New Stubborn Valves Won't Seal After Lapping on an EJ25 After a Timing Belt Break

[dirty_mech]

This is a continuation of my timing belt saga from this post:

http://www.ultimatesubaru.org/forum/topic/154617-2000-legacy-ej25-timing-belt-broke-on-highway-seeking-opinions/

I followed the advice of  the posters and tried installing a fresh timing belt kit, which revealed that the threads for one of the idler pulleys were toasts.  After a successful thread repair job with a Time-Sert kit, I did a compression test which revealed zero compression in all cylinders. As it turned out, nearly every valve in the engine was bent, but there was no other visible damage beyond the bent valves, broken timing belt, and the busted idler pulley threads.

After fixing the idler pulley threads, I removed, disassembled, cleaned, and reassembled the cylinder heads with new valves.  I lapped all the valves with Permatex valve grinding compound and some lapping sticks.  I am in theory ready to reinstall them into the car. However, I'm having trouble getting all the new valves to seal.  It's not entirely suprising since I did not have the cylinder heads machined and opted to do the work myself.  However the engine had no problems prior to the timing belt failure and I figured the valve seats were not damaged with the valves, so why bother paying $300 a head for machining when there's no major damage to the heads beyond the valves?

All valves passed the light test, so I went to the passive water pressure test to ensure the valves were completely sealed.  I set the cylinder heads so that the intake / exhaust manifold ports on the heads face up, and then pouring water into the ports and waiting to see if any leaks through.  I was able to eliminate some leaks I found by doing extra lapping to the valves.  Currently, about 8 valves are completely watertight, 6 leak a drop of water about every 30 second to 1 minute, and 2 of the valves leak a drop of water about every 10 seconds.  It's these two valves that I'm particularly worried about.  I know valves don't have to be perfect to make the engine work, but I don't want to have issues with rough idling or backfiring, and possibly have to pull the heads off again after this whole ordeal.

Is this fear merited?  Should I worry about that amount of leakage?

No matter how much I lap these valves, the leaking did not stop.  All valve seats and seating surfaces have smooth, even surfaces.  On this basis, the valves appear to be making full and even contact with the seats.  So I don't know what is the problem.  Perhaps the seats are no good and need to be ground?  Perhaps the aftermarket valves have micro-bends in the stem and are not perfectly square?  The cause is unclear.

So I'm here looking for advice on what I should do to make the valve seal better.  Here are some ideas that come to mind, but I'm not sure if they would help:

- Try a different lapping compound?  Most lapping kits have coarse and fine lapping compound, but this Permatex stuff is a one size fits all.  Comments by Youtube mechanic Jafromobile suggest this might help me make a better seal:

- Lapping Technique.  What is the best way to rotate the lapping stick?  Should I use multiple rotations, or keep my rotation within an 180-degree area?  I don't see much guidance on this issue in the forums or online; Jafro's video suggests you should spin the stick between your flat hands as if you were trying to start a fire.  Beyond that I'm not sure if there is much that can be done.
 

- Additional Measures.  Not sure what could be done beyond either additional lapping, or taking it to a machine shop.  Perhaps someone has some ideas or experience that would be useful on this point.

 

- Install As-Is.  Perhaps the amount of leakage is not enough to warrant concern?  I don't need this car for racing, just daily utility.

Any advice is much appreciated!

[ocei77]

may not be the valves, but the guides/seals..

 

If they were tweaked a little in the original bending of valves, they won't seal.

 

O.

[dirty_mech]

The seals were replaced, but I could see the guides getting pressure applied and tweaked in the bend.  The direction of the bend should be predictably towards the vertical line of the length of the cylinder head based on how the valves would all contact the piston crowns.  

1.  Any way to detect?

I tried looking for wobble on the valve face while rotating.  At first they looked wobbly, but then I noticed the valve faces are not perfectly even either, so that made it difficult to say.

All new valves went into the guides smoothly during installation, appeared square with the seats, and passed the light leak test in full dark with flashlight at ports.  So it doesnt seem like these stems were bent by a very substantial angle.

