Main bearing clearance

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Model T Ford Forum: Forum 2009: Main bearing clearance
Top of pagePrevious messageNext messageBottom of page Link to this message  By Rob Mills on Sunday, December 06, 2009 - 05:43 pm:

My dad came over today and we were fitting the crank in the block I found, we scraped the bearings and got the high spots out and were trying to get the clearence set using the if you cant turn it it is to tight method but now that we have the 3 mains done it seems too tight, does anybody know what the clearnce should be using plastiguage?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Michael Deichmann on Sunday, December 06, 2009 - 05:53 pm:

Do you have all bearings pt together? Or do you mount them and check. When OK, loosen it again and take next bearing.
Once all are OK - put it all together and tighten all. Now it may be hard to turn and the first time you start then engine you may have to pull it after another car.
Once it fires - let it run in fast idle for 5 minuttes.
The first many miles - drive slowly and no high revs.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Seth Harbuck - Shreveport, LA on Sunday, December 06, 2009 - 06:06 pm:

The clearance should be 0.0015" to 0.0020" but since they are scraped rather than burnished with Timesaver, my recommendation would be to err on the low side (0.0015"). There is no way that scraping is going to give you as much bearing surface area as burnishing them would and the clearances will increase more once the engine is run.

Michael's advice on running-in agrees with mine 100%.

Seth


Top of pagePrevious messageNext messageBottom of page Link to this message  By gene k. french on Sunday, December 06, 2009 - 06:17 pm:

Rob:
.001 to .0015" is proper clearance for main or rod bearings in your T engine ...you might try ordering and using "time saver" lapping compound to lap bearings to fit ...i have used this method on 2 engines that were simple ring and valve jobs on otherwise used components ...this worked well and i set clearance on a 4 cyl. chev. and a model t at .001" ...word of CAUTION with this process...the center main on chev. block was worn to .004" clearance ,i had to shim insert .002" to bring in alignment with front and rear bearing in block before lapping...also main journals on crankshaft were within .0007" of being round and crankshafts indicated straight within .001"...even with these reasonably good crankshafts this is only a temporary repair and not a longterm quality job...crankshafts turned with little effort by hand using rod throws as handles,but actual clearance will run from .001" to a near interferance sliding fit at large sections around bearing diameter...bearings blued very nicely and actual fit is quite functional on the short term...not the same as a re-ground crankshaft and properly fit re-babbitted bearings ,but the customers are happy with results and also price,and expect the engines will serve well given the limited parade and short tour use they will see...P.S. Tim Foye @ gen3 antique auto sells a time saver lapping compound kit...contact him for more info...best regards and Merry Christmas gene french


Top of pagePrevious messageNext messageBottom of page Link to this message  By Norman T. Kling on Sunday, December 06, 2009 - 06:36 pm:

I just got through tightening rod bearings. Two of them were re-poured. I adjusted each one individually to where it would turn with the crank, then tightened all. I could still turn it barely, with the crank. After I installed the head and spark plugs, it would not turn with the crank or the starter (could barely turn with both hands on the crank). This afternoon I had my son pull me with the pickup about 100' and it started right up. I backed it up and parked it in the garage. Jacked up the rear wheels and ran it about 5 minutes in high with wheels up at fast idle. Then I re-torqued the head. About 1/2 hour later, I started it with the crank and ran it until the motormeter got to the normal summer level and turned it off. Re-torqued the head again. It turns over with the crank and it will even idle at the same speed it did before I worked it. As long as you are sure it will turn with each bearing tightened individually, it is not too tight.
Norm


Top of pagePrevious messageNext messageBottom of page Link to this message  By Rob Mills on Sunday, December 06, 2009 - 08:46 pm:

I did each bearing individually using preshin blue, How easily should it turn by hand? I can it with a little force with each bearing but when they are all together I need to use a breaker bar on the end of the crank, my dad thinks that is to tight but I dont know.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ken Kopsky on Sunday, December 06, 2009 - 10:40 pm:

How should it turn? With mains tight, you should be able to turn the crank with one finger. Given that you are scraping the bearings, that's not likely to happen. Follow the wise advise already given and use the Time Saver lapping compound. It will save you a lot "take-up" time later.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ted Dumas on Monday, December 07, 2009 - 01:02 am:

Did you oil the bearings after you scraped them?

Sounds like you are fitting a crankshaft to another block, not just taking up the clearance. Did you check the crank for straightness and more importantly did you have the crank magnafluxed?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Noel Keefer on Monday, December 07, 2009 - 01:29 am:

Rob,

For once every post is right on.

If the clearances were set while rebuilding using machines, Ken Kopsky is correct. All of the clearances will be set properly and will not be binding. There will, however, be drag.

OTW, the Timesver is a great method of setting up all of the 7 running babbit bearings. The instructions say you don't even need to clean out the abrasive after you have lapped, or whatever you want to call it, each bearing! This I couldn't allow myself to do. The bearings come out with a patena, or dull finish. I don't think most of us find a need to pull a T anymore. With the proper setup lube it should turn over, maybe with a breaker bar to get it loose after sitting. My personal preferance is a fine layer of Lubriplate. But others will all have their own pet lube.

