Breakaway Torque for 304 Rotating Assembly

[jdcxyz]

Hi everyone, newbie here hoping for some advice from the gear heads. I'm doing a frame off restoration of my '79 CJ7 . Rebuilding the engine of course. Got my motor back from the machine shop last weekend. Had the motor line honed, balanced, crank ground,etc. Used a very reputable shop where I live. Dropped the crank in, all main oil clearances were checked with plastigage and within tolerance. Used plenty of assembly lube and torqued down the main caps. Crank rotated smoothly by hand. Checked ring gaps, indexed them correctly, oiled pistons and cylinder walls and installed pistons. Used new pistons but the old rods. Checked rod journal oil clearances and all were good. Rod side clearance was good. Used plenty of assembly lube. Obviously the rotating assembly got a little tighter as each piston went in. Once the final piston went in, it took about 90-100 ft lbs of torque to break the assembly, Once broken it took about 45 ft lbs to keep it spinning. Rotated very smoothly, no binding whatsoever. Put #1 at TDC and proceeded to install the cam and timing chain. Cam rotated very smoothly. Once the timing chain went on I could not break the assembly at all. Actually stretched the crank bolt trying to do so. Fortunately I didn't strip the crank. Removed the timing chain and still could not break it. So my question is should I be concerned, should I continue to assembly the motor and will the starter break everything loose? Or should I disassemble and use more lube, oil, etc?

Any insight would be greatly appreciated.

 

[jafo]

First. What was the crank turned at? .10/.10? Make sure you have the correct bearing set for what the crank was turned to. Something doesn't sound right. I would not go ahead with assembly until that is figured out. The engine should be stiff but shouldn't need that much to turn it over. Also, what torque wrench are you using? Torque wrenches can be off. What type of assembly lube? Ambient temp. At assembly? Make sure main caps are back where they used to be as well as rods to respective cylinders and rod caps back on exactly how they came apart. Could be several different things.

 

[jafo]

Oh, and if you can't figure it out, I'd be contacting the machine shop that did the work. It may not be a bad idea to do that first.

 

[Lumpy Grits]

Do you plastic-gage the con rods to the crank?
Did you oil the wrist pins?
LG

 

[jdcxyz]

Thanks for the response guys.

I'll check with the shop, not positive what the crank was ground at, but the machine shop said the bearings were matched to the grind. Used Torco assembly lube. Have a Craftsman torque wrench and had it checked at the shop and it was spot on. Temp in my garage is 50-55 degrees, have a small heater but it just keeps it from freezing.

All caps were correct, and crank spun freely with one hand. Once the pistons went in it spun smoothly, no binding it was just tight. The motor sat for two days before i got the cam in, that's when I couldn't break it. Plastigaged the rod journals and they were tight, but in tolerance. I actually did not oil the wrist pins, I was following the instructions in my Chilton and Haynes manuals, and neither mentioned that. Is it something I should have done? All pistons were installed correctly, and rods were on correct cylinders.

Thanks again!

 

[jafo]

If it moves in the engine, it needs lube. LG is right, wrist pins need oiled.

 

[Tinman22]

We have 5 motors in the shop right now. One just got finished for Christmas. 496 bbc 25ft/lb then 19ft/lb... 383 sbc 27 then 20...Lm7 5.3 heads on, yellow springs 31ft/lbs then 29..lq9 6.0 heads on same springs same numbers...and a worn out 350 for a derby car that rolls over at 12 lbs.

Ring package and cylinder finish can affect roll over numbers significantly. All of these are standard ring pacs except for the 496 which is gapless. The 5.3 gapped loose for nitrous.

Check piston orientation on rod. It wouldn’t be the first time a piston was pressed on the rod backwards. You said it got harder after cam and lifters. How easy did the lifters go in ? did you lube them ? Same for the cam. Lube the wrist pins. Lg is correct if it moves it needs lubed. How loose is the timing set? Is it new? I’ve seen sets that had tight spots when you turned them over.

 

[jdcxyz]

I had not put the lifters in at the time, timing set is brand new.

Looks like I'll be taking this thing apart!

 

[jdcxyz]

Well I tore this thing down. With all the pistons removed, the cam and timing set in place, the crank rotates with just a light touch. Nice and smooth. SO I decided to break out my micrometer and make some measurements. Measured the rod journals, and they were consistent at @2.065" which tells me that my crank is ground .030" under, the machine shop told me it had been ground before. I did an inside measurement of the rods with the bearings installed, rod bolts snug, but not torqued. They were consistent at @2.055". I'm not a machinist, but I'm thinking my machine shop gave me the wrong bearings. Simple math, but I think they may have ordered me bearings for a .040" under grind instead of a .030" under grind. Make sense or am I way off?

 

[Lumpy Grits]

I've seen shops do worst-Does sound like it's on their shoulders.
Tell'em you want to see the parts order sheet for your engine.
Also says you didn't plastic-gauge those bearings either.
LG

 

[jafo]

The back of the bearings should be marked what size they are. Should be on back of bearings down by one end.

 

[jdcxyz]

Thanks for the responses everyone, I got .030 under bearings from Sealed Power and this thing spins like a champ, with the entire valvetrain installed.

 

[Colorado Yeti]

Something is definitely wrong. I have had machine shops provide the wrong bearings for me in the past. Luckily I caught that before fully assembling the engine. As stated above, be sure the plastigauge all clearances again.