Tried a valve seat test on the M50, need advice.....

[Dave M]

Not sure what to think of this, so I'll tell the story.

Background: Swapping the M50 block for a rebuilt one. I'm preparing to see a cracked/broken ring in cylinder #5 due to it dramatically 'failing' a dry/wet test. As the head was rebuilt <35,00 miles ago, and I saw few signs of leakage on exhaust valve stems other than in #5 (others are a nice toasty brown), I was wondering what, if anything, i should do with the head.

I asked yesterday, and someone (thanks) reminded me of the 'liquid' valve seat leakage test. So, I manually set each cylinder as close to TDC as I could and filled the 'bowl' with varsol (spark plug in of course). Now, assuming I'm doing this procedure correctly, here is the interesting part. Of the two cylinders that showed no leakage at all, one of them was dirty #5. Two others showed slow leakage (20 sec for a drop to reach exhaust and/or intake manifold) and I could see a ray of light through the remaining two when looking through the exhaust manifold with a flashlight shining on the 'bowl' (substantial leakage).

So, unless this is within spec, I'm head back to the shop. I had brought it to a supposedly reputable 'head shop' this morning and the gentleman pretty well said, "Ahh, it doesn't look so bad, pretty clean. Its OK if the valves leak a bit, and the exhaust stems/guides are usually looser than the intake. I wouldn't worry about it"

So, if I've done the test properly, and the results are telling, I guess I should find someone a bit more serious about diagnosis. I don't mind spending the $$, just want to make sure i should,

Thanks for listening,

Dave M

[632 Regal]

are you sure the valves are completely closed when you do this test? Is it hard to remove the cam to be sure the valves are seating?

After you redo the test (if needed) I would definetly take it to a different shop, these heads should last quite a while and 35k isnt that.

Some shops still knurl the guides for a tighter clearance, which doesnt last long at all and in my oppinion is totally hack.

[Dave M]

are you sure the valves are completely closed when you do this test? Is it hard to remove the cam to be sure the valves are seating?


I hope you're on to something. I assumed (hopefully incorrectly) that with cams installed and at TDC, that the valves should be seated. It may very well be a stupid question, but I'll risk asking it.....Is this test better performed with cams out? If so, yes, it would be hard to remove them (no tools), but if it warrants it, i may have someone do it for me.

I was also going to mention my compression values (test performed twice before dissasembly) as they don't jive with valves that don't seat. All cylinders but #5 were between 110 and 120 on the first stroke and between 175 and 180 on the fifth (stable). #5 was in the toilet except when wet, it was the same as others. And as I mentioned, the exhaust valve stems are toasty brown in all but cylinder #5.

Thanks Jeff,

I love this $hit,

Dave M

[Kalevera]

Dave, I agree with the statement that the exhausts are loose-er than the intakes. When I saw the first thread on this, I thought, "man, it takes like 5 minutes to check the axial play in a valve guide," but it does require a dial gauge (as shown in the bentley diagram). I can outline the procedure, if needed.

All of our serious machine work goes to Leo Goff @ Memphis Motorwerks; he's one of, if not the best out there. Returned yesterday was a 2.5l bored to 3.0l; beautiful work. This engine is going into a 20k mile E36 factory mtech (rare). Although we do head rebuilds in house, I'm considering sending an M30 head down to him as part of an FI project for a 5 angle valve job and all the other goodies. So, you might consider calling him up.


best, whit

[Bellicose Right Winger]

So compression in cyl 1,2,3,4 and 6 w/rebuilt head was 175-180 after 5 compression strokes and valves in cyl 5 passed leak test. Clearly cyl 5's low compression wasn't due to bad valves. This is great news. I'd put the head on the new(er) block and move on.

Paul Shovestul



I hope you're on to something. I assumed (hopefully incorrectly) that with cams installed and at TDC, that the valves should be seated. It may very well be a stupid question, but I'll risk asking it.....Is this test better performed with cams out? If so, yes, it would be hard to remove them (no tools), but if it warrants it, i may have someone do it for me.

I was also going to mention my compression values (test performed twice before dissasembly) as they don't jive with valves that don't seat. All cylinders but #5 were between 110 and 120 on the first stroke and between 175 and 180 on the fifth (stable). #5 was in the toilet except when wet, it was the same as others. And as I mentioned, the exhaust valve stems are toasty brown in all but cylinder #5.

