is this a stock shortblock?

to my knowledge, gm doesn't balance any rotating assembly, aside from maybe the LS7, or LS9, idk.

so 5.x grams more weight on the big end of the rod might make things better or worse, either way, I doubt it's going to make that big of a deal. there are dozen's of guys in my area that put arp bolts in their stock block LS1 cars and have no issues, and they are no stranger to the abuse either.

 

hmmm..

Heres a picture of the counterweight balance drillings on my 03' LR4 Vortec 4800 out of my truck, correct me if i might be wrong, but those wouldn't be there unless it was dynamically spun and balanced with slung weight attached to the crank, would they?

My question is, do they batch together piston/rod assemblies according to closest weights, modify the slung weight on the balancer and install from there? Or are things far less technical than i think?

 

Here, bare with me on this little further, i thought this was interesting, using F=mv2/r according to Newton's third law of motion dealing with centripetal and centrifugal force an engine with a 5 gram heavy throw and a 4inch stroking crankshaft, 2 inch radius, spinning at 6000rpm converts roughly into 50 pounds of force per inch heavy on that stroke. Maybe someone else can try to calculate that out, my brain is starting to hurt.

F=mv2/r (Force = mass x velocity squared / radius)
I used some online calcs. to convert to lbs. etc, to make it more tangible.

 

I'm not sure about any "dynamic spin balancing" to my knowledge GM only did that on the syclone engines, supposedly (not sure of that, just what I heard)

all truck cranks are cast, forged, and machined (including drilling) to a given standard. meaning they drill the counter weights to mimic what they try to make every rod and piston assembly weigh.

the only control over rod weight is the mold that the molten powdered metal is poured in to, then hammered on, in a given set of dies. the big and small ends are machined accordingly, not to weight, but the size specs.

GM figures that their quality control is good enough to mass produce 10's of thousands of cranks each year, all of which are drilled to compensate for the weight of any of the 100-some odd thousand rods that are hammered in to existance in a production year.

the crank in your 4.8 has seen no different treatment concerning balance, than any other 4.8 built in '04. 5.3's would be different, given the larger (heavier) piston being used, but that's about all that's compensated for.


it would cost WAY to damn much money to dynamically balance every truck motor before installation. think of all the extra labor and machine work involved, when they can charge just as much, and not do it.

 

Yea, that was more or less what i was thinking, a somewhat "generic weight" that all cranks are balanced to. Have you ever weighed a set of rod/piston sets to see what they are like?

 

what year did they start putting in stronger bolts? I have read in a few places and build books that replacing the rod bolts is a recomendation even when keeping stock pistons and rods. but the book was printed in 01-02, I have a 05 lq4 and was planning on upgrading the rod bolts. but if it isn't needed then I wont worry about it, especially if it turns into another headache.
I'm planning on this thing spinning to 6500-6800ish, but not very often.

 

they started sometime in 2000 your 05 lq4 is updated.there are different opinons has how many rpms they can handle.some limit rpm to 6200,but others have gotten away with more. guess it depends on ifits your day or not

 

I have absolutely no idea. lol

I do machine work for a living, but have never machined an engine block before.

 

yea, would be interesting to know anyway, obviously gm's process is accurate enough to allow these motors to spin to 6000rpms + smoothly. You know an engine is pretty well balanced if you can set a glass of water on it, and it hardly ripples. Might have to pull them all out since its upside down right now and find out!

 

the 5th gen z06 had its rev limiter set at 6500 rpms from the factory. considering we only push our engines to 6000+ rpms once in a while I wouldn't worry about it. even once a day shouldn't kill it as long as you warm up your engine.