Cam spin in towers after head work HELP!

[Ben's Z]

Posted this over at hybrid too. Mostly a lot of snarky comments from ****head n chief Tony D.

I had my P90 machine 15 thousandths but the head was warped more than that, so they heated and straightened it. They told me the cam spun fine, which it does to a certain degree. I have read that the cam should spin with 2 fingers about 360 degrees with minimal effort. With mine torqued to 12 ft lbs. it spins about 300 degrees but is tighter then this finger spin everyone talks about and for about 20% of the rotation it is even tighter. It never doesn't spin. I am convinced the shop did not machine the top of the block after all of this. I ran it over to another machine shop questioning my first yesterday and they thought that once the car was warm the aluminum towers would expand more than the cam and all would be well. This just doesn't sit well with me.

I also thought about putting the head on the block with the head gasket and torquing it down to see if that last bit of twist makes it spin better. Thoughts? Here is my post at hybrid.

http://forums.hybridz.org/topic/110330-how-easy-should-a-cam-turn/

[EuroDat]

Hi Ben, Looks like nothing is going to be easy for you with this rebuild:mad:

Your idea trying the head on the blok sounds good. I would do it without the gasket. Not a good idea to retorque a new gasket.

If the head was slightly warped and the shop machined it flat than the problem will not get any better. Only option then is to have the tunnel bored.

A Second problem could be a bent cam. You could get that checked.

Chas

[olzed]

All I see on HybridZ is guys offering help.

Are you sure you are not seeing a problem where there is none?

With an engine running, there is so much oil at the towers, it is doubtful a sieze could occur.

[madkaw]

Yes Tony can be grating on the nerve, but you have to read between the lines sometimes. You have started many threads on this build with seemingly nothing but problems. Some might think that your project has not been well thought out(searched) and you seem to be in a panic in all your postings. Take a step back and reevaluate things.

As far as the cam, retorque the cam while striking the cam towers(deadblow or runner mallet) to assure they are seating properly. Torque in steps and check the cam every round. If it starts to bind, try a different order of torqueing. It should spin easy, but it will get in a bind sometimes. From there, you might bolt it to the block and try also.

[Ben's Z]

Here is my update from hybridz

Well I tried a few things this morning.

1) I took my NA cam out of my P90 and put it back in my NA head which is still on the block to get an idea of how free the cam should spin. Knowing that I took it back out.

2) I installed my P90 head with the head gasket with the theory that perhaps with the head torqued the cam might spin easier. Sort of a reverse torque plate theory when machine shops bore cylinders. I put the cam towers on loose and put the cam in. I did the torque sequence checking the cam for spin after each sequence. I torqued it to 20 ft lbs first go around and then tightened the cam towers to 14 ft lbs. The cam was even tighter than my bench top spin. Went once more around to 40 ft lbs., no change. Still too tight, I stopped there.

My question is this. When Nissan align bored the cam towers at the factory did they torque the head to spec first?

I believe they did straighten the head but if they didn't resurface the top the I am pissing in to a 100mph head wind and torquing the head made it worse.

I am going to take it to a shop and have them plane the top. Is there anyway they should simulate the head being torqued to the block when they do this?

[Ben's Z]

I get it. So because the machine shop first rebuilt the spare parts NA head, I didn't think that out. When the machine shop put in NA exhaust valves when I went to go set the lash, I didn't think that out. Because the machine shop didn't mill the top of the head as well I didn't think that out. Because one ***** from hybridz sold me a 10 pound paper weight cam with a f*cked up dowel, I didn't think that out. I have done all the **** you said about 50 times. It is not spinning like it did in my old head.

Yes Tony can be grating on the nerve, but you have to read between the lines sometimes. You have started many threads on this build with seemingly nothing but problems. Some might think that your project has not been well thought out(searched) and you seem to be in a panic in all your postings. Take a step back and reevaluate things.

As far as the cam, retorque the cam while striking the cam towers(deadblow or runner mallet) to assure they are seating properly. Torque in steps and check the cam every round. If it starts to bind, try a different order of torqueing. It should spin easy, but it will get in a bind sometimes. From there, you might bolt it to the block and try also.

[black gold man]

This is how it read to me

"I get it. So because the machine shop first rebuilt the spare parts NA head, I didn't think that out."