Thanks Jeff,

I love this $hit,

Dave M

[632 Regal]

Dave, once you turn the cams to TDC, it could be TDC or between cycles leaving the valves slightly open due to overlap.

Bring it to TDC and then "wiggle" the rockers to make sure they arent holding anything tight and try the test again, if they are tight then rotate the cams to the other TDC and they should be loose (lol im losing myself). This should at least narrow down the playing field.

[Dave M]

Bring it to TDC and then "wiggle" the rockers to make sure they arent holding anything tight and try the test again

Jeff, I know where you're coming from, but the M50 head is hydraulic and I don'y know how to make sure the valves are fully seated at TDC. Am I out to lunch?

As Paul stated above, most signs point to drop the head on, and, of course i'd love to believe that and 'move on'. The guy I took it to did come well recommended and, from his apparent age, has seen a few cylinder heads in his day. Can he look at it and say it appears OK? Who knows.

Lowell, as good as your guy might be, I'm in Thunder Bay, Canada. Shipping would cost more than the head job :) But thanks.

What to do?

Dave M

[632 Regal]

sorry bout the hydraulic thing but the rockers shouldnt be tight...anyways cyl 5 didnt leak and its probably good to go.

Pull the piston on #5 and see what is wrong, then you can move on without worrying about the head.

[Dave M]

Thanks for the peace of mind (for now). I'll try and pull #5 piston ASAP and let the board know either way.

Later,

Dave M

[Bill R.]

results either way, by simply rotating the cams enough to ensure that each chamber has the valves closed when you do the liquid test. And no is the correct answer to leakage on the valves.. none.. Thats not your problem since 5 does seal but i still wouldn't bother putting a head back on if i already have it apart without regrinding or recutting the seats (depending on the equipment your machinist has) and doing a clean up cut on the valves. When the head is cleaned up and the valve stems clean and dry is the only way to accurately check the clearance on them .5 mm , exhaust and intake is the same on that head although a number of heads do specify greater clearance on the exhaust guides and also the exhaust guides wear quicker than the intakes... all that aside you still have a ring or cylinder problem with number 5# as you've already surmised.







I hope you're on to something. I assumed (hopefully incorrectly) that with cams installed and at TDC, that the valves should be seated. It may very well be a stupid question, but I'll risk asking it.....Is this test better performed with cams out? If so, yes, it would be hard to remove them (no tools), but if it warrants it, i may have someone do it for me.

I was also going to mention my compression values (test performed twice before dissasembly) as they don't jive with valves that don't seat. All cylinders but #5 were between 110 and 120 on the first stroke and between 175 and 180 on the fifth (stable). #5 was in the toilet except when wet, it was the same as others. And as I mentioned, the exhaust valve stems are toasty brown in all but cylinder #5.

Thanks Jeff,

I love this $hit,

Dave M

[R1daveg]

i still wouldn't bother putting a head back on if i already have it apart without regrinding or recutting the seats (depending on the equipment your machinist has) and doing a clean up cut on the valves.

I agree with Bill's advice, you will only want to do this job once, so do it all properly now.
From the km done by the head, it should be OK, but if nothing else but for peace of mind get it checked. A quick visual and bearing blue check of the seats and valves will determine if its necessary to re-cut and grind.

BTW, what was the spark plug like in cyl 5?

[Bellicose Right Winger]

Dave M,
I thought point of this exercise was to replace the block that has trouble with #5. If so, pulling #5 just delays forward progress.

I don't understand the logic that says rebuild a recently rebuilt head that has such good compression readings. But only you can determine if the reward of avoiding rebuild cost warrants the risk you might have to pull head again.

In the interest of avoiding the rebuild cost, while exercising caution, you could bolt head on new(er) block and check compression BEFORE you attach intake, exhaust and all accessories, saving a good amount of labor. If you don't like compression numbers you could pull head again and have it rebuilt. Of course your new block may have similar ring problems, and others have said that M50's that sit for a long time don't have good compression readings.

Paul Shovestul





Thanks for the peace of mind (for now). I'll try and pull #5 piston ASAP and let the board know either way.

