Quote:
Originally Posted by Adrock
Thanks for the replies guys. So, my assumption is correct then? That the correct placement of rods from top to bottom is:
PULLEY
4
1
5
2
6
3
FLYWHEEL
?
My understanding of having my pistons and rods balanced is that the pistons, rods and pins are arranged so that they are matched to the closest matching weight opposing pistons, etc. My machine shop has gone through and numbered my parts 1 - 6.
I will call the machine shop today to confirm, but I believe that to setup the engine correctly - using the numbers on the parts, I should have the rods setup:
1 - 4
2 - 5
3 - 6
|
Somewhat of an old wife's tale here. You do have to go with what you are told, but a lot of that is similar to the flat earth society stuff.
The reciprocating parts (pistons, pins, clips and rings, and Rod SE) should be balanced equally to at least 0.5 grams of each other to a maximum and typically good balancing is to zero or 0.1gram.
So look at it this way, you match up the heaviest parts opposite each other on the crankshaft. If the parts were really heavy for example to make this point, what you are actually doing is inducing an in balance rocking motion along the length of the crank. In your case the parts are probably not that heavy and the difference slight, hopefully. An exaggerated example to explain the principle.
Have the parts balanced as close as possible and it should not matter. This is a dynamic balance and can be measured the same way any other crankshaft is balanced by adding bob weights. The bob weights if measured the same as the pistons weights etc., any in balance can be seen and the weights changed per journal to balance out the crank.
This is over the top but it is way of making sure. The point is, it is not required if the parts are balanced correctly. If the crank balance is checked at 350 RPM and is balanced and re checked up to 750 RPM, it will be dynamically balanced at 6000+ RPM. Same for the pistons etc.
With these engines, the crank can be balanced on its own without bob weights as it is expected that the parts attached to it are balanced equally. And Porsche cranks have 12 counter weights 2 per rod journal.
In some engines we change the weights on the crank to balance out any 2nd and higher order in balances, but this is done with V based engines.