1955 ford 800 with 172 engine gas

[rdjinny]

Could anyone tell me what size rod bearings I need, I measured the journal and came up with 2.301 inches and the crank measured at 2.499 I don't know if it would be standard bearings or not appreciate your feedback

thanks Rick

 

[Janicholson]

Could anyone tell me what size rod bearings I need, I measured the journal and came up with 2.301 inches and the crank measured at 2.499 I don't know if it would be standard bearings or not appreciate your feedback

thanks Rick

Well that number .198 is far from good. I think you are making the mistake of measuring the steel diameter of the big end of the rod, with no insert in it. The correct method is to look up the journal Diameter (crank diameter) and compare that to the existing 2.301. if within .002 to .003, standard inserts are to be chosen. Then assembled and plastigauged to assure reasonable clearance. If the size measured is .010 smaller, then .010 unser size inserts are ordered. If .020 smaller, then .020 undersize inserts are ordered Etc., Plastigauge is a mandatory aspect of this. Jim

 

[rdjinny]

Don I don’t know where you came up with .198 the measurements are for the journal and the crank

 

[used red MN]

rd, you have some misunderstanding of engine terminology. The “journal” in most all cases is the round metal part that the bearing rides on. In the case of a crankshaft that is either the main bearing “center shaft” that mounts it in the block and allows it to spin as an assembly. Also the outer diameter of the crank pins which appear to be your topic of concern. The ID of the big end of the rod that the outside of the bearing mounts in is of no concern. That is finished to a certain diameter to properly crush and grip the OD of the bearing shells. It is the same no matter whether you have standard or undersized bearings. The .198 Jim gave is the difference in the two numbers you gave which 2 tenths of an inch would be about the thickness of the bearing shells a tenth of an inch thickness doubled for each side. Measure the crank pin journals and proceed as Jim instructed. Please return with questions if what we are explaining is not being grasped.

 

[Janicholson]

Don I don’t know where you came up with .198 the measurements are for the journal and the crank

2.499 is almost 2.5 but 2.301 is a smidge over 2.300 There is almost 200 thousandths difference.

 

[rdjinny]

Ok thanks for clarifying I was confused by what he meant appreciate the clarification.
Thanks

 

[Gary Reif]

Could anyone tell me what size rod bearings I need, I measured the journal and came up with 2.301 inches and the crank measured at 2.499 I don't know if it would be standard bearings or not appreciate your feedback

thanks Rick

rd, I just looked up the crankshaft journal specs. and the main bring journal dia. new would measure 2.4980-2.4988 and the rod brg. journals new measure 2.2980-2.988. Going by the measurements you posted your crankshaft is in very good standard condition though i've never known one to measure oversize so you might want check the calibration of your mics. you might also look at the backs of the brgs. you removed, some time the size/undersize is stamped on the back of them. You didn,t indicate if this is a crankshaft that has been in a running engine. Sorry for my rambling, just a few thoughts.

 

[showcrop]

Generally you have the machine shop measure and evaluate your major components and order your bearings etc. Kind of like measure twice cut once, LOL.

 

[rdjinny]

rd, I just looked up the crankshaft journal specs. and the main bring journal dia. new would measure 2.4980-2.4988 and the rod brg. journals new measure 2.2980-2.988. Going by the measurements you posted your crankshaft is in very good standard condition though i've never known one to measure oversize so you might want check the calibration of your mics. you might also look at the backs of the brgs. you removed, some time the size/undersize is stamped on the back of them. You didn,t indicate if this is a crankshaft that has been in a running engine. Sorry for my rambling, just a few thoughts.

Thanks for the reply you were right about the crank measurement, as far as I can tell with the bearings they have the ford logo guessing they’re the originals which actually look pretty good guessing standards for replacement….
Another concern is ring gap tolerance max is 20 and I measured 26 thousand does this mean the sleeves have to be replaced?

 

[used red MN]

Thanks for the reply you were right about the crank measurement, as far as I can tell with the bearings they have the ford logo guessing they’re the originals which actually look pretty good guessing standards for replacement….
Another concern is ring gap tolerance max is 20 and I measured 26 thousand does this mean the sleeves have to be replaced?

There is some amount of experience involved with this but this is a general approach. Run your finger up the cylinder dragging your nail and if it catches the ridge where the rings stopped your are in the “iffy” zone of whether or not just replacing the rings will last very well. Unfortunately Ford decided to build a lot of engines without replaceable cylinder sleeves. This means the block needs the cylinders bored and oversized pistons installed. As said a machine shop can make the determination, your ring end gap being out of tolerance is not a good indicator. It all depends on what kind of job you want to end up with, what you want to invest in it and what you can tolerate after doing all that work and it performs in a substandard way. If you are just taking it out somewhere to mess with some deer plots it may be fine. It will probably smoke, burn some oil and occasionally foul the plugs. On the other hand it may work perfectly fine and use no oil, the odds are against that.
Here is a link to the manufacture’s parts catalog.
CNHI Ford 800 parts catalog
That is not for ordering parts, but you can. More for the diagrams that shows no sleeves. You must have an outlet to get parts through if you already have bearings. YT has an excellent line of parts that they offer.
And in my reply above I said the inside of the big end of the rod is of no concern, which is true to a degree as far as measurements for bearings. Generally my thought is if the old bearings showed relatively good wear patterns the conn rod big ends are fine, especially if you see the printing from the back of the bearing has transferred to the ID of the rods. This means the bearings were being held tightly and not moving. In my opinion a in a diesel engine the proper sizing of the rod ID is more critical.

 

[rdjinny]

There is some amount of experience involved with this but this is a general approach. Run your finger up the cylinder dragging your nail and if it catches the ridge where the rings stopped your are in the “iffy” zone of whether or not just replacing the rings will last very well. Unfortunately Ford decided to build a lot of engines without replaceable cylinder sleeves. This means the block needs the cylinders bored and oversized pistons installed. As said a machine shop can make the determination, your ring end gap being out of tolerance is not a good indicator. It all depends on what kind of job you want to end up with, what you want to invest in it and what you can tolerate after doing all that work and it performs in a substandard way. If you are just taking it out somewhere to mess with some deer plots it may be fine. It will probably smoke, burn some oil and occasionally foul the plugs. On the other hand it may work perfectly fine and use no oil, the odds are against that.
Here is a link to the manufacture’s parts catalog.
CNHI Ford 800 parts catalog
That is not for ordering parts, but you can. More for the diagrams that shows no sleeves. You must have an outlet to get parts through if you already have bearings. YT has an excellent line of parts that they offer.
And in my reply above I said the inside of the big end of the rod is of no concern, which is true to a degree as far as measurements for bearings. Generally my thought is if the old bearings showed relatively good wear patterns the conn rod big ends are fine, especially if you see the printing from the back of the bearing has transferred to the ID of the rods. This means the bearings were being held tightly and not moving. In my opinion a in a diesel engine the proper sizing of the rod ID is more critical.

I don’t want it to be substandard, especially after what I’ve done already and I’ll check out the site in the link. Thanks again