Later,

Dave M

[Bill R.]

problem before continuing. Why fly blind when the motor is already out of the car even if he does have another bottom end to use. Its not like it takes long to pull the piston/rod assy when the motor is out and on a stand. And recently rebuilt means nothing on a head that leaks liquid. Imagine how much vapor or gases it leaks. Leaking valves lead to burnt valves, may as well address it while its out. I'd fix that before putting it together for a compression test, since its not a good idea to torque a head gasket down and then remove and reuse it. Small leaks on valves that won't hold liquid over a 2 hour period won't make a big difference on a compression test but they will on a leakdown test. I don't like r+r ing motors so i try to do everything to insure thats its correct the first





Dave M,
I thought point of this exercise was to replace the block that has trouble with #5. If so, pulling #5 just delays forward progress.

I don't understand the logic that says rebuild a recently rebuilt head that has such good compression readings. But only you can determine if the reward of avoiding rebuild cost warrants the risk you might have to pull head again.

In the interest of avoiding the rebuild cost, while exercising caution, you could bolt head on new(er) block and check compression BEFORE you attach intake, exhaust and all accessories, saving a good amount of labor. If you don't like compression numbers you could pull head again and have it rebuilt. Of course your new block may have similar ring problems, and others have said that M50's that sit for a long time don't have good compression readings.

Paul Shovestul

[winfred]

this means the head needs work



and I could see a ray of light through the remaining two when looking through the exhaust manifold with a flashlight shining on the 'bowl'


"Its OK if the valves leak a bit, and the exhaust stems/guides are usually looser than the intake. I wouldn't worry about it"

[Dave M]

I don't understand the logic that says rebuild a recently rebuilt head that has such good compression readings.

Of course your new block may have similar ring problems, and others have said that M50's that sit for a long time don't have good compression readings.

Paul Shovestul

I understand the logic (Bill), but like you (Paul), don't understand why I would get such consistent compression values and visually clean exhaust manifold and valve stems with inconsistently leaky valves. My fear is that I'm doing this incorrectly. My other fear is that I don't live in a city with a plethora of reputable auto machine shops, hence part of my hesitance to persue the rebuild. Its not all about the money. The re should be no problem with the 'new' block as I had it rebuilt (rings, main/rod bearings, good hone marks still present, head came off clean).

Bill R, even without pulling the piston (which I will do), I am quite certain it is the culprit. Further supporting this is the fact that the valves in #5 seal tight.

From R1dave: A quick visual and bearing blue check of the seats and valves will determine if its necessary to re-cut and grind.

What is a quick visual and bearing blue check of the seats....? The golden fleece? Quite interested.

Without any more definitive opinions (which i could never expect in this situation), I think I'll hit the yellow pages and search for a good machinest.

Thanks guys, your time is much appreciated,

Dave

[Dave M]

Well, I’ve just called the VW, Volvo and MB dealers in town and sked where they send their heads. All three gave me the same answer, and when prompted, Volvo said they have the ‘newest’ equipment and do a good job on their ‘complex’ heads.

So, if need be, I may have a winner,

Just thought I’d update instead of working,

Dave M

[Bellicose Right Winger]

The compression test is the real issue. It's next to impossible to get a false HIGH reading on a dry compression test. I've never had a problem with a cylinder with 175 psi on a compression test. Combine this with 5 of 6 exhaust valves being the same color and I see very uniform combustion. There are NO hot gases leaking past valves that hold 175 psi.

I've never done the liquid leak test so I don't have a sense of what leakage to expect. I'm inclined to think the reported leakage is insignificant, a position that's supported by the machinist that inspected the head, but I expected it to be zero. It wouldn't take much debris on the valve seat to create a leak. This is hardly a clean environment like a freshly ground valve and seat on a machine shop bench.

Assuming the cams were on their base circles when tested, the 2 cyl's that pass light are a mystery. This has been reported by guys reassembling M50 heads, that is the valves aren't completely closed after cams are bolted down. It seems to take a while for the hydraulic lifters to settle down. But I can't explain why this would happen on a head that came off a running engine. Pulling cams would put all this to rest and might be worthwhile.

I wasn't suggesting reusing the head gasket, I expected to replace it if the compression test after assembly showed a problem. I just don't think he'll have to remove it again, particularly with a re-ringed bottom end.

I've always disassembled the heads I've had valves and seats cut on. It saves a tremendous amount a labor and improves the bonding experience with your ride. What's the cost to overhaul a 24 valve head these days?

