Rod bearing clearance question

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Model T Ford Forum: Forum 2016: Rod bearing clearance question
Top of pagePrevious messageNext messageBottom of page Link to this message  By John Seelman on Monday, October 03, 2016 - 03:51 pm:

Need to file up the rod cap (no shims). I read a thread that said they filed the cap to a point where if a page of newspaper was used as a "shim" the crank would not turn over the engine (or at least with some significant resistance). Once there, remove the newspaper shim and viola you have the correct clearance...... have any of you used this method? and what is the correct clearance?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Roger Karlsson, southern Sweden on Monday, October 03, 2016 - 04:02 pm:

Yes, that's a method I've learnt here at the forum and it works just fine. The end result is about 0.0015" clearance as is should be.

If you make the clearance a little tighter, like only 0.0005 or so, you'll need to pull start the car and you have to run it very carefully for the first miles to avoid galling or babbitt failure - but usually it'll soon self adjust to the proper 0.0015" by itself :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Chris Bamford, Edmonton AB on Monday, October 03, 2016 - 06:39 pm:

I set the clearance on all four rods in my '24 Speedster using this method in a parking lot two years and several thousand miles ago.

The babbitt later broke up on the #4 rod (which I assume was an unrelated failure) but the other three checked out this summer still at right around or slightly under 0.0015 clearance.




Top of pagePrevious messageNext messageBottom of page Link to this message  By Les Schubert on Monday, October 03, 2016 - 07:37 pm:

John
Please get some new rods and avoid wrecking another set of caps. Do the job once and do the job right please!!!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Roger Karlsson, southern Sweden on Monday, October 03, 2016 - 08:04 pm:

Les, I don't see how the caps would be wrecked by filing them according to Ford's recommended service (page 97-101 in the Service Manual)
When they eventually need to be rebabbitted I suppose it would be possible to compensate for the filing with shims?


Top of pagePrevious messageNext messageBottom of page Link to this message  By JohnH on Monday, October 03, 2016 - 09:10 pm:

I've used the newspaper method for all the bearings and it works perfectly. My engine is still going 14 years later with the filed caps too. Never a knock to be heard.


Top of pagePrevious messageNext messageBottom of page Link to this message  By gene french on Monday, October 03, 2016 - 09:21 pm:

Les is mostly right about many ruining their rods by doing a poor job of filing the caps ...depending on how much material must be removed and how careful a person is ...it is very easy to file the opposite sides of the cap "out of parallel" and ski nose the edges ...this results in a cap that will shift around under the pressure of tightening or when running ...VERY BAD ...if a " roadside " repair were necessary i would probably lap the caps on a flat surface ( surface plate if possible ) with probably not courser that 180 sandpaper ...still only a short term repair that could go south in a heartbeat ...always an optimist...gene french


Top of pagePrevious messageNext messageBottom of page Link to this message  By Les Schubert on Monday, October 03, 2016 - 09:37 pm:

Gene
Precisely
I've been handed enough badly filed caps that people then want rebabbited and machined. They get choked when I explain that their caps are ruined and I don't have any to replace them with


Top of pagePrevious messageNext messageBottom of page Link to this message  By Roger Karlsson, southern Sweden on Monday, October 03, 2016 - 09:50 pm:

OK, I understand you can't rebabbit a poorly filed cap that shifts around when tightened, but if it gets squared up on a surface plate with some emery paper, then it should be possible to compensate for the loss of material with shims during the rebabbitt process if I'm not missing something in my thinking?
(haven't rebabbitted rods myself, just trying to understand the process..)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Les Schubert on Monday, October 03, 2016 - 10:13 pm:

Roger
So you square it off. Not too hard. But now the distance from the parting surface to the top of the steel is now a lot less than the nominal 11/16" that you need to bore a good bearing without risking boring into the steel of the cap.
You set your rod boring machine up to bore 7" from the wrist pin centre. So now maybe you need two or maybe 3 sets of shims to space the cap away far enough. So what should be a easy job you can stand behind, gets complicated and risky. Also add in the extra cost of more shims. A currently running thread is about "low grade vendors ". One doesn't want to be trashed when they are just trying to help someone.
Think about it
And my last point;
We aren't the owners of these historic pieces. We are just custodians preserving them for the next generation. If we destroy them we are not doing our job right!!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Roger Karlsson, southern Sweden on Monday, October 03, 2016 - 10:31 pm:

3 sets of shims?? Why?
http://www.mtfca.com/encyclo/doc24.htm
From March 23, 1924 there was only 1/32" of babbitt thickness in the rods from new - and production rods that were delivered in engines never had any shims from start, so you can only file less than 1/32" until the babbitt is worn through (considering it wears mostly in the rod part) and by then I think less than one shim pack thickness would be enough to get almost all filed caps back in position.


