valve job questions

BlackVert · Aug 30, 2006

if you have been following my threads, you know i am having oil loss problems.

i am burning about a quart of oil per tankful, or about every 200 miles

the compression test indicates that my rings are most likely not the problem. phew!

people say that the next most likely culprit is the valves.

i want to talk to some local shops about what would need to be done if the oil is coming through the valves somewhere, but this is one of the many areas in which i am ignorant, so i don't know what questions to ask, and i don't want to come across sounding like a total idiot when i talk to them. sooooo ....

what should i be asking them to quote me a price for?

exactly what is a valve job?
what is a 3-angle valve job?

what are valve seals and should they be checked/replaced?
what are valve guides and should they be checked/replaced too?

BlackVert · Aug 30, 2006

WhiteDevil · Aug 30, 2006

If oil is coming into your clylinders from the heads it is going to be through the valve seals. They are little rubber caps that sit on the valves to prevent this. But after time and lots of heat get to them get get hard as rocks. Mine were like hard plastic. Then they start to leak. How many miles are on the car? Most likely a lot of things need to be serviced but its hard to say what you budget for this is.

BlackVert · Aug 30, 2006

the car has about 110K miles on it.

the heads have about 20K miles on them, i got them from thumper.

could having the blower on there have had something to do with a valve seal failing? i didn't have a problem before the KB was on there. maybe too much crancake pressure or something?

maybe i can do the valve seals myself? i've been reading up on it and it looks sort of doable

are they like this in our engines?

http://www.totalrpm.com/article/449

AznStanger3v · Aug 30, 2006

this is strictly my opinion, so take it like a grain of salt.

I disagree with everyone when they say its the valve seals. That is A LOT of oil loss for the seals. there really isnt that much oil in the rocker area. I still think its your rings. I havent been following your threads so i dont know your compression results. but here is my take on it. I sure you got decent readings because you were doing a "wet" compression test without knowing it. the difference between a wet and dry compression test is the use of oil during the compression test itself. the oil might be sealing the rings during your compression test and not burning due to no spark.

so, im still saying its your rings. a leak down test would prove more useful in my opinion.

SorsCode · Aug 31, 2006

I was having the same problem you describe. But I was burning oil a little quicker. Mine was so bad I could let it idle for 10 minutes pull the lower intake and look into the intake port of the cylinder giving me problems and oil would just puddle on top of the valve. Mine was an AFR. here to find out the valve guide was not installed to tolerance. Wish we would of found this out the 3 times I sent them the head. Rings are still a possiblity in your case compression test won't always show that. leak Down test does though. But I figured I would tell you my case. Might help might not.

PS lets just say the outcome of mine wasn't good. Ended up breakin the valve. Thats when AFR came back the 3rd time and told me my problem.

BlackVert · Aug 31, 2006

17yrOldStanger said:
this is strictly my opinion, so take it like a grain of salt.

I disagree with everyone when they say its the valve seals. That is A LOT of oil loss for the seals. there really isnt that much oil in the rocker area. I still think its your rings. I havent been following your threads so i dont know your compression results. but here is my take on it. I sure you got decent readings because you were doing a "wet" compression test without knowing it. the difference between a wet and dry compression test is the use of oil during the compression test itself. the oil might be sealing the rings during your compression test and not burning due to no spark.

so, im still saying its your rings. a leak down test would prove more useful in my opinion.

so are you saying that the oil is creeping up the cylinder walls past the rings and getting into the cylinders that way, or is air making it past the rings during the compression stroke and pressurizing the crankcase, causing oil to be forced through the PCV valve into the intake?

final5-0 · Aug 31, 2006

When rings get tired .................

They can't seal the wall as tightly as thay once did.

You have more oil left on the wall and it gets pushed up to the top and then gets burned with the rest of the charge.

The whole process is called ... high milage oil consumption

Some times you have oil that gets past loose guides and then it is only a matter of time before the seals can't do their job as John talked about.

Since your heads were redone not too long ago ... Like has been said ...
Most likely ... that ain't your prob

Grady

BlackVert · Aug 31, 2006

final5-0 said:
When rings get tired .................

They can't seal the wall as tightly as thay once did.

You have more oil left on the wall and it gets pushed up to the top and then gets burned with the rest of the charge.

The whole process is called ... high milage oil consumption

Some times you have oil that gets past loose guides and then it is only a matter of time before the seals can't do their job as John talked about.

Since your heads were redone not too long ago ... Like has been said ...
Most likely ... that ain't your prob

Grady

but i also have the big cloud at startup?

is oil in the upper intake also an indication of old rings (excess pressure getting thru and overwhelming the pcv system)? i wouldn't think a valve seal problem would result in oil in the upper intake

oil in the upper could also explain the big cloud on startup as it would settle at the valves while it sits and then get burned upon startup

should i stop in on my mechanic and schedule time for a leakdown test, or is that unnecessary if we really doubt that it is a valve seal issue?

AznStanger3v · Aug 31, 2006

i highly doubt the seals, but i would still have a leak down done on it. your PCV must be overwhelmed by the blowby that it is putting oil in the intake. that is my theory.

final5-0 · Aug 31, 2006

BlackVert said:
but i also have the big cloud at startup?

When you see that ...... some of the time ..............

That is an indication of bad seals.

You kill the motor and over night, oil runs down the valve stem past the seals and into the chamber.

Cloud city on the first fire up in the morning.

btw ... I got a bit of oil in my upper intake as well due to me being too lazy to rig up a splash guard in the fill tube of my modded fox vc's to replace the original one that met a violent death from my die grinder and porting burr.

I don't get a cloud startup thing from that little bit of oil in the upper.

Grady

WhiteDevil · Aug 31, 2006

Yeah with valve seals that new i would start to look elsewhere for your problem. Mine were 100k old and lost about 1qt every 3k miles.

reddy351 · Aug 31, 2006

I'd say that your next stop should be a leakdown test. I wouldn't recommend just throwing parts at it, to try to fix it.
If/when you call a machine shop (20k mile heads shouldn't need rebuilt.) you'll ask them what they charge for a valve job. What type? A valve job is matching the angle of the edge of the valve to the valve seat. Most shops do a 3-angle valve job. This means that in addition to matching the seat and the valve to each other, they also use an additional cut to "round off" the seat area. This reduces the amount of turbulence created by the valve seat. A 5-angle uses 4 additional cuts, almost like porting the seats.

Guides can be "knurled" or replaced. Knurling is really a band-aid repair. It's used to bring slightly worn guides back to service. They can be cut out and replaced with bronze "bushing" type guides at much more expense, but also more longevity.

Seals are just popped off and new ones popped back on when disassembling the heads for service.

I hope this helps.>>>>>>>>LEAKDOWN test, FIRST!

94-302-vert · Aug 31, 2006

Take that PCV line, run it into a 2 liter bottle of soda, plug it off at the itake and drive it around the block.

If oil is getting into the upper at 1qt every 200 miles then you will have plenty of oil in the bottle after a 5 or 10 mile run...

final5-0 · Aug 31, 2006

One more possible thing to think about Chris

Was it you that had some vt geom issues not too long ago

If so ... you may have put more wear & tear on the guides/seals.

Several years ago ... when there were not as many options with head choices ... you would see peeps convert oem iron heads over to stud mount

Some of the time, when they did that and did not ensure the vt geom was up to snuff ... You'd see them crying about trashed vg's not too long after the conversion. If the angle is too radical ... you very well can get some binding going on in that area.

Again ... Just a thought

Grady

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