My LS1 01 Z28 Dropped a valve (I think).

**first01SS** · 10-18-2011, 12:29 PM

Car is very lightly modified-- Lid, factory exhaust, stock heads and cam, 100 wet shot nitrous, which hasn't been used in over a year. After a long road trip (with cruise control and a few oh s*** WOT moments), drove the car the next few days with no issues. After a really short WOT run, pulled off highway, and found my engine was severely "knocking", no power loss. After stoping, and turning off the car, attempts to restart failed. (Engine locked). After having the car towed home, i used a wrench to back the crank off a bit, and attempted to start the engine. Engine started , still knocking, no issues. Oil pressure fantastic even knocking, never seen anything but royal purple, only premium fuel, everything is in great working order, except for the knock, there is no smoke from the tail pipe, no check engine lamp, all fluids ok. What are my options at this point? Should i be budgeting for a new engine? Rebuild what i have? replace heads? I'm terrified that my car with less than 80k original miles is done for, and i need to budget a replacement engine.. I don't post often, so be gentle, but i'm very desperate to get back up and running. Reliability and moderate power levels (300RWHP - 450RWP) are very important to me. I also would like to get fair MPG (23-30) if possible.. please help..

**Knight** · 10-18-2011, 01:00 PM

First off, stop using RP. It's not a good oil.

But on to the problem, an engine locking up is not a good sign. You could drain the oil and check for metal. You could also pull the valve covers and check things there. Depending on how bad the knock is, and where it is coming from, it could be a number of things - varying from fairly easy and simple, to a full blown rebuild/replacement. But the engine locking up has me worried.

**first01SS** · 10-18-2011, 01:09 PM

Engine idles smoothly when its actually running, negative the knock. It only locked up after i turned it off, and under the power of the starter. Once I backed it off a bit (reversed the crank about 1/3 turn) started right up.

**cammed goat** · 10-18-2011, 01:23 PM

I would do what Knight said, and if there is nothing broken in the cylinder heads, I would check the starter as that could be binding and not retracting fully.

**first01SS** · 10-18-2011, 01:34 PM

Just drained oil/no metal. (used a speaker magnet and a fine grease fryer/screen just to make sure. wife will get over it.) Should i start removing the valve cover? This occurred, FYI on the passenger side. I believe thats where the knock is coming from.

**Knight** · 10-18-2011, 01:38 PM

No metal in the oil is a better sign. I'd pull the valve cover/s and inspect things there.

**cammed goat** · 10-18-2011, 02:11 PM

Check for a broken valve spring or rocker arm and see if there are any needle bearings in the head. This sounds all too familiar.

**first01SS** · 10-18-2011, 03:19 PM

The last bolt on the ignition coil rail is located far underneath the cowl. How can i get it out. I don't want to loose more fingers.

**cammed goat** · 10-18-2011, 03:52 PM

You could try a box-end wrench for added length to get to that bolt. It'll take longer than using a ratchet, but if you don't want cut-up fingers, then try the wrench.

**Knight** · 10-18-2011, 05:24 PM

Most people will not install the bolt again after removing it, either. Me being one of them

I used a ratcheting box wrench to remove mine - a valuable set of tools to have.

**first01SS** · 10-19-2011, 03:45 PM

Got the valve covers off. Checked all the valves; one spring seems to be excessively compressed. Removed the rocker arm, pushrod looks fine, valve still looks like it's there. None of the springs appear to be broken. Also, of note, once I removed the rocker arm, the spring immediately became uncompressed.

**redbird555** · 10-19-2011, 04:25 PM

the valvesprings will depress quite a bit when the pushrod is on the top of the cam lobe so i'd say thats not the issue unless one is visible broken or wiggles in you hand theyre probably fine why not post a video of the sound so we can better diagnose

**first01SS** · 10-19-2011, 05:14 PM

Well.. Is the an easy way to hook up the coils with the valve cover off so I can do that without having to reassemble everything and getting a decent view of the valve train while the engine is running? I can easily take a video post it.

**twozs** · 10-19-2011, 05:47 PM

these motors are notorious for collapsed lifters from over revving

**pajeff02** · 10-19-2011, 05:51 PM

How about a compression test? You can do that with the covers off. You can also pull the plugs and have a friend roll the engine over by hand to see if anything looks amiss.

**cammed goat** · 10-19-2011, 05:55 PM

Did any of the springs look like they were "bulging"?

**Danger731** · 10-19-2011, 06:43 PM

Hate to add but air in the water pump makes a heck of a lot of noise. Did you do anything with the cooling system lately ? I'm at 101 K on my motor after doing wet shots and just drove here from San Diego with some good runs at times, these motors are strong. I used to power shift and I hit the rev limiter more than I'd care to admit.