BTW, the bluing test requires a complete disassembly of the head. At that point you may as well cut the valves and seats.

Paul Shovestul




....... And recently rebuilt means nothing on a head that leaks liquid. Imagine how much vapor or gases it leaks. Leaking valves lead to burnt valves, may as well address it while its out. I'd fix that before putting it together for a compression test, since its not a good idea to torque a head gasket down and then remove and reuse it. Small leaks on valves that won't hold liquid over a 2 hour period won't make a big difference on a compression test but they will on a leakdown test. I don't like r+r ing motors so i try to do everything to insure thats its correct the first

[Bill R.]

Slut" skits? Paul pumping 175psi on a compression test and holding 175psi are two entirely different things, you cannot accurately measure the condition of a valve and seat with a compression test, only a leakdown test will tell you that, or physically taking the head apart and inspecting the valves and seats.. Will everybody who's worked at least 5 years in a automachine shop raise their hands? i've got mine up. You are correct that bluing must be done after the head is disassembled, but bluing is also a poor indicator of valve seating, a liquid leakage test is a much better indicator of whether the job is done correctly or not. It takes more time than most shops can afford to spend on your heads though. Bluing is better used as an indicator of where the seating is occurring on the valve face, the typical m50 bmw seat is supposed to .055 to .075 thousandths wide so on the valve face thats a small portion of it. The bluing shows you whether its seating to the outside ,inside or center of the valve face.
And the valves are designed to rotate as the engine runs so that the valves and seats tend to be self cleaning helping to keep carbon etc from causing leakage at the valve seat. So if it won't hold liquid then they need to be taken care of before you put the motor back together,
And yes, I would pull the cams anyway and check for leakage again to eliminate the possibility of any valves being held open.




The compression test is the real issue. It's next to impossible to get a false HIGH reading on a dry compression test. I've never had a problem with a cylinder with 175 psi on a compression test. Combine this with 5 of 6 exhaust valves being the same color and I see very uniform combustion. There are NO hot gases leaking past valves that hold 175 psi.

I've never done the liquid leak test so I don't have a sense of what leakage to expect. I'm inclined to think the reported leakage is insignificant, a position that's supported by the machinist that inspected the head, but I expected it to be zero. It wouldn't take much debris on the valve seat to create a leak. This is hardly a clean environment like a freshly ground valve and seat on a machine shop bench.

Assuming the cams were on their base circles when tested, the 2 cyl's that pass light are a mystery. This has been reported by guys reassembling M50 heads, that is the valves aren't completely closed after cams are bolted down. It seems to take a while for the hydraulic lifters to settle down. But I can't explain why this would happen on a head that came off a running engine. Pulling cams would put all this to rest and might be worthwhile.

I wasn't suggesting reusing the head gasket, I expected to replace it if the compression test after assembly showed a problem. I just don't think he'll have to remove it again, particularly with a re-ringed bottom end.

I've always disassembled the heads I've had valves and seats cut on. It saves a tremendous amount a labor and improves the bonding experience with your ride. What's the cost to overhaul a 24 valve head these days?

BTW, the bluing test requires a complete disassembly of the head. At that point you may as well cut the valves and seats.

Paul Shovestul

[Dave M]

Well, the head is now sitting at the machine shop.

I wish I, or anyone else could explain how the 5 cylinders could have such consistant compression, yet such inconsistent valve sealing.

Last thought/question. Could the fact that the head has been sitting in a cold garage (heated only when i'm working in it) influence the valve seating. I'm interested to see whether they seal after being at the machine shop for a day.

I'll get to Paul about the 24 valve head job cost,

Thanks again,

Dave M

[Dave M]

I wish I, or anyone else could explain how the 5 cylinders could have such consistant compression, yet such inconsistent valve sealing.
Dave M

Well, i guess Bill just gave us the answer. Since its sitting there (no work authorized yet), I will also ask them to remove the cams when its warmer and check again.

Dave M

[Bill R.]

valves open because the cam was in the correct position on each chamber as you did your liquid check and that the hydraulic valve elements aren't holding a valve open. If you still have leakage then there is a poor seat between the valve and seat in the head. A compression test because the piston is moving rapidly and pushing a large volume of air can give you that 175psi briefly even if you have some leakage at a valve. Fine , it won't show up on a compression test. It will show up if you do a leakdown test however. And small amounts of leakage will show up when the engine is running in the form of a slight miss or not as smooth an idle as you would expect.







