Hi everyone I'm Jerry from Fort Collins, Colorado. My first post, rather sad, but here it goes - I recently bought 97 disco with 200,000+ miles. She ran sluggish so I did a basic tune-up. 2 plugs were wet (and remained wet) indicating misfiring #1 & #8 cylinders. Eventually tested 0psi compression on those two cylinders and a subsequent leakdown indicated exhaust valves. Off with the head:





I'm a shade-tree mechanic trying to keep the costs minimal but want to do it right (and make it home for Christmas). The two valves look very burned, my question is what now?
=Overnight 8 new exhaust valves - lap/grind, reassemble, and cross fingers?
=Take the heads to a local machine shop (A.M.S Automotive Machine & Supply) and see what they say?
- Upgrade to the newer carbon cutter valve?
- New guides?
=Dig deeper for a cause such as a cam, spring, lifter, seats?
- Any inspections for the lifters while I have the engine apart apart?
- Can springs be checked with a micrometer?
- Max seated valve stem height & can it be checked w/o a dial indicator?
- Visual inspection for cam from valley without removal?

I realize this is a lot for a post but if anyone can provide me with advice on ANY portion of this that would be fantastic, thanks!

 

Wow! How do the valve seats and pistons for those cylinders look? Lapping those seats for new new valves might take some effort, but will probably work. With 200k on the engine, it will probably run well enough. Check all of the other valves for signs of burning also. Might be worth lapping all of them while you are at it. When the valves don't have as much seat area to transfer heat out through, they can burn.

 

If you need that much work on an engine with 200K miles on it, you might as well go all the way and do a full rebuild - rings, bearings, oil pump, timing chain and complete valve job. I would let a shop do the valve job, maybe supply them with valves and valve seals. I had a sticky exhaust valve on number 8. Fortunately, I caught it before the valve got burned. Man, that engine looks like it's been seriously abused.

 

Anymore questions about running premium vs regular gas from the partz vulturez in the higher branches of the shade tree?

Another option that is cheap - heads from a Disco in the boneyard. You are already poised to do the head gasket anyway.

 

All grades of fuel contain detergents. Deposits like that can also come from oil leaking past the valve seals and guides. For an engine with 200k on it, they aren't that bad (aside from the missing chunks).

 

Make sure you read in the sticky tech section the post that Disco Mike posted about doing head work. There's a link to RPI site with a ton of tech info on these engines from an engine builders standpoint. Good luck

 

when you put new valves in, this is a must!


id take it to the machine shop and see what they can do. how do the seats look for those two?

 

Replacing just the burnt valves and lapping them will work if the seats aren't too trashed, but it is a quick and dirty fix. If those two went, there are probably others not far behind. Burnt valves on a fuel injected engine are usually from worn out valve train components so you will likely need to look at the rockers, shafts, cam, lifters, etc. Also, with that many miles on it the engine probably needs bearings, a chain and an oil pump too. You'll have to decide where to draw the line.

Used heads if you can find them are probably the best way to go in terms of bang for the buck. New valves and some lapping compound will get you home, but getting to those valves is an awful lot of work so you should consider doing more than that if you can afford it. Taking your heads to a machine shop will get them in the best shape, but you'll need to check out the cam and lifters to make sure you aren't throwing that money away.

 

Those missing chucks are the "carbon cutters" that were built into the valves and valve seats in the heads.
It is supposed to prevent carbon from preventing the valves from sticking or not closing all the way.
They were introduced in the 4.0 because they had a carbon build up problem in earlier engines.
It looks like the ones on his valves have been made bigger by the exhaust blowing by and extreme temps and rates.

 

Nope, I was wrong.

http://www.landroverclubvi.com/uploa...e_cleaning.pdf