Talk about engine building here. New products, tricky questions or showcase your work - If it's engine building related it's welcome here.
I thought this would be easy with the special tool I got to compress the spring and compressed air to hold up the piston. Not easy. What’s the trick to this or should I use the nylon rope method? And if so what are the do’s and don’ts of the rope method?
First thing I notice with the compressed air method is as soon as you start compressing the spring to release the keeprs you are in effect opening the valve and you quickly loose air pressure in the cylinder. That scares me that the valve will just drop.
I decided to go for it anyway but didn’t get that far.
My first attempt with compressed air (100psi) the engine let out a loud groaning noise and then you couod hear the air blowing around in the sump. The air had turned the crank 180 degrees, good thing the cams are out and all the valves are closed.
My second attempt I locked the crank into position with a wrench on the crank bolt and a zip tie which was effective. However as soon as I started compressing the spring to release the keepers air started coming out strong from a vaccuum nipple I had open on the intake manifold since compressing the spring has the effect of opening the valve and I’m working on an intake valve spring.
My third attempt I put a tight vacuum cap over that nipple on the intake manifold and went at it again. As soon as I started compressing the spring to release the keepers the engine started making the loud groaning noise again. I wouod say it sounds like a whale under water. Quick as I could removed the tension from the spring which shut the valve again and the horrible sound stopped. I think the sound is air rushing into the intake manifold as soon as the valve started opening and then the air found it’s way into another port in the intake manifold pushed the valve open some and found a piston that was at BDC and the air squeezed by that and who knows what else, maybe the throttle plate too, a lot of places for air to squeeze by and play the Tuba.
Didn’t sound like a good idea to continue.
So is this all to be expected for this sort of procedure?
Or am I better off with the rope method? I started piling rope down the cylinder and then cranked the cylinder back up and decided to pause and ask for help as how do I know the rope situated itself beneath the valve I’m trying to change the spring on and not some other valve. How much rope should I put in there?
Or am I being completely dumb and because the piston is at TDC anyway the valve wouldn’t be able to drop but so far which makes all these clever ideas unneccessary?
It’s a Honda b18c.
Some advice would be awesome!
Sounds like your keepers are stuck to the retainer. You should not be pushing the valve open as you compress the spring retainer and the keepers pop out.
You definitely need to lock the crankshaft from being able to turn. I use a flywheel lock. What tool are you using the compress the valve spring? -- are you sure the force is going directly parallel to the valve stem?
The rope should try to fill most of the cylinder volume, so it will find its way underneath all the valves at the same time. How much rope. As much as you can get in there. Move the piston down the bore -- jam a bunch of rope in there, then turn it back to close to TDC (doesn't need to be exact as the rope will fill the space between the valve and piston. But you do need to have the crankshaft locked from turning.
Doing the valve springs on an assembled head is nerve wracking, almost worth the trouble to remove the head and do it on the bench. Especially if this is your first time.
See attached. I’ve got a rig like that for the task. It’s purpose made for the job. The instructions said to lightly tap the retainer with a socket first to loosen the keeper. Maybe I tapped it too light?
That aweful groaning noise... you think that caused a new problem? Pretty sure it was air moving past somemething like throttle plate etc... like a reed on a clarinet.
Success! I got one done. The deal was I had to smack it harder with the plastic socket and runner mallot. I also removed the vaccuum cap from the nipple on the intake manifold so if air escaped into there I’d hear it and it wouod go out that way.
Now, thank goodness it isn't a 4-valve Ferrari V12.., then you would have 47 more to go...
The hammer socket tapping is pretty scary too. It’s not really as gentle a tap as I’d like.
True, David, but I don't think he'd be doing them with the heads still on the engine, let alone with the engine in the car :-D
Regarding the rope in the cylinder method, came across this many years ago and was never happy with it because of the almost certaintly that some material would be left in the chamber, so if I had to, I'd use a natural fibre rope so any debris 'should' burn up cleanly, and not melt like a synthetic might. Could be wrong there, but that was my thinking. Hmmm, typing that, the starter cord used for small engines came to mind - it uses a woven outer sleeve that is resistant to abrasion and is thin enough to easily feed through the plug hole, so would probably be my choice if needed.
As for the engine rotating, that is to be expected unless the piston is very close to TDC or BDC. Remember, you're applying, say, 100PSI to the piston crown which for an 86mm bore will mean a force of 100 x 9 (area in square inches) = 900 pounds force. An 86mm stroke means at 90 degree crank angle the radius the force is applied through is 1.7", which means a nominal peak torque of ~127 lb.ft applied to the crank - your engines dimensions will be a little different, but any 2 litre 4 cylinder engine will be the same, with it changing proportionally with the cylinder volume for other engines.
That loud echoing groaning sound it made when, especially when the I opened the valve a little and the air got into the intake manifold... should I be concerned that that might have caused a problem? I figure the sound was air squeezing past small spaces, maybe throttle plate, maybe going back into another chamber through another port etc... Could this have made trouble for the map sensor or maybe IAC bypass? I don't think it would have been the full 100 psi going in there since the valve was only open a small amount.
I would be very surprised if there was any damage.