2.  Any way to fix?

Earlier I considered valve stem bend and tried compensating for the potential of micro-bent stems by marking a point on the valve face radius and tried lapping it within an 180-degree twist.  Obviously that didn't work.

Is there any possibility of knocking them back into place with a rubber mallet and rod, or some other method?  They look built into the block so not sure if replaceable.

[mikaleda]

Best way to check valve guides is to slide the valve part of the way down and sew if you are getting any side play. There should be little to non

[mikaleda]

Also, when lapping valves male sure not to use too much compound because it can get into the valve guides and eat them out as you are lapping them in

[forester2002s]

You say that you have the heads ready to reinstall.

Have you checked that you have the correct clearances between the valve-stems and the rockers/lifters?

These clearances should be very small (see the FSM), but more than zero.

Otherwise the valves will not seal completely.

Edited October 28, 2015 by forester2002s

[Fairtax4me]

I normally chuck the lap tool into a drill on low speed. You just pull back on the drill to lift the valve off the seat every few seconds and that draws the grind compound back under the cutting surface.

 

 

There is a specified width for the contact area of the valve. Too wide, the valve may not seal properly, and it can cause carbon buildup on the seat or the valve which will cause it to not close all the way.

Too narrow and the valve can't cool properly, which can cause it to burn.

[DirtyMech]

I did not notice any side play when lapping and installing the valves but I will double check. I made very sure to get no compoun in the valve stems. I do not yet have the rocker arms installed because I am doing the job with the engine in car, but I will be sure to follow your advice when I get to that point.

 

Right now I am suspecting the permatex compound sucks, so I am getting some fine grit compound. I will probably use the 220 grit by Versachem but the 280 and 400 grit by Locktite Clover looks even better, so I will get that if its available.

[ocei77]

Perhaps Emily at CCRINC will chime in here.

 

O.

[ccrinc]

I did not notice any side play when lapping and installing the valves but I will double check. I made very sure to get no compoun in the valve stems. I do not yet have the rocker arms installed because I am doing the job with the engine in car, but I will be sure to follow your advice when I get to that point. Right now I am suspecting the permatex compound sucks, so I am getting some fine grit compound. I will probably use the 220 grit by Versachem but the 280 and 400 grit by Locktite Clover looks even better, so I will get that if its available.

 

Permatex is good compound (and is made by Loktite).  We use 180 grit water based Permatex and have for years. (Plus, we hand lap our valves: we haven't found any decent "automated" tool that does them to our satisfaction.)  What Fair said is true: the ring on the valve needs to not cover the whole surface but not be too thin either.  Actually, it is uniformity that is most important.  You can't "fix" a high or low spot except by cutting the seat, refacing the valve and starting over.  They must be uniform, both in measure of the "ground" surface, measure of the length (as mentioned above) and size of the seat. 

Also, how thoroughly did you clean off the valves after lapping? 

 

In truth, new engines come out of the factory without the valves being lapped at all.  But, everything is new at that point.  If you have a decent amount of sealing AND correct valve stem length measured via micrometer, actual running of the engine should finish the sealing. 

[dirty_mech]

It's been a while but I wanted to give a conclusion to this story.  I tried some different lapping compound with coarse and fine grades; it didn't seem to improve the valve-seat seals by much.  However, I put the engine back together and it seems to be a working fine.  The audible pitch of the engine is a bit lower on startup, likely due to uneven cylinder compression at low RPMs. However this goes away once the engine is warmed up, and doesn't occur at all at high RPMs.  There is no noticeable difference in engine performance now than compared to before the timing belt snapped and bent the old valves.

So all in all, it was a successful fix!  I have been back on the road for six months and am doing fine.  These engines can be resurrected after valves get bent.

[Bushwick]

Why didn't you just grab a set of used heads? 

 

To anyone else reading this, it really is worth having a shop do head work as they can get everything exact, check for deck warpage, back-cut the valves, do 3 angle valve jobs, verify spring pressure is consistent, etc. 

[dirty_mech]

Because... I'm an idiot?