For the cylinders I use Steam Oil. Guess where that comes from? It's the gunk called 600 wt rear end oil. I have used steam oil on every aircraft engine I have ever rebuilt. STP will kill the breakin process. It glazes over and prevents the rings from breaking/wearing in.

If you don't bore, you ought to consider honing the cylinders.

Timesaver is available from Snyders and other suppliers.

In my youth my Dad had me scrape a 6 cylinder Studebaker and I would now call scraping a waste of time and the results are not nearly as good.

Have fun,
Noel


Top of pagePrevious messageNext messageBottom of page Link to this message  By Art Wilson on Monday, December 07, 2009 - 03:04 am:

On of our members had a main bearing fail in a fresh T engine. When he disassembled the engine he found the oil hole to the bearing was packed full of grease and wouldn't let any oil into the bearing, which he believes caused the failure.

I am not positive that was the exact cause of failure but it definitely is something to think about.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Robert Ducharme on Monday, December 07, 2009 - 10:48 am:

One more thing to consider. I had an engine that I poured and line bored. I set each bearing using timesaver and the boring to .0015". With only 1 bearing cap tight, turned very nicely. However, when I tightened all three, could not turn the crankshaft. I had the crankshaft checked and it turned out that the company doing the crankshaft had not straightened it. After it was straightened, it turned easily. Even if you had someone do the crankshaft, I would recommend checking that it is straight.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Rob Mills on Monday, December 07, 2009 - 02:11 pm:

I havent checked the crank for straightness, I am putting together a low buck engine to put around town in and it has not been repoured or anything. It is a crank from another block because it seemed to be a better crank. After going back to it last nite I realized the front bearing was too tight. I ordered some Timesaver last nite so I will give that a try and see how it works. Thanks......


Top of pagePrevious messageNext messageBottom of page Link to this message  By Noel Keefer on Tuesday, December 08, 2009 - 03:10 am:

Art,
I suspect grease in an oil hole could stop oil flow.

In my post I said a fine layer of lubriplate. I didn't want the lubriplate filling any holes upon startup.

I am trying to recall whether the original T's had ANY holes in the rods. All of us have drilled so many holes I don't recall what was original.

Regards,
Noel K


Top of pagePrevious messageNext messageBottom of page Link to this message  By Art Wilson on Wednesday, December 09, 2009 - 03:34 am:

Noel,
All the unmolested T rods I have seen had no holes. The real late models may have had oil holes but I can't say for sure.

In my opinion, adding oil holes and Chevy dippers are a good addition for providing oil to the rod bearings. Also the ends of the dippers can be bent up to lock the rod nuts in place.

I also am a fan of using Time Saver to fit the bearings. It works great and is easy to use.

I got both of the above tips from this forum. Thanks to all for your great ideas and tips.
Art


Top of pagePrevious messageNext messageBottom of page Link to this message  By Noel Keefer on Wednesday, December 09, 2009 - 11:37 am:

I believe I read on this forum where a fellow used his T to go to work via a freeway. He ran it wide open and had no modifications to the engine. Unknown year.

I contacted him and he stated it had no mods.

Noel


Top of pagePrevious messageNext messageBottom of page Link to this message  By Rob Mills on Tuesday, December 15, 2009 - 12:35 am:

Just finished using time saver for the first time and I am now a huge fan of it, mains and rods are all done and its time to asemble the crank. I checked everything with platiguage after using the time saver and it is right on at .002. Thanks for the advice, next I have 2 valves that have .030 of clearance and I really dont know what to do about that.


Top of pagePrevious messageNext messageBottom of page Link to this message  By gene k. french on Tuesday, December 15, 2009 - 01:11 am:

Rob:
congrat.!back to your origional question regarding crankshaft being too tight...how does the crankshaft turn now?
regarding valves...probably the easiest repair is to replace tappets with adjustible tappets...also while you are at the valves probably should consider replacement there also,especially if the valves are the old style with cast head ...
best regards and Merry Christmas gene french


Top of pagePrevious messageNext messageBottom of page Link to this message  By Rob Mills on Wednesday, December 16, 2009 - 12:16 am:

Once it was all bolted together it was a little stiff but once you get it to budge it turns by hand. I have the rods bolted in and pistons in now and you can turn it with a short bar without much effort.


Top of pagePrevious messageNext messageBottom of page Link to this message  By gene k. french on Wednesday, December 16, 2009 - 01:51 pm:

Rob:
sounds about right ..."that being able to turn by hand with little effort"...probably more damage done with clearances being too tight than by a little too loose ...now it's time to assemble and enjoy ...P.S. our local AACA group started a New Years Eve tour about 15 years ago...it has been well attended ever since, inspite of often very low temps.(-18F. one year)(i drove a DB roadster that year! )...you may be able to start your own New Years Eve. tour if you get with it!...best regards and Merry Christmas gene french


Top of pagePrevious messageNext messageBottom of page Link to this message  By Rob Mills on Wednesday, December 16, 2009 - 11:37 pm:

Yeah Gene I dont think I am going to make it. Maybe next year.


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