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Old 05-17-2003, 10:55 PM
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Post 355 stiff rotating assembly

I just put my block back together well, to an extent. I have the crank in and the rods and pistons attached. the only way I can turn this over is with a pry bar in the flexplate. It dosnt take much effort with the pry bar but im told the flexplate should turn it with out prying. I was wondering though if my forged pistons and new rods might make things stiffer. I know the forged pistons fit the bore differently than the hyps or cast could this be why or maybe the rod bolts havent stretched fully and are overly tight. I dont know how tight the assembly should feel as before this all my engines were 70,000 + assemblys. those turned easy. some a little too easy. I have a good deal of oil on my cyl. walls and I used moly graphite assembly lube. also what can I do about a scratch on a rod journal, my friend managed to ding the cap on it and scratched it what will this lead to? other than bearing wear? The crank is a chevy hd forged crank alredy at .010 .010 I dont have the cash to have it turned again, any other fixes. thanks for your time.

[ May 19, 2003: Message edited by: Jared ]</p>

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Old 05-18-2003, 04:08 AM
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I always check the rotation as I assemble in case something gets tight,then I know what caused it. You said that the pistons were forged, did the machinist have the pistons and specs when he bored, forged pistons require more clearance. The description you gave doesn't really tell how much effort is required. Have you used an old style (BCC, before click-click)torque wrench to see exactly how much torque is required? It may be fine, but too tight a bore can cause those problems and that's why I asked about the clearance when bored.
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Old 05-18-2003, 04:38 AM
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if you look at your rod bearing you may see a scratch. you should buff the bearing with scotch brite and have the journal polished. i build a few engs and always ck clearences before i do final assy. i use a set 24 ft lbs of torque on my short blocks, minus the cam, it usually runs about 18 lbs. never had a bearing failure or scuffed piston in over 500 engs. just my 2 cents. thanks.
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Old 05-18-2003, 07:16 AM
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the shop had the pistons when they bored it. It takes just a bit more power to turn over than i can provied with my hands. when I assembled it it got a little tigher with every rod. how ever with all the rods on there and not torqued just snug it isnt easy to turn. I have had to torque and loosen a lot, arp says 5 times to get proper rod bolt stretch. How much does it cost to get one journal polished? thanks again. sorry for the choppy responce i just woke up, off to work yay fun

[ May 18, 2003: Message edited by: Jared ]</p>
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Old 05-18-2003, 07:31 AM
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If you just have a nick polish it yourself, all you need to worry about is the high spot.
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Old 05-18-2003, 06:36 PM
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Put a torque wrench on the front pulley bolt and measure the reading. then post back. I not real sure that what you are describing is abnormal. All my engines are hard to turn.
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Old 05-18-2003, 07:40 PM
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I have never seen a new engine you can turn with your hands. It is not abnorml. I have a home built spacer in place of the balancer and use the balancer bolt to turn the engine. I would suggest this to you. Then you can get a torque reading like mentioned above. The finish left in the bores will cause the rings to have alot of friction. This is what breaks them in on startup.

As for the nick in the crank you need to fix it and replace the bearing. You can use a very fFINE file and VERY CAREFULLY file out the high spot. When you get the high spot off, finish it with the finest emery clothe you can buy. Tear a 1/8 inch strip of the cloth and wrap it around the journal. Put some engine oil on the journal and work the cloth back and forth until any small rises in the journal are removed. Now polish with a high speed buffer.

If you dont feel comfortable with the above, or this is a super high output engine I would take it to a machinist. I have used the above procedure many times before with no problems, but it was always on street stuff and used parts. For a race engine, I would not do this.

Chris
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Old 05-18-2003, 07:48 PM
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your hard turning engine may also be because of ring drag, if the block was honed with medium stones and not fine or cork honed you will notice qiute a bit of drag, also if you use standard tension cast rings you will also get more drag. As long as you have bearing clearance and rod side play is within specs, don't worry about ring drag, it will go away as the engine breaks in.
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Old 05-18-2003, 08:58 PM
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Ok new news, i rechecked all my rods my no.4 rod is freezing when torqued. i loosen it and i can turn it over by hand. its bearing is wearing just from me trying to turn it over. The scratch is on my no.7 I think I will bring it in and have it polished again especily on the no.4. The bearings are all made for a .010 undercut so thats not the problem. The no.4 measures out at 1.191 thats just with a caliper though dont know how accurate that was. Is that far off? I dont know what the stock measurement was so i have no base. I have a 5140 forged crank would it be worth it to have it renitrated? it was when it was at stock. I am thinking I should just get it re cut except on the mains since there fine as is at .010 and just have the rod journals cut to .020, if possible and get it nitrated, that should be as strong or stronger than the .010 cut w/o nitrating(right?). I am sick of the crank problems I am having. This is the first new bottom end I have built and I am alredy sick of it. I did a bunch of stock ones and havent had a problem, why must this happen when i have some money into it? I will need at least 2 new rod bearings so I wouldnt loose much there. why not just clean it up and restart fresh.
With out the no.4 it breaks loose and spins at around 25-30 ft lbs. Thats on the inaccurate pointer type torque wrench. any ideas would help thanks for your time. ps for the measurement its a 350 chevy.
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Old 09-02-2003, 06:20 PM
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Hey guy think back when did it get hard to turn the crank. If you cant't remember take it back apart until you find when it gets hard to turn. Also, check all your main caps there are arrows they point forward. Let me know Bryan
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