Diesel Place banner

Busted Valve (pics)

17K views 195 replies 24 participants last post by  juanfo 
#1 · (Edited)
OK guys, hope you don't mind me tossing this one out for the masses. I'll try for the condensed version, but I usually end up detailing it out. most won't read a long post.
1983 C-30 cab and chassis, with an 8' bed tossed on, and on my 2nd motor, even tho the truck just turned 100K. In 95 it broke the #2 piston in half, so I found a replacement 6.2 out of a Blazer, and rebuilt the bottom end, (+.030).
It has about 50K since the rebuild.
My buddy borrowed the truck a few weeks ago, and it ate an exhaust valve.


To be continued.
 
See less See more
2
#2 ·
So because I had some "mule" heads in the garage, I yanked a couple valves for that cylinder, and cleaned up the heads. Then I refaced the replacement valves, to fit the new seats. Here's something for your entertainment. My old dry face grinder, that has a patent from 1928. not sure how old it is, but it's tight and works fine. Once all was said and done, I lapped all the valves from that head. (And because I can't comment after inserting photos, my pics are out of order. This has happened to me on other threads, and I haven't figured out how to get around it)



Then I needed to put my B+D seat grinder to use, and square up the stone guide, before cutting.

 
#3 ·
After a thorough washing of all parts,
and inspecting the piston and walls for damage, I bought a new 6.5 Fel-pro gasket, and torqued it to spec. (20-50, 90*). Now, I realize the piston has some dings in it,

But even tho it's ugly, it should hold compression. This truck sees limited duty, and I just flat don't have the cash to go into the bottom end, so for now I'm just trying to patch it to work. there are no scratches on the cylinder wall, so the little flakes that came off the valve seat, went out the exhaust. So I installed the head

Now comes the fun part
 
#4 ·
nice job, dont worry about the piston, as long as its not cracked it will run fine.... seen several like that, banged up, although its usually a glow plug thats to blame...LOL
 
#5 ·
That is very impressive that the cylinder wall survived that, very lucky.

You should add that to our Carnage thread.

Go forth and diesel on eh.....
 
#6 · (Edited)
Before I tried to prime the fuel system, I decided to do a static compression test. This engine has always had over 400lbs in all cylinders, except when it ate the valve. (natch). Now, I won't bore you with the "in-between" details, but as of this moment, all cylinders are good "except" the #2, which shows less than 50lbs!:eek: It's as if I didn't even fix the valve.
I liquid leak tested the ports of that cylinder before I installed the head, and they were tight. so to try and find out where the leak was, I leak tested it, and it shows good!? Same as the #4 cylinder. maybe 10-15% leak in both cylinders.

I've gone back over each test multiple times, and even ran it (temporarily), and that #2 is still leaking. I had the compression gauge on it one time, while it was running, and I watched it from the drivers seat, it built up pressure for a second, (1/2 scale or 400lbs), then started bleeding off, started to climb again, then nose dived to less than 50lbs. i guess I'll be yanking the head (again) and leak test the cylinder by itself, to see if the ring (s) is broke. Don't know how the leakdown test shows good, but static compression is bad. I'm over looking something, and just can't see it....yet.
(You guys are fast, I haven't even finished with my posts, and you're already commenting THANX!)
 
  • Like
Reactions: chevy410
#7 ·
Ok, that is not Ok....

Where is the air coming back out?
 
#8 ·
When listening through the oil filler tube with the leakdown tester, I can hear some hissing, but no louder or more than the #4 cylinder. They sound the same. Nothing from the intake, exhaust, or radiator. Just some crank-case noise.
 
#10 ·
It appears to be OK, seeing that the injector is captured in it's own protective chamber, (pre-combustion) and not exposed to the valve area. The only remaining pieces of metal left behind were small thin flakes imbedded in the piston crown. I flicked them off with my thumbnail. The bigger pieces must be in the muffler I'm guessing.
 
#11 ·
Very good post, good luck with finding and fixing the leak. :thumb:

Looks like what ever it swallowed got stuck in the valve or the piston nailed it into the valve.
 
#12 ·
Aint never seen that before!! Glad you're fixing it though!!
 
#15 ·
I was thinking of that Terry, but I'm very hesitant to pour any liquids into the cylinders, seeing there's really no combustion chambers. I know a little may be all that's required, but what is "a little"? I've sprayed a squirt of ether a couple times to help start it, (Yrs ago) and it makes the most "God awful" noise, that I thought the pistons were gunna come through the pan.(I don't do this any more). And GM states, "Don't ever pour diesel into the motor to start because "Severe" eng. damage could result" But I have seen it done successfully.
 
