1930 Hudson 8, engine connecting rod caps, how tight?

[timecapsule]

I'm in the process of seeing if I can get my 1930 straight eight running again.  But I don't know anything about the history of the engine other than some receipts saying it was rebuilt.  But I think it was only partially rebuilt.  

Anyways while I had the oil pans off, I noticed something unusual with the connecting rods.  Some of the cotter pins had come out and were in the top oil pan. I also noticed that the reason was because the hole in the bolt, was past the end of the castle nut.  So I decided to put washers under the nuts to build them out so that the turrets of the castle nuts would be on either side of the cotter pin hole. 

But here's my question.  How tight should the connecting rod cap be?  There are 3 shim sizes.  I suspect that since Castle nuts are used, that the torque setting isn't critical.  I'm thinking just tighten the nut as tight as I  can get it without farting, and then tighten to the next opening so the cotter pin will slide through.

But once that was done, I noticed that some of the rods were looser ( side to side) than others.  Some were quite loose, some sort of loose and 2 had no side to side movement at all. I have lots of spare shims in all 3 thicknesses.  No mention of it in the manual so is there a rule of thumb used here? 

Edited December 28, 2023 by timecapsule (see edit history)

[JFranklin]

Safe at 35# usually for most connecting rod nuts.

[mikewest]

My 31 -8 had hard SAE flat washers under every nut.  Im thinking you shoulkd get some  from McMaster Carr or  other supply house.  Make sure you get SAE  hard washer.  And yes 35LBS like  Mr Franklin suggested. 

Edited December 29, 2023 by mikewest (see edit history)

[timecapsule]

Perhaps, I'm not being clear on what I'm asking. 

Like I said, the torque setting really isn't the issue.  It's a matter of how many shims I should be using.  Obviously I won't get any up and down play on the connecting rod.  So the only other way of determining if I had the appropriate space between the crankshaft and the connecting rod/cup, would be how easily it slides back and forth. 

For instance the picture of the shims that I included, one bolt had a stack of shims measuring a total of 1/8"  the other stack measured 13/128" That seemed odd to me that they wouldn't be the same.  But perhaps, whoever built the engine the last time, ran out of appropriate shims to make it even, and felt the difference was appropriate.  Visually they all seem to be around 1/8". 

But if there shouldn't be any side to side movement then I'll go over all of them except the tight one and reduce the shims.  Or if there should be some side to side movement, I'll add some to the one that won't slide from side to side.

 

To accentuate my point, I could stack 1/4" of shims and torque the nuts to 35 ft. lbs, but obviously I would have tons of clearance. 

 

[timecapsule]

48 minutes ago, mikewest said:

My 31 -8 had hard SAE flat washers under every nut.  Im thinking you shoulkd get some  from McMaster Carr or  other supply house.  Make sure you get SAE  hard washer.  And yes 35LBS like  Mr Franklin suggested. 

I'm curious why you suggest "hard washers"? 

[JFranklin]

Use some plastigauge and set the clearance to 1.5-2 thousandths. Add or subtract shims as needed. keep the caps parallel to the rods.

[timecapsule]

3 minutes ago, JFranklin said:

Use some plastigauge and set the clearance to 1.5-2 thousandths. Add or subtract shims as needed. keep the caps parallel to the rods.

What do you think the back yard mechanics used back in 1930? 

My point being, I just want to see if I can get this engine running again just for fun.  I'm pretty sure, it won't be put back on the road unless it is thoroughly stripped down, and that;s not going to happen.  There are brand new pistons in the engine.  It came with left over engine parts.  Pistons, connecting rods, crankshaft, etc.  However there is a significant sign of wear on the crankshaft that is in the engine now.  So the state and history of the engine is a bit of a mystery.

 

1.5-2 th.  sounds like I should be able to slide the connecting rod back and forth with some resistance. Not sloppy, but not tight either.

[mikewest]

25 minutes ago, timecapsule said:

I'm curious why you suggest "hard washers"? 

As opposed  to using washers from Tractor Supply?  I use hard washers because thats what  engine builders used.  I suppose a soft washer could squash or flatten out . Any advise i give is always "In my opinion"

[Bloo]

3 hours ago, timecapsule said:

How tight should the connecting rod cap be? 

