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Hello,
I have a 1993 Honda DX with a D15B7 engine. I recently pulled the head and was extremely thorough about finding and marking TDC. When I pulled the head cylinders 1 and 4 were just as I would expect right at the top and cylinders 2 and 3 were at the very bottom. What I noticed though is that while the valves (exhaust and intake) for cylinders were 1 and 4 were closed tightly, cylinders 2 and three were partly open. I think cylinder two head its exhaust valves open and cylinder three had its intake valves opened (could be vice-versa). Is this normal?

The reason I ask is because I saw a thread on this site where people talked of doing a pressure/leakdown test on the valves with air pressure when the head is out.

I thought I would just double check...is it normal that two sets of valves would be open at TDC? If yes, then I guess I would have to turn the cam to the point where the valves in cylinders 2 and 3 were completely closed....then run the test on them.

Thanks in advance.

 
Rep Power: 519

Yes. When you set your marks at TDC, that's TDC for ONLY #1 cylinder.

All other cylinders' valves are not at TDC and not at the same point in the 4 stroke cycle.

You saw #4 with the valves closed, but that's not actually at TDC on the valves, it's at "overlap" because one pair is closing and the other is opening. Yes the piston is at the top or TDC, bit it's 180 degrees away from number one in the firing order.





This head was pulled with #1 at TDC and some valves are open..... other cylinders have valves that were doing something.

 
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Thanks Ezone for the quick and very helpful reply. So I guess if I run the test where one pours water into the exhaust or intake ports to see if they leak from the valves...I'll be sure to move the cam so they are all completely closed.

If I may, I have another question related to this. The real short story is that over a year ago I tested my compression and it was in the 90's for all cylinders (not good I know). As I think back I've been losing coolant for over a year or more. Then, two weeks ago after sitting for a month I drove my civic. It was low on coolant again (know this because the heat was rising). I pulled over, filled the coolant, and almost immediately it begin running very poorly and coolant began coming out the muffler.

Fast forward to today and I have had the head checked for cracks, resurfaced, lapped the valves, cleaned everything thoroughly, and am waiting for the head kit to arrive to finish the job.

I've seen some people talk about removing and replacing the piston rings since the head is off. Evidently it can be done without removing the engine. I understand why this is not as good as a proper rebuild but I have no evidence of bearings or thrust washers being severely worn. In fact the cam was in great shape.

Considering my low compression, which I started to possibly attribute to the head gasket, or possibly the rings...do you think it would be wise to take the extra step the replace the rings as well? Or is this not suggested without a full rebuild?

 
Rep Power: 519

With this method you can only test one at a time. Start with the #1 that already has the valves closed and do your checks. Then go to the next cylinder, simply rotate the camshaft until its valves are fully closed and the rockers have clearance. If you don't make certain the rockers have clearance, the cam lobes may not be in the correct position to have those valves truly closed.

Example: With cylinder #1 at TDC marks, #4 is on the Valve "overlap" right now, at least some of its valves may not be truly closed, they may have no clearance in the rockers (valve adjusters)...while #1 has clearance on all of its valve adjusters.


Another thing: Don't use water to check valve sealing. Water has too much surface tension.
I might use gas, brake cleaner, something with low surface tension.
Soap solution (Dawn plus water) that we use to find tire leaks may work too...and I can then blow air into the ports and look for bubbling at the valves.
I might grab a jug of washer fluid (methyl alcohol solution) just because it's really handy in the shop.

All 4 read exactly 90PSI?

Did you pursue a reason why the compression appeared to be drastically low?

There are many possible reasons, including faulty test equipment.
How well did the engine run at that time?

You've overheated it often enough to know when it's out of coolant? Bad bad bad.

Bad bad bad. The water you poured in just entered the cylinders through the head gasket breach.

The machine shop should be able to tell you exactly what was wrong with it. I expect it was severely warped due to overheating.

Yes, just pull the oil pan for access. Not much more work compared to getting the head removed.

Mark rod caps to the rods, so they all can be reassembled exactly as they were. This is a must!

If the bearings look good and there wasn't any bearing noise when it ran, then it's not a huge deal IMO.

We do this all the time in the shop, when we have engines that consume oil and get rings replaced under warranty....pull the heads off and replace rings, no bearings.
We do not hone cylinders at all...Just clean the pistons and replace rings (properly aligned of course) and stuff it all back together.

If you have a bunch of miles on the engine you may want to consider bearings while it's apart now, even if it's just sliding a set of standards in. I know at high mileage a lot of those engines can have main bearing rattle.
That's a good thing.

See above. Rings are often done to address oil consumption issues, but if the engine has been severely overheated then the compression rings could have been compromised and lost spring tension.
..... Plus you don't know for sure why the compression read as low, so right now since the head is already off all you can do is guess. To be safe, you may as well do rings while it's apart this far already, just because it would suck to have to take it apart all over again soon.

Big thing to look for is the crosshatch hone marks in the cylinder walls. If they are all intact and all visible, none worn smooth, then I'd probably be ok with sticking rings in.
If the hone marks have been worn off then I'd look for another block or used engine or something. A used engine is probably cheaper than machine shop charges and all the parts to go with it.


HTH

 
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Ezone, I can't say enough how much I appreciate all the help and guidance. I'll either use some gasoline or soap and water to test.

The cylinders were all in the 90's (low to high). The car ran but not with tons of power. I live near a 9500 foot pass (in Hawaii of all places) and the last time I made a run over it, the engine really struggled more than in the past.

I am fully aware at this point that my laziness caused this head warping. I had a radiator leak for awhile and didn't do anything about it in time. On a few occasions it got high before pulling over. Then later after replacing the radiator the problem arose again but as I think about it now it was probably due to coolant leaking into the engine...due to the warped head...due to the overheating....due to me.