Well, the head is now sitting at the machine shop.

I wish I, or anyone else could explain how the 5 cylinders could have such consistant compression, yet such inconsistent valve sealing.

Last thought/question. Could the fact that the head has been sitting in a cold garage (heated only when i'm working in it) influence the valve seating. I'm interested to see whether they seal after being at the machine shop for a day.

I'll get to Paul about the 24 valve head job cost,

Thanks again,

Dave M

[Bellicose Right Winger]

Bill, Certainly a leakdown test will pinpoint leakage, but there's absolutely no reason to "accurately measure condition of valve and seat" when compression test results are as good as these. 175 psi is 20-30 psi ABOVE the minimum BMW spec shown in the TIS and it was achieved on only 5 compression strokes. I test to 10 strokes to give cylinders benefit of the doubt. Compression tests made at 120 rpm cranking speed are valid because the slow speed allows far more time for pressure bleed off then will occur when engine is running. Compression stroke at 120 rpm takes .251 sec, but at 720 rpm the compression stroke takes only .042 sec, 1/6th the time at which test was conducted and virtually no time for leakage to occur. Compression pressures also aid sealing by forcing valve into it's seat.

Paul Shovestul
AKA "The Ignorant Slut"

Bill, it may be time to change my screen name. As you know you've been very helpful in this process throughout the years! :D



Slut" skits? Paul pumping 175psi on a compression test and holding 175psi are two entirely different things, you cannot accurately measure the condition of a valve and seat with a compression test, only a leakdown test will tell you that, or physically taking the head apart and inspecting the valves and seats.. Will everybody who's worked at least 5 years in a automachine shop raise their hands? i've got mine up. You are correct that bluing must be done after the head is disassembled, but bluing is also a poor indicator of valve seating, a liquid leakage test is a much better indicator of whether the job is done correctly or not. It takes more time than most shops can afford to spend on your heads though. Bluing is better used as an indicator of where the seating is occurring on the valve face, the typical m50 bmw seat is supposed to .055 to .075 thousandths wide so on the valve face thats a small portion of it. The bluing shows you whether its seating to the outside ,inside or center of the valve face.
And the valves are designed to rotate as the engine runs so that the valves and seats tend to be self cleaning helping to keep carbon etc from causing leakage at the valve seat. So if it won't hold liquid then they need to be taken care of before you put the motor back together,
And yes, I would pull the cams anyway and check for leakage again to eliminate the possibility of any valves being held open.

[Bellicose Right Winger]

The simple answer is there's some debris on the valve seat. I can't see cold temp being an issue. The bigger question is why don't all valves close. Hopefully the machine shop will clean valves and seats, remove cams so lifters aren't an issue, and redo leak test.

Is this the same shop that inspected it previously?

Paul Shovestul




Well, the head is now sitting at the machine shop.

I wish I, or anyone else could explain how the 5 cylinders could have such consistant compression, yet such inconsistent valve sealing.

Last thought/question. Could the fact that the head has been sitting in a cold garage (heated only when i'm working in it) influence the valve seating. I'm interested to see whether they seal after being at the machine shop for a day.

I'll get to Paul about the 24 valve head job cost,

Thanks again,

Dave M

[Dave M]

The simple answer is there's some debris on the valve seat. I can't see cold temp being an issue. The bigger question is why don't all valves close. Hopefully the machine shop will clean valves and seats, remove cams so lifters aren't an issue, and redo leak test.

Is this the same shop that inspected it previously?

Paul Shovestul

Paul,

First, before I forget, they quoted $320 CAN (@$250 USD) for a complete job, not including parts. Let me know what you think.

I did not take it back to the first place I mentioned. The place its sitting at now impressed me (I called a number of dealerships to make my decision). They took an immediate interest and offered to pull the cams and inspect the valves closer before I decide what to do. I'm not afraid to do the work, just more interested in the 'how's and why's' .

On that note, you and Bill have provided a great commentary on the situation, which I much appreciate. I don't doubt either of you, I just wish Paul was right:D

As most shops are winding down for the holidays, they won't be looking at it until next week. I'll be sure to post their opinion.