Really tight.

 

3 hours ago, timecapsule said:

I suspect that since Castle nuts are used, that the torque setting isn't critical.

It affects bearing clearance. You might be limited by the quality of the bolts, typical prewar metallurgy (not good). There are default torque tables by size. You might need to assume soft (grade 2) but I would maybe go a bit too tight because it is a rod. Since you have an actual number from @mikewest and @JFranklin i'd use that instead.

3 hours ago, timecapsule said:

No mention of it in the manual so is there a rule of thumb used here?

It's too early for torque wrenches. Specs started appearing about 1941. The manual probably said "tight". In other words not stripped, but tight. That isn't much help, but thats how it was.

 

3 hours ago, timecapsule said:

But once that was done, I noticed that some of the rods were looser ( side to side) than others.  Some were quite loose, some sort of loose and 2 had no side to side movement at all. I have lots of spare shims in all 3

One method was to tap sideways with a mallet. You should be able to. Quite a few of the 4cyl Chevy guys swear by this, and don't trust plastigage. There shouldn't be different looseness on different rods. Tight is good. They should all have the same tightness on the journals. If you don't have correct thicknesses to make that happen in the 3 sizes you have, make some shims. I might also try plastigage.

1 hour ago, timecapsule said:

I'm curious why you suggest "hard washers"? 

Bad things happen when connecting rod bolts loosen, and that is exactly what would happen if a soft washer compressed. Soft washers are just begging for trouble. Get the best you can get. Grade 8 or better.

 

 

 

 

Edited December 29, 2023 by Bloo (see edit history)

[timecapsule]

6 minutes ago, Bloo said:

Really tight.

 

It affects bearing clearance. You might be limited by the quality of the bolts, typical prewar metallurgy (not good). There are default torque tables by size. You might need to assume soft (grade 2) but I would maybe go a bit too tight because it is a rod. Since you have an actual number from @mikewest and @JFranklin i'd use that instead.

It's too early for torque wrenches. Specs started appearing about 1941. The manual probably said "tight". In other words not stripped, but tight. That isn't much help, but thats how it was.

 

One method was to tap sideways with a mallet. You should be able to. Quite a few of the 4cyl Chevy guys swear by this, and don't trust plastigage. They shouldn't be different looseness on different rods. Tight is good. They should all be the same tightness on the journals. If you don't have correct thicknesses to make that happen in the 3 sizes you have, make some shims. I might also try plastigage.

Bad things happen when connecting rod bolts loosen, and that is exactly what would happen if a soft washer compressed. Soft washers are just begging for trouble. Get the best you can get. Grade 8 or better.

 

 

 

 

"tap sideways with a mallet"  that definitely suggest all but one are way too loose.  

[Bloo]

But you might want to be careful with it and keep speed down for a few miles right after you tighten it up. Standard procedure in the old days.

[timecapsule]

23 minutes ago, Bloo said:

But you might want to be careful with it and keep speed down for a few miles right after you tighten it up. Standard procedure in the old days.

If I manage to get this engine running.

This was my first attempt at rebuilding an updraft carburetor, that of course doesn't have a rebuilt kit available for it. All replaced parts are home made.

The only use it will get is at our annual car club car show.  I built a run engine stand for it on wheels.  I might fire it up for 5 minutes or so at a time a few times throughout the day, just to show people what a 1930 8 cylinder engine looked like and sounded. 

[timecapsule]

I appreciate all comments and suggestions.  I don't mean this to sound like I'm being critical.  But I do like things to make sense to me.

You guys have suggested that I use "hard" washers 8 grade.  Because soft washers could compress and cause issues.

 

But the shims are brass ???

[Bloo]

Use soft ones if you want to. I wouldn't. Brass might not be a good idea either, but it work hardens fast and gets very hard. It probably isn't as bad as it sounds. I doubt it will compress much. You also don't have the nut digging into it. It's against a flat machined surface. Nuts dig into soft steel washers. The metal of the washer squirts into any available void. It is not confidence inspiring. I don't like them too much even in situations where it doesn't matter.