Crank/Pistons Lock up.. Help- Im building

ok something like this happened to me when i built the motor in my sig. somebody told me that the main thrust bearing goes on the first main cap like a chevy, maybe the last. either one was wrong. anyway, that put the whole assembly out of allignment and i could not turn the motor over without a breakover bar. i called my machine shop and he said that the thrust bearing goes on #3 main cap. so i took every bearing back off and had to replace them as well as get my crank turned.

Notched said:

i got brand new bearins, and oiled all the bearing that touch the crank..

help please!!!!!

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You did everything fine for the assembly, what are you using for lube? did you lube all the right areas? did you check you main cap tolerances? connecting rod to crank tolerances?

Make sure you didnt get your rod caps mixed up and put them on different rods. This will make a difference in most cases. Also, the deeper groove on the side of the rod goes against the crank counter weight....for better oil control.

CHECK ALL CLEARENCES!!!!!! Never skip that step, if you don't it will get you in the long run. Check what Mizark347 said as well. I know people that have put the rod cap on facing the wrong way and it causes binding and next to nothing for oil control. Never mix them up either.... both rod and main caps.

Definitly check all the tolerances,, main and rod bearings, rod side clearance, thrust, etc.... all are very important and should not be skipped. I'd use a good assembly lube on the bearings and surfaces to ensure good protection while you are assembling.

Are you use file to fit rings?

3rd vote for checking clearances. Especially (but not limited to) bearing clearances (main & rod journals) & connecting rod side clearances.

Did you have the block align honed? If not, it's possible that you've torqued the crank into a slight bind that doesn't show up until some of the rods are torqued at the outer radius of the crank. If it is in a bind it it might not be enough to affect it with no rods in. But the further away from the centerline you go, the more it'll show up.

Definately check your clearances. Measure everything. I just built up a brand new block and found that the mains were not equal from one side of the main to the other. Endedn up needing a line hone to stop it from siezing up with the coated bearings.

-Craig

There are a few too many factors that we don't know to give you all the proper specs. We can give you general information, but you need specifics. Some of the things we don't know: What kind of machine work was done to the block in preparation for rebuild? What kind of parts are we building with- stock, cheap aftermarket or quality race parts? If stock rods, were they reconditioned? Was the factory crank ground & polished? What kind of bearings are you using? What application will this motor be used for: N/A, nitrous, boost, daily driver? How many rpms will this motor need to turn: 5500, 6250, 7500?

Some precision measuring tools that you will need: bore micrometer, outside micrometer, feeler guages & a rod vise.

I'd recommend investing in a few books. No matter what you read on internet forums, it's always nice to have it in print when you go to do the work.

I'd suggest these 2 for starters: How to Rebuild Small Block Fords & the Engine Builder's Handbook. both of these are published by HP Books.

I'll try to get you started. Clean the backside of all your bearings with some 2+2. Assemble the rod bearings in the rods w/caps fingertight. Hold the rods with the rod vise and torque the caps. Remove the rods from the vice and measure the inside diameter of the bearings using the bore mic. Take measurements at 3-4 different spots around the bearing. Do this at each edge and around the center to verify that the bearing is 'true'. Write down your measurement for each rod.
Now using your outside mic, measure the rod journals on the crankshaft. Again, measuring at each edge and the center, 3-4 different spots around the journal. Write down these measurements. It'll help if you keep your rod measurements in order and then you can put the journal measurements write down along side. The difference in the diameter of the rod bearings and the rod journals is your clearance. I don't know what the specs are for what you're building. Probably somewhere in the range of .003"-.006".

You can use the same process for clearancing the main bearings. And the specs for those should be about the same. They could be more, but the most likely will not be less than .003" unless you're building a serious performance motor.

I know you're on a tight budget, but those books I mentioned will be invaluable to you now & in the future. Both of these books are available from Summit: Book 1 & Book 2 or checkout your local bookstore.

BTW, where are you located?

Please forgive me for any technical inaccuracies, it's 4:00am and I still have 3 more hours to go.

Make sure on the big end of the connecting rod that the tapered side faces outward from crank journal (toward the counterweight). If the pistons are installed backwards on the rods the flat side will fall on the slightly raised portion at the outside of the journal and could lock it up.

Notched said:

i looked at the rod cap... by taper, u mean, the side that is angled out (and has more room on the side of the bearing??)

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I think you got it. Hard to describe.

Go out and get some good assembly lube and use it liberally on the bearings, most auto parts sell it, Clevitte bearing guard, Holley, ARP, Redline, etc... this will keep the bearings from getting scratched. Also make sure everything is very clean before installation.

No, the tapered side has to face out toward the counterweight. Also definately use assembly lube. I assumed you were.

Personally, I think you should stop where you are. Don't buy anymore parts or borrow any tools.

Then you should buy the 2 books, wait for them to arrive, read them cover to cover (at least once, more if necessary). And then go back to square one and restart your project with your improved knowledge, making educated decisions instead of using magazine guesswork. JMO.

I think you're only about 2-1/2 hrs from me. If I had more free time on my hands, I'd be willing to come up and lend a hand and probably some tools. But as it is, I've got my own ongoing project that I can't seem to keep up with.

Will if you didn't take the pistons off the rods then you alos had them facing the wrong way with the rod turned around.

Most local machine shoips would charge less then $300 to assemble that complete shortblock for you...