Camshaft rotation

[spetz]

If the timing belt is taken out, is it safe to rotate a camshaft a full 360 degrees or will valves hit pistons?

[Slow96GSR]

What do you think? You answered your own question. The reason the belt is there it to time the vales to open and close not only to let the air/fuel mix in and exhaust out at their desired time but to keep the pistons from hitting them. If you want to turn the cams make sure all (ALL) the pistons are down, it would be midway-1/4 turn on the crankshaft from top dead center. That would make it so the valves can open and close safely.

[string]

What do you think? You answered your own question. The reason the belt is there it to time the vales to open and close not only to let the air/fuel mix in and exhaust out at their desired time but to keep the pistons from hitting them. If you want to turn the cams make sure all (ALL) the pistons are down, it would be midway-1/4 turn on the crankshaft from top dead center. That would make it so the valves can open and close safely.
He didn't answer his own question at all. You generated some false information to confuse him with.

There are many toyota engines for example which are "non-interference" engines, which means that the piston will never hit the valves even if the timing belt fails and causes a valve to be open when the piston is at TDC. By your definition, in these engines, the timing belt is there to stop the valves hitting the piston, which is impossible.

To answer your question, your honda engine is of inteference design, and you will hit pistons if you try to turn the camshaft at TDC.

[Slow96GSR]

He didn't answer his own question at all. You generated some false information to confuse him with.

There are many toyota engines for example which are "non-interference" engines, which means that the piston will never hit the valves even if the timing belt fails and causes a valve to be open when the piston is at TDC. By your definition, in these engines, the timing belt is there to stop the valves hitting the piston, which is impossible.

To answer your question, your honda engine is of inteference design, and you will hit pistons if you try to turn the camshaft at TDC.


Except if he does turn the crankshaft 1/4 turn after TDC not the camshaft he will make it safe to turn the camshaft. You misread what I put. I never said turn the camshaft. Also by him having a V6 MIVEC Lancer Coupe I kind guessed it was a noninterference motor. I do kind of have an idea of what I am talking about... I do build racecars for a living!

See by putting the pistons half way down the cylinder there is no way the valves will hit, thus making it safe. He will of course need to leave the timing belt on when he does this. Then once the pistons are at a safe position he can then remove the timing belt and turn the camshaft as much as his heart desires!

[Weq]

this is a honda forum. we assume interference. No its not safe to do so.

[spetz]

I thought they would hit
But after looking at pistons they have the grooves for the valves I thought maybe they wouldn't?

What about, in a DOHC engine, if the pistons are half way down, and only the intake cam would be rotated, is there a chance it will hit the valves on the exhaust side?

[Weq]

if u rotated the engine to TDC like you should have, u will hit. the valve reliefs in the pistons are there to set compression, they dont stop contact. I know this all too well :(

[ECU-MAN]

you have not told us what engine,

some you are interference fit
some are not