Something is seriously wrong here...

[racerx]

(note: this is on a 16 valve B20A, but I'm hoping most of the same priciples apply)

Ok, so I snapped a timing belt... Bent all valves on the #3 cylinder, so I had them all replaced at a shop. All the other valves were fine and holding pressure.

So I've put the head back on and got the cams down with the timing set.

However... the rockers on the #3 cylinder seemed to need adjustment waaaay out far, but I didn't think anything of it since there were new valves in it.

I go to turn the crank to get ready to adjust the next set of rockers, but it won't turn once the exhaust valves on the #3 start opening more... I loosen the rockers, and it spins fine, until the intake valves on the #1 cylinder open up... (also causing interference, after it was adjusted)

What the heck is causing this??? The rockers are properly adjusted to 0.030" on the intake side and 0.060" on the exhaust side...


Are the rockers specific to intake and exhaust sides? Are the big bolts that they pivot in also specific? Is it something else entirely?

[A18A]

maybe the rockers were bent?

weird, most b20s i hear about have snapped cam belts :(

[Oldblueaccord]

(note: this is on a 16 valve B20A, but I'm hoping most of the same priciples apply)
Ok, so I snapped a timing belt... Bent all valves on the #3 cylinder, so I had them all replaced at a shop. All the other valves were fine and holding pressure.
So I've put the head back on and got the cams down with the timing set.
However... the rockers on the #3 cylinder seemed to need adjustment waaaay out far, but I didn't think anything of it since there were new valves in it.
I go to turn the crank to get ready to adjust the next set of rockers, but it won't turn once the exhaust valves on the #3 start opening more... I loosen the rockers, and it spins fine, until the intake valves on the #1 cylinder open up... (also causing interference, after it was adjusted)
What the heck is causing this??? The rockers are properly adjusted to 0.030" on the intake side and 0.060" on the exhaust side...
Are the rockers specific to intake and exhaust sides? Are the big bolts that they pivot in also specific? Is it something else entirely?

Double check that measurement on the valve adjustment. it shoiuld be like 10 mm and 12 mm i think.

wp

[racerx]

Ya i double and triple checked it. I also rechecked the valve timing (t-belt) and that thing is dead on.

It's extremely odd... It's like the cam shaft grew larger lobes over the weekend or something... (and yes, I have the right cams in the right place)

... I didn't forget to put the head gasket in (duh) so that couldn't be the reason it's sitting closer...

[accord upset]

make shure when the valves where replaced that they were replace with the right ones.make shure your whole cam is turning not just the front of it i twisted one in a scoh crx once and it took me like 4 hours to find out why the rotor wasn't turning and the cam gear was.

[Oldblueaccord]

yeah might be the wrong lenght valves? I saw .030 which is not 10mm BTW.

DO they valve stems (tops) look all even across every cylinder?

You did the right thing by turning it over by hand.



wp

[racerx]

Oh, I didn't mean 0.030 for the valve length, I meant the valve clearance of the rocker.

The valve lengths are correct. It's totally closed without any pressure from the cam (as should be), and the ONLY distance that it should travel is the exact size of the lobe of the camshaft. That's the only distance it should travel. It shouldn't be magically going too far...

[accord upset]

are ur pistons going back down when u turn the crank??? (rod maybe???)

[Robs89LXi]

You say you put the head back on, then you are installing the cams? It could be that the valves are too long. You cannot conclude they are closed (seated), just because the stem is touching the cam at the lowest part of the lobe; how do you know they are actually seated at this point if you cannot see the bottom of the valve? Is #3 piston at or near TDC right now? If the valve is too long, it may be hitting the piston when you try to open it by turning the cam.

[Oldblueaccord]

Oh, I didn't mean 0.030 for the valve length, I meant the valve clearance of the rocker....


Right so .030 is 30/1000 of an inch 10mm is .393 393/1000 of an inch,if that even the correct spec.




The valve lengths are correct. It's totally closed without any pressure from the cam (as should be), and the ONLY distance that it should travel is the exact size of the lobe of the camshaft. That's the only distance it should travel. It shouldn't be magically going too far...

Well there no magic involved if the length of the stem is too long the valve will seat in the head but the stem will be to long and stick out too far. Its very common for valve tips to be ground to spec or lash caps used to make up the differance. You can use a small ruler to check the installed height of the valve springs and compare it to one that not been touched. The only thing else I can think of is the springs might be binding.

Thats about all I can do for you.


wp

[accord upset]

the little half moon locks are at the end of the valve nearest the rocker arm so if the spring locks that hold the spring on the valve it would not stick up any higher than the rest but it would be further down in the cylender and not seat like rob was explaining. also why dont u just set your valve lash with the head off? then try putting it on and turning by hand then you could see wtf is going on?

[racerx]

settin it without the head on would be excruciating... I'd have to loosen all the rockers and cam holders to get to the head bolts, put it all back together, set the clearances, watch what's goin on, and take it all apart again to get it on the block...

I know the valves are seating just fine cuz they were all checked at the shop. I watched em to make sure.