Now that I'm looking online, I see them all over for about $100 a piece, listed as "cores" but probably just as good as mine were prior to the timing belt breaking.  I had thought of getting them in a junk yard, but pulling heads is such a time suck and junk yard rats swarm on Subaru engines like piranhas around here, so I figured the best bet was to just use the old ones. 

Ahh lovely hindsight.  Guess I will try it that way the next time it happens. =D

As for machining, I considered having a shop do the heads, but it would have added an extra $600 to the job and this Subaru is just a work vehicle that's
about two dents away from being a trashwagon anyway, so I figured I'd sacrifice perfection for savings.

[idosubaru]

used heads are the simple solution and usually cheap. 

 

used EJ25 heads often come from a block block - which has a good chance of being run out of oil, oil having metal bits run through it, or overheated significantly.  you at least now have heads that were known good. 

 

i was wondering if the valves were bent uniformly or varied?  and if the variations corrseponded at all to the locations you had trouble sealing. 

[dirty_mech]

grossgary:  Every single valve was bent, but I don't think they were all bent uniformly.  Some were sticking out of their seats, while others were barely unseated at all, and the damage had to be revealed through the light leak test using a flashlight at the intake port.  I inspected the valve seats for damage or warp as best I could.  They seemed fine to the naked eye, but I did consider the possibility the seats became misaligned when the valves were bent.  Given that almost all the valves were bent quite badly, I'm surprised that more of the valve seats did not give me trouble. 

I also noticed the cylinder closest to the driver's seat has had oil leaking through the compression rings, which explains why I have to add a bit of oil every thousand miles or so.

[Bushwick]

Because... I'm an idiot?

 

 

 

No no. You are talking to someone that walked his turbo CHRA into the compressor housing after dishing out an extended butthurt against an EVO and clipped his compressor wheel, cracked a dog dish heat shield, and put stress cracks into the exhaust turbine, and with ZERO turbo tear down knowledge at the time, rebuilt it and upgraded it in the process to a larger hybrid despite it being an uncommon turbo to do so with and little info floating about, as it was cheaper to do all that than buy new and used would be potentially have the same issue eventually as stock. Basically did what no one said was possible w/o machining experience and had it professionally balanced after. I'm one to go the DIY route if/when possible.

 

My NA Legacy has rust but is mechanically sound. So I get the notion about wanting to avoid putting money into one if you think it'll exceed the base value. I've taken to looking at it a different way though. If a new car on average costs $200-500 a month depending on what it is, and I don't own a new car, that's a huge savings every month and every year. If the older car being driven is worth $1k, and needs $600 worth of repairs, but is otherwise 100% dependable and easy/cheap to keep on the road otherwise and has an easy 5 years left in it if it just doesn't rust apart, that's roughly 2 months worth of new car payments (not including 10-20% down, etc.) and you are back to having zero car debt; Subaru really isn't a money pit unless you have a lemon; I wouldn't suggest doing this with say an early/mid 90's Dodge or Chrysler as they had a ton of issues from engines to electronics, etc. So while you might think of it as expensive and maybe not worth it, if you look at the entire car owning expense from a different perspective, you'll see it might be worth investing $600 for a couple years worth of reliability. Every time you start over used, regardless of price, you inherit a new can of worms.

 

Anyways, complete running EJ22 engines from specific yards go for for $150 roughly, locally. Other yards might be closer to the $350 range, and the wagons are plentiful (97-99', 00's are getting more common now). car_parts.com you can get heads shipped from various yards for $75 and up. So going used would be cheaper in this area. But if that wasn't an option and valves were bent and heads needed to come off, $600 would be worth the extra attention to detail that an actual head shop could provide as they can mic everything, do legit leakdown tests, find tiny stress cracks, thoroughly clean the head, etc. etc..

 

Your heads might outlast the car, then again in a 1k miles, you might end up with excessive carbon build up on a valve that's not seating correctly and it decides to bend then lodges in the open position, trashing the piston and the engine, and you are back at a more painful and expensive repair. I was trying to say to the more casual reader that might decide to tackle a head repair, that they really need to be careful. No attack against you personally. I hope it holds up over time.