Stomp feet on ground

"When the machine shop put in NA exhaust valves when I went to go set the lash, I didn't think that out."

Stomp feet on ground

"Because the machine shop didn't mill the top of the head as well I didn't think that out."

stomp feet on ground

"Because one ***** from hybridz sold me a 10 pound paper weight cam with a f*cked up dowel, I didn't think that out."

stomp feet on the ground

I have done all the **** you said about 50 times. It is not spinning like it did in my old head.

[Ben's Z]

This is how it read to me

"I get it. So because the machine shop first rebuilt the spare parts NA head, I didn't think that out."

Stomp feet on ground

"When the machine shop put in NA exhaust valves when I went to go set the lash, I didn't think that out."

Stomp feet on ground

"Because the machine shop didn't mill the top of the head as well I didn't think that out."

stomp feet on ground

"Because one ***** from hybridz sold me a 10 pound paper weight cam with a f*cked up dowel, I didn't think that out."

stomp feet on the ground

I have done all the **** you said about 50 times. It is not spinning like it did in my old head.

Keep you day job d0uche bag.

[Ben's Z]

Did a little more looking. I took all my cam towers off and used my potentially not perfectly straight Stanley 18" level and found that a .010 feeler gauge has a little drag under where the center cam tower would bolt down. I put in 1,2,4,5 cam towers and torqued to spec, and it really didn't seem to make a difference. Odd.

From hybrid z.

[djwarner]

Ben, I feel your frustration. I'm not an engine mechanic, but I know my way around a machine shop. Perhaps I can give you some places to look.

You are assuming the binding began when the head warped and wasn't corrected when the machine shop tried to warp is back to flat. You are looking for a tower that is not aligned with the others when they are not torqued down and you are using the cam shaft as a go-nogo gauge.

To do anything other than hunt and peck, you are going to need a weightless indicator or at least a drop indicator mounted on a magnetic base. The first objective would be to qualify your go-nogo gauge (cam shaft) by verifying it was not bent. To do this, mount the numbers 1 and 5 towers properly torqued and then mount the cam shaft. Place the indicator to ride on the bearing surfaces for towers 2, 3, and 4. With the indicator riding on each bearing, slowly rotate the camshaft and note the runout (highest reading minus the lowest reading). If the cam shaft is straight and true, the runout should be minimal and simlar from bearing surface to bearing surface. If the runout get progressively larger towards one end, the cam shaft might be bent towards that end. To verify, remove the offending out board tower and mount the next tower inboard and again observe the runout.

Assuming your cam shaft is straight and true and assuming the rotation is smooth using only towers 1 and 5, add tower 2, 3, or 4 one at a time to find which tower causes the binding. (From your last post, I doubt it is number 3 since you removed it and there was no change.) Don't stop when you find the first binding tower because it may be ok and an end tower is out of kilter. Once you have identified the culprit, mount all the other towers and verify the cam is happy.

With the other towers inplace, again measure the runout on the problem bearing surface. Note the location of the high spot and mark near it with a magic marker in a place you can see with the last tower installed. Re-install the last tower and find the point of rotation where the binding is the worst. Locate the mark for the high spot and this is where the contact is being made. (Remember the tower may be too high, too low, leaning left or right, or twisted.)

If these steps haven't isolated your problem, you may have one tower marginally shifted one way and the adjacent tower marginally shifted the other.

[Oiluj]

I understand your frustration. I had my share of warped head issues when rebuilding the engine on my 1st Z many years ago. After spending a bunch of money trying to fix it, I ended-up having to find a replacement head in a junkyard.

As an engineer, djwarner's post (above) sounds like a reasonable approach to diagnosing the problem.

[EuroDat]

Ben, If you follow djwarner's instruction and find the source being one or more caps binding you have only one option imo.

Have the cam tunnel bored and the head gasket surface shaved (just to make sure any warp is gone). Take as little as needed off. This way you with take any distortion out that can cause the binding. Six cylinder engines have a slight disadvantage of having such a long cam compared to 4 and v8 engines.

The machine shop doesn't accually bore it larger. They shave the caps to close the tunnel enough to take the runout and then bore it to spec.

The other thing I would check, while your at it, is the block deck. If the deck is out of true, its only going to warp the head when you retorque it and then your back to square one, sts.

Chas