I recently bought a 350 off a guy who said it was just rebuilt and never fired. when i got it home, i tore the heads off of it and to my surprise, the pistons werent facing the same way. im not real smart when it comes to engines, but i thought all of the notches on the side of the pistons were supposed to face the front of the motor. well some are facing the front and some are facing the back. the rods match up w/ the pistons so the rods are not facing the correct way on the crank either. the motor will turn over fine, but will this create a problem if i drop the engine in my car like this?

Are they all facing the same way on the same side of the block? I mean, all facing the rear on the drivers side, and the front on the passenger side?? Are they flat tops with the 4 valve reliefs? The tangs on the rods should face the crank, not each other, if I remember right.

i would not run this engine. yes the "tangs" on the rods should face the crank not each other!!!!!! if you look the bearing is not in the center of the rod. it's looks off to one side and the rod has more room on the 'tang' side to make room for the slight bevald edge on the crank. if you put the tangs facing eachother they will make noise and you wont have proper rod end play...but the engine will still turn over!!! as for the pistons ALL DOTS point to the front of the motor. there is a thing called the thrust side off the piston and the non thrust side of the piston!!!!! the thrust side will be the side of the piston that the skirt faces out ( like to the headers ) the non thrust side is the side with the skirt that faces in ( like to the intake side ) the engine might run but not to long i don't think. you should pull the pistons out and have a shop flip them for you.

Please post pics of the engine and we can help you. :cool:

Smitty,
Without some pictures or more details, it sounds to me like you need to have someone look at it that knows what they are looking at. All of the notches on the pistons should be facing the front of the engine. If they are not, and the engine still turns over ok, then it sounds like they put half of the pistons on backwards. 99% of the time, if you put the rods in wrong, the engine will not turn over.

Like I said, you need to have somebody look at it. It would help if you filled out your profile so we would know where you are located, then we might be able to suggest someone close to you to help.

i went ahead and flipped the pistons myself. i reused the rod bearings???is that ok? is it ok to retorque rod bearings...i don't think that the motor hasn't been started yet. i was told by jegs that it was ok to re-use them so i went ahead and did it w/ out replacing them. is that ok? also, when timing an engine w/ a gear drive, the dot on the crank gear has to be at the very top, and the dot on the cam gear has to be at the very bottom, and they have to line up, right? what happens if they line up semi close but not dead center? i played around w/ it for a while and could never get them to line up perfect, but fairly close. will the motor run ok?

If i were you i'd take this motor apart, take it to a competant engine builder and have them measure everything. Money well spent.
Sounds like whoever put this motor together didn't have a clue and it's now your problem.

when you flipped the pistons. what did that do to the rods. tangs have to face out !!!!!!!!!! no you didnt hurt the rod bearings by takin the rod out and puttin it back in. as long as it is clean and lubed. do you know what tangs we are talking about? it is important that they face out. does anyone have a pic. to post.

i went ahead and flipped the pistons myself. i reused the rod bearings???is that ok? is it ok to retorque rod bearings...i don't think that the motor hasn't been started yet. i was told by jegs that it was ok to re-use them so i went ahead and did it w/ out replacing them. is that ok? also, when timing an engine w/ a gear drive, the dot on the crank gear has to be at the very top, and the dot on the cam gear has to be at the very bottom, and they have to line up, right? what happens if they line up semi close but not dead center? i played around w/ it for a while and could never get them to line up perfect, but fairly close. will the motor run ok?
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What do you mean by you flipped the pistons yourself?
Did you just turn the pistons around in the bores?
You need to be sure the piston is installed on the rod correctly.
As the above posts states, rod orientation is very important.

On a Chevrolet engine the piston needs to be installed on the rod with the bearing tang on the rod facing down or towards you so you can see it when your piston notch is facing forward,,

In other words the tangs will be to the outside or pan rail side (away from the cam side) in a Chevrolet engine & the "notch" on the piston needs to face the front if it has one.

As Bill stated, you need to take this to a competent machinist or someone who does this & let them check that everything is correct.

Also, as was correctly stated, the bearings are not centered in the rod, they are offset so when installed correctly they will be almost touching each other where the two rods meet & away from the fillet side of the rod journal.

I would also suggest that you put down your wrenches,, back away from the tool box & buy the book entitled How to Rebuild Your Small block Chevrolet & read it cover to cover a few times. :D

Lot's of very good basic information in it. A few things have changed since it was written like over oiling the pistons & rings due to the surface finishes & ring quality of today but overall good basic info complete with pictures :D
Another outstanding book is "Engine Service" by Gary Lewis (no relation) & goes into a lot of detail about what goes on in a machine shop including the correct way to install pistons on rods, both "pressed" & floating.
He is or was an instructor at DeAnza college,, good people with a lot of good info

i got instructions from jegs. i just loosened the rods that were facing the wrong way, tapped the pistons out. then i turned them the right way, using a ring compressor i pounded them back in and put the rod cap back on....tangs facing out. i see now how important it is to have the tangs facing out b/c of the bevelled edge of the rod. i made sure the bearings and the crank looked ok, then torqued the rods back together. pretty sure i did it right, jegs told me that it wasn't really that hard to do, and it wasn't all that bad.

thats good! sounds like you got lucky.you didn't have to have the rods pressed off the pistons and turned around so as long as all the pistons are pointed to the front and all the "tangs" are pointed out...... you sound like you are ready to run!!!

The Machinist that did my old junk301 put ALL my pistons on backwards to get a better pin offset!!

Sure, it slapped a liitle cold but was fine once warmed up..

pdq67