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Old 06-24-2012, 08:04 PM
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Rzeppa Rzeppa is offline
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Default Cam Keyed Upside Down?

I was pre-adjusting my valves this afternoon. The manual said 1,2,3,5,7,9 at TDC for the #1 firing stroke, and the others at 360 on the crank. Duh, done this many times. Usually with the engine in the rig so you can see the mark on the flywheel. I've done it before with the engine on a stand too, never had any issues.

But I am beginning to wonder if my cam is keyed upside down, because 7 and 9 are open when it is supposed to be at TDC on the #1 firing stroke. I think.

Following are photos, please follow along and tell me if I'm losing my mind or what?

First picture is the SST I made for turning the crank assembly more easily. I took a chunk of pipe I had laying in a corner, drilled some holes for some bolts and voila!
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Old 06-24-2012, 08:06 PM
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Next, is a shot I took when I was tightening down the cam thrust plate. Them (thank you high res cameras!) a close up showing where I lined up the marks in the teeth of the timing gears.
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Old 06-24-2012, 08:13 PM
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Finally, we have a shot of 7 and 9 open at TDC for the #1 firing stroke, followed by a shot showing 4 and 6 open.

This is an aftermarket cam that came with the kit I got from MHP. I plan to call them tomorrow, but I was wondering if I was losing my mind, or if it looks like they milled the keyway 180 off.

If they did, I am thinking I will need to pull the cam and rotate it 180 so the tooth with the mark on the gear is 180 off from lining up with the mark on the crank gear?

Obviously this would be a major PITA, will have to pull the rockers, pushrods, lifter, crank pulley, timing gear cover, etc. Or just assume that it is off 180 for the purposes of ignition timing and call it a known issue?
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Old 06-25-2012, 07:40 AM
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So Jeff, I do not know if I fully follow this. But the way I am understanding this is that only 7&9 are off, not every thing. If only 7&9 are off, then the whole cam is screwed up. But if as I am reading, you think the cam is cut wrong for the key way.
Anyhow one quick check if you have the old cam around. visually locate the key way the same and see if the lobes are visually aligning. Another way to write this, With the cam still in the block, align the key way in such a manor to get the key way straight up(lets say). Then hold the old cam along side the block with the key way in the same clock position(if the cam in block is a 12, the the cam on side is at 12).
Then check and see if cam lobe are up in the same positions along the length of the cam. If not, some thing is a miss and the cam could be cut not only 180 out, but all screwed up.
Sorry to hear about the screw up, Robbie
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Old 06-25-2012, 09:31 AM
SteveH SteveH is offline
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Do you have an OEM cam that you can lay on the head (next to the rockers) and visually scope out the valves that should be open and closed at any given cam position? This might give you a sanity check. Wish I had a better knowledge of this...
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Old 06-25-2012, 10:45 AM
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great advice above...

Also, I have confused myself before when I built a motor and the adjustment screws for the rockers were all too tight. I backed them off to make sure they were loose, but when the motor went together some of them were still touching. This made it confusing where TDC was for #1 and made it confusing that some others seemed like they weren't closing.

Do you have them all backed way way off? Take them all all the way back and see if you can start from scratch again. If you are unsure of where TDC is, leave all the valves backed way way off and just try to adjust the #1 cylinder. Turn the motor over SLOWY and make sure it behaves like you think it should. IF it does find TDC and do the rest. If it doesn't go one more turn around and adjust again.
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Old 06-25-2012, 01:40 PM
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I am 100% sure where TDC is. Both of them - before I put the head on, I rotated the crank so the crank keyway was straight up, #1 and #6 were both at the top of their stroke, and when I pressed on the crank timing gear, it happened that the mark was directly toward the cam gear, so that made me feel pretty darn sure it was oriented for TDC on #1 firing stroke.

Then I put the cam thrust plate on the cam, and pressed the cam timing gear onto the cam. When I installed the cam, I simply made sure that the mark on the cam gear was lining up exactly with the mark on the crank gear, as per the photo above. The fact that the mark on the crank gear happened to be closest to the cam gear reassured me that everything was lined up properly.

When I put the lifters in, 7 and 9 were up and the rest were down, so I'm not going by the rockers, I'm going by the lifters.

In fact the object of this exercise was to adjust the clearances on all the valves.

I have thought this through and if the cam key way is 180 off, all I need to do is simply have that knowledge when I go to stab the distributor.

Robbie, I did go through a full 720 rotation and verified that all 12 valves open at some point in that cycle.

And I not only have the old cam but I have several lying around. That is a great idea, to simply verify that each of the 12 valves opens at the proper point in the 720 compared to the old cam. While I'm at it, I could record the point at which #1 exhaust is open to verify the opposite is where it fires.

Again, this is mainly to know the proper orientation for the distributor. I want to make sure this thing fires right up when I start it for the first time and I don't have to crank it excessively and wear out the assembly lube before it builds oil pressure.
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Old 06-25-2012, 03:05 PM
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I have a cam sitting in the garage.. you want me to take a pic down the top?
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Old 06-25-2012, 10:06 PM
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Quote:
Originally Posted by Rzeppa View Post
I want to make sure this thing fires right up when I start it for the first time and I don't have to crank it excessively and wear out the assembly lube before it builds oil pressure.
you can always take a steel rod and grind it so it has a flat, chuck it up in the drill, then stick it in the oil pump without the distributor in place. Spin it up till it bleeds oil from the rocker shaft.

If that's a possible technique (don't remember on the F series motors) I usually do it.
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Old 06-26-2012, 10:40 AM
SteveH SteveH is offline
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you can always take a steel rod and grind it so it has a flat, chuck it up in the drill, then stick it in the oil pump without the distributor in place. Spin it up till it bleeds oil from the rocker shaft.

I have done this - I found that you need a corded, 1/2" drill (powerful) that will run in reverse, to run the FJ oil pump. It requires a lot of power to run it. I think I cut off a screwdriver head to use as the pump drive, since it's a slot-type pump (like a Chevy). It does a dandy job of prelubing the engine.
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