Again, thank you all. I'll get in back in the engine bay before the snow melts,

Dave M

[R1daveg]

From R1dave: A quick visual and bearing blue check of the seats and valves will determine if its necessary to re-cut and grind.

What is a quick visual and bearing blue check of the seats....? The golden fleece? Quite interested.

Without any more definitive opinions (which i could never expect in this situation), I think I'll hit the yellow pages and search for a good machinest.

Thanks guys, your time is much appreciated,

Dave

Sounds to me like the quote you got is very reasonable.:)

BTW - bearing blue is just a sticky ink goo, and is used on all sorts of things. In this case its spread (thinly) around either the seat or valve, and when installed and seated/rotated a few times will leave a print of the area that is touching. It is only a guide for this case, to show whether there is a complete seal or not. The fluid leakdown test is a more thorough method.

And my 2c, if it were my motor (and prolly will be in about 100k) i would just get the head recoed now. I expect when i put it back together, it will stay together for another 4-500k. Attention to detail, and not cutting corners, will pay off in reliability.;)

Really interested to hear if cam followers are an issue here. Will also be interested in any other findings as you go through your rebuild. Post em up!

[Dave M]

Sounds to me like the quote you got is very reasonable.:)

BTW - bearing blue is just a sticky ink goo, and is used on all sorts of things. In this case its spread (thinly) around either the seat or valve, and when installed and seated/rotated a few times will leave a print of the area that is touching. It is only a guide for this case, to show whether there is a complete seal or not. The fluid leakdown test is a more thorough method.

And my 2c, if it were my motor (and prolly will be in about 100k) i would just get the head recoed now. I expect when i put it back together, it will stay together for another 4-500k. Attention to detail, and not cutting corners, will pay off in reliability.;)

Really interested to hear if cam followers are an issue here. Will also be interested in any other findings as you go through your rebuild. Post em up!

After an night of sleep, I'm in agreement and will do the rebuild regardless of further findings. I was out nordic skiing last night and passed plenty of folks with $400 poles. I figure my $75 poles have already payed for the head :D

So many ways to justify, plus..... its christmas

Have a good holiday,

Dave M

[R1daveg]

LOL nordic skiing. It was 35 deg C. here in Melbourne today, and its only just starting to get warm!!

Maybe you'll get lucky and have Santa deliver new poles too:p

Merry Christmas to you and beemer.

[Bellicose Right Winger]

Dave M,
I expected cost to be higher. If tests show this is the best solution, you can give them the valve stem seals from your head set to keep parts cost down.

I'd be interested in hearing what new shop says about acceptable leakage. Also be sure you understand what is holding valves open.

How long ago was your compression test done?

This is a GREAT board. The knowledge transferred here is unsurpassed. The different opinions/approaches expressed can be confusing, but in some cases they're based on the different perspectives of the contributors. As a shop owner, Bill can't and shouldn't take the chance that a car comes back after he's made a repair. The bill for the valve job goes directly to the customer. This isn't a criticism by any means, reputable business' have to err on side of caution, or they will no longer be reputable or in business. The customer gets a fresh head and shop minimizes chance of a come back making it a win-win. On the other hand, back yard hacks like me have a big incentive to minimize cash outlays, and conflicting evidence like good compression, liquid leaks and valves that don't close make this difficult. It all boils down to understanding the risks and rewards of any decision. The tests proposed by all will identify what problem(s), if any, exist.

Paul Shovestul


Paul,

First, before I forget, they quoted $320 CAN (@$250 USD) for a complete job, not including parts. Let me know what you think.

I did not take it back to the first place I mentioned. The place its sitting at now impressed me (I called a number of dealerships to make my decision). They took an immediate interest and offered to pull the cams and inspect the valves closer before I decide what to do. I'm not afraid to do the work, just more interested in the 'how's and why's' .

On that note, you and Bill have provided a great commentary on the situation, which I much appreciate. I don't doubt either of you, I just wish Paul was right:D

As most shops are winding down for the holidays, they won't be looking at it until next week. I'll be sure to post their opinion.

Again, thank you all. I'll get in back in the engine bay before the snow melts,

Dave M

[Dave M]

Dave M,
I expected cost to be higher. If tests show this is the best solution, you can give them the valve stem seals from your head set to keep parts cost down.

