tight crankshaf

[Charner (MS)]

I acquired an old 8n engine that was all to pieces, parts in box. I decided to put in together. Put in new sleeves, pistons, etc. Had the crank turned. 20 on mains and 30 on rods. Installed crank and bearings properly. Torqued mains to 100. Would not turn. Installed 3 thousand shims on each bolt and turn with ease. Same with rods. Tighten to 35 lbs. engine would not turn. Installed shims and turns oK. I talked to the crank technician. He thinks the problem is in mismatch of caps on rods and mains. Probably right. I have no history on engine. By the way, mico-ed the crank and it's right on. What do you think about running with shims, will it hold up?
Buying an engine in a box is like buying a pig in pole.

 

[TheOldHokie]

(quoted from post at 18:54:03 01/16/19) I acquired an old 8n engine that was all to pieces, parts in box. I decided to put in together. Put in new sleeves, pistons, etc. Had the crank turned. 20 on mains and 30 on rods. Installed crank and bearings properly. Torqued mains to 100. Would not turn. Installed 3 thousand shims on each bolt and turn with ease. Same with rods. Tighten to 35 lbs. engine would not turn. Installed shims and turns oK. I talked to the crank technician. He thinks the problem is in mismatch of caps on rods and mains. Probably right. I have no history on engine. By the way, mico-ed the crank and it's right on. What do you think about running with shims, will it hold up?
Buying an engine in a box is like buying a pig in pole.

Mismatched caps were my first thought. If that is the case shims will not fix the geometry and you will have wasted the money you spent on the crankshaft work. Sounds like every one of them is out and I would expect a short life for the crankshaft and bearings.

If you intend to use this engine I would have the caps inspected by someone who has the proper measuring instruments and matched up if any of them are originals. Based on your description more likely you will need to have the big ends on the rods resized and the mains align honed.....

TOH

 

[Bob]

STOP, back up, and take a deep breath.

"Shims" have no place in an engine with "precision bearing inserts".

Have a respected nearby machine shop check the "line bore" of the block, and check out and "recondition" the connecting rods as needed.

(What do you think "ralphing down" the main bearing bolts and rod nuts does when things don't line up, or are not the size they're supposed to be???)

 

[Walston]

Did you use plastigage when you assembled the engine? If not I would first disassemble and check each bearing with plastigage. You may be able to identify where the problem is. If this is not clear, I suggest taking to a reputable machine shop as mentioned and have them check it and rebuild it.

 

[pinball]

don't forget you put new seals in the front and rear. if not installed properly they will lock you crank up. I agree shims has no place on bearing caps. if It were mine I would double check those seals and make sure you use stp on them, around them ever where before you install them and tighten the caps. a good friend of mine who has overhauled several 8ns told me that sometimes he actually has to pull an 8n to get it to turn over and it will reset the seals itself if there just a little off. if your bearings re the correct size then I would suspect your seals may be the problem.