bill_lee_3

I haven't been on here lately, but the other day, my engine blew and now I am having some problems with the new one.
My new motor is a 350 from a 69 camaro, with high nickel and magnesium content. It was rebuilt not too long ago, and doesn't even have an hours run time on it. The reason I bought it for only $150 is because when all the rod caps are tightened and torqued down, the engine won't turn over. I have narrowed it down to the number 6 cylinder. I took the rod cap off and checked the bearing, and it is marked as STD. I also pushed the piston away from the crank so I can get the other half of the bearing, it too is marked STD.
I thought that maybe they were just stamped wrong, so I got a new bearing. I got STD again. I put it all together and if tightened above 30 ft lbs. then it won't turn over.
Does anybody have any ideas for me?

87zjeff

iTrader: (4)

check you clearance in the bearing. the rod cap could be out of round were it rides on the crank. there could also be some kind of flaw on the crank.

OhioYJ

I actually just ran into this assembling my new motor, had one rod if you put it in the thing would not turn over for anything. I should have plastigauged all the rods, and not just a couple, after I plastigauged that one rod I found out the bearing tolerances where too tight, then I pulled that rod out and measured it, and sure enough its, 0.003" smaller than the rest. Ran it up to the machine shop this morning to have it en-larged some.

zracTA

only way to figure it out is to grab a good set of micrometers and go at it

Supervisor42

You might want to be carefull. I encountered a tight rod not long ago when I was helping a friend rebuilding a jeep engine.
We tend to measure the big end in line with the rod.
I measured it and the .002" that it was too tight, had been added to the rod end 90º to the axis of the rod. It had obviously been dropped while it was out of the engine, rendering it oval shaped. It was too wide across the parting line.
If I had it resized, it would have still been .002" too big widthwise which would have led to a spun bearing. Remember, you can't grind holes smaller.
We tossed the rod and got another used one...

funkdubie

i would (if it were me) take the time to move one of the other piston assemblies to that hole leaving out the one in question and retorque and see if it spins...time is free when doing it yourself..

bill_lee_3

I decided to take the rod cap off and exchange it for one that I knew was good. I just switched no. 5 and 6 rod caps. They are labeled so they were in the right order. After I switched them, i tightened both to 20 ft lbs and it turned over freely. I then retightened them to 35 and it still spun freely. I went back through and made sure they were all tightened to 45 ft lbs and tried it again. It spun freely. I'm not sure if when they put the engine back together if they mixed up the number 5 and 6 rods. I don't have any plastigage left, so I am going to pick some up at work tomorrow and check them out.