I would imagine properly torquing the rockers down while on heel of the cam.

Voluptuous-V

iTrader: (2)

Sooooooooo 6 years later.... what was it??!!

LilJayV10

iTrader: (39)

watch out. the old thread ****'s are going to be after you.....

G Atsma

Phozzy hasn't been here since January of 2016.