Rebuilt Engine now too tight

Recently I rebuilt a Ford 9n, the engine was fairly tight with new rings and bearings but I could turn it over until after the new rope seals went in. The engine now is so tight 12 volts won't turn it over. Any suggestions? Pull Start?..

Pressurize the oil system from an external pump. Or take the rod and main caps off and put some engine assembly grease on the journals. Smear the cylinder walls with that grease or oil so you don't have metal against metal. Even a film of oil in the seals can help.

Gerald J.

I don't want to say you did anything wrong but are you sure the mains and rods aren't too tight? I used to build with a beam style torque wrench. Each time I made up a bearing, I rolled the crank with the torque wrench a full turn and noted the required torque. I did this the first time way, way years ago and had my a number 1 rod only 3 lbs tighter than all the rest on a big V8. It spun that bearing in a few miles. At the time I thought it was just a "little too tight". Each part should add the same load to the crank torque. So if it takes 5 lbs to turn one piston, two should take 10, four takes 20. Big V8 might take 35 to 50 lbs to roll fully made up

did you plastigage on the bearings????if not why not? did you use GOOD engine rebuild lube, oil , or STP, or the like on all bearings were the rods re sized and new wrist pin bushings installed,and honed, did you oil the piston rings,pistons and cyl. real good

If the engine won't spin fairly easily, the starter may be on the way out. Or it is not right inside. As stated We hope you used assembly lube, and oiled the pistons and rings. If the ring gap was not checked, it may be seizing in the bores. Was it to spec when checked in the bore? JimN

I just put together an engine for an 8N. It was stiff like expected before I put the seals in. With the seals in, I could not turn the engine easily. The starter was able to turn it.
When you put the seals in, did you roll them into the cover with something round like a socket to press them into the covers? That's what I did and had no problems.

Basically what your saying is that as the bearing caps (both rods and mains) are tightened the amount of torque required to turn the crank with just one tight should increase that same amount as each of the others are tightened. As good of an idea as it may be to turn the engine over after each component is installed to insure that there are no clearance issues that are locking it down it"s no way to know whether the bearing clearances, etc are right, if for no other reason than it would require throwing the torque specs out the window for nearly every, if not all of, the engine mfg. in existance. The mfg comes up with the torque specs for the bolts for a reason, to keep them from loosening while the engine is in operation. If you don"t tighten the bolt to the proper torque you stand more chance of engine damage from a lose bolt than you do from having a bearing "too tight" in the way you describe. Giving a "set torque" for the bolts and not for the bearing its self is one one reason that every bearing has a range of allowable clearance, and yes, those clearances are going to effect the torque required to rotate a shaft within that bearing. Think about it this way if you had one bearing with maximum allowable clearance that took say 7 inlb of torque to roll the shaft over and another with minimum clearance that took say 14 inlbs to to get it to turn then based on what your saying the engine isn"t going to run properly even though the mfg says it is within their tested tollerances to do so. Given the allowable plus and minus specs needed in just about every part made due to imperfect manufacturing processes it"s not at all unreasonable to think that, whether it happenes every time or not, eventually parts of minumum amd maximum tollerances are going to get mixed. Over the course of my life I"ve seen it happen many times, often with no problems, but just as often it causes fit up problems and I"ve had to trade off one piece or the other to make the assembly work.

On top of that you also have to look at the friction of the rings on the walls of the cylinder as they are also going to add to the force required to turn the crank. Whether we admit or not no two rings are guaranteed to be identical. Given that fact if one was a little more sprung than another it"s going show a little more torque needed to turn the crank than the other one would. In this case the torque difference isn"t even in the bearings and is, in reality, a factor that the engine builder has no control over.

As far as the bearing clearances there are some engines that have to have the parts machined to match the bearings and if they don"t then your out of luck. At the same time there are also engines that are designed with tight clearances and you have to shim the caps to get all of the clearances within the given specs.


Whatever type of engine someone might happen to have if it doesn"t turn when assembled then it"s guaranteed something is wrong. Now whether it"s a ultra tight bearing, or something as simple as a fastener that was too long used somewhere and rubbing against an internal part is hard to say. Either way the only thing to do is to start dissaembling the engine and trying to turn it at each step until such time as the problem is found. To that all I can say is Good Luck.

If it turned over until he put the seals inn,wouldn"t the seals be the problem?

After pulling the front end off and lube the front rope, rechecking all of the wiring connections and sliding in a new starter she turns over well now, not too fast though as she is snug but the 6V turns her over, Thanks for all the help....