Looking for engine help ideas...

[cngodfather]

Cool, thanks!
When I start to find my cam button gap, would it be correct to mount the sprocket to the cam first.
Second, slide the cam sprocket towards the block until it contacts the block.
third, take all my measurements with the sprocket against the block?

 

[Schurkey]

Yup.

Make sure the measurement between cam button and timing cover isn't corrupted by flex in the timing cover, or by gasket crush.

A thousand years ago, when I installed a cam button in a SBC 400, I built a reinforcement from the rear of the water pump to the outside of the sheetmetal timing cover, so that cam thrust wouldn't bend the thin steel timing cover. Cast timing covers are rigid enough. Some stamped-steel timing covers have had metal supports welded-in to strengthen them. Whatever works in your situation.

Because the timing cover gasket also acts as a spacer for the timing cover, all your measurements have to include the COMPRESSED thickness of the timing cover gasket.

All of this is a time-consuming procedure compared to the OEM thrust plate, I'm sure you'll agree.

 

[cngodfather]

Yes I agree! I am weird though. I like the challenge of modifying things and make them work. I purchased a cast aluminum timing cover for the reason that you stated. The compressed gasket thickness is something I will have to figure out.

 

[Schurkey]

Easiest way is to set up a dial indicator on the REAR of the camshaft, after removing the cup plug that closes the cam tunnel at the back.

Install the cam sprocket, cam chain, cam button, retainer, etc. Bolt up your timing cover, use all the bolts and torque as required.

Reach through the lifter valley to push the cam forward and back. The dial indicator should show the cam button clearance. Generally, there's too little, and you'd (remove the timing cover for access, and) progressively shave/file/grind the tip of the cam button to get it where you want. A few thousandths is fine. As I said, the OEM system results in about .002--.003 clearance. I bet anything up to .005, maybe .007 is acceptable, but then I've only installed one cam button and that was twenty years ago. Maybe more.

I think that if this were me, I'd degree the cam first. Then set the clearance for the thrust button. At whatever point I felt that the clearance was right, the timing chain, the cam bolts, the button, the timing cover are all torqued into place; all I have to do is pop in a cam-tunnel plug at the rear, and go on assembling the engine.

 

[cngodfather]

The machine shop already had the plug in the back when they were done. I am going to have to come up with a different way. I think I will try to copy a device I saw that was horseshoe shaped metal with a dial indicator. Measure the cover, measure the block, contact felpro for their compressed thickness, and do the math.
That is the first plan. .002 is pretty tight. I am going to keep thinking on this one. Things happen slow at my house. I get up at 4 to get ready to take my son to practice. Then go to work. Then come home,make dinner. then around 6 I can play with the engine. Bedtime is around 8. I just mention in case someone is wondering why this is going to take weeks/months. By the way, thanks Schurkey, you are a lifesaver.

 

[Schurkey]

It's gonna be faster and more accurate to rip out the existing plug, take your measurements, and then pound a new plug back in.

Plug kits are under fifteen bucks. If you get lucky, you'd maybe find someone to sell you just the cam tunnel plug--perhaps $3.

 

[cngodfather]

After some cautious thought, I set aside the timing chain that I was going to use and bought a lunati double roller with the torrington bearing. I did not like the idea the back of the cam sprocket rubbing against the block.

 

[evilunclegrimace]

After some cautious thought, I set aside the timing chain that I was going to use and bought a lunati double roller with the torrington bearing. I did not like the idea the back of the cam sprocket rubbing against the block.

After you have done a few of the you will worry less about it, there are millions of engines that are operating this way and have for decades

 

[cngodfather]

I do not disagree with you. This is my first roller conversion. -- I have an engineering background. This helps in ways, and also hurts. The timing sprocket block location is machined. It is not machined enough to give a slip mechanical joint to let the oil have enough hydrodynamic lubrication. The thought did arise that after some wear that it will smooth out to make it work. For this to happen, metal will have to wear down the face. The extra metal would enter the oil. I did not like any idea of metal in the oil. Am I overthinking it? Maybe and probably. Would have it been fine? Maybe and probably. I have never done this before. With any bit of doubt, I can say I did the best to what I think is right. I still do not regret this decision. Moving forward.... gotta degree my cam.

 

[Schurkey]

When/if all those tiny roller bearings on the cam gear end up in the oil pan (it happens! Hell, it happened BEFORE all the bearing manufacturing went to Communist China.) don't say you weren't warned. And if one of them makes it's way past the oil pump inlet screen, you've just seized the oil pump, which may destroy a lot of other stuff.

I've got NO use for roller-bearing cam gears. A bronze thrust washer is as far as I'd go, and I'd be using aftermarket trickery to cram in an OEM thrust-plate and step-nose cam long before I put in a bronze washer.

My favorite machinist repairs the thrust damage on the front of the block by carving iron out of the block face around the front cam bearing, then driving in a hardened-steel valve seat insert of the appropriate size. The hardened valve seat insert is then a "lifetime repair"; if you can hurt that, you're really working at it.

Again, you needed to put a cam bumper ahead of the camshaft, to tighten-up the clearance between cam gear and timing cover, because the only rearward thrust on the roller- camshaft is from oil pump drag, and the camshaft is pretty-much just "floating" in the bearings. It was as likely to float forward as rearward; there's so little rearward thrust on a roller cam that you've got essentially no load on the cam gear-to-block thrust faces.

There'd be more rearward thrust load when using a flat-tappet cam due to lifter crown and lobe taper; and there'd be more load if the thrust bumper on the roller cam doesn't have a few thousandths clearance to the timing cover--the thrust button could preload the block/timing gear interface.