priming a dohc?!

[dohcfiend]

i have always wondered what every1 does to prime the engine besides fill up the filter be4 putting it on?

do you prime it be4 installing the heads and put some assembly lube on the lifters/springs/cams etc??

[series8217]

lots of assembly lube on everything, then spin the motor over with the spark plugs removed until it builds oil pressure, right before you start it.

[series8217]

oh yeah... do NOT prefill the filter. if the pump is not primed it will not be able to pump oil with the filter full of oil instead of air. i've encounted this problem myself.

[OldSkoolGP]

What I've done the last two times I built my motor is put everything on except the int. shaft belt sprocket and the timing belt. That way the cam will still spin free and turn the oil pump WITHOUT turning the motor. then fill it up with oil, put a bolt in the cam, get your favorite drill and go nuts. WARNING: Your drill must have some serious cojones or it will burn up, it's a lot of resistance.

[dohcfiend]

sounds good, so doing it that way will the timing chain sprocket on dummy cam just freewheel then when you turn the int. shaft?

i always thought you filled up the filter be4 priming?

what about using an impact gun for turning the int shaft, that would have enough ballz right?

[OldSkoolGP]

The timing chain can't turn because it is keyed to lock into timing belt sprocket. Only when the two are bolted together would the entire rotating assembly turn. What turns the cam when the engine is running is the force of the two being pressed against the front journal of the shaft. I would not use an impact gun because there's on telling what the pulsing would do to the bearings or the pump. Those parts are desinged to operate with continuous fluid motion, not rapid jerky motion.

[dohcfiend]

gotcha
do you fill up the oil filter or do you leave it empty like series8217?

[OldSkoolGP]

Leave it empty. You're going to pump it full when you spin the cam anyway. That's the first place the oil goes.