Hey guys so I have a sbc 350 I've been working on I striped it all down had it cleaned and honed and what not got all new bearings, pistons and rings the works I recently started re assembling it I got the crank back in the rods and pistons are back in it as well the the problem is with all that back in it it is incredably hard to turn it over by hand even with a bar the specs I have say that the rods get torqued down to 45 ft lbs but if I do that I can't move it as soon as I back the nuts off it immediately frees up. IS it normal to be so hard to move the pistons and assembly when it's all torqued? or do I have something wrong going on here any help would be great
Did you keep the rod caps together with the rod that they came off of?
They are sized together and can not be mixed up.
Also, the chamfered side of the rod goes outboard on the journal. And the pistons need to be in the right orientation on the rods. 4 forward facing chamfers, four rear facing.
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Did the crank spin freely before you added the rods and pistons?
The main bearing caps need to be numbered (if they aren't already) so they can be re-installed in the same position and location they were before you took the engine apart.
If you didn't mix up the main bearing caps, then it sounds like you mixed up the rod bearing caps.
Each rod cap must be returned to the rod it was removed from (just like the main bearing caps).
All is not lost though, even if they have been mixed, it is still possible to determine where each part came from if you know what you are looking for and take your time.
Guaranteed this is what happened though.
Before the engine is taken apart, it is required that you stamp the rods and caps and the main caps with a number set for exactly this reason (again, assuming they haven't either been stamped by the factory or during a previous disassembly).
Take a very close look at the rods and the caps for a number that will range from 1 to 8 ... match the number 1 rod with the number 1 cap and so on.
-- Edited by DB Cooper on Tuesday 6th of May 2014 08:31:36 PM
Everything previous is very much valid. A couple of questions though, did you assemble the components dry...or did you use oil and/or assembly lube? Also did you stagger the ring gaps? By the way, what were the ring gaps?
To add what the other guys have said about getting the right caps on the right rods and mains, they also need to be turned the right way.
You can often tell by the bearing tabs, they are usually on opposite sides on the rods. In other words, you could turn the cap around 180 degrees. Take care and make sure you have it right.
If you can't figure out which way they should be, you should get the rods resized.
A well assembled engine without heads etc. should rotate at about 20 to 30# on a torque wrench on the front damper nut.
Race engine builders use a fish scale on the individual piston/rod/ring assemblies in the oiled bore and get it as low as possible, usually somewhere around 15# of pull on the fish scale.
You have something VERY seriously wrong.
Do not complete the engine until you have it rotating as I stated above.
If you do and start it up it will not last for 5 minutes before you spin a bearing or it seizes up completely.
One other thing that hasn't been mentioned, was the crank ground or polished? Was it a nominal size journal? Are you new bearings for nominal size journals or are they -.010"?
You have some serious binding happening there.
first off its nice that some on here are quick to point out how wrong you did it, why not first narrow it down to what exactley is binding? you say the rod bearings are causing it not to move? if this is a stock rebuild with no machining you dont need to plastigauge it. it could be oversized bearings on a stock crank. i would slack each one off at a time and find the cause, maybe the rings are tight in the bores like a tiger. i havent done a whole lot of engine building but the rotating assembly should turn by hand with some effort. one thing i do know, there should be enough play in the bearings you should be able to slightly rock the crank back and forth with some noticable movement in all the rod bearings.
-- Edited by fatstax on Tuesday 6th of May 2014 09:48:15 PM
ok - here is what I know of small blocks or any motor for that matter
when installing the crank - one must use plasti gauge or a micrometer to make sure you have clearances correct
one must snug down all main caps - but not overly tighten - then you take a rubber mallet and drive the crank forward and back several times - this squares the bearings, - and is a MUST - cuz if you dont - the crank will be hard to turn otherwise
next - did you check ring gap - if you are too tight - even on one piston , it will be hard to turn over, especially if the block was not bored with a block plate - as the piston moves up and down the bore - it will get tighter and looser, as the mains would have distorted the block when tightened. So ring clearance is VITAL
when you tightened the rods - did you rol lit over between torque steps? you must for the same reasons as the crank - to square the bearings
if you followed all of these things the motor should turn over with about 25 ft lbs torque - give or take
Sorry it's been so long since I've gotten on here and updated you guys on anything but anyways to get back to all your questions and surgestions yes I checked all bearing clearances ,gapped all the rings lubed cylinder walls the works I did it all. What it ended up being was a slightly bent conecting rod
I think Dick is saying "really" because this problem should have been discovered during assembly if the proper procedures were taken. This is how you learn.
-- Edited by hemi43 on Tuesday 3rd of June 2014 06:25:03 PM
