Camshaft Install, Some Tips For AMC V-8 Engines -
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post #1 of 8 Old 11-03-2013, 09:18 AM Thread Starter
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Camshaft Install, Some Tips For AMC V-8 Engines

Just had a discussion about camshafts on another forum, and though some of you might need a quick refresher on AMC Camshafts/Installs.

For those of you that aren't TOTAL camshaft geeks...

Stop me if you have heard this one... "A camshaft walks into a bar..."
So you have heard it!


1. "Anti-Walk Button", "Thrust Button", Ect.
I know most of you have heard of these things. Something you put inside the aluminum timing chain cover to keep the camshaft from 'Walking' forward...

I've raced AMCs since the '70s, I've owned AMC engines in Jeeps since the early 70s and I've NEVER needed 'Thrust' control*
(Other than a full on roller camshaft that turned 7,500 RPM regularly)

Flat Hydraulic Tappet, Factory style camshafts DO NOT need this.
I've seen 200,000 mile factory engines popped open with nothing more than a slight 'Rub' on the front cover, and most won't even have that...

2. Camshaft lobes are ground Slightly Higher in the back than they are in the front of the engine.
The purpose of this is to rotate the camshaft LIFTER so the camshaft doesn't wear a hole in the lifter by rubbing on the same spot all the time.

As the camshaft rotates, the high side pushes BACKWARDS on the bore plug in the back of the block.

In the VERY EARLY days of camshaft development, the lobes were flat, and they walked a little.
When flat tappet lifters came along, they needed to be rotated, and some camshafts had the 'High Side' in the front, that walked the cam out.
Once this was discovered, the makers put the 'High Side' in the back, problem solved.

Camshaft lobes on modern ROLLER LIFTERS need to be retained, but your AMCs do not need a 'Thrust Button' for any reason I know of...

In the back of the camshaft bore in the block, there will be a 'Plug'. Some people call it a 'Freeze Plug', but it's a Bore Plug.

Most people drive these plug in all at one time... Bad idea.
The camshaft bore plug is what locates the camshaft under the lifters.

If you are keeping track, the camshaft moves BACKWARDS, so that plug driven in too shallow lets your lifters ride on back edge of the camshaft lobe, and you will see an almost immediate loss of valve lift because that back edge of the camshaft won't last long.

If you drive it in too deep, the edge of the lifter will gouge the camshaft lobe face...

That rear bore plug should be the LAST THING you install before you button up the engine. MAKE SURE your lifters are hitting the camshaft lobes SQUARELY, and the timing chain isn't misaligned. Both will cause SERIOUS problems over time if you don't.

Every bit of the oil the pump moves runs up to the front camshaft bearing.
There is a manifold cast into the block right behind that bearing, and this is where the oil volume turns for the lifter galleries, moves back to main bearings, ect.

If that front bearing isn't installed correctly, you WILL have issues!
You will notice a groove in the front bearing boss on the camshaft, or at least an oil hole that MUST align with a groove in the bearing...
If that oil hole doesn't align with the groove in the bearing, your front camshaft drive accessories WILL NOT get sufficient oiling.

Now, back to that oil gallery manifold cast into the inside of the block just behind the front camshaft bearing...
And the WEIGHT/VIBRATION of the camshaft & drive accessories...

Every bit of your oil volume is right behind that front camshaft bearing, and the camshaft bearing has a 1/4" to 3/8" hole in it...
If that front bearing wears out and becomes over sized, it will dump an amazing amount of your oil volume, and virtually all your oil pressure down the front of the block...

This starves your camshaft, lifters, main bearings, ect.

Now, there is a lot of weight hanging off the front of that camshaft,
Distributor drive gear, fuel pump eccentric, timing sprocket and timing chain, ect.

Remember, since all that crap is turning, there is a 'Hammer Drill' effect going on, the front of that camshaft is hammering on that soft bearing, further beating the crap out of it...

This makes some pretty large clearances fairly quickly for the oil volume to escape down the front of the block and NOT REACH YOUR LIFTERS/BEARINGS.

Consider replacing that front bearing when you have the timing cover off the engine... That front bearing can be replaced without tearing down the engine, so consider it...

Everyone I know overlooks these. Push rods that have a 'Worble' in the ball ends should be replaced. If the ball end isn't HEMISPHERICAL without a 'Warble' or 'Ridge' in it, then you can probably reuse it without issues.