Here's the thing. It does not matter how long the valves are. If you have 0.5cm travel from a lobe, it'll push a 10mm valve 0.5cm, and it'll push a 5 mile valve 0.5cm.

So if the valve is closed, and it's supposed to travel only 0.5 (that's just a made up number), why does it now interfere? It didn't before I took the head off...

Also, it's happening on the #1 cylinder, which had no valves replaced.

[accord upset]

i believe that your timeing of cams/crank is serouisly off then in my personal opion.since you already checked them over and over you should check and make shure all you gears are on right and the keyways are still in them,, and that you are lining them up with the right markers.??? o and the idea of setting them with it off is from personal experince with my a20a1 which i can get to the head bolts after i have set my valves(only a sohc with 12 valves). it was just a sugestion but if you have the head on the car i wouldnt want to pull it either(im lazy and thats work).

[Robs89LXi]

Here's the thing. It does not matter how long the valves are. If you have 0.5cm travel from a lobe, it'll push a 10mm valve 0.5cm, and it'll push a 5 mile valve 0.5cm.

Yeah, but the 5-mile valve might be hitting up against the schoolhouse in the next county (piston) because it is too long, while the 10mm valve is still pretty far away.

Are you sure your cam/crank timing is correct?

[Deadhead]

hmm.... odd problem, are you sure you didn't set your valve timing off 180 degrees? It's a common problem i hear about people doing by accident, so i thought i'd mention it.

Good luck, too bad that belt snapped, you just rebuilt it :(

[racerx]

I'm sure. But I'll check the keys and whatnot as well. I don't see how the gear could have spun, but it's worth a look.


Allow me to illustrate my 0.5cm example with some shitacular MS Paint work:
http://i5.photobucket.com/albums/y175/academyracer/prelude%20stuff/stems.jpg

It doesn't matter how long the stem is because it's only going to travel the set amount of the cam lobe. Additionally, some of the valves that were NOT replaced, adjusted, touched or anything are also doing the same thing.

[Robs89LXi]

Hey, I didn't know you were an artist! ;)
Actually though, think about only your top left illustration. If you keep everything the same in that drawing, but change the length of the valve stem only, your valve would not be seated, right? It would be partially opened, thus puting it closer to the head of the piston (if it is at/near TDC). As you turn the cam, it now pushes the valve down, and since it already had a head start in being closer to the piston, it allows it to come in contact with the piston before the cam reaches the apex of the lobe. Still, this should not happen unless the cam/crank relationship is off, as the valve and piston should never be trying to occupy the same space at the same time. If you can mark your crank, try turning it 180*, then see if the valve is still hitting when you turn the cam.

[A18A]

also notice that in that pic the rocker is longer ;)

[racerx]

Hey, I didn't know you were an artist! ;)
Actually though, think about only your top left illustration. If you keep everything the same in that drawing, but change the length of the valve stem only, your valve would not be seated, right? It would be partially opened, thus puting it closer to the head of the piston (if it is at/near TDC). As you turn the cam, it now pushes the valve down, and since it already had a head start in being closer to the piston, it allows it to come in contact with the piston before the cam reaches the apex of the lobe. Still, this should not happen unless the cam/crank relationship is off, as the valve and piston should never be trying to occupy the same space at the same time. If you can mark your crank, try turning it 180*, then see if the valve is still hitting when you turn the cam.

lol, ya 4 years of college in art! It's totally paying off now, huh?! :)

I'll do that 180* check, but I don't see how that could be the issue... the "T" mark is right there next to the timing mark, and the cams are lined up fine... I'll have to take some pics.

Also, the rocker arms are there for the purpose of adjusting for different valve stem lengths. Trust me, it's seated 100%

[racerx]

Ok it's not out 180*, everything is dead nuts on...

Any more ideas??? I wanna get this thing running!

[racerx]

There's not a second "T" on the flywheel, right? ... I know, kinda crazy, but worth asking I guess...

[racerx]

Okaaaaaaay... mystery SOLVED (not fixed)

The valve stem was cut too short!!! It was cut so short that the rockers had to be adjusted almost all the way out to make it fit spec. However, since the rocker was adjusted way too far out, the lock nut is touching the Cam lobe and thus stopping the engine from turning. Removing only these 2 rockers allows the engine to spin freely.

Here's a pic of the culprit:
http://i5.photobucket.com/albums/y175/academyracer/prelude%20stuff/cam.jpg

Just great, huh?

[Robs89LXi]

See, I told you it was too short.

[racerx]

See, I told you it was too short.

:rolleyes: just had to say it didn't you?

[A18A]

http://i5.photobucket.com/albums/y175/academyracer/prelude%20stuff/cam.jpg
thats pretty fucked up :S are you gonna get another set of valves now??

[accord upset]

not fun o mysterious one. but i hope the rest of ur build has better luck cause u come up with tricky questions.

[88Accord-DX]

If you don't use another head gasket on it, use some copper head gasket sealer after you put a few new valves in it

Edit- Personally I think that who ever rebuilt the head should be responsible for the work needed done now.