jefflatham

Good evening ChevyForum -

My plea for ideas, knowledge and guidance comes from the recent replacement of the right-bank cylinder head on a 1997 GMC Yukon with the 5.7 Vortec. This is a buddy's truck and, being (so far) always capable of these jobs, I offered to do the job in exchange for beer last Saturday. No big deal - just a cylinder head. When all went back together clean and easy, we turned the key and now there's zero ignition occurring in the right bank (2-4-6-8) cylinders, and only the occasional stutter from the left side bank.

In synopsis, the existing cylinder head was diagnosed as having a stuck exhaust valve. He was quoted $2200 to do the job at a Pep Boys. Instead, he purchased the head through Pep Boys, drove the Yukon into my shallow suburban driveway and I got to work.

The job was seemingly basic - no stuck or broken or lost fasteners; no struggles with fitment; nearly no rust; no unforeseen challenges. Everything went too smooth until we turned the key after 10 hours and it wouldn't fire.

The facts of the job:

- Replacement (remanufactured) head from Pep Boys, visually the exact same with verified part #s (on the box, at least)
- New head bolts, torqued properly with a torque angle meter
- New Felpro gaskets on everything removed
- The engine was judged at #1 TDC through the compression stroke and by the notch on the balancer corresponding to the mark on the front of the engine
- Nothing unusual or sloppy with the install; everything fit and tightened and fell into place as hoped
- All the fluids are fresh and the battery is fully charged

The symptoms:

- The plugs are verified as firing properly on all 8 cylinders
- The timing has since been verified by a shop as correct (yes - we towed it to a professional on Sunday night)
- The gripe is persisting with a different known-working distributor
- Fuel delivery is indeed occurring
- The plugs on the right bank are dripping with fuel when removed
- Blowing the cylinders out hasn't resulted in anything
- Cranking the engine with the fuel injector harness unplugged hasn't resulted in anything
- You CAN occasionally get the whole motor to barely lump along on a few left-side cylinders by cranking it over at WOT and holding it there when it starts
- The right bank is judged completely inoperable as the exhaust manifold is stone cold
- There is no evidence of coolant/oil mixing together (i.e., a failed gasket)

Fuel. Spark. Proper timing. Nothing.

My thoughts:

- The "fire triangle" implies that fuel, ignition and oxygen create a burst. I have fuel and ignition...am I lacking air? If so, how can this be?
- I have NOT run a compression test as I didn't have a replacement gasket for my compression gauge...I'm kicking myself now.
- Is it possible that the intake valves used in the remanufacturing are of the wrong length, i.e. the intakes are barely opening? Is this even possible?
- I torqued the rockers to 22 ft-lb as listed in a chart of torques for the engine, but not through the 1/2 - 1 turn method I've since learned about.
- I installed the head without doing ANY adjustments as this is what I thought I was dealing with
- This IS the first 350 I've worked on (somehow...seems like most folks start there...) I'm an AMC 242 guy, a Jeep guy, a 5.0 guy...I'll admit that up front gladly.

The only thing I changed was the head and gaskets. The vehicle drove its way into my driveway and had to be towed out due to time constraints. I'm mortified because my colleague trusted me to help him out and I arrogantly trusted my own abilities - abilities and knowledge of which I'm still quite confident of, though I'm DEFINITELY humbled at the moment.

To at least validate myself a bit, I'm no stranger to engines and their principles. I've built a dozen solid engines in the last decade for friends' cars and my own and they've all turned out solid as can be.

Any suggestions or advice - anything - is overwhelmingly appreciated. I would really like to see this through and make good on my friend's trust and learn something along the way. Thank you in advance!

-Jeff
San Diego, CA

jefflatham

Good evening ChevyForum -

An update for anyone who may have read this through or may read it in the future...

I replaced the gasket on my compression gauge and verified that the entire right bank of cylinders had ZERO compression. Therefore, I dug around the info banks and learned that I had made a real schoolboy error and torqued the rockers too tight. What resulted was an entire valve train of open valves, 4 bent pushrods and one shattered rocker arm where the pushrod blew a hole clean through the top. (Pictures below...)

Luckily all pieces were accounted for and it looks like nothing escaped into the oil passageways or intake.

What I've learned:

- Don't trust random torque values for things on the internet; if you don't know, confirm, confirm, confirm.
- Trust your instinct; it DID seem odd to torque the rockers to 22 lb-ft, but I didn't stop and think.
- There are a thousand opinions on whether or not this engine was an interference-type; in this case - thankfully - it was not. All valves survived.
- I now know how to properly time and set valve lash on an L05 Vortec. Kickass.

What I'm reminded of as well is that every engine that's built right generally starts right up. If it doesn't, don't bash your head...stick to the basics first. Hopefully this quick write-up helps someone else out along the way. Cheers!

-Jeff

V12TT

Thank you for the follow up. I appreciated. Currently I'm researching the issue with no compression on #4 cylinder of a 97 K2500 and this information is helpful.