Burned Valves
 

My 1962 K1001 failed a compression test pretty miserably. It has a 305D V6 and here are the readings Cyl 1 = 125, Cyl 2 = 47, Cyl 3 = 135, Cyl 4 = 47, Cyl 5 = 130, Cyl 6 = 100. The heads are off now and it is pretty obvious that I have two burned inlet (yes inlet) valves in 2 and 4 plus damage starting in 6. I'd like to get your opinion on what might have caused this. Several coincidences here: all inlet valves, all on the passenger side head, all damage at the point where the valve edge is closest to the spark plug.

The heads are off now and disassembled. I cleaned the bad valves and the damage is pretty obvious. I attached a picture, but the lighting is not good.

What else should I be checking to possibly prevent this damage in the future. Appreciate your help.

Re: Burned Valves
 

I don't know anything, but wouldn't a burned intake valve mean you're getting early ignition? I'd look at timing and pinging. If the timing is fine you may need to run a higher octane fuel. That's just a guess based on the logic of how intake and exhaust valves work.

Re: Burned Valves
 

I don't see a burnt valve. Describe where you see a burnt valve in that pic. Low compression on one head is usually a blown head gasket....or a crack. Something wrong with the valve train on that side. Broken springs, etc. etc. Maybe even timing.

Just to repeat, I don't see any "damage".

Re: Burned Valves
 

Take a look at the circled area Ken.

Re: Burned Valves
 

Prowbar has circled the exact area of the damage. I apologize for the bad camera work. In the right light it looks pretty bad. I was hoping to find a blown gasket, but it looked fine.

Re: Burned Valves
 

Not definitive enough. The extra low pressure in multiple cylinders, on same bank, just doesn't feel right. Together with sketchy pic of alleged burnt valves. The pics below are actual burnt valves. You can see a clear compression leak path. I will leave the analysis up to you, other members and the OP. This is all I can offer from one pic and test results. Just something to consider.

In the pic, all I see is possible pitted seat, normal. Depending on mileage. Don't think that causes 47 PSI. Need to see the gasket and if there are witness trails on the head......or better pics of all the valves showing definite seat lip failure as in: "burnt valves"

It is the nature of troubleshooting from afar and it is necessary not to take the ideas of the poster as to what is wrong. I must go by what I see and read. I don't see the gasket, I don't see a burnt valve. I didn't see the compression test. If I trusted a OP without seeing or testing, I would never find the issue. I would just be following them around in a circle. If it seems stubborn, it is. Don't mind being wrong but I don't give up until I see proof. Otherwise what good would I be as a yes man?

Of course, the poster being right there examining parts, can be completely correct in their analysis....but they did ask for comment.

If I saw a burnt valve I would say obviously it's cased by excess heat. Improper cooling or valve train failures I've already mentioned.

Re: Burned Valves
 

Yeah Ken I didn't see it in the second picture either but my eyes aren't what they used to be. If you click on the first from CMCamp then click it again it'll blow up to super magnified. It looks like (and again we're looking through a straw here) but it looks like he had a pretty good burn but when he cleaned it up he cleaned off all the burn. With it being shiny it's tough to see, but the lip on the valve is definitely pitted and maybe even chipped along the edge.
Because it's so shiny and clean (good job CMCamp!) you can't see anything through the shine unless you blow it up. Next time I'd probably take the pic while it's still dirty and marked up.

Re: Burned Valves
 

Fetch, we are buddies, so this is not at you.

To whom it may concern :)

I did blow up the first pic before I commented. The second pic is just the first pic..... rotated, No clarification by rotating a pic. I don't need to be convinced of anything. It's my opinion until, if, and when, there is more info. No big deal here. If I'm wrong I will be last to admit it.
Thru my eyes, thru the computer, thru the glare, thru the shine, with the angle, with rotating, with zooming, I don't see a burnt valve.
I do see, on one part of the valve, the face of Homer Simpson.

Re: Burned Valves
 

OK Ken your point is clear :lolsmack2:

Re: Burned Valves
 

We're always buds! :thumbsup:

And there's the trouble! Homer Simpson should definitely NOT be working on your V6! He repairs everything with a hammer, including his nuclear reactor. I bet he chipped it while "fixing" it after a few rounds of Duff beer with the boys :rowdybeer:
I recommend a trail of donuts from the motor to the nearest pub to solve the problem, and still checking the timing for preignition.

