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Discussion Starter #1
I have a 90 civic with a sohc zc in it. The head that was in it had a shredded valve but it ran like a champ, I would take it in the canyons and take it to red line all night. It was obviously down on power, so I swapped the head with one I had decked cleaned and all the good stuff. I put the head on and it ran like a champ! Sounded much healthier and I took it in the canyons and the throttle response was 10 times better. But I look behind me and I see a cloud of smoke following me. I thought i must have messed up the head gasket. But I check the oil and coolant, and the oil has gone down significantly but the coolant hasnt????
I read that it. Could be the valve seals and the way to test that would be to go down a hill and engine brake, at the bottom burp the throttle and if a cloud of smoke comes out, it's the guides. And I did it and got the cloud of smoke.
Just to make sure it's the head and not the block I did a compression test, and all 4 cylinders had 180 psi. I called the machinist who did the head work and asked him what he thought. He said he definitely changed the seals and he checks guides when he works on heads. He said a compression test wouldn't tell me if the oil rings are bad. But it wasn't burning oil before I had the head swapped?
I'm really lost and this is my daily driver. If anybody knows anything I'd love to hear what you think. 20180518_195054_1528225860734.jpg
 

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The Great Weldini
91 civic
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its not hard to change the valve seal. i do mine in 20 minutes, then again ive done several times but again its not hard.
 

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use a magnetic valve retainer tool, and find a way to keep the valves up. nylon rope, air compressor adapter, or something.

then simply use the mag tool and a hammer, pop the valve retainers off, pull the spring caps and springs out, use a curve jawed vicegrips, carefully and lightly bite into the valve stem seal, and see-saw rotate it up and out. oil the new stem seals, and pop them into place.

If they are a proper set of seals, they will have a different color seal OR different color spring.

some brands foolishly use the same seal for both intake and exhaust, but they actually are different part numbers and ever so slightly different.


Ask your machinist what brand of parts he put into your cylinder head. Better yet, ask for part numbers. That way you have some info to research and see if he unfortunately used a set of seals that matched all 16, versus the factory style of exhaust being one part number and intake being the other.
 

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Discussion Starter #5
its not hard to change the valve seal. i do mine in 20 minutes, then again ive done several times but again its not hard.
I want to find the problem before trying to fix it. I'm really trying to avoid spending more time and money.
 

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Meat Popsicle
91 CRX Si
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Cylinder leakage test would spot any differences in leakage percentage between cylinders and would also allow you to hear any air hissing from the guides with the valve cover off.

Maybe you know someone with a leakage tester or can rent one locally?

I know the auto parts stores here only loan compression testers but maybe it’s different where you’re at
 

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The Great Weldini
91 civic
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What tool do you use? i've been looking for a valve spring compressor that i can use for the DOHC ZC so i don't have to remove the head for redoing valve stem seals.
its less of a headache when its off.
tools i have to make it simple.

Tool, Overhead Valve(to remove and install keepers)
Pliers, Valve Stem Seal or a long tip needle nose pliers
Valve Holder(valve lapper)
valve lapper compound

and for later to lash valves

Tool, Metric, Valve Adjustment (for cars with 10 mm jam nut valve screws)

I want to find the problem before trying to fix it. I'm really trying to avoid spending more time and money.
ok then...
 

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If you are careful, it wont cost you anything to pop the valvecover off and take a peak, and see what the stem seals look like. Might only be able to clearly see exhaust side, but you should be able to see if they are new, or if machine shop simply overlooked it.

Remember, machine shops are crazy busy all the time with them disappearing left and right across the country
 

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Discussion Starter #9
remoer

its not hard to change the valve seal. i do mine in 20 minutes, then again ive done several times but again its not hard.
Wouldn't the valve seal burn oil on start up, and not as much while driving? I heard that the seals allow oil to build up in the cylinder and after a prolonged start up it would burn the oil away.
 

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Meat Popsicle
91 CRX Si
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If it’s the guides then it would certainly burn oil in small quantities all the time but it probably wouldn’t be evident enough to see smoke during idle.

If I understand correctly, the long engine brake followed by the throttle blip allows the engine to decelerate under the highest vacuum condition with no combustion (due to the fuel cut), which draws in oil through the guides and burns it when you blip the throttle (combustion), causing the visible smoke.
 

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If it’s the guides then it would certainly burn oil in small quantities all the time but it probably wouldn’t be evident enough to see smoke during idle.

If I understand correctly, the long engine brake followed by the throttle blip allows the engine to decelerate under the highest vacuum condition with no combustion (due to the fuel cut), which draws in oil through the guides and burns it when you blip the throttle (combustion), causing the visible smoke.
Wow, this is one of the most useful posts I've ever read on this site.

I'm having an extremely similar oil burninig problem (burns when the car starts, a little smoke when given throttle, but then no other issues while driving) and it seems like its probably exactly what you're describing.

Thank you so much!
 

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Discussion Starter #12
Cylinder leakage test would spot any differences in leakage percentage between cylinders and would also allow you to hear any air hissing from the guides with the valve cover off.
Wouldn't the pressure leak past the valves into the intake or exhaust manifold before it passes the guides?

If it’s the guides then it would certainly burn oil in small quantities all the time but it probably wouldn’t be evident enough to see smoke during idle.
There is no smoke at idle, only on medium to hard acceleration
 

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its an oil pressure thing mostly

at idle, especially warm idle, you are under 15-20 psi.

at over 3k rpm, you are double that at a minimum, more if everything is healthy.


high geared engine brake means the oil pump is still turning pretty good, but the engine has a higher vacuum with the throttle plate closed, creating a wicking effect of drain oil from cylinder head past the worn valve guides.

My civic smells a bit of burnt oil under hard acceleration, and coasting down a long steep hill in drive (im auto) results in a throttle burp showing its presence.
 
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