Got the crank installed and all the mains torqued then went to put the pistons and rods in. I always place the flat side of the rod torward the front of the motor and never really pay attention to the dot on the top of the piston because they always co-ordinate with each other. Well, apparently when my machine shop installed the pistons on the rods, they installed four pistons backwards. I am curious if the the dot really matters? Im thinking it was a "production" thing to simplify their process and kinda "dummy proof" the assembly.

 

Dot on piston faces forward and tang on rod/bearing faces cam on even side 2,4,6,8, and tang faces pan rail on odd side 1,3,5,7. Confusing but that's how they do it. Not like a sbc, and BBC where all tangs face pan rail. When using aftermarket rods you usually will run it like the sbc.

 

what do you mean by tang? This is all factory stuff.

 

What year is the engine??? dot on piston should all ways face forward as mentioned even in the factory manual. If it is the early type pressed pin, the flat side of rod faces forward. If it is the later floating pin. The fatter side of the casting faces forward Which I believe the Dot on the rod faces backward.

 

Where tang on rod bearing fits it.

 

Exactly. Its the earlier style. i had 4.8 pistons installed on 5.3 rods but, when they pressed the pin into the rod, they used the "old school" method as stated before They installed four pistons one way and then the other four were pressed the other way.... If that makes since.

Thanks, i see what you are saying.

Decided to say F it and I installed them anyway. There is four pointing to the back of the motor and four pointing toward the front. The rod orientation are all the same and pointing the correct way. At this point if the thing blows up, i really dont give a ****. After all the pains i have had through machine shops i may cut a hole in the damn floorboard and fred flinstone this thing down the road. I dont understand how a "machine" shop can function and be so oblivious to details..... California Sucks California

 

Doesn't matter which way the rod is. This is somewhat unique to the LS engines, and not what we're used to. Just the way it is.

But the dot on the piston should be toward the front.

 

Thats interesting. Where did you hear this? IMHO opinion, the dot means nothing. The piston is symmetrical in every way, all the way around it, up and down. The only difference is the top.... which has a dot lol. The rods on the other hand, have two different surfaces that ride against each other if you put them the opposite way. I am more concerened with the rods.

 

I worked in GM dealer service departments for 14 years.

 

I have been told it's for orientation and have heard it does mater at least on the piston side.

I have been told the rods in these engines can be run back wards with out ill effect.

My self I am **** retentive and went back to machine shop and had them swapped. We "Discussed" it for atleast 10 minutes. I brought the Gm manual and explained that I simply wanted to do it the right way from the start. I have a good relationship with my machine shop so he let me help. At least that way if I made a mistake assembling it, I only have my self to blame.