Re: Burned Valves
 

What is required for troubleshooting (not a complete list)(Like Ken said without seeing it we need a lot more information):
What prompt you to check the compression (rough idle)?
Did you do a compression leak down check (different than a compression check) on the cylinders to verified it was the intake valves and not the rings?
Did you check the valve clearances before disassembly?
Did you take a picture before removing the valves from the head?
Did you take a picture of the valves before cleaning?
Did you take a picture of the valve seats before cleaning?
The last time the engine was running, was there a lot of vapor coming from the crankcase breather vent?

Being it is the intake valve, was there a lot of carbon on the valve stem/head and the intake valve pocket/seat?

The way the valve look (I'm guessing here) worn in one spot, I suspect carbon on the seat had worn the valve face off. If the carbon was on the valve seats then it could help seal the valve until it broke away. Then the engine could have been running rough at idle.

What I suspect:
If there was a lot of carbon on the valve, guides are worn out (the o'ring inside the valve retainer don't stop oil vapor from entering through the valve guide, even with a shroud on the spring). With worn guide I suggest a bronze sleeve be installed (In my opinion knurling the guide is at best a temporary fix) on both intake and exhaust guides. I would also have all guides machine for positive seals.

Both heads should get the same repair work.

It look like you might have enough valve margin to grind the valve to new condition.

There is a possibility the valve job will not fix the low compression, if the rings are worn out (this is where a compression leak down test would help).

Re: Burned Valves
 

I have attached a picture of that valve before it was cleaned. Should have sent it along with the cleaned shot. Thanks for the feedback.

Re: Burned Valves
 

"Listen son, Now that there is some bad car...I say listen son, that there is some bad carbon"

Re: Burned Valves
 

With two cylinders with bad intake valves, was it popping back through the carb ? that's a definite sign of a burnt valve or was it just running ruff.

Re: Burned Valves
 

I bought this truck back in August and started a detailed restoration in October. It has under 15K miles on it, so I wasn't expecting major issues with the engine. What I was chasing was significant black smoke on startup. I thought it might be my getting use to the choke setting on startup, so I kept backing it off until it was very hard to start. Then I ran a compression test and found very low compression in cylinders 2 & 4 plus moderately low in 6. I decided to pull the heads. The first thing I saw was a very dirty intake manifold, lots of carbon buildup. The intake valve in cylinder 1 was damaged beyond repair. I decided to replace the intake valves in 2, 4 and 6. I worked with Jude of Obsolete Automotive Wholesale in VA. He was a tremendous help in identifying and supplying the correct valves. The heads are back on the engine now, but I haven't run a compression check yet; waiting on some other parts. I'll post an update when I have the new numbers. Should be later this week.

Re: Burned Valves
 

Fwiw, seems awfully strange burning intake valves. With cool air gas mixture running through intake, my experience has been that intakes never burn unless they were improperly adjusted and couldn't close all the way. I can't see any other reason for intakes to burn and exhaust valves to hold up.
Regards
Steve
New Orleans.

Re: Burned Valves
 

Well, the results are in, compression test is complete. First, a recap of readings before we worked on the heads.

Left bank (psi):
Cyl 1 - 135
Cyl 3 - 135
Cyl 5 - 130
Right bank (psi):
Cyl 2 - 47
Cyl 4 - 47
Cyl 6 - 115

Now the readings I took yesterday.

Left bank (psi):
Cyl 1 - 137
Cyl 3 - 135
Cyl 5 - 125
Right bank (psi):
Cyl 2 - 135
Cyl 4 - 135
Cyl 6 - 132

Looking good, but curious that we lost some compression in Cyl 5.

I'm left scratching my head on how these valves were damaged. I haven't owned the rig long enough to know its history. The best theory I've seen is the one suggested by sclor. Perhaps at some point someone incorrectly set the valve clearances, allowing the inlet valves on 2, 4 and 6 to remain slightly open. They must have gone back in and corrected the clearances, but the damage was done.

Thanks to all for the back and forth on this. Now on to figuring out how to get the exhaust system replaced. Muffler shops up here don't want to bend pipe anymore.

Re: Burned Valves
 

To locate a leak in the combustion chamber you need to do a compression leak down check. With equipment similar to this:
https://www.amazon.com/gp/product/B0...?ie=UTF8&psc=1