Look into the 'Ball Socket' end of the rocker arm. If the shiny wear mark reaches the oiling hole in the rocker, it's JUNK. This means part (or all) of your oil supply is being cut off when the rocker moves.

Look at the valve end of the rocker. There will be a wear groove where the valve stem tip hits the rocker. If you can catch your fingernail on the groove edges, the rocker is junk.

Also, if the wear groove is way off center of the rocker, it's junk. That means the rocker was stamped 'Off Center', or lopsided, and it's pushing SIDEWAYS on the valve stem, wearing out your valve guides...

Now look at the pivot in the middle, and the pivot 'Ball' or 'Shoe'.
There should be oil grooves (dark color) in the shiny wear pattern. If you don't have oiling grooves anymore, They are junk.

Remember! These all work TOGETHER! They have VERY specific wear patterns and SHOULD NOT BE MIS-MATCHED!

When you take these off, KEEP THEM IN ORDER so they get back to where they were!

Doesn't matter if you 'Pour Oil' over this stuff after you assemble, but you MUST lubricate these parts on final assembly! Starting up a 'Dry' valve train will prematurely wear, or outright destroy parts in a matter of a minute or two!
I prefer to use a 'Molly' assembly grease on everything, so I KNOW it's staying in place until this engine gets oil!
Cheap, reliable and saves you from yourself!

Hundreds of times I've seen camshafts installed INCORRECTLY, and it's just not necessary! This couldn't be more simple...


*IF*... The crank moves while the timing set is off, and 'Stuff' happens...
Just take the #1 Cylinder Spark Plug Out, Turn the crank until #1 Piston is at TOP DEAD CENTER, and you are aligned again.

Without the timing set on the engine, the crank doesn't care what the camshaft is doing, you simply locate TDC Of #1 Piston, and start from there, Align the timing marks on the timing set per instructions, and go from there.

There is no 'Intake TDC' or 'Exhaust TDC' until the camshaft is connected to the crank. TDC is simply TDC.

Same rules apply for any engine that broke or slipped the timing chain.
If chain is broken, no issue, no connection between crank & cam.
If the timing chain slipped or jumped tooth or teeth, simply take the timing set off and turn crank to TDC of #1 and start over installing new timing set.

10. As the cam lobes on the camshaft wear with time, the 'High Side' will wear off and the camshaft lobes will become 'Domed' in the middle of the high spot on the lobes. You may not be able to see it with the naked eye, but your lifter faces will be 'Concave' (depressed in the center).
This is a pretty good indicator it's time for a new camshaft/lifters.

If you see 'Chatter Marks' or 'Lines' in the lifter face, this is a pretty good indicator you have oiling/lubrication issues at the lifters.

If you see 'Chips' out of the edges of the lifter, this indicates your valve springs have given up.
Lifters rely on valve spring pressure to keep them in contact with the camshaft. When the spring pressure drops, the camshaft is able to move out from under the lifter, and the lifter slams into the camshaft, digging in and chipping off pieces of the lifter.
Lack of oiling can cause this also, but you will see extensive wear on the lifter face along with the chipping, and you will see excessive wear on the camshaft lobe wear faces.

Your lifters pump oil from the block, up to the rockers via the push rods.
If your lifters have been starved for oil, so have the rocker arms!
If you find a lack of oiling condition, VERY CAREFULLY check the rest of the valve train parts, everything from bores for lifters, push rods, rocker arms, valve stem tips, and even valve guides. These all rely on oil from the block/lifters...

No such thing as 'Too Much' lubrication! Most camshafts come with a high quality 'Moly' lube... USE IT! Use it on EVERYTHING, but especially the camshaft lobes and lifter faces!

A good 'Assembly' Moly based lube is good when you run out of 'Camshaft' lube that came with the cam set...
This camshaft/valve train is expected to run over 100,000 miles without complaint, so give it every chance to break in correctly, and make every effort to make sure it gets lubricated while it's operating!

'Blue' on old camshaft bearings is a pretty good indicator that camshaft wasn't getting sufficient lubrication, so what makes you think the new camshaft will 'Magically' get sufficient lubrication?

Galling or 'Blue' marks on camshaft lobes, lifters or lifter bores will indicate poor lubrication. You might want to run those oil galleries with cleaning brushes, or in really bad cases, with a gallery drill.
Oil galleries are usually accessible from both front and rear (Threaded Plugs) and you really should knock the crud out of them, use air or liquid to verify clean and sufficient volume in the passages.

