Engine – Day 2
When I build my engines, I’m aiming to meet basic VW tolerances as well as some other things I’ve learned from reading about engine building from the high-performance world.
While I would love every engine to have a completely balanced internal crankshaft with a balanced flywheel, that is just not practical living where I live and not having access to shops that can quickly and affordably do balanced systems.
But, there are still some things that I can do try to internally balance things for longer overall life and less wear.
I always balance my pistons (and wrist pins) as well as my rods. And in the previous engine builds I’ve added a counterweighted crank to help with the force balancing.
There’s still quite a bit I can do with the parts without having a case to start building on.
And since it is rare to get matching weighted parts, this is a critical basic step to preparation.
Pistons and Wrist Pins
I balance the pistons and wrist pins as a weighted unit down to the gram level.
(Yeah, I use a kitchen cooking scale. Someday I’ll have a more accurate scale.)
The key thing that once they are unpacked and weighed, they cannot be separated. It is fairly easy to not mix things up if I go along slowly and work on only 1 piece (or assembly) at a time.
There was a 3 gram difference between the lowest weigh and highest weigh piston/wrist pin assembly.
Piston 1 – 538g
Piston 2 – 537g
Piston 3 – 536g
Piston 4 – 535g
Within the next few days I’ll shave some internal metal off of Pistons 1 through 3 to get them down to the 535g of Piston 4.
Now there are different ways to do this, and someone doing a major blueprinted engine would do connecting rods by a special setup in which the big end (crankshaft end) gets weighed separately from the small end (piston end) but for the sake a basic stock engine, a cumulative total weight for the entire rod is fine.
I was surprised the rods were mostly matched.
Rod 1 – 549g
Rod 2 – 551g
Rod 3 – 549g
Rod 4 – 549g
I may need to reweigh them with the rod bearings in. I can’t recall if they need to be in or not.
If not, then I’ll remove 2 grams off of rod 2.
The goal will be to have 4 piston/pin/rod assemblies with matching 1084g weights.