Top of pagePrevious messageNext messageBottom of page Link to this message  By gene french on Monday, October 03, 2016 - 11:09 pm:

i think the point here is ...if you are in a situation where an emergency roadside repair may seem appropriate , you are also probably not equipted with a precision surface to lap and check your work ...or a file that is both sharp and of a proper size to work in this situation ...also if you need to remove more than a few thousands from a cap , then you probably should be replacing parts ( rod bore is no longer cylindrical ) ...and like Les states ...i have discarded many rod caps that were filed in excess...often so far out of parallel that you could see a large gap on the ends ...sometimes on opposite ends ...probably done in a rush and without decent tools to work with or any means to check the work...if you are going to attempt this "fix" work slowly and with care ...check your work often and also use prussian blue to check the actual bearing profile and locate points of interference or excess clearance...it is very easy to get a "point interference' that will seem like a slight drag that would be typical of a close fit on a bearing fit ... always an optimist...gene french


Top of pagePrevious messageNext messageBottom of page Link to this message  By Les Schubert on Monday, October 03, 2016 - 11:50 pm:

Roger
I've not encountered very many cranks that are worn standard size ones. Virtually all of them have been ground before.
Therefore almost all of the rods have been rebabbited at least once and usually several times. So IF they got filed a couple of times over the last 90-108 years, they start to get a lot of material removed. So now you start with a nice crank that cleans up at maybe .015 undersize. And the caps have had .030 filed off of them. And then you need to surface another.010-.020 off of them to correct the crooked previous work. I've encountered lots that are more than .060 thinner than they should be. Easily.080" thinner
I trust this explains it clearly


Top of pagePrevious messageNext messageBottom of page Link to this message  By Les Schubert on Monday, October 03, 2016 - 11:55 pm:

And yes if I was by the side of the road 500 miles from home, then I would consider filing a cap, AFTER I kicked myself for getting in the jam in the first place. The reality is I carry a spare finished balanced ready to use rod. Fortunately I've never needed it!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dave Huson, Berthoud, Co. on Tuesday, October 04, 2016 - 12:14 am:

I try to stay off the Forum but this time I can't! Boy it burns me when I hear some one has filed any thing or any way on the Caps. If any one thinks they can file caps and still have a round rod and cap I don't know what they are thinking. Listen to Les Schubert, he is right. Once you have filed a cap it is ruined because if you ever want to rebabbit it You will NOT be babbiting a round hole. I guess I should not say any thing about filing caps because I always have a bucket full of caps that are not ruined and sell them to walk ins. So go ahead with all your schemes about how to file your caps and when you have ruined them for rebabbiting them some day I will sell you some caps that HAVE NOT BEEN FILLED.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Roger Karlsson, southern Sweden on Tuesday, October 04, 2016 - 12:22 am:

Ok, completely different experience than I have.
I've never seen such abuse of rods - and it shouldn't be necessary. If the rod is rebabbitted with one shim pack (that should be sufficient) in place, then it's easy to fix a knock while on tour - just pull a shim.

And if you still have factory babbitt, then maybe it's best to file a little extra on the good surface plate at home - and put one or two 0.003" shims in place to get it in adjustment, then it's never needed to file beside the road, you can just pull a shim :-)

And Gene - indeed it'll be line contact, thet's why I was writing about the alternative about setting it a bit tight in my first post above - that would get more of a contact surface..
Other alternatives would be scraping babbitt (difficult work) or using timesaver for increased bearing contact (much easier)

Getting a babbitted replacement rod isn't just $77 a piece for me overseas - it's the core charge of $25 extra since sending cores might be just as much, plus shipping $$$ and customs $$$, so I'll have to keep my old rods running as long as possible. And I have spent lots of time balancing them - I'm not sure I'll get new rods that are even possible to match as good?

May have to buy molds from you Gene to do them myself once it's inevitable :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Frank van Ekeren (Australia) on Tuesday, October 04, 2016 - 12:28 am:

Dave
That would have to be the biggest load of BS I've read on the subject!! an un-poured rod couldn't give a hoot if it's a round hole or not when being rebuilt.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Roger Karlsson, southern Sweden on Tuesday, October 04, 2016 - 12:30 am:

Dave, I asked Les above, and it seems like it's possible to add shims when babbitting to get the steel back to round.

And if someone really need unfiled caps - I bought a box with 33 caps for $20 at a swap meet this summer and most of them seems to be unfiled with excellent babbitt. Most of them will be available cheap to those that really needs some, but shipping overseas would be high, of course.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kohnke Rebabbitting, Clare, Iowa on Tuesday, October 04, 2016 - 03:06 am:

That would have to be the biggest load of BS I've read on the subject!! an un-poured rod couldn't give a hoot if it's a round hole or not when being rebuilt. "END QUOTE"

Frank, your on the "BS" end.

an un-poured rod couldn't give a hoot if it's a round hole or not when being rebuilt. " END QUOTE "

Frank, that statement tells me you don't know S$%& about rod building, so I will enlighten, you.

