Big Cam Problem, need experts here
12-30-2006, 11:43 PM
#1
Big Cam Problem, need experts here hey guys i just got my cam installed the other night and well today i was hearing alot of ticking coming from my drivers side of the engine, so i went to my friends house, the one who helped me install it and asked him what he thought about it, and we checked for a little bit, and he told me just to hit the key, just enough to make the engine move but not fully crank, and he told me that one of the lobes on the cam had grinded down, he said that the valve spring wasnt moving as much as the others were, does that mean that the cam is grinded down and now its trash? please help, btw its on my '94 chevy silverado truck, its not a vortec engine tho, its just a regular 5.7L 350
12-30-2006, 11:50 PM
#2
I hate being the bearer of bad news..
If a lobe has grinded down (flat tappet hydraulic cam correct?) then yes it is trash. Not only is the cam trash though, all that metal that used to be on the cam is floating through the oil passages, and the block needs to come out and be cleaned.
When you get it redone, make sure the engine is at 2000 rpm+ for 20-30 minutes flicking the throttle up to 3000 now and again (with good oil pressure of course). You also can't break a hydralic flat tappet in reliably on a strong spring pressure, so make sure your springs aren't too stiff. While the block is out for machinging and cleaning, have your machinist check and make sure the lifter bores are true as well.
edit: you can have the block machined to accept roller lifters too, and go with roller cam and never worry about this again.
If a lobe has grinded down (flat tappet hydraulic cam correct?) then yes it is trash. Not only is the cam trash though, all that metal that used to be on the cam is floating through the oil passages, and the block needs to come out and be cleaned.
When you get it redone, make sure the engine is at 2000 rpm+ for 20-30 minutes flicking the throttle up to 3000 now and again (with good oil pressure of course). You also can't break a hydralic flat tappet in reliably on a strong spring pressure, so make sure your springs aren't too stiff. While the block is out for machinging and cleaning, have your machinist check and make sure the lifter bores are true as well.
edit: you can have the block machined to accept roller lifters too, and go with roller cam and never worry about this again.
12-30-2006, 11:54 PM
#5
also check and make sure a valve spring didn't break, or a pushrod didn't break, or a rocker broke.. there's a few reasons for a valve not to move too much.
no metal in the oil is a good sign.
no metal in the oil is a good sign.
12-31-2006, 12:00 AM
#7
Yes, I do.. if the rocker broke that's your problem.
when you take the rocker off, just pull the pushrod out and roll it on a flat surface. that will tell you if it tweaked when the rocker broke.
when you take the rocker off, just pull the pushrod out and roll it on a flat surface. that will tell you if it tweaked when the rocker broke.
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12-31-2006, 12:09 AM
#9
if the rocker is broken, replace it, 1 single rocker. (do you have a shaft mount set of rockers on that?) if it just came loose, then retorque it to spec.
if a pushrod is tweaked, yes, replace 1 single pushrod (like 6 bucks). if none are redily available, and the tweak is very minor, put it back in and drive normal until a new one shows up.
I guess I'm not the bearer of REALLY bad news
if a pushrod is tweaked, yes, replace 1 single pushrod (like 6 bucks). if none are redily available, and the tweak is very minor, put it back in and drive normal until a new one shows up.
I guess I'm not the bearer of REALLY bad news
12-31-2006, 12:11 AM
#10
lol lets hope not, but i didnt mean to say that the rocker is broke, i meant to say that he said it isnt broke. do i still need to take it out and roll the pushrod just to make sure? or what? i mean anything i can do to eliminate the problems until i dont have to buy another cam, i dont have the money.
12-31-2006, 12:18 AM
#11
ah, I thought you said the rocker IS broken.
well, a pushrod is easy to check, just take the rocker off and pull it out.
the cam lifts the lifter, the lifter pumps up and lifts the pushrod, the pushrod pushes the rocker, the rocker presses down on the spring and opens the valve.
if the rocker is ok, and the spring is ok, and you find the pushrod to be ok, then your next stop is the lifter. with no metal in the oil, this is likely as far as you'll have to go, but you'll need to take the intake off. did you soak the lifters in oil for ~2 days before you installed them? one could have collapsed.
well, a pushrod is easy to check, just take the rocker off and pull it out.
the cam lifts the lifter, the lifter pumps up and lifts the pushrod, the pushrod pushes the rocker, the rocker presses down on the spring and opens the valve.
if the rocker is ok, and the spring is ok, and you find the pushrod to be ok, then your next stop is the lifter. with no metal in the oil, this is likely as far as you'll have to go, but you'll need to take the intake off. did you soak the lifters in oil for ~2 days before you installed them? one could have collapsed.
12-31-2006, 12:30 AM
#13
That's probably fine. A new lifter can still collapse though. Could just be a bad part. The "lifter factory" won't know that a part will fail once it's been run in an engine under pressure and load. lifters tick, a wiped lobe is more of a dead miss, not as much noise.
12-31-2006, 12:34 AM
#14
yea thats a good point, well we are going to check it tomorrow, we will pull the rocker off and check the pushrod, and then if it aint that i guess we will pull off the intake and check the lifters. is there anything else it could be beside those? and is it possible for the cam to grind down and not have any metal at all in the oil? and i did check it correct? i just checked it a few mins ago and i havent drove it in a few hours so i know all the oil is at the bottom, if it dont have any metal thats a good sign? and i checked it the right way? sorry this is my first cam install and im really nervous, plus this is my only ride which means i need it
12-31-2006, 12:48 AM
#15
if you have a magnetic drain plug it would have a lot of shavings on it. if you don't, drain the oil completely and let it sit overnight then SLOWLY pour it out a little at a time and check what sunk to the bottom.
and there is not much left to rule out. you have the pushrod, the lifter, and the lobe left.
and there is not much left to rule out. you have the pushrod, the lifter, and the lobe left.
12-31-2006, 12:54 AM
#17
yes, if it's just the lifter you can replace it, then go through the break-in procedure again. note! - you can run new lifters on a used cam, but you can't run a new cam with used lifters on a flat tappet hydraulic.
if it's the lobe itself.. then yeah man.. bad news, see my first post. I can't recommend not doing it the right way to clean the engine, though some will put a new cam and lifters in, then change the oil after the break-in and look for shavings.
if you want, you can always cut the oil filter in half and check for shavings there.
if it's the lobe itself.. then yeah man.. bad news, see my first post. I can't recommend not doing it the right way to clean the engine, though some will put a new cam and lifters in, then change the oil after the break-in and look for shavings.
if you want, you can always cut the oil filter in half and check for shavings there.
