Just a quick valve question

[corey6969]

I had a rocker arm fail for whatever reason, wore a nice hole in the rocker arm and that wore one side of the valve enough so the rocker arm doesnt sit flat on it anymore. Never even made a noise.

What I am wondering is can I just replace the valve without having to grind the seat. These heads have had a valve job 40,000 miles ago so it definatly doesnt need a valve job. I am hopeing to just buy a cheapo spring compressor and a valve and be done. Can it be done this way or does somehow the valve have to be ground to match with the seat?

 

[4X4HIGH]

You can change the valve and then pour liquid down the port to see if it will hold, if not then you'll need to have a shop grind the seat so the valve will seal properly. Chances are pretty good though that with only 40K miles you will be able to just swap a new valve in and be good to go.

Look very carefully at the rocker stud to be sure it isn't sawed about in half (common with the failure you've described) and if so then you'll need to pull the rocker stud out and have the required tools to install a Dorman #693-005 .003" oversize press in stud, or drill and tap the rocker hole and install a Dorman #693-006 screw-in stud with the small shoulder.

 

[corey6969]

Awsome, thats the news I was looking for!! I already got screw in studs and guide plates and the stud is good so hopefully this will be a cheap fix!!! Thanks for the quick reply. Who wooda thought ide have so many problems the first time out rebuilding and engine,experience can be expensive!!

 

[4X4HIGH]

Awsome, thats the news I was looking for!! I already got screw in studs and guide plates and the stud is good so hopefully this will be a cheap fix!!! Thanks for the quick reply. Who wooda thought ide have so many problems the first time out rebuilding and engine,experience can be expensive!!

Are you running the hardened pushrods also, if not you will end up with broken pushrods from the guide plates eating through them.

 

[corey6969]

Are you running the hardened pushrods also, if not you will end up with broken pushrods from the guide plates eating through them.

Yup i am, u asked me that a little while ago,u probly dont remember, when I asked another question about coolant surging i think, its all the same engine, thats why i say lots of problems,lol. Although i used my original stock push rods with the guide plates for 40,000 miles before I rebult my 400 and it never wore on them at all, and the push rods were rubbing on the plates. The rod or the plate didnt wear, it was weird

 

[my92k5]

not sure if you care, but a friend of mine who was a mechanic (he's gone now)
he used some kind of valve paste, you stick the paste on the seat of the head and you stick some on the valve, then you attach the valve to a drill on the end it sticks out, and you pull upward gently while drilling and the paste shines the valve seat up and sands it down to seat with a fresh valve.

let me know if this is wrong, ive only heard of it never done it, but it made sense to me and he was a good do it yourselfer mechanic.

 

[chulisohombre]

not sure if you care, but a friend of mine who was a mechanic (he's gone now)
he used some kind of valve paste, you stick the paste on the seat of the head and you stick some on the valve, then you attach the valve to a drill on the end it sticks out, and you pull upward gently while drilling and the paste shines the valve seat up and sands it down to seat with a fresh valve.

let me know if this is wrong, ive only heard of it never done it, but it made sense to me and he was a good do it yourselfer mechanic.

ive done this before to clean up the seat on my camelhump heads.it will help the new valve reseat itself better.and it also will clean up the valve seat if it wore it uneavenly.i used a little plunger dealy and you push on the valve itself and did it by hand.i think i got it from napa.it comes in a kit.

 

[4X4HIGH]

That's called lapping compound. Usually people use it when they remove a used valve and reinstall the same valve without refacing the valve itself. The OP is going to install a new valve, he could still use lapping compound but probably not needed in his instance.

 

[corey6969]

Thats pretty neat, ill keep that in mind incase this new valve wont completly seal. Thanks guys

 

[76zimmer]

Scott; with the side loading that it sounds like may have occured, maybe the guide would need to be checked too?

 

[4X4HIGH]

Scott; with the side loading that it sounds like may have occured, maybe the guide would need to be checked too?

Naturally since the head would be off and the valve out it is easy enough to check the valve guide clearance. It's doubtful though that the guide is bad from the damage he has but there is always the exception and it "could" be bad. The OP did not say if it was an intake or exhaust valve that has given a problem but i can tell you that the exhaust guides go through the water jacket and can leak when they are changed. Also it is VERY important that the guide be removed from the correct direction IF it needs to be replaced as the exhaust guide is of varying size, the intake guide however does not go through a water jacket and is a straight size the whole length of the guide. The exhaust guide must be removed toward the valve spring side of the head and must be reinstalled from the valve spring side down toward the deck surface of the head.

 

[chulisohombre]

That's called lapping compound. Usually people use it when they remove a used valve and reinstall the same valve without refacing the valve itself. The OP is going to install a new valve, he could still use lapping compound but probably not needed in his instance.

i used it because the seat had a little pitting in it and i wanted to get rid of that to make sure it sealed right when i rebuilt the heads.i had 2 burned exhaust valve and my buddy said this would help to make sure the new valves sealed good without having to machine them.prob not as good as machining but it makes the valve sit pretty nice in the head.i never had a problem with compression doing it this way.