How easy should it be to rotate the bottom end?

[imamachine]

I bought a rebuilt 1.9 a while back that has sat on the shelf for many years. I felt that at was very difficult to rotate the short block by hand so I pulled the pistons out and found that I was unable to move 3 of the 4 rods on the pistons. I took these to a shop and had them freed up. I put them back in and retorqued the main bearings to 72 ft lbs and the rod caps to 36 ft lbs. I did the main bearings first and the crank rotated freely by hand. I put in two pistons and it still rotated realively easily. I put in the third piston and it was a little difficult and when I put the fourth in it was very difficult to rotate the whole assembly by hand. I went back and forth losening things and trying to pinpoint the issue and it seems to be that the whole assembly rotates easily with two or three of the rod caps torqued, but when they're all torqued it's very difficult. Any thoughts on this?

[jeff denton]

Have you checked your rod bearing clearance?
Also you may have a bent rod, or two or three or four, which can tighten things up drastically.
A short block assembly should turn over easily with a 12" long wrench on the front pulley bolt. Twice during each revolution it should be real easy, as two pistons are rolling over at TDC and two are rolling over at BDC.
So called rebuilt engines are the scariest, need checked over real good. You don't know what kind of knucklehead put the thing together. Huh, Joe?

[dallasmanta]

Reading your post you do not say that the rods were connected in this exercise so my educated guess would be a bent crank shaft or one that has a bearing that does not match the crank machine surface. Did you check the brearing compressed clearance when you re assembled the lower end..

Reasons for bent crank shafts are storing them laying down vs sitting on the fly wheel end. Improper machining / matching of the bearings to the crank shaft. Hope this helps. Ron

[yellaopelgt]

Originally Posted by jeff denton So called rebuilt engines are the scariest, need checked over real good. You don't know what kind of knucklehead put the thing together. Huh, Joe?

Yea............tell me about it......3 words for ya....Plastigauge....Plastigauge...Plastigauge. And then do it again. Sometimes its best to start with a known good worn block and do everything yourself!!!!! At least that way, you KNOW where any problems may be.
Silly question here,but you are tightening the caps down in the correct sequence right?
Joe

[Dennis Texas]

Originally Posted by imamachine I bought a rebuilt 1.9 a while back that has sat on the shelf for many years. I felt that at was very difficult to rotate the short block by hand so I pulled the pistons out and found that I was unable to move 3 of the 4 rods on the pistons. I took these to a shop and had them freed up. I put them back in and retorqued the main bearings to 72 ft lbs and the rod caps to 36 ft lbs. I did the main bearings first and the crank rotated freely by hand. I put in two pistons and it still rotated realively easily. I put in the third piston and it was a little difficult and when I put the fourth in it was very difficult to rotate the whole assembly by hand. I went back and forth losening things and trying to pinpoint the issue and it seems to be that the whole assembly rotates easily with two or three of the rod caps torqued, but when they're all torqued it's very difficult. Any thoughts on this?

Just a couple of question for ya: you are priming the oil pump before trying to rotate crank? When you assembled the engine after machine shop loosened up your pistons you did lube the bearing surfaces before assembling? I think what your going to find if you have lubricated the moving parts and it is still difficult is someone did not keep rod and rod caps in order and two or more are mismatched (Plastigauge the journals or micrometer but it needs to be looked into before forcing rotation). HTH

[imamachine]

To clarify a few things:
I have not checked any of the clearances using plastigauge, although I will do so now.
I kept track of everything so all of the parts I put together were matching, hard to know if they were originally assembled correctly. Everything went back together with assembly lube.
When I say it's difficult to rotate, I'm pushing on the crank with my hands. I have not installed the crank pulley bolt, but I will try that and see how it feels.

I wasn't aware of a specific sequence for tightening the main bearing caps, that I'm sure I did not follow. What is the sequence?

Thanks for the responses!

[Anonymous D]

Interesting that the "rebuilt" block may have been insufficiently inspected or incorrectly reassembled.
What color was the paint on it? Was it "blue"?

[CDN OpelNut]

I had similar concerns when reassembling my block. I certainly could not have rotated the crank by hand, but it's fine.

Check this post from the thread

http://www.opelgt.com/forums/125072-post42.html

[Dennis Texas]

Originally Posted by imamachine To clarify a few things: I have not checked any of the clearances using plastigauge, although I will do so now. I kept track of everything so all of the parts I put together were matching, hard to know if they were originally assembled correctly. Everything went back together with assembly lube. When I say it's difficult to rotate, I'm pushing on the crank with my hands. I have not installed the crank pulley bolt, but I will try that and see how it feels. I wasn't aware of a specific sequence for tightening the main bearing caps, that I'm sure I did not follow. What is the sequence? Thanks for the responses!

I think you have some wrong ideas about this. If your motor was truly rebuilt when engine is primed with oil and lets make this easy use the flywheel, you should be able to rotate without much issues with the spark plugs out. If that is difficult or binding then you will need to mic or plastic gauge or take to machine shop and have inside diameter of rod connecting area matched. From what you have said and your symptoms about the only thing it could be is a mismatch of the rods and rod caps ( bent rods as was posted also but I was assuming there is that word again that when it was rebuilt that was determined to be ok before the original assembly before you bought it) by previous person who rebuilt it ( I was not referring to you on mismatching caps).
I'm not a weak person, I have engine in my shop ready to install I can grab the front pulley and turn it over (without plugs in it) it is not easy due to the short leverage but I know with the flywheel on it should be no problem to roll right over.
Main caps are independent of each other all I do for sequence is tighten evenly to specs and tap cap and head of bolts with 2 lb hammer (tap not beat) loosen and retighten to torque specs. If anyone has better way then enlighten me as well.
If you can actually rotate the crank even being hard by just using the crankshaft you probably don't even have a problem. IMO
Feel free to correct

[jeff denton]

[quote=Dennis Texas;179631]From what you have said and your symptoms about the only thing it could be is a mismatch of the rods and rod caps /quote]

Ah, that's it. Good one, Dennis!
I have piles of such rods. They're useless unless someone wants to have them resized. Not worth it. I only use aftermarket rods now, it's really really cheap insurance.
You'll need to put the caps on the rods without bearings. Make sure the bores match, in other words, where the big end of the rod meets the cap, it is smooth. Look real closely, get your magnifying glass out if your eyes are as close to fifty as mine, see the hone marks? Do they meet and match top to bottom? If there's any problem seen, try switching them around until they match correctly.
I bet Dennis wins "best answer" on this one.

[imamachine]

Originally Posted by Dennis Texas I think you have some wrong ideas about this. If your motor was truly rebuilt when engine is primed with oil and lets make this easy use the flywheel, you should be able to rotate without much issues with the spark plugs out.

I don't have the head or flywheel on. After reading the previous post with the attached link I think I may be making a bigger deal out of this than I need to. but I definitely will go back and check all of the clearances and the hone marks on the rods. Ugh, I bought this damn thing so I didn't have to worry about all of this. Again, thanks for the responses, I appreciate it!