Use air pressure on camshaft bearing galleries after bearings are installed. This will VERIFY you got the bearing in correctly and didn't block some, or all of the oil passage...

VERIFY EVERYTHING! It takes a little time, but the time you take is very small compared to the time you are expecting this engine to haul your butt around!

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post #2 of 8 Old 07-11-2014, 10:24 PM
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JeepHammer, after reading this very resourceful post I have no doubts that you're the one that can give me the answer I'm looking for. I'm in the middle of my camshaft swap and have run into (what I believe) is an issue with the rear cam bore plug. The block I'm working with only has about 4,000 miles on it since last rebuild, but the previous owner let it sit for a couple years and I'm going back through it. While removing the previous cam with a gear puller (no hammer), I think I may have pushed the cam bore plug back a bit (ab 1/8"), but I'm not sure if that's possible.

The reason I'm concerned is bc after placing the new cam in, I'm able to push the cam about 1/8" in from the block face. Looked through the lifters holes and when the cam is pushed all the way back, the lifters aren't centered. So my question: is there supposed to be a gap between the cam and the bore plug? Or does it sit flush with the plug and/or the block face? I'm having the transmission cleaned up next week so I'll be able to see the plug from the back side, but until then I was wondering what your thoughts were on this. Here's a few photos to better picture what I'm talking about.

Attached Thumbnails
cam 1.jpg   cam 2.jpg  
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post #3 of 8 Old 07-12-2014, 06:02 AM
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I'm surprised this thread went unnoticed.

I'm curious what controls the AMC cam's movement backwards. I have a real hard time believing it's supposed to ride against the rear plug but I don't know AMC's. Is there some sort of thrust surface on the back of the cam sprocket like a Chevy, thrust bearing,... etc.?

Oldskool, the lobes will be offset in the bores but I'm not sure how much. That also helps with lifter rotation.


Edit: I'd snug the cam sprocket up and see where the lobe is. Then install the front cover, run a dial indicator through the back of the block and check the end play by gently moving the cam back and forth through one of the lifter bores.

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post #4 of 8 Old 07-12-2014, 12:38 PM
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Shawn, I don't believe they came stock with a thrust bearing (mine didn't). I've seen a video of someone mod one in, but it's a little too much machine work for my abilities.

Apparently the lobes on the flat tappet cams are ground slightly higher in the rear to help with rotation. JeepHammer mentions that there's some backward "walking" of the cam, but that the lobes should be lined up squarely.

After I drop the tranny, I'll check the plug and the end play and get back, thanks for the suggestion!
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post #5 of 8 Old 07-12-2014, 05:09 PM
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shawn is correct,the camshafts rearward movement is stopped by the rear of the timing gear against the engine block.also it is the resistance of the oil pump through the distributor drive gear that forces the camshaft to the rear.The cam bore plug should never come in contact with the camshaft.the only purpose of the bore plug is to seal the bore.there should be an 1/8 on an inch of space between the rear of the cam and the bore plug so that the oil that comes out of the cam bearing is able to return to the oil pan through the hole drilled through the rear of the camshaft or through the block itself.
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post #6 of 8 Old 07-12-2014, 05:25 PM
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Exactly what I needed to hear, now I can get back to completing the install, thanks guys!
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post #7 of 8 Old 07-12-2014, 05:51 PM
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I have just completed my 401 build. i installed a roller cam and had issues. this could possibly be a issue with any cam and the cam was custom made by a Crower. during my pre-assembly i noticed #4 i think it was. the lifter would not go completely back into the lifter bore. turns out the lifter was sitting on one on the edge of a journals.

So i took the cam out and measured the positions of all the journal and lobes. turned out the machine work was not correct and the lobes were in the wrong places. just like your #2 picture.
Crower cam to the party and reground me a new one. which worked out find

Point being your new cam might be a dud.


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post #8 of 8 Old 08-13-2014, 07:44 AM
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This was exactly the question I had when I slid in my new cam last night and it too went into the block about a 1/8 of an inch and I scratched my head. Great to know that this is normal and the timing chain will determine the correct depth for the cam (if I understand that correctly).

I have one addition question / clarification since it has been so long since I've taken my 360 apart. Is there anything that goes between on the cam before the cam gear (that would sit between the cam gear and the block) or not. I don't remember there being anything and from this diagram it doesn't look so but it looks like if the cam moves slightly into the block the cam gear will contact the block.

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