Dave tried to tell you, but it's over you head.

When the rod cap is filed, the Babbitt in the cap is thinner, a chance to hit steel, when machining. We have found that about 80% of the rods that we have rebuilt, needed TWO .032 solid shims, and one .032 laminate. When the shim pack is right, using an Original Bolt, and Nut. the hole in the bolt, and the castle will have NO space on the bottom of the hole where you see bolt thread, where you insert the key.

We have seen many rod builders do like you would do and bore the rod that way with, as Dave told you, with a hole that is NOT round. That is S*%# kind of work. We have also seen more times then not of boring the cap out, to make room for the Babbitt that wouldn't be there. That is a very bad practice, as it weakens the cap, letting it twist, stressing the tinning bond, and taking out the Babbitt.

We have also seen builders changing the center distance to fix the problem, very bad idea.

When a Rod bearing has .006 thousandths out of, or off of the part line, the rods service has about had it any way, and goes double for a pressure system, as the side of the bearings will never touch again, so all you have is top, and bottom to clearance the bearing.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Frank van Ekeren (Australia) on Tuesday, October 04, 2016 - 03:40 am:

There you go again Herm!!
Not reading what my response was too!

Dave said, Quote,

'Once you have filed a cap, It's ruined because if you ever want to rebabbitt it you will NOT be rebabbitting a round hole'

That my friend is the BS!

And you confirmed that by your statement of putting it all back in spec with shims.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Seelman on Tuesday, October 04, 2016 - 07:56 am:



Her is a picture of my cap


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Seelman on Tuesday, October 04, 2016 - 08:44 am:



and another. It doesn't look like there is too much material remaining compared to Chris's above


Top of pagePrevious messageNext messageBottom of page Link to this message  By Roger Karlsson, southern Sweden on Tuesday, October 04, 2016 - 09:03 am:

I don't think you'll have to worry - the main wear is usually on the rod part of the babbitt. No need to change the rod until the babbitt cracks or if it's seriously dirty from metal shavings that would grind the crank down.

By the way, when you have the rod off the crank - always inspect the crank throw for wear and check with a micrometer so it isn't worn oval - if oval, the babbitt will soon need another adjustment and will eventually crack from fatigue. Time for crank grinding and new babbitt.

I suppose the hole goes all the way through? Then you should use the Chxxy style dippers sold by the vendors to splash up a little more oil into the bearing - but the main entrance for oil is at the chamfers at the parting line between rod and cap :-)


Top of pagePrevious messageNext messageBottom of page Link to this message  By Les Schubert on Tuesday, October 04, 2016 - 09:37 am:

John
Looks like it could be a good candidate for rebabbiting. Redoing your rods could be a good winter project. Please check the centre main while you are at it. It is often worn by the time the rods start talking. And just perhaps that is actually what you are hearing!!!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kohnke Rebabbitting, Clare, Iowa on Tuesday, October 04, 2016 - 01:43 pm:

And you confirmed that by your statement of putting it all back in spec with shims. "END QUOTE"

That's right Frank, fix it with shims, Fix it with weld, it all costs. We have to pass the cost on, that makes it a waste when rebuilding. Dave pointed that out to only those that could Grasp the Reality!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Frank van Ekeren (Australia) on Tuesday, October 04, 2016 - 03:51 pm:

The Reality of the Grasp Herm,
is at this end of the world good caps are very hard to find and re-sizing and pouring with shims in the molds is done to put a rod back into service!


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Seelman on Thursday, October 06, 2016 - 07:45 am:

OK guys, so the plstigauage tells me I am somewhere between .001 and .0015 clearance. So that tells me its not the rod. The valves look like they could use some adjusting. They are cast valves that I haven't touched in years. Could they be the source of the knock?


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Doolittle on Thursday, October 06, 2016 - 08:14 am:

Describe the knock for us.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Seelman on Thursday, October 06, 2016 - 08:28 am:

John, the knock is after it's warm, running slightly above idle. Grounded #1 and while the knock did not go away it did change. all of which originally led me to believe the rods, and the start of this thread


Top of pagePrevious messageNext messageBottom of page Link to this message  By Roger Karlsson, southern Sweden on Thursday, October 06, 2016 - 09:31 am:

There are lots of stuff that can make sounds inside and outside the engine..
Check how much the rod can move fore - aft, maybe it's slightly bent, that can be hard to diagnose - maybe if one lies under and looks how it behaves while someone else cranks the engine?
Maybe the front main has been starved for oil in the past? Maybe the crank pulley is loose, lots to check :-)
The piston pins can also be too tight or too loose causing sounds.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Les Schubert on Thursday, October 06, 2016 - 09:36 am:

Excessive end play in the cam can sound like a rod. The difference is it is sort of intermittent


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