HoveyBayou

iTrader: (3)

How many miles are on the motor?

cams 98 silverado

109986 miles. since 80000 miles its had a slight tick that has slowly gotten louder. finally kicked the check engine light... so im almost sure its rocker and pushrod.

regcabls6

maybe a lifter? did your oil pressure change at all?

cams 98 silverado

oil pressure is absolutely fine. no smoking. no coolant burning, oil is good. no oil mix in coolant or vise versa. fuel pressure is good. its 5% higher because computer trying to correct misfire. guy that did the testing complimented on my gauge pod. said most guys get the narrowband gauge and something stupid. mine actually helped him out because my gauges are fuel pressure and trans temp lol. nothing changed really. when i drive, i hear what kinda sounds like a tazer going, which is the louder tick in my rocker arm. guy said he heard it and agrees its valvetrain.

Sc00by

If a lifter fails will that change your oil pressure?

cams 98 silverado

I think it wont, but i would know when i play with the pushrod because i would believe it would be easy to push the plunger down or something.

cams 98 silverado

oh, in case i hadnt said, the truck is a 98 silverado ext. cab l31 5.7L and the tapping or tick, comes directly from the 5 cylinder. and if it was a bent valve, wouldnt my compression be bad or not hold well? im real happy though that after 109K miles, i still got 150 psi across the board and stock is 160. at 98K miles i took my pan down and each cylinder still had the cross hatching marks from the cylinder honing from factory. thats a big plus. but, if running compression is down 25psi, i would say valve not opening enough to let air in maybe?

08k1500_3

iTrader: (2)

valvetrain noises can be very difficult to isolate without pulling it apart. You are right about the bent valve causing compression loss and burning oil, but I have seen it before where no oil or compression loss and have a bad valve. So most likely it is a pushrod or lifter failure, Those 5.7L (R) motors did have issues with lifters so seems like a good time for those mods.

How long before you start tearing into her???

cams 98 silverado

well, im gonna drive it to the body shop tomorrow morning, and hopefully my guy will take a long time to play with it, so i can have fun in a rental!! and then get it back, and tear into her. because ill have no classes, and wed-friday to tear it all apart and do it and then clean the hell out of it. funny thing is i just registered for auto engine design and all these auto classes, which woulda helped me now, but o well... not only do i get to play with the valvetrain, i get to re-take this auto basic electricity cuz my teacher somehow gave d's to the whole class after telling us we were in no way failing and all got at least c or better but o well. cant wait to tear into her, and tear into my auto classes.

if my lifter failed, being its a hydraulic roller, wouldnt the oil pressure at start up cause it to at least pump up enough to correct itself? my pressure at idle cold start with 5w30 is 75psi. idle warm temp is 26, low running rpm 40+psi.

cams 98 silverado

ok i guess I will say I am going to start tearing into my truck today. the best autobody guy i know was kind enough to delay my truck work for a few days so i could use teh rental car to get to work and such. that rental car was absolutely fun. i drove over 650 miles on that thing in a week. i drove everywhere, best part, i was getting 32 mpg lol. anyhoo. got my tools ready, just waiting for the motor to cool down (drove it from body shop slowly) and then its off to tear into it, then hopefully fix it. perhaps if im lucky enough, i wont have to tear off the lower intake, but at the same time, wouldn't mind so i could hot tank that thing to get the carbon out lol.

*EDIT*:_:__: ok, got the driver side cover off, and rocker arms out and in with the new roller tipped and also new push rods. i did not see anything really wrong with the valvetrain on cylinder 5 as i took things out, the lifter plunger felt just like the rest. the spring looks to be like the others, the rocker arm, however, had uneven wear. these rockers are the flat tip style that are self guiding. theres wear marks on the raised edges of the guide area that tells me the rocker tip must have been walking around the valve stem. so, hopefully that is what it is, although somewhat doubtful. i would think that such a little bit extra push on the valve would not leak out 25 psi, or maybe it did. unsure. what do you guys think? sounding more like a bad lifter? the pushrods were all straight as well, normal wear nothing fancy.