Drop Valve Seat, How do you know? Options

[SLITS]

OOps!  Hey Slits, the Datsun thing was mine.  Just didn't know how to edit. Sorry. (IMG:style_emoticons/default/biggrin.gif)

???????? What Datsun thingy?

Ooops, I spotted it.

[mattillac]

Take the valve cover off and see if any of the valves have tightened up or see if one is really loose.

Other than that 1.) a leakdown test and 2.) Pull the suspect head

after doing the valve inspection and finding the loose or tight valve, i'll then remove the head. when i'm looking at the head, what am i looking for? do i need to actually remove the suspect valve or valves to tell if it's ready to drop?

[SLITS]

I've never caught one before it dropped - the seat will probably look different from the others as the seat is loose in the head. You could pull each valve and see if the seat drops out with it or have a auto machine shop inspect it. Sorry.....................

[mattillac]

so is the valve seat part of the head or is it pressed in or something? does anyone here have experience rebuilding their 2.0 heads? just wondering how much i'll be able to do myself and how much a shop/my dad the machinist will need to do. i trust myself to put in springs and rockers and such, but obviously cant do machine work and stuff.

[jporsche914]

I was just wondering if a dropped valve seat sounds like?? Does it just sound like a loud valve?? I think my car might have a dropped valve because one of my valves is quite a bit louder tha the rest and i think it runs on three cylinders when the motor is really really cold but after it warms up it runs on all four cylinders. I have driven it like this for about 110 miles and it hasen't got any worse from when it started.

[newto914s]

It sounds to me like maybe you sucked something into the fan housing. You would check by reaching into the center of the fan hub .......I have had my alternator cover thingy sucked into the fan a couple times, and it sounded like what you described.

I think that's what it is too, it's very much like something is tying up the belt and pulling the eninge speed down.
I reached into the impeller fan, nothing, and looking inside the heater ducks, no luck.
What's the alternator thingy you mention and where would I find it?

[mattillac]

I was just wondering if a dropped valve seat sounds like?? Does it just sound like a loud valve?? I think my car might have a dropped valve because one of my valves is quite a bit louder tha the rest and i think it runs on three cylinders when the motor is really really cold but after it warms up it runs on all four cylinders. I have driven it like this for about 110 miles and it hasen't got any worse from when it started.

well, i don't know if mine is going to drop the valve yet, but it sounds like slight rod knock or maybe some excessive valve noise: like a piece of metal slapping another piece of metal. don't know exactly what kind of exhaust is on my car, but it's pretty loud, and i can hear the slapping noise easily over my exhaust note. doesnt make the noise all the time though, at least not yet.

[SLITS]

The seat is pressed in, but there are those that have "special" processes to do so. The heat the head and freeze the seat to get the tightess fit possible as the steel seat is pressed into aluminum.

Image one - seat is cocked - caught before it got loose in the combustion chamber:

(IMG:http://www.rccauto.com/ebay/head.jpg)

Image two - seat completely came out and bounced around the combustion chamber for 150 miles (my head)

(IMG:http://www.rccauto.com/ebay/head1.jpg)

Image three - comparison of the non-dropped seat to the dropped seat - looking thru the intake port you could see light around the valve.

Less costly to check as you can see.

(IMG:http://www.rccauto.com/ebay/head2.jpg)

[jporsche914]

Does it stop making the noise when your engine is hot??

[SLITS]

It came and went over a period of time. Even when driving, I would hear it and then it would go away. One day, it just didn't go away right after I overspun the engine in a spin. I could still do 100+ on 3 cylinders though (IMG:style_emoticons/default/biggrin.gif)

In the aftermath, at the shop, it sounded like a real bad rod knock.

[mattillac]

thanks for the pics! seems like it's pretty easy to tell where the problem is once you get the head off. in the pic of the head that you caught before the seat actually dropped, it looks like it still damaged the head pretty well. is a head with that type of damage still good. would any good shop that does head work be able to repair this damage and install a new seat, or should i see a vw/porsche type shop?

[SLITS]

That can be heliarced and milled back out. Most any aluminum head can be fixed - it's just a matter of money - the real bad one of mine is a paperweight now - if it were a race head I would spend the money and time to fix it - yes, I had access to a machine shop at one time and we fixed ones worse than mine - they were racing heads we had a lot of money into.

[mattillac]

guess it's time to give my old man a call. he's been a machinist for most of his 60+ lifetime. i'd trust him to do the work before anyone else. and he'll do it for free! SCORE!!! (IMG:style_emoticons/default/aktion035.gif)

[redshift]

Here.... loose valve seat....

stststststtststststststststststststststststststststststststststst

Here.... minor exhaust leak...

ftftftftftftftftftftftftftftftftftfttftftftftftftftftftftf -fritter-

Here... valves need adjustment...

-hair comb being stroked from end on rev-

Here.... bent valve..

-radio edit-

M