First start after cam change ls1

[johnno010684]

cool what size cam ?

Comp 222/224 @ 112 lsa so only a mild one, I didn't wana go too big for my first change. But I'm sure I can get some decent power out of this when I take it to be tuned.

 

[cander24]

I was told you don't need to check lifter preload as there hydraulic

If its an off the shelf cam with all the bits provided to go into an otherwise stock motor, its probably fine. But, this should always be checked as your new cam is likely running a different radius base circle on the lobes to stock, and can therefore require shorter or longer pushrods to suit. Idealy, you want about 0.030" of preload on the lifters. From the rocker bolt tightening point which just takes up the slack on the pushrod so you can just spin it in your fingers, this is approx 1/2 - 3/4 turn crush. Not enough preload will give noisy valvetrain and too much preload will give low oil pressure feed to the rockers.
This may not be your problem at all, but something to be aware of as you dive deeper to find the source of the noise.
Very unlikely, but did you check all the pushrods tubes were free of any obstruction/foreign material that would prevent oil flow?
Cheers.

 

[johnno010684]

yea it was a complete cam package all the bits to suit the cam, i blew thru all the pushrods to make sure and soaked them in oil before i put them in, same with the lifters.

 

[johnno010684]

how do i tell if its running a different size base circle than stock?

 

[johnno010684]

COMP 275 XFI RPM HI-LIFT GM LS LS1-LS2-LS3-LS this is the package i bought

 

[johnno010684]

If its an off the shelf cam with all the bits provided to go into an otherwise stock motor, its probably fine. But, this should always be checked as your new cam is likely running a different radius base circle on the lobes to stock, and can therefore require shorter or longer pushrods to suit. Idealy, you want about 0.030" of preload on the lifters. From the rocker bolt tightening point which just takes up the slack on the pushrod so you can just spin it in your fingers, this is approx 1/2 - 3/4 turn crush. Not enough preload will give noisy valvetrain and too much preload will give low oil pressure feed to the rockers.
This may not be your problem at all, but something to be aware of as you dive deeper to find the source of the noise.
Very unlikely, but did you check all the pushrods tubes were free of any obstruction/foreign material that would prevent oil flow?
Cheers.

ok so i just took off the pass side rocker cover, theres plenty of oil in there sitting by the head bolts. some of the rockers i can wiggle a little bit with my hand, when i installed them i just torqued them up at 22/lb ft, should i have torqued them up when the lifter was on the base cirle of the lobe?
Thanks heaps for all your help so far guys.

 

[cander24]

That link doesn't work for me for some reason, but the specs provided by the manufacturer often don't give this detail. Usually though they match the base circle to stock if it's ground from a new billet. A reground cam will use a smaller base circle. Your pushrod length 'should' be fine though if this was a specifit kit for your application.

 

[cander24]

ok so i just took off the pass side rocker cover, theres plenty of oil in there sitting by the head bolts. some of the rockers i can wiggle a little bit with my hand, when i installed them i just torqued them up at 22/lb ft, should i have torqued them up when the lifter was on the base cirle of the lobe?
Thanks heaps for all your help so far guys.

Wiggle how? They should be pretty solid. I don't know the rocker bolt torque figure off the top of my head, but they should be a torque to yield i.e. tension to a specified torque, plus an additional Xdegrees.
Yes it is more accurate to torque the rocker bolts when the respective lifter is on the base circle. This way you are only tensioning against the lifter preload pressure, and not compressing the valve spring aswell.

 

[johnno010684]

i can lift a couple of them up off the valve stem a few cms! i "think" this was when no 1 cylinder valves were both closed

 

[cander24]

With both valves closed the lifters will be running on the base circle (or there abouts anyway) for that respective cylinder. This is when there will be the least tension on the lifter. Um, do you really mean 'cms'??? Have you re-checked the rocker bolt torque? With new lifters fitted it is not uncommon to momentarily have a little lifter compression by hand, until they pump up, say, 1mm on the compression stroke. This should have happened long ago though with the amount of time you've run the motor for.