Al2011

I noticed the piston to rod orientation is wrong. The side where the bearing is offset faces the other rod instead of the crankshaft counter weight. I read that the offset side goes towards the counterweight to clear the journal radius. Some say it matter others say it doesn't. Should I go back to the machine shop??

https://classicoldsmobile.com/forums...ientation.html

http://speedtalk.com/forum/viewtopic.php?t=8315

Piston To Rod Orientation On
Oldsmobile V-8 Engines

AERA members have reported confusion over piston to rod orientation on Oldsmobile V-8 engines. The confusion centers around the fact that not all Oldsmobile V-8 connecting rods have squirt holes at the parting lines. It has also been reported that engines using the later type connecting rod without the squirt hole have random piston to rod orientation.

When using connecting rods with a squirt hole, assemble the piston to the rod with the squirt hole facing the center (inboard) of the engine.

When using connecting rods without squirt holes, there is no specified piston to rod orientation. Because these rods have neither a squirt hole or front and rear side, they can be assembled to the pistons at random. For purposes of uniformity, it is recommended that a specific procedure be adopted for assembling this type of rod to the pistons. A good choice would be with bearing
tangs to the outside of the engine, which is common with other GM engines.

The AERA Technical Committee

Al2011

My rods do not have a squirt hole as they say some do.

cutlassefi

Then it shouldn't matter. The crank journals are undercut at the radius unless they've been ground much further.
Install one piston, then look at how the rod bearing sits on the journal, it should have enough clearance for the radius/undercut.

Sampson

This is a question that has been bothering me ever since I put the engine together. (Not started yet but in the car). Would the same be true for a 350? I installed pistons with notch to the front, but did not pay attention to rod orientation. I am not sure about the squirt hole but do not remember any holes,in rod or bearing other than oil journal hole. Any suggestions?

Al2011

Thank you Cutlassefi (Mark). You've been so helpful throughout my build. When I first started the build I thought I knew enough to build it in two days. 1 year later i'm still at it. Anyone who needs camshaft contact Cutlassefi for a custom grind for a good price and fast service. You are appreciated!!

joades

I just started the teardown on a 1973 455 rebuild and I noted that the rods all have the bearing slightly offset. The side with the larger gap or relief side was installed facing the front of the engine on every rod. I have every reason to believe that this engine is factory original. Does this sound right you guys? I took some time and documented the removal with photos as I have seen a lot of discussion around how to orient these going back in. I'd rather not be guessing....so photos....just wanted to grab some opinions to ensure this is right.

cutlassefi

joades

So all of the larger gap sizes should face the journals and the sides with less gap are the side where the rods face each other.? Could the factory have done it wrong or should I be resigned to the fact that someone has been in this engine before?

64Rocket

Rods with squirt holes go to the inside, ( some say facing the cam}
without squirt holes, the bearing tangs go to the inside, just as if it had squirt holes.
super easy...

Gene

Al2011

My macinist installed the pistons on the rods like a Chevy. Tangs towards the oil pan and valve pockets in the wrong location. The rods were also resized with ARP bolts. Question: Since the rods were resized do they have to go back in their original stamped location? #2 If they can be moved around will my balance be totally screwed up for a street car low to mid RPM no more than 5500 RPM rearly during burnouts. I measured rod and piston combo #1 & #2 the weight difference was about 10 grams. All the clearances are the same for all rod jounals. I've attached the clearnce sheet. I really don't feel like going back to another machine shop but I also want a long lasting reliable motor. Thanks for looking!!

joades

I looked again at how my rods came out and based on some of the other posts that I have found believe that they were in wrong. They came out with all of the larger gaps of the bearing offsets facing forward. If I change this to an orientation that has all of the tangs facing the cam this will put every large side of the offset facing the crank journal (opposite of the rod next to it). This the right summary? You would not think this would be such a discussion, but the rod bearings are definitely offset which makes me believe it matters in the end.

wls559

So how did it turn out, I am going through this problem with the machine shop that mated my rods to my Hypereuteptic pistons! I have a thread on it. My shop put 7 of 8 tangs outboard and 1 of 8 inboard. 1 piston was done correctly! 7 wrong. When I orientated my rods correctly 7 of my quenches were down!

joades

My machine shop agrees with me and stated that the offset side of the bearing should face the crank journal for all of the rods. This means that each rod pair has the non-offset sides facing each other. That is how he is setting up my pistons when they arrive next week.

Octania

As I understand it, the bearings are offset, if they are, in order to accommodate a generous radius from rod journal to crank.

If the crank has a radius there, you better have room for it in the rod by moving the bearing over a little... therefore on each pair of adjacent rods, the bearings reside close to the other rod, and farther from the crank. That is, odd cylinders 1-3-5-7 have the rod bearing gap forward, and 2-4-6-8 rods have the bearing gap to the aft side.

If the crank has no rod journal end radius, or an undercut, then it can't matter much which way 'round the rods are mounted, unless they have a spurt hole, in which case we know what to do- oil the cam with 'em.

TripDeuces

Not really part of this topic but it was brought up.
I've never seen rod bearings with a relief in them for the oil squirt holes. Does oil really squirt through that hole or is it bs and have another purpose?