A Case For Replacing the Freeze Plugs

[hanleyclifford]

Actually the manifold in the picture has since developed an internal leak and has been sent to A4 Valhalla. The replacement has been similarly modified for 3/4" NPT plugs instead of freeze plugs. This provides convenient locations for temp sensors or future coolant routing modifications. The O2 sensor is tapped for 18mm which I think is industry standard.

[13jeff13]

Manifold

I recently got my Block and Misc parts back from my machinist. I believe I am going to Paint the block with a Clear High temp Paint. Meant for Manifolds.

Hanley,, my machinist advised against tapping the threads for the 3/4 NPT. He said it would need to be tapered and didn't feel there would be enough room to do it properly without running into the back wall before he got enough threads,, and was worried about cracking the exterior wall.

Had some issues with machinist,, he had to do the Cam Bearings 2 times, the first set one of the bearings buckled when pushing it in its hole,, Long story,, second set he got it right,, he paid for the new bearings,, just a hassle.

[67c&ccorv]

Wondering if you had those new cam bearings "line reamed"?

[Carl-T705]

It does look like something is going on with those cam bearings , I thought it may have been the camera magnification.

[13jeff13]

cam bearings

Nope....not a photo problem... A machinest helper problem. He got the bearing started in a little crooked, and it crinkled/ disfigured the bearing. THEN he thought it wouldn't be noticed, after he tried to polish it up.....
The owner bought me new bearings and pressed them in himself. Just a pain.

I do still have the other 2 bearings which appear to be ok if this should happen to anyone else. I ordered the set of 3 and watched him press out the old and in the new. The others look fine if someone could use them. Like i needed just one ....

[67c&ccorv]

Nope....not a photo problem... A machinest helper problem. He got the bearing started in a little crooked, and it crinkled/ disfigured the bearing. THEN he thought it wouldn't be noticed, after he tried to polish it up.....
The owner bought me new bearings and pressed them in himself. Just a pain.

I do still have the other 2 bearings which appear to be ok if this should happen to anyone else. I ordered the set of 3 and watched him press out the old and in the new. The others look fine if someone could use them. Like i needed just one ....

A cam bearing pressed in (or out) with the proper tool will not damage the bearings in any way;

...the cam bearing still needs to be line reamed with the proper reamer which is long enough to bridge to the cam bearing in the opposite side of the engine.

These are the sort of techniques that mean the difference between rebuilding an engine once; or tearing it down shortly after start-up and having to rebuild it twice.

Just ask Moyer Marine...

[13jeff13]

A cam bearing pressed in (or out) with the proper tool will not damage the bearings in any way;

...the cam bearing still needs to be line reamed with the proper reamer which is long enough to bridge to the cam bearing in the opposite side of the engine.

These are the sort of techniques that mean the difference between rebuilding an engine once; or tearing it down shortly after start-up and having to rebuild it twice.

Just ask Moyer Marine...

The second set of bearings went in well. The cam turns freely. Do you have to line bore?

Jeff

[67c&ccorv]

The second set of bearings went in well. The cam turns freely. Do you have to line bore?

Jeff

You don't ever have to do any thing you don't want to do...but if you want the engine rebuild to last (and it appears to me you have been working diligently on the motor)...then line boring (reaming) of the new cam bearings should be done;

"Our new block is fully machined, including line boring of the main journals and cam bearings. It also has new valve guides, new cam bearings, an oil pump bench-tested to insure original performance, and a pencil zinc for additional corrosion protection located directly in front of the water jacket side plate."

[Loki9]

The second set of bearings went in well. The cam turns freely. Do you have to line bore?

Jeff

No, you don't have to. If the cam spins freely, I'm not sure what boring will accomplish.

"It aint a Porsche," is a reply I've often received from Moyer when asking similar questions.

[ILikeRust]

When I disassembled and reassembled my engine, I replaced the main bearings, but not the cam bearings. I detected no play whatsoever in the cam, it spun nice and smoothly, the bearing visually appeared to be in excellent condition, so I figured there was no point in pulling them out and replacing them.

[67c&ccorv]

No, you don't have to. If the cam spins freely, I'm not sure what boring will accomplish.

"It aint a Porsche," is a reply I've often received from Moyer when asking similar questions.

Yes, you have to.



Inserting the cam bearing (with the proper tool and using the proper technique) in an interference fit bore decreases the I/D of the much softer cam bearing. Line reaming ensures that the I/D is the correct diameter for the cam shaft journal and more importantly - that the bore axis of the cam bearing is parallel with it's mate on the other end of the block.

Porsche or not - the A4 still requires a correctly installed and prepared camshaft bearing.

Read Moyer Marines quote from the on-line catalogue that I posted above.

[Loki9]

I agree, newly pressed in bearing are (or can be) too tight and line boring is required to achieve a correct fit.

However, if the cam already turns easily in the new bearings as stated, all line boring can do is make the fit sloppier.

[sastanley]

hey 67, I wonder if the pencil zinc Moyer puts in the block is the same one in the HX they sell?

My old engine ain't got no zincs, that's for sure.

[hanleyclifford]

Hanley,, my machinist advised against tapping the threads for the 3/4 NPT. He said it would need to be tapered and didn't feel there would be enough room to do it properly without running into the back wall before he got enough threads,, and was worried about cracking the exterior wall.

Actually the landings on your plug holes are in good shape and you will have no trouble replacing the freeze plugs. I must admit that the first time I did the tapping thing it was because the landings were so bad they would not seat new plugs. But once I did it and realized how easy and effective the procedeure is I began doing it on all my manifolds. Your machinist is mistaken/a little timid on this point. But if you are going to go to antifreeze cooling and promise not to crud the thing up again (which you will do if you have RWC), you will most likely not have to open the holes up again. But I do enjoy the option of the extra threaded access...

[13jeff13]

I agree, newly pressed in bearing are (or can be) too tight and line boring is required to achieve a correct fit.

However, if the cam already turns easily in the new bearings as stated, all line boring can do is make the fit sloppier.

I do appreciate all the input. I am not extremely happy with the cam bearing having to be pressed in 2 times, because a simple procedure was buggered up by a rookey. However. The second time they were pressed in the cam slid in nice and easy and spun freely. I showed the owner of the shop this site, and the cam bearing warnings,, and he said line boring wouldn't benefit the bearings any,, and could make it sloppier.. Like You Said. So,, for now I am forging ahead as is. He pointed out how soft the material is, and disappointed his apprentice tried to "polish out" and Pass off as Ok, the bad bearings. But, all the other work was done satisfactory, ,and he gave me all the Numbers, for a reasonable price I feel. (see attached)

I did tell him how WE all like pics, ,and Numbers, ,so here they are..