Topic: Low compression, suggestions?

[Dr Beans]

Lol I was going to say just put the cylinder at BDC since you have no cam in place to control valve timing.

Just something to think about, and not saying this is happening, but leak down tests can return false positives. For example, if you did have the piston at TDC and had 90% leakage it could be because of a bore issue (out of round) and when at BDC only 10% because this part of the bore sees the least amount of abuse and may be in spec. This is why compression tests are done along side leak down. That said, it sounds like a valve issue.

You need to ask yourself how this happened though. It's unlikely it was assembled this out of tolerance so there's probably something else going on. When you take off the buckets you may see the top of the valve stem mushroomed which is creating the valve "drop" or lash issues.

Does the lobe look like there's been significant wear?

[BoMbS]

the piston at TDC had 90% leakage it could be because of a bore issue (out of round) and when at BDC only 10% because this part of the bore sees the least amount of abuse

Thanks, I've never heard of that, but good to know and keep in mind.  That said, I did achieve 10% leak at both TDC and BDC after removing the cam.

You need to ask yourself how this happened though. It's unlikely it was assembled this out of tolerance so there's probably something else going on. When you take off the buckets you may see the top of the valve stem mushroomed which is creating the valve "drop" or lash issues. Does the lobe look like there's been significant wear?

I've been asking myself HTF this happened since the beginning... Any insights are appreciated in this aspect. 

I don't own a micrometer to measure to current bucket thickness, but I can borrow one tomorrow.  The buckets all look nice and smooth, nothing unusual on the lobe(s) or the top of the valve(s).  The two things I will mention, is that the leaking valve bucket is also the thickest one I removed (from factory anyway), and that same bucket was stubborn to come out, whereas the rest almost fell out on their own while removing the cam. 


Exhaust cam with cylinder 2 at the left and 4 at the right with the corresponding buckets.


Top of the two exhaust valves in cylinder four, leaking one at the right.


Top of the head with exhaust cam removed.

[Dr Beans]

Well this is weird.

So if I'm understanding this correctly, the valve can fully close and the cylinder retains 90% of its pressure when the cam is removed. Which indicates that when the cam is installed, the back side of the lobe is making contact with the shim and the valve is slightly opening (while removing shims would help, the cam shouldn't be making contact on the "off side" of the lobe so shims aren't the issue).

The top of the valve stem looks like there is more wear than the left, but the retainer gap looks roughly the same as the valve on the left, the cam lobes look fine, and I'm assuming the top of the bucket is fine too? Take a picture of the tops of the buckets.

The cam cap lobes that ride on the cam cap look fine (although the middle has a bit of wear but nothing crazy) which indicates the came isn't slightly bent. I wonder if the line hone from the factory was on a slight angle?

Things to still rule out would be the valve seat, valve install height, and if the line hone was square in relation to deck height. You can check the line hone by using the bucket thickness plus the amount of lash from left to right where the problematic valve is. If the total thickness gets tighter as you make your way to the right then its a line bore issue. That's really the only way I can think of because blueprinting from the center bore of the crank is too difficult now.

Do you have dial indicator? By zeroing it out with the top of the retainer as a reference point and then rotating the exhaust cam we will be able to see how far the exhaust valve is extending. Comparing that result to the valve on the left would tell us a lot.

You sure there wasn't some crud between the stem and the bucket lol?

You need to confirm that the first part of what I wrote about the cam always making contact with the bucket.

[darthekai]

if you did have the piston at TDC and had 90% leakage it could be because of a bore issue (out of round) and when at BDC only 10% because this part of the bore sees the least amount of abuse and may be in spec.

You need to ask yourself how this happened though. It's unlikely it was assembled this out of tolerance so there's probably something else going on.

Lol I half typed out this very thing.
I don't know how easy it is to measure on an ej but valve installed height will tell you a lot about what's wrong.
Measure a good exhaust valve and this exhaust valve, up from the top of the spring shims to some easy surface on the head, then up from same spot to top of retainer, then down the thickness of retainer.

Potentially the seat is effed, the valve is effed, or maybe nothing is effed and you just need to remove some bucket shims?

[RockThePylon]

Your choices are;
Small investment in thinner shim/bucket and send it.
Or
Pull the head and have a look.

[BoMbS]

Busy couple days coming up, but I’ll be working on the car and updating as I go.  I can’t thank you guys enough for lending your combined knowledge.

I’m going to assume the line bore for the cam is okay, and just try adjusting the valve clearances. The tops of the valves, cam lobes, and both sides of the buckets have no usual wear. Same for the sides of the buckets, so it’s not sticking that way.  Also, everything came off clean, I was especially looking for chunks of valve cover sealant because it’s clear that they were done by the PO, but there was nothing.

