s10 engine rebuild question : pistons

Rebuilding a 4.3 Cevy 91 S10, when I installed the crankshaft I was able to turn it by hand after the torque., after I started installing the pistons I noticed I could not turn the engine anymore by hand. The book says I should be able to turn it by hand to check for binding, Does it matter what pistons go in which cylinder? I did match up the bearing caps to the rods via the lettering on each. I would think it should get harder to turn since it has new rings but I can not turn it at all anymore by hand. take a wrench to turn it now and its hard to turn.

Each piston is facing the front. I have a new rebuild kit I am using.

what are the markings on each piston for?
I have 2 marked A, 1 B, 1 C, 1 L,1 M.

btroy

Did you forget to use assembly lube on the jornals? you have to remeber if theres new main/rod bearings it going to be harder to turn, they are not broken in yet

yes I did use assembly lube.

Does it matter what pistons go in which cylinder? I would not think so?

what are the markings on each piston for?
I have 2 marked A, 1 B, 1 C, 1 L,1 M. Are they relevent?

I did not disconnect the rods from the pistons either. This is basically a re-ring, new lifters, oil pump, bearings, etc..

Did you forget to use assembly lube on the jornals? you have to remeber if theres new main/rod bearings it going to be harder to turn, they are not broken in yet

Re: s10 engine rebuild question : pistons


Quote: Originally Posted by compmikey I always scribe a number in the rod cap indicating which cylinder the piston/rod assembly is coming from. I suppose you could get the mixed up and be okay. but the side of the engine that they came from is important too. Looking closely at the rod bearing you'll see where the two bearing halves come together, forming what the old timers call the oil-slinger hole. This side of the rod should face the cam when installed.
mv



Ok, I took the pistons back out and see the rod caps have different lenghts of weight on the cap its self. Meaning 2 rod caps have a shorter center piece, 2 with medium center piece and 2 with longer centers. I hope you understand that? Anyway do the shortest of the rod caps go to the front or to the back of the engine? I would assume the medium would go in the center cylinders.

thanks

You should have numbered the rods before removing them from the engine! YES, it matters where they are. I am not too familiar with these V6 engines as I haven't torn one down in a while, and that was a 3.8 (229) back in 1989.

The 'center piece' things that you refer to as having different sizes - these are called 'machine pads' and they function to allow the rods to be balanced to their particular cylinder. Weight is removed from the rods by machining these down. You cannot tell what cylinders the rods came out of by looking at the pads. ALSO - if you mixed the rod caps up so they are not with their original rods, stop right now, take the rods down and have them resized as they won't otherwise work. The rod caps MUST be installed on the rod they came off of, ONLY. This may be your issue. If not-

In small block V8s, the rods are offset and the small of the offset goes toward the center, with the large of the offset to the outside - in other words, the rods are installed as close together as possible. Put these in backward, and they bind. The V6 is a bit different due to the offset-ground crank journals, but I would think a similar rule would apply.

Also, note that the dots/marks/arrows on the pistons always orient toward the front of the block.

Do note however, that due to the honing of the bores and with the new pistons and rings, a properly assembled engine is going to be difficult to turn by hand once all of the pistons are installed. This is due to the friction of the rings against a rough cylinder bore surface, and is normal.

Except for the offset ground rod journals on the crank, all the conventions applicable to a SBC V-8 apply to the 262 V-6.

Silicon is correct. Unless the rod caps are match-marked to their respective rods, the entire set now needs to be resized. It won't hurt to check the static balance, either. If you're going to spin the engine up past 5,000 RPM regularly, crank balancing (with the rod/piston weights) is also a good idea.

FWIW, I've never been able to turn a rebuild by hand at the crank. If the flywheel or flexplate is installed, that can be used to turn the assembly. You also have the option of using a crank socket.

http://72.19.213.157/files/SBCCaseFront01.jpg

Then again, you can "cheat" by connecting the starter and polishing it up that way:

SBC Cranking Video (http://http://www.finemotorcars.org/files/SBCCrank.mov)

I have the rods and rod caps lined up from when I took them off.

Just need to know what pistons go in which cylinders. Typically does the rod caps with the most machine pads weight go to the front of the crank or the back?

Thanks

Except for the offset ground rod journals on the crank, all the conventions applicable to a SBC V-8 apply to the 262 V-6.

Silicon is correct. Unless the rod caps are match-marked to their respective rods, the entire set now needs to be resized. It won't hurt to check the static balance, either. If you're going to spin the engine up past 5,000 RPM regularly, crank balancing (with the rod/piston weights) is also a good idea.

FWIW, I've never been able to turn a rebuild by hand at the crank. If the flywheel or flexplate is installed, that can be used to turn the assembly. You also have the option of using a crank socket.



Then again, you can "cheat" by connecting the starter and polishing it up that way:

SBC Cranking Video (http://http://www.finemotorcars.org/files/SBCCrank.mov)

Got it, after re-reading your post it makes since now.
THANKS!!!!

Troy


You should have numbered the rods before removing them from the engine! YES, it matters where they are. I am not too familiar with these V6 engines as I haven't torn one down in a while, and that was a 3.8 (229) back in 1989.

The 'center piece' things that you refer to as having different sizes - these are called 'machine pads' and they function to allow the rods to be balanced to their particular cylinder. Weight is removed from the rods by machining these down. You cannot tell what cylinders the rods came out of by looking at the pads. ALSO - if you mixed the rod caps up so they are not with their original rods, stop right now, take the rods down and have them resized as they won't otherwise work. The rod caps MUST be installed on the rod they came off of, ONLY. This may be your issue. If not-

In small block V8s, the rods are offset and the small of the offset goes toward the center, with the large of the offset to the outside - in other words, the rods are installed as close together as possible. Put these in backward, and they bind. The V6 is a bit different due to the offset-ground crank journals, but I would think a similar rule would apply.

Also, note that the dots/marks/arrows on the pistons always orient toward the front of the block.

Do note however, that due to the honing of the bores and with the new pistons and rings, a properly assembled engine is going to be difficult to turn by hand once all of the pistons are installed. This is due to the friction of the rings against a rough cylinder bore surface, and is normal.