Bent Camshaft?

[blue_vl_t]

that title makes me laugh just saying it

ok, i'm aiming this at the gurus, i'm not a rocket scientist, but i don't think i'm a f**king idiot either!

here is the story

I'm building an r32 gtr, recently we replaced the stock turbos with gt2860 -5s, wopped it back together and went for a spin

it was a nice drive, thanks for asking.

however, the waterpump spilt and the motor got hot, not cooked but not ideal in the old temp. department

chucked a new waterpump back on and I was just checking everything and noticed the engine was nearly impossible to turn over by hand, we found the inlet camshaft was so hard you had to stick a bit of wood against the camgear and hit it hard with a hammer to turn the camshaft, warped head from getting it hot we figured,

pulled the engine out and stripped it down, took the head off and found its perfectly straight, checked straight down and diagonally.

The exhaust cam always moved freely so is it possible the inlet camshaft is bent??

i fail to see what else could possibly have gone wrong, i'll put the cam in the lathe tomoz and see if its bent

i'm just wondering am i really off the mark here, or if i'm right, what is the go and is has it happened to others etc

what can possibly bend a cam, or cause this

[blue_vl_t]

before i get the question, stock cams

[Duncan]

did you trying turning the cam with the head on the motor, including timing belt, or was the head off the motor?

I have had to tunnel bore the cam tunnels before. When you say the head is straight do you just mean the surface that bolts to the block of have you checked the cam tunnels

[blue_vl_t]

we turned the cam while the head was bolted to the block fully assembled, i was just getting the timing belt in position when i came a cross the problem.

I have only straight edged the bottom face of the head atm, will be checking the cam and tunnel as best i can today

[Duncan]

OK...I trust you are sure the valves were not impacting a piston. depends on where the motor and cam were when assembled of course.

[blue_vl_t]

no, i have built a few motors, defiantly not valve to piston interference.

some results.......

spinning the cam by hand mounted vertical on two points i set up a jig and measured to see if the cam is bent

very back cam journal 0.08mm our of round

close to center journal 0.20mm

and very front journal 0.35mm

while spinning it by hand and looking you can see the journals wavering a little, although its not as bent as i would have though i may take the other cam and do the same for a comparison

[blue_vl_t]

no i look at it, checking the exhaust cam is difficult as it has the CAS gear in the end of the cam.....

[Deano 1]

ive never heard of anyone bending a cam, this is interesting

[Dobz]

no i look at it, checking the exhaust cam is difficult as it has the CAS gear in the end of the cam.....

Just put it on rollers to check it.