Date: Mon, 16 Dec 1996 20:14:45 -0800 From: Mike West Subject: Balancing CR. Long n' short jugs We covered finding the long and the short pistons and rods in the "Balancing" articles. All being in the name of a "balanced" Compression Ratio. Here's some more on the subject: "The long and short jugs". Having finally recieved an hours clear sky, I painted my jugs. Ala Hoover, tho I used paint thinner in lieu of gasoline. Then they sat on the oil heater for a week drying. It's cold and damp here so pay no mind to drying time. In sitting here looking at them, it occurred to me that they represent another stack of tolerances in the continued quest for the perfectly balanced CR. In fact, there is another stack out in the shop on the case where the jugs sit. The distance the spigot is from the center of the crank. The guy had to have some tolerance to work from, + - .005", .001, who knows? So there is a long and short spigot face also. Getting back to the jugs, I "miked" them. There's a + - .005 on them too. One as low as 4.430" and one up to 4.440". The other two are in beetween. It's not much again but it can help with the stack-up of the pistons and rods. It also might be worth-while to put the closest matches together since any difference will be a tweak in the heads when they're bolted on. On the spigot faces, I'd hate to start messing with that, tho it could be done. A little grinding could change them some. The caveat there tho, is what if you stick another set of jugs in later and the numbers run the other way? Looking at these volumetric balances: Assume a .005" difference on a stock jug of 85.5mm diameter. Running thru the numbers, that equates to .7 CC. That isn't too bad for the balance we're looking for but when it does the same thru four parts and gets into the .020" (.5mm) then you're looking at a couple, three, CC's. Plus the + - .5 CC you left in the combustion chamber. Any of it is livable but if you don't have to have it, why do so? Where do you draw the line on this stuff? Assume you have a car entered in the Baja 1000. How far will you go to get reliability and performance? The car won't see a repair shop for a thousand miles, or is it kilometers? Now assume you're "Jane Average" with 2 kids and just drive back and forth 30 miles to work every day. The car needs tires but Billy needs a doctor. That Baja racer will see complete refurbishment long before Janes "daily driver" will see an oil change. So who's the long distance runner? What about mileage? Does the racer with a sponsor need better gas mileage than Jane? She doesn't have a sponsor. "less you count food stamps. Every dollar spent for gas is money the kids can't eat. You get my drift here. So let's look at important from the point that it has to be running again no later than Tuesday. Balance the weights of the components and get the CG's of the rods the same. Take a look at the combustion chamber and keep it under 1 CC difference. After that it's all relatively minor improvements and tho the "beater" should have the best, the world doesn't work that way. In fact you really want to save some gas, re-build that howling transmission. That noise is horsepower leaks. west