3B valve mystery (1 Viewer)

[Smithtec]

So, the truck began starting hard, and would run on three cylinders for awhile. I thought maybe just a bad glow plug. It got worse to the point it would never fire on all four. Last time I drove it, the engine was smoking and shaking and really not sounding good. Did a cold compression check, not wanting to inflict further damage. #1, a big fat ZERO. 400 psi in all the other holes. Removed valve cover to try checking valve clearance, and noticed #1 exhaust valve rocker was sitting high and I could spin the spring. So, off with the head. At this point I was afraid of a broken precup making a mess in there. But what I found is a new one for me. It looks like either an intake valve was put in, or somehow it bashed the edges off the exhaust valve and sucked it up in the seat. Anybody ever see this?

 

[Smithtec]

Upon further consideration, I don't think it's the wrong valve, because it has 3 stamped in the middle like all the other exhaust valves. So how in the world....

 

[Smithtec]

I almost forgot.... This pushrod was bent as well. I'm at a loss to explain what happened here.

 

[bj70bc]

wow, thats perplexing
i dont get what force was applied to shove that up and bend a pushrod.
The only force going that direction is the explosions....so that would mean to me that the valve was too small somehow to be able to push past the seat.
whats behind the valve ?

 

[fitzmooney]

No 1 inlet valve is not seating properly. It could be seized in the guide, which would bend the pushrod.
Also the pushrod could have fallen out of the rocker or lifter and get bent.

 

[Smithtec]

So, I pulled another intake valve(I said exhaust before, it's not). It looks like the face has just worn away and left a knife edge around the top. The one that failed is just straight, like the edge broke off. Still not sure what bent the pushrod, but it looks like I need new valves at a minimum.

 

[duncanrm]

No valve impact marks on the top of the piston? (appreciating that you said the pushrod was bent, not the valve).

 

[bj70bc]

this is a new one for me
huh

 

[AirheadNut]

Just a guess here, but based on the wear showing on the other valve I'd say that the outer edge of the valve completely wore away, then the straight sides jammed in the valve seat (higher than normal) bending the pushrod.

 

[Smithtec]

Just a guess here, but based on the wear showing on the other valve I'd say that the outer edge of the valve completely wore away, then the straight sides jammed in the valve seat (higher than normal) bending the pushrod.

That's my guess as well. There is no damage on the pistons or the tops of the valves. I don't know the mileage on this engine, but I'm guessing a lot for the valves to wear like that. Everything else looks fine though. I'm going to swap the valves from my spare head, they are in much better condition. Give them a bit of lapping and put it back together.

 

[fitzmooney]

I would get the valve seats re-cut and the valves refaced before lapping them in.

 

[Smithtec]

I would get the valve seats re-cut and the valves refaced before lapping them in.

That would be good, just not sure I want to spend the money.

 

[fitzmooney]

You just can't just fit a valve from another engine into what is a damaged seat. It is doomed to failure and will have to be pulled off again. Do it once and do it right.

 

[bj70bc]

Is your spare head in better condition? there are visible cracks between your valves on the one you took off.... might be better to put the spare on

 

[Smithtec]

You just can't just fit a valve from another engine into what is a damaged seat. It is doomed to failure and will have to be pulled off again. Do it once and do it right.

What makes you think the seat is damaged?

 

[Smithtec]

Is your spare head in better condition? there are visible cracks between your valves on the one you took off.... might be better to put the spare on

Welp, I didn't notice those cracks until you mentioned it.... The other head might be better.

 

[fitzmooney]

Take my word for it. If that valve has been failing and hammering into that seat, it will be damaged.
It may even be beyond repair.

 

[Gimme a 60]

Precups cracked too.

 

[Smithtec]

Precups cracked too.

Yes, I ordered new precups. I'm contemplating just switching over the valves and running the head in spite of the cracks. Seems a lot of people get away with that. The valve seats do not look damaged. I have a spare head, but it's a little different. The seats are not as beefy. It doesn't look to have cracks, though. Does anybody know anything about these serial numbers?

 

[lacalvette]

Looks like 3B head and the number ending with 58010 may indicate something around 82-83. Some people said that internal cooling passage may be different.
It is compatible.
If this one have no cracks, I would say it is definitely better IMHO.
With cracks, if you drive around town, it may be ok. If you plan a long road trip,well not so good.
A head shop can change the valve seat, they are in cast iron. (Not available from Toyota)