valve replacement and brands?

[reebadoo]

i have a ford 400 engine and the heads have been done once before with sealed power valves. the valves are v-2075 and v2075 and i was wondering if the sealed power valves hold up well or if there are any other similar options for valves. and if you are cleaning up the valves and two of the eight are bad would you replace all eight? one out of each head was bad. any advice would be of great assistance!  

[PetesPonies]

OEM quality valves are fine for a street driven vehicle. If the valves have already been replaced, what makes two of them bad now? Some pitting, especially on the exhaust valve, is typical and what is removed when a valve job is done.

[ArdWrknTrk]

How many miles since the last valve job was done?
What kind of use does this truck see?

Define "bad".
Are they worn out?
Bent?
Burnt?

How do the seats and guides look?
What springs are you using?

[reebadoo]

two of the valves are cracked. i will put up a few pictures once i get a chance. but one valve is cracked from the edge in about 1/8th of an inch and the other is maybe 1/16th cracked through from the top to the bottom.

[PetesPonies]

Exhaust valve?

[ArdWrknTrk]

Only time I've ever seen a cracked exhaust valve was from running the engine without any exhaust.

[PetesPonies]

Burned valves are a common problem. It most always happens to the exhaust valve as it only has hot air passing by it for the nano second it is lifted off the seat. It works much harder and hotter, than the intake valve.

[Gary Lewis]

I've never seen a cracked valve. Burned ones, frequently. But not cracked.

[PetesPonies]

A "burned valve" is a generic term to mean many things. Typically, its when a piece is missing. That piece that is missing starts as stress cracks. I'm assuming this is what the poster saw, the beginning of a burned valve. The craziest thing I have even come across was a "tulipped" valve. The valve had deformed such that it no longer sealed against the seat. Imagine the shape of a tulip  :)

[ArdWrknTrk]

Imagine smashing *your* head against the seat 30-40 times a second.

Once a guide starts to get sloppy and the valve does not land concentric they will deform and also get too hot because of the lack of heat sink.

[PetesPonies]

30-40 times a second is slow  :)  When I was teaching Auto, I used to use an Indy engine as an example. 15000 RPMs and explain to the students how fast things were moving at that speed. It's scary fast.

[ArdWrknTrk]

Yeabutt it's a truck engine.....

I've seen plenty of seat recession where the valve pulled right up into the head.

No one needs really fancy valves in this application.

I'm looking to redo a set of heads for my truck asap.
Light porting and a compression cut once I get the short block worked out.

[reebadoo]

im not sure how many miles have been put on the engine sense the heads were done.

[PetesPonies]

I don't think anyone suggested fancy valves. I wanted to know if they were the exhaust, as i suspect. I would replace all 8 exhaust and leave the intakes after a cut.

[PetesPonies]

THat is exactly how a burned valve starts. Typical. What causes it? Well if your seats and valve faces were not matched, there is less contact area at the seat. The small the contact the less time to transfer heat back to the head. The result is what you are showing. Replace all the exhaust, get a valve job done, checking guides,  grinding the seats, etc.

[reebadoo]

i ground down all the other valves to make a nice face. the intake match up really well so i just need to do the valve seats on the exhaust and the intake all seat really nicely. so im just trying to figure out what to do with the exhaust valves. and exhaust valve seats. and the valve guides are aout .002 over spec so i think i will need inserts to make sure that the valves dont go sideways.

[ArdWrknTrk]

Look at the first post.
I got the impression that he felt maybe 'better' valves would not fail like these did.

Re: seat width...
For a given cam, time on the seat is what ever it is.
But *area* for heat transfer, over time on seat goes up dramatically.

As you said it's pretty amazing that ice's hold together as well as they do.

I don't teach but I DO learn.

[PetesPonies]

So OP, you have a valve grinding setup?

[reebadoo]

i am going to school for diesel technology. and they have everything to do heads in the building and the block will be machined either at the school in the high performance engine shop or at an engine shop in town. im not sure which yet. unfortunately i dont have much money so im trying to do it right but do it on a budget because i am a student in school haha.

[Gary Lewis]

You originally asked about Sealed Power valves.  In my limited experience of buying valves those are fine.  And those two need to be replaced.