How long ago was your compression test done?

Paul Shovestul

Yep, this is a fantastic resource, not sure what I'd do without it.

As far as the cost, If they do the work, I'll make sure they hold firm to the price. Is re-using the seals an acceptable practice, I would have thought not. As stated, the seals are less than 35k old. Just checked 'realoem' and it showed $31 for a set of two???? If thats the case, the seals would cost far more than the job. Hmmmm, is that the case?

The compression test was done moments before tearing into the job and were consistent with the results produced a year previous.

Let me know what you (or others) think about the valve seal thing.

Thanks yet again,

Dave M

[Bill R.]

life of a valve job. I wouldn't ever consider reusing valve stem seals. They typically come in the head gasket set as Paul stated so you don't need to buy them separately. Also you can get any number of aftermarket stem seals for a lot less than that, and they will live as long or longer than the stock ones.





Yep, this is a fantastic resource, not sure what I'd do without it.

As far as the cost, If they do the work, I'll make sure they hold firm to the price. Is re-using the seals an acceptable practice, I would have thought not. As stated, the seals are less than 35k old. Just checked 'realoem' and it showed $31 for a set of two???? If thats the case, the seals would cost far more than the job. Hmmmm, is that the case?

The compression test was done moments before tearing into the job and were consistent with the results produced a year previous.

Let me know what you (or others) think about the valve seal thing.

Thanks yet again,

Dave M

[winfred]

they run about $20-30 a pack and two packs needed for the job, but your head set will have them allready, replace them like bill said

[Bill R.]

I am not a shop owner, i'm a self employed mechanic, there's a big difference. No employees work under me. Second, the opinions outlined here as to a valve job are what i would do on my own cars based on my experience working at a machine shop in the past. For a customers car i will tell the customer the options and then do exactly what the customer chooses. I charge strictly by the hour and do exactly what the customer wants. I will attempt to advise them the correct thing to do but ultimately its their choice. I don't profit off of the machine work and don't mark up parts so i don't care whether they bring their own parts or not.

Case in point , i have done at least 4 honda's in the last year and a half that lost a timing belt, in every case i explained to the customer that the odds are very good that one of the pistons hit a valve and bent it. 3 out of 4 chose to do the timing belt without further investigation. So they paid me to change the belt only. None of them got lucky so they ended up paying me to remove the belt again when i pulled the head. But this was their choice and their gamble. But on any car of my own that had 20k miles on it , if i already had the head off, i would have a valve job done, This is not remanufactured, not rebuilt. This is grinding the valvefaces, grinding or cutting the seats, measuring the clearance between the guides and stems and replacing any valves as needed with oversize, cleaning up the head , measuring the spring pressure at the installed height, reassemblying. I would also tear it down on my own as Paul states, to check it myself first before taking it to the machine shop. But i have everything needed to make my own checks. I can understand Pauls point on backyard hacks trying to minimize expenditure's and agree, since its commonly known how cheap i am. But when you already have the amount of labor involved in pulling a head it definitely makes no sense not to have a valve job done while its out.





Dave M,
I expected cost to be higher. If tests show this is the best solution, you can give them the valve stem seals from your head set to keep parts cost down.

I'd be interested in hearing what new shop says about acceptable leakage. Also be sure you understand what is holding valves open.

How long ago was your compression test done?

This is a GREAT board. The knowledge transferred here is unsurpassed. The different opinions/approaches expressed can be confusing, but in some cases they're based on the different perspectives of the contributors. As a shop owner, Bill can't and shouldn't take the chance that a car comes back after he's made a repair. The bill for the valve job goes directly to the customer. This isn't a criticism by any means, reputable business' have to err on side of caution, or they will no longer be reputable or in business. The customer gets a fresh head and shop minimizes chance of a come back making it a win-win. On the other hand, back yard hacks like me have a big incentive to minimize cash outlays, and conflicting evidence like good compression, liquid leaks and valves that don't close make this difficult. It all boils down to understanding the risks and rewards of any decision. The tests proposed by all will identify what problem(s), if any, exist.

Paul Shovestul

[Dave M]

They typically come in the head gasket set as Paul stated so you don't need to buy them separately.

Thanks Bill, shows you how many head gasket sets i've ordered. I ordered whatever BMA carries, so hopefully I'll be all set.

Dave M