Hi all,

I hope that somebody can help out with this.

Last week we installed a cam in my Camaro. When done we set first piston to TDC and then made sure that the timing marks lined up on the gears and finished install.

Once we got everything put back together, we turned engine by hand and everything moved freely. Got to point of cranking the engine and when turned over we heard noise inside of valve covers. Result was several bent pushrods.

It is our feeling that although we lined the marks up at 12 and 6 that somehow the valve timing is off 180 degrees.

Anybody got any thoughts on this and what are the odds that at least a few valves are #@*'ked.

Thanks for the replies

 

factory timing gear set? dot to dot would be firing on #6, both dots straight up, or at 12:00, would be firing on #1

 

Yeah, we used the factory gear set with a new chain. Does this explain why #1 piston is coming up when the valves are going down. My fear is that the valves hit the pistons which is what caused the bent pushrods. What about the valves, what is damage likely to be on just cranking it over once??

 

This part grabbed me: "the valves are going down."

If both valves are moving downward simultaneously, you got a defective cam.

Yank it and send it back to the manufacturer.

 

Which gear did you position at 6 o'clock?

 

of course both valves don't go down at same time. one on the intake stroke and one on the exhaust stroke. Both are going the opposite of what they should and I am concerned about damage to the valves.

Please respond if you are going to be helpful as I would think that anybody who would strip a car down to the block would know that the valves don't both move at once.

The top gear was placed at 6pm

 

Sorry to hear about that Scot.

My new motor had a stuck valve from the factoy - contacted the piston and bent the valve - doesn't take much - needed a new valve and guide.

 

Thanks George,

Yeah, I think that at least the first couple are toast, all rods weren't bent so I hope it didn't fire all of them as we only turned it over once. What's a few more bucks for some valves. It's the time it takes to get back to there, pull the heads and then re-install that sucks

 

Evidently your post wasn't worded very well.

I would think anybody who would undertake a cam swap would be able to get the car running successfully afterward.

Are you sure it wasn't at 6am?

 

I dont know, I've seen a few motors bend push rods with no valve damage. I wouldnt expect the worst just yet. You need to first figure out why this happened. Any time I've even see this happen was a defective/worn timing chain that came off the cam or crank sprocket. What cam is it and what push rods did you use?

 

I smell incorrect valve adjustment. U need to be sure that the lifters are on the base circle of the cam when you adjust the lifter. Tighten till no more up and down motion is felt in the pushrod then go 1/4 to 1/2 more of a turn for preload.

 

 

And there you go.

And it's clock positions, not daytime hours.

 

Red Devil just pointed out the obvious problem's reason.

now that you've bent pushrods and added stress to the camshaft that it wasnt built for, before you even got it broken in, your chances of wiping a cam-lobe are muuuuch higher than even before, if it hasnt done-so already.

 

The sad/funny part of this post is that positioning the dots the way he did doesn't cause valve-piston contact, it just messes with your distributor installation...you aim the rotor at #1, but #1 is at TDC exhaust stroke not compression stroke.

 

I must have mis-read this as the forum that offers help and technical advice and instead got the smart *** comments forum??

Sorry for my confusion

 

I would post a pic of how the dots are lined up on the timing chain, along with the specs off of the cam card.

How was the valve lash set?

I see three possibilities of what went wrong:

1-Installed timing chain incorrectly

2-Valve lash set incorrectly

3-Cam too big

 

4- used wrong key way on crank gear
5- rocker arms use differant locating method than heads
6- incorrect push rod length

 

Thanks for the feedback from those whose intent was to help.

Just an fyi, it is a 350 roller block and the cam being installed is a zz4 cam with World Products S/R torquer heads. We used stock length pushrods which was 7.19...". Valve lash was set to a 1/4 turn past where the play in the pushrod was removed at TDC on #1.

I am going to check the timing gear positions on the weekend and start there. I don't think that cam is too big as I have seen on here that lots of people have done this swap or swapped to hotcam which is similar.

 

You lashed every valve at TDC on #1?

 

that might explain a few bent push rods

 

It would also explain why it turned over freely by hand but ate itself when it fired.