The head was pressure tested and passed...and then resurfaced down 0.007 inches. Probably not a little warp...but it didn't sound like a horrible warp. What was bad bad was the head gasket when I pulled it. It was gone in several place and in large amounts.

Thanks also for the advice regarding the piston rings. I think I'll go ahead and tackle those as well. I was on the fence but considering that my low compression may have been due in part to the head gasket or perhaps in part due to the rings...I might as well fix both issues.

Really really appreciate the insight.

 
Rep Power: 519

That's a LOT of warp. Without looking at specs, I'll guess that was darn close to the machining limit.
Meaning...if it warps again, the head will probably be junk.

Altitude will lower compression test readings, but I really am not familiar with how much it will lower. I live at about 600' above sea level here.

Also, something as minor as an incorrect check valve in the compression tester hose can cut readings in half. A tire Schrader valve core is not the same as the one for the compression tester.

 
Rep Power: 519

Drive to sea level and do the compression test? LOL

 
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I live at around 950 feet but I'll be sure to check in next time at sea level. I used a tester from O'Reilly that is a rental. Considering how much use it gets I do wonder about it's accuracy.

What are your thoughts on using a honing tool to hone the bore if it's too smooth? I assume I would need to take real care to prevents and minute shavings from falling to the crank case. Is this an option in your opinion?

 
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950 feet or 9500? Big difference!

Probably garbage.

Read my long post again.

If the original hone markings in the cylinder walls look good I would not touch the cylinders at all.
Slap new rings on and run it.

We do not do anything to the cylinders on the warranty re-ring jobs, and we are doing them far beyond 100,000 miles.
Slap new rings on and run it.

If you hone, you have to then use hot soapy water and scrub the hell out of the area you worked until it can pass the white glove test. Literally, a white glove test. If the hone leaves any grinding material and you miss it, the rings can be ruined in short order.
Plus, the depth and angles of the crosshatch determine normal oil consumption.
What's already in there is correct.
If you get it wrong, you lose.


There are more reasons to NOT hone-it-yourself too, but I have to type a lot elsewhere.

 
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I've got the parts I need and I'm starting to reassemble the head after lapping the valves. When I removed the rocker assembly initially I was not thinking and removed the bolts which caused the assembly to start to come apart and I had to then rebuild it. The rocker assembly took a little bit of tapping here and there to get it most of the way in and then I started very gently tightening the bolts in order. I don't believe I am anywhere yet near the spec because I have this question.

When I turn the cam crank over the rockers ride over the cam lobes but as soon as the lobe has passed the valves quickly shut back instead of easing back into place like I would expect.

In trying to understand why this may be happening I came up with a logical explanation and wondered if anyone else agreed. My guess is that the reason the rockers and consequently the valves don't ease back into place but instead snap back is because there is no resistance/friction to allow for them to do that. Typically when you turn an engine over by hand there is the resistance from the timing belt, crankshaft, pistons, etc. This resistance I believe is what allows the rocker to ride gradually over the backside of the cam lobe. Without this resistance (i.e. with just a cylinder head) there is nothing to keep the compression of the springs from pushing the rockers abruptly and rapidly over the backside of the cam lobe.


Anyone else agree....or did I do something wrong when I assembled the rocker assembly?

Thanks

 
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Valve spring pressure is what causes each rocker arm to follow the profile of its cam lobe.

If you have any that don't, that's a problem..

If you meant the camshaft snaps to the next quarter turn position without the timing belt attached, that's normal-also due to pressure exerted by the valve springs.



I can't picture exactly what you described, but that's what it made me think of.

HTH

 
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The camshaft snapping to the next quarter turn is what I was referring to.
Thanks

 
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Wanted to say thanks to everyone, Ezone especially, for all your help. I'm nearing the end of this project and have another question.

Any reason the valves and cannot be adjusted with the head off the block? In addition to the rocker arm assembly being removed it unfortunately came all apart and so I figured to be safe I'll adjust the valves. Sooooo much easier with the head off.

So far from what I can tell the valves (exhaust and intake) are quite tight.
Exhaust - Spec is 0.25 (+/- 0.02) - My readings are anywhere from 0.08 to 0.13
Intake - Spec is 0.20 (+/- 0.02) - My readings are around 0.10 - 0.13

 
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Caught my mistake (at 12:30am). Forgot I was working on an import...hence mm and not inches. So the valve clearances are more in line with what hey should be.

That said, is it still ok to do a valve adjustment with the head off?

Thanks

 
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i can't think of any reason why not, as long as the cam is in the proper position/rotation while you are taking the measurements

 
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I have no problem with doing it that way.

Just be careful, be aware of what is under the head and valves (shop towels get caught as valves close and throw off your clearance checks LOL), and keep the head up off the bench so you don't tweak any valves as they open.

I prefer to adjust to the max or "loose end" of the specs, because Hondas tend to tighten up clearances as they wear and age.
I don't like to use metric feeler gauges either.

 
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Thanks Ezone for letting me know about Honda's tendencies to have their valve clearances tighten over time. When I set them I probably erred on the side being slightly tight. Now that I know I probably will go ahead and reset them just a tad looser.

I'm hoping this is my last real question regarding this job as I am ready to put my cylinder head back in place. And yes, this is my cheap side asking this question.

Can I get away with cleaning up and reusing my past old head bolts? I kept them in order and I don't believe they are the torque indicating bolts which are basically one time use bolts.

 
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Are the bolts TTY? What is the torque spec?
This will be the clue.


Unless you can find in the Honda factory service manual a statement saying to replace them, reuse them.

Even Hondas TTY bolts can be reused IF they pass the inspection-measurements, unless otherwise noted in the service manual.