JaredAdams97

Hey guys! Long time no see. Its been a while since I've had any issues with the Z28 but I feel like this is a great place to seek some help...

Okay so last week I finally got a conversion to true duals. It sounds great. Two pipes straight back and super 10 flowmasters make her purr. But anyways, to the issue. On sunday I was traveling home and there was a knocking sound coming from the engine. Knowing that it could be serious, I stopped the car and pulled over in fear that I was about to throw a rod. I waited on the side of the road for a friend to pick me up because I was going to get her towed but when my buddy got there, I started it up and it was ALMOST at a normal sound. Still a little bit of shaking though.

Well I thought it could be the oil and it was somewhat low so I added some and it helped a little. I also adjusted the fuel air mixture on the carb and that also helped some. Well I finally took it to a mechanic the next day and he completely changed the oil for me and checked the compression and i have a low compression of 90 psi on cylinder #6. every other cylinder is at 120. The mechanic says it could be a bad lifter. Oh and btw its a Chevy 350 that has been completely rebuilt. What Could this issue be?

Barlow8869

iTrader: (1)

sounds like it was getting hot, my crate 350 sounded like all the rods were coming out one night when i wasnt looking at the temp, and let her get to hot ... let it sit for an hour and a half, and was able to get it to the store for some tools and water, drove that motor for another 4 years before i sold it, never another problem from it

sofakingdom

iTrader: (1)

2 things:

Check the oil on a perfectly clean white cloth, in bright sunlight. Let the oil itself soak into the cloth, and focus on what stays behind. See if it glitters.

Then:

Pop the valve covers off and observe the valve motion. Odds are, you have one or more that don't move as much as the others.

If so, rolled cam lobe. The glitter is the remains of the lobe & lifter.

jokerZ71

Since you already have a cylinder identified,Ck valvesprings,rockerstuds,& adjustment on that cylinder.Could be a broke spring,stud pulling out,but,it does sound like you may have wiped a cam lobe.As said above,sparkling oil will tell you for sure.

JaredAdams97

Okay so today I checked the oil and there is no glittery metal in the oil. I popped the valve cover on the side of the cylinder that has been giving me issue and found that one of the rockers were completely off and one was partially off where it was supposed to. I removed the rockers and found that two of the pushrods are bent.. what could have caused this? Do I need to take off the intake to check the lifters? Also is the car safe to drive with both rockers and pushrods removed?

sofakingdom

iTrader: (1)

Most likely, over-enthusiastic test-driving.

No you shouldn't drive it like that.

Now you need to check the rocker studs and make sure they're not pulled out of the casting... lay a straight-edge across the top of them, and if any are up higher than the others, esp the ones with the other damage, then they need to be repaired before putting new rockers & push rods in.

Probably wouldn't hurt to verify that the valve springs don't go into coil bind at full lift; since the engine "has been completely rebuilt", there's no telling how well/poorly that part of it was set up, what cam is in it, etc.

JaredAdams97

Yeah.. I will admit that when I got the new exhaust done, I just sat in my driveway and revved it a good bit..

To check the valve springs, do I need to remove the intake manifold to check the two lifters that may or may not be damaged? I mean if I can just buy two new pushrods and reuse the rockers then wouldn't that be okay? (taking the rocker studs are already aligned)