rear main questions

[diomed]

My engine was making a noise that sounded like a rod knock. I tore it down, and the babbitt rods looked beautiful. Now I'm on the mains and got a couple questions about the rear main.

1. There was only one thin shim, and the clearances with it were .003. I removed the shims and it's right on .001-.0015. Is it OK to have no shims? This engine probably has 1500 miles on it, so I was hoping there would be more adjustment left. I guess if it needs more adjustment later, it'll need babbitt poured.
2. Is there supposed to be a rubber seal at all in the block or cap? The block looks like the seal is made out of babbitt and the cap has nothing in it. It didn't really leak that bad considering there's really nothing there.

This is the first "A" engine I've ever tore into, just want to make sure everything is cool so I'm not doing it again soon. Thanks!

 

[Patrick L.]

Its too bad there was/is only the one shim. But, its OK to run with no shims. Some have been know to sand the caps when the shims don't work, but, I wouldn't recommend that.
The clearance seems fine to me [ .001-.0015"] as long as the engine still turns freely[ it should]. Make sure the drain tube is there, secure and clear.
If the rear had .003", then, the center just may have more and could well be where the noise was/is coming from.
Usually the fronts are pretty good, but, I'm wondering if your crank was initially set up 'loose'. 1500 miles isn't much and I wouldn't think the bearings should need to be tightened. But, .003" is a bit on the loose side for me.
What are the rods set at ?

 

[diomed]

The rods were all dead on .001, couldn't be better. The quality of the babbitt looked better on the rods than on the caps. I assume the rods and block were done by different shops. I didn't have the engine rebuilt, it was done a couple owners ago, so i can't be 100% sure on the mileage but I know it wasn't much more than 1500.

Thanks for the info Patrick, I appreciate it

 

[Bob C]

I wonder if it was line bored off center, look how thick the babbitt is
on one side and thin on the other. Also shouldn't there be an oil
dam at the parting line??
This picture from J and M Machine is what it should look like.

Bob

 

[diomed]

The center main had one shim per side, and with those shims it was .003 at best.

 

[Brian T]

I wonder if it was line bored off center, look how thick the babbitt is
on one side and thin on the other. Also shouldn't there be an oil
dam at the parting line??

Bob

It sure looks that way, this is what scares me about having engine work done, I have seen some crap work done on the modern engines I have sent out for repair, who to trust ?.

 

[1wonton]

Blue the crankshaft and check the bearings. If it is too tight the crank will knock until a slight film of oil becomes present; too loose it will knock, too tight it will knock.

 

[Patrick L.]

The center main had one shim per side, and with those shims it was .003 at best.

OK, I guess you're in for some more de-shimming. The front may need it too as it appears the crank was set up loose. At least, with only 1500 miles, the cotters should come out almost maybe easy.

I've heard too many engines make funny noises at .003".

Most fellas will remove a shim from one side and have unequal stacks. Nothing wrong with that. I sand the shims and use equal stacks per side which is probably more time and work than needed, but.....


Upon a second look at the pics, it does look like there is a bore issue. But, maybe the engine will still run for quite a while if the crank will still turn freely when tightened up. That may give some time to save up for another engine.

 

[Fred K-OR]

Kris, could your "rod knock" have been a loose adjustable valve? Just a guess on my part because I am not an expert. But your specks you noted seems like your bearings are not to bad.

 

[George Miller]

Good luck but I do not think your troubles are over. It sure looks like it was line bored on a angle. You can also see the the crank was ridding on the rear of the bearing only. You might be having a cam gear that is to loose and that is where the noise is coming from. Did you try shorting out the plugs to find where the noise was. At this point I would put it back together and see what it sounds like.

 

[diomed]

It does look like it was bored at an angle, not exactly what I wanted to find.

All three mains were pretty close to .003. Makes me wonder if it was machined like that. Removing the shim from the mains brought them all down to .001-.0015 and it only took about 20ft-lb to turn the crank over. That was reassuring, at least I didn't make it worse.

I'm just going to put it all back together and see what happens. Cam gear looked good, The valves aren't adjustable, but it didn't sound anything like a valve noise.

Thanks again for the tips and info. It sure is helpful having the Ford Barn to research how to keep these cars together. I don't post a lot, but I sure have read volumes of posts!