#16 ·
I'm getting to the point of working this pig again, and really only see 2 options.
1-Retorque the head, put water in the system and fire it up for a while to let everything heat-up and reseal. Or...
2-Pull the head, make a thick plexi-glass template to cover the top of the bum cylinder, affix the leakdown tester adapter, squirt some oil onto the top of the piston, (1/2 way down the bore, and pump 50lbs of air in it, to see if any oil leaks out. With the head removed, it will eliminate this as the problem, but only if I see oil going somewhere out of the cylinder. If the cylinder holds oil and pressure, then I guess I'll blame it on the head install.
Any opinions on either option 1 or 2, or is there another option I'm overlooking....PLEASE.
 
#18 ·
Ouch! I've had that same thought, and will be my last resort. My concern tho is why won't it leak through during the leakdown test? when I check the #2, it leaks the same as the #4 which static tests good. Plus the "sound" check of the air bypass, is the same as the good cylinders. and also there's no scoring of the cylinder walls. That's what's confusing me. but I appreciate your input.
 
#22 · (Edited)
This is out of left field......
Are you sure the valves are completely closing? Maybe weak valve springs? Bad lifters?
I like left field. That's where Yaz use-ta play. And that's a good thought. But to insure this wasn't a problem, I unbolted the rocker shaft, to make sure both valves were shut, yet the leak down reading didn't change. So I really can't see the valves being the issue. P.S. The leakdown test is OK. It's the static compression tests that's very low. (50lbs compared to 400).
And DP, I think squirting some oil down the glo-plug holes is a good idea too, and then crank it over a few times B4 static testing again. Thanx for the thoughts men. I'll try it tomorrow.
 
#20 ·
May be misreading your thread but I would get out and run the truck a bit before condemning the cylinder. You can easily get a bad reading on the leak down test right after your repair. A lifter could still be pumped up, a bit of trash under a valve or just lack of oil on that cylinder after repair. If you do want to put a liquid in the cylinder i suggest squirting oil thru the glowplug and spinning it over quite a few times to rid the cylinder of oil before spinning it over again. This will prevent hydrolock.

I once started a diesel that had virtually no compression by oiling all the cylinders that way.

Oh, by the way that's some neat valve grinding equipment you have. Reminds me of the good ole days of engine repair.
 
#24 ·
I had hoped for this from the very beginning. When doing the static compression test, I can watch both valves operating normally. Before I pulled the head for rework, while I had the pusrods in the clean tank for inspection, and when installing back on the eng. for re-test. The rockers and pushrods (unfortunately) are serviceable. When doing the leakdown test, on the bad cylinder, (on the compression stroke), there isn't any air leaking past the valves, because I can't hear anything audibly.
 
#27 · (Edited)
Another good question. I was thinking something similar Jason, in that, maybe 50lbs isn't enuff pressure to cause "where-ever" it's leaking, but under more pressure such as the static test, it does. I wish I knew. now that Fathers Day, is calming down, I'm hoping to go out and play some more.
 
#28 · (Edited by Moderator)
And play I did. Wasn't very enjoyable tho, or at least the results weren't. I decided to put some water in the system, and let the thing heat up, to see if I can gather any more evidence. It still is dead on that #2 cylinder, and while it was heating up, I noticed some small bubbles in the radiator. Was it because I just topped it off, and the air was rising, or is it from compression loss? I pulled the glo-plugs on that head after I ran it, and didn't see any water in there. (Like I have many years ago). And there is a bit of blow by too. The noise to me, sounds like an exhaust manifold gasket leak, but it's not.
So I made a couple quick videos if anyone is interested. Any comments or opinions are appreciated.



 
#29 ·
Yes, unfortunately there is some thing not right in there....
 
#30 ·
Are you trying to compete with JC for his trophy? :hehe:
 
  • Like
Reactions: Bigboytoys
#31 ·
Well, as a last resort you could pressurize the crank case and see if the pressure escapes through the bad cly either through the glow hole or elsewhere...... but I believe removing that piston will tell the tale.....
 
#39 ·
Well, as a last resort you could pressurize the crank case and see if the pressure escapes through the bad cly either through the glow hole or elsewhere.
That's actually easily do-able,and not a bad thought, and could be used as a last resort. However that would entail the entire motor, where I want to isolate it to the #2 cylinder. Thanx for the idea.
 
#32 ·
My guess is broken ring, in the first video you can see the pulses of blow by,

With a worn out motor the pulsing is less noticeable.

Here is a vid of the motor I pulled out of my k20, ran like crap and the blow by is more uniform.

 
#33 ·
:missedwhat:
Who's JC, and what trophy? (Sorry, another "Newb question)
But I'm sure it's "very funny" to the knowing.:HiHi:
 
#37 ·
I do own various trophies but none are too glamorous:HiHi: Not sure which one old school may be referring:idea: maybe this from my 6.5 but it came that way from the po:HiHi:..
We
 

Attachments

This is an older thread, you may not receive a response, and could be reviving an old thread. Please consider creating a new thread.
Top