Today at lunch I went to Rally Subaru and asked if they had any buckets in stock so I could buy a thinner one, reinstall the cam and measure the new clearance so I can then calculate the correct bucket thickness to buy.   When I explained that, the parts counter woman asked the shop if I could just borrow one from their collection and they gave me two sizes to test.  Very grateful for the good service, however, the buckets are $42 a piece. Holy ball$.

Unfortunately, I just got home and the borrowed buckets are a different height than mine...  is this going to matter?  As long as the edge of the bucket doesn’t bottom out into the spring pocket in the head, I should be ok?

Do I need to worry about the weight difference? Will it throw off the engine balance if some buckets are heavier?

[Dr Beans]

Unfortunately, I just got home and the borrowed buckets are a different height than mine...  is this going to matter?  As long as the edge of the bucket doesn’t bottom out into the spring pocket in the head, I should be ok?

Do I need to worry about the weight difference? Will it throw off the engine balance if some buckets are heavier?

As long as you have the correct lash and the bucket isn't binding on anything, then it should be fine. Since the bucket isn't rotating there won't be any balancing issues. All that's going to happen is that particular valve will require a little less energy to open the valve (like the smallest uckfaying amount).

[Mason]

So did this cause the low vaccuum numbers?

[BoMbS]

So did this cause the low vaccuum numbers?

I won’t know until I can start the car. 

Last night using the borrowed thinner lifters, I was able to calculate which ones to order, and $170 later, I should have 4 new ones by Monday.  Then if everything fits, I still have to put the engine back together before I can test vacuum. 

I’ll definitely compression test and leak down test again before I try to start it.

[tperkins]

I won’t know until I can start the car. 

Last night using the borrowed thinner lifters, I was able to calculate which ones to order, and $170 later, I should have 4 new ones by Monday.  Then if everything fits, I still have to put the engine back together before I can test vacuum. 

I’ll definitely compression test and leak down test again before I try to start it.

You seem very competent, but I would be hesitant about cold engine compression numbers apart from % difference.

[Mason]

You seem very competent, but I would be hesitant about cold engine compression numbers apart from % difference.

cold engine numbers will still tell you if they are close in %

[Dr Beans]

I'm not sure why we are talking about compression testing when the engine is cold?

We have already verified that the valve is the issue. The test would simply be if the cam can be put back in the engine without compressing the valve once the bucket and shims are changed. Checking the lash before hand will give you the answer, but it certainly doesn't hurt to check compression as well.

I'm most curious about whether the engine came out of the Subaru factory with the current lash settings.

[tperkins]

I'm not sure why we are talking about compression testing when the engine is cold?

We have already verified that the valve is the issue. The test would simply be if the cam can be put back in the engine without compressing the valve once the bucket and shims are changed. Checking the lash before hand will give you the answer, but it certainly doesn't hurt to check compression as well.

I'm most curious about whether the engine came out of the Subaru factory with the current lash settings.

Again, I am sure you know. But just preparing for the knee jerk reaction when the numbers are low to not worry so long as they're relatively similar across the engine.

I am curious how this goes! I have been reading along as it goes.

[BoMbS]

Quick update from my iPhone while in the garage.

Wife is angry. Spending too much time out here apparently. I wish there was appreciation of the $$$ saved.

Picked up the new lifters (buckets), all of them were superceeded by newer part numbers compared to my 2001 STi manual. They all look like the ones I borrowed from the Subaru dealership.

3 different packages though, odd.

Time to install and check all clearances again!

[BoMbS]

First: Please let me apologize to everyone for completely disappearing for 6 weeks. 

Second: The engine is running better than it ever has since I imported it!   

SO many things happened along the way of reassembling it, that I will probably forget to mention something, but here is a quick summary:

• Installed the new lifters (buckets) and camshaft and checked clearances, all were perfectly in specification.  Measurements worked out, phew.
• Installed new cam seals x4 and front crank seal.
• Spent FOREVER cleaning the old valve cover sealant off, and re-installed the RH side cover, since that side checked out, and the RH inner timing cover obstructs part of it so I had to do it first.
• Went to reinstall timing set, that is 9000 kms old, and two of the idler pully's (the toothed one, and the small one by the tensioner) were already making too much noise for my liking... Please wait while parts arrive...
• While waiting, started replacing old brittle breather hoses and ended up replacing the entire system with new red hose.  New PCV valve installed as well.
• Removed the turbo inlet pipe (very difficult without removing the intake manifold, FYI), to replace the leaking rubber fuel hoses that hide underneath it.  If you are not familiar with this fuel leak issue, it was a Subaru recall in the early 2000's.
• Purchased and installed a new silicone turbo inlet, yay!
• Timing parts arrive and engine is finally timed.  After manually rotating the crank many times, rechecked all LH valve clearances, and nothing had changed from previous measurements, phew.
• Completed a leakdown test on cylinder 4 again to be sure, and leak rate was only 8%.  YAY!
• Had to CLEAN and reinstall the LH valve cover before I could do a compression test...  HOURS....
• Compression test numbers were low, slightly lower than before which was also a cold test, but at this point the engine is "super cold"...  So I put little value in the numbers themselves, and instead paid more attention to the difference between them...   Only 7.6% from highest to lowest and cylinder 4 was in the middle of the pack!!!  Good news!
• Finally got everything back together, and it fired up like it was running the day before...  Total time past since I had parked it was 40 days.
• Test drive at no boost felt good, so I cranked up the boost and made it SCREAM.  Damn I love this car.

Other things that happened along the way to add to the delays...

• Ranger I was using decided to burn a spark plug lead wire and leave me stranded.
• Ranger I was using decided to start seeping coolant out of it's water pump.  I chose to ignore it.
• Ranger I was using had coolant run down the engine into the starter motor and seize it, leaving me stranded, and focing me to fix the starter and the water pump.
• Wife's 06 FXT decided to sh!t a U-joint in the center driveshaft, forcing me to find one and replace ASAP.

Merry uckfaying Christmas to me!

Just to finish this way too late post, to explain why it has "never run better", the engine at warm idle is now making 16-18 inches of vacuum, versus the 11-13 it was before, and is running at 14.7 A/F ratio, whereas before it was around 13.8-14.0 consistently.  It would also stumble on random WOT pulls in the past (now I know that it was likely cylinder 4 misfiring under high load), and it has not done it once since.

All that remains for me to do is to re-test the compression (with the engine warm), but I'm struggling to be motivated due to all the car-work lately and the beautiful way that it's running.   

Thanks again for everyone's help, feel free to ask if you have any questions.

[Dr Beans]

Link to the fuel hose recall? Mine are doing the same on my EJ207.

Also congrats! Glad to see its running correctly now.

[darthekai]

I just wanna say: THANKS FOR COMING BACK AND UPDATING THE POST.
I usually just have to assume the last thing that was suggested was the thing that fixed it.

[RockThePylon]

I love it when the "easy" fix, actually is the fix.

[BoMbS]

I just wanna say: THANKS FOR COMING BACK AND UPDATING THE POST.

Oh gawd I felt so guilty about not posting so many times before I finally did.  You are welcome, and thanks again.

Link to the fuel hose recall? Mine are doing the same on my EJ207.

This is the best I could find quickly as to something official: https://static.nhtsa.gov/odi/rcl/2009/RCDNN-09V468-8866.pdf

The Technical Service Bulletin that Subaru issued is TSB 09-36-03, but I couldn't find it quickly.  It lists 2002 as the earliest year, but that's due to that being the first year in North America, my 2001 obviously has the same problem.  Also, I should clarify, I only replaced the old hoses with supple new hose and bent my lines straight again.  I did not replace the metal lines with the shorter ones, so mine may leak again, but I also used better clamps, so fingeys crossed.  I've attached some pics below for reference.  There is lots of info online about this problem, just google Subaru fuel hose leak and you'll see.

These are the two rubber bastards that live under the turbo inlet pipe, you can see the awesome clamp orientation, but it turned out they were so loose I could spin the clamps around easily...  You can also see how the bottom hose is crooked as hell, which I'm sure helped it leak. 



I couldn't believe how friggin close together these were after I removed the hose, but the top one was even CLOSER together...  This made fitting the new hose very difficult, as I'm sure you could imagine.





Oh and don't forget there's one more connection behind the A/C pump which was also loose AF.  Don't have a close up picture, but you can see it in this photo marked with a green arrow.



No stinky cold starts yet!

[Mason]

Awesome to see the solution. I am impressed that you did all that without pulling the engine! I was considering pulling my engine when i do my valve covers and cam seals just to check valve clearance

[Dr Beans]

I ordered three new fuel line hoses.

Did you also change to more of a worm clamp used around coolant or intake systems (I can't tell in that last picture)?

[BoMbS]

Did you also change to more of a worm clamp used around coolant or intake systems (I can't tell in that last picture)?

They're not pictured, but I used SS worm gear clamps, but ones that have a solid inside band for more even pressure and less hose damage.  Like this:

[Mason]

Just a thank you for this thread. I didn't realize how much knowledge  I gained from this read until I had to do it myself