Mick at John Sidney Racing referred me to another workshop when they realised that they were not able to push the pins out of the pistons. This morning I drove about 40 mins to go and get the pistons swapped over on the rods. The guys in the workshop were real nice fellas. First step was to separate the pistons from the rods.
After cleaning the pins and piston I reordered them to match the cylinder sizes as calculated. In order to get the pins back in you need to heat them with an oxy acetylene torch.
They made it look so easy. It makes a difference when you know what you are doing and have the right tools!
Time to balance the Piston/Rod assemblies. First I weighed each assembly. I also then made a jig in order to weigh each end and measure the weight distribution. The actual values are not important, but rather the relative values to understand the where the weight is for each assembly. I found the only way I could get a consistent reading was to place a steel weight on top of the piston to hold it frim in the Vee Block.
When it came to weighing the Piston end, I really struggled to get a repeatable result. I found that any twist or torsion on the scales affected the reading. I placed a couple of skewers under the Vee Block on the scales (to act as rollers) to eliminate any stress, and the numbers became repeatable!
The results were as follows (all weights in grams):
|Cylinder||Total||Big End||Piston End||Adjustment|
|2||1461||444||+7||1162||+4||-5 Big End|
|3||1458||445||+8||1161||+3||-3 Big End|
|4||1461||447||+10||1161||+3||-5 Big End|
|5||1457||440||+3||1158||0||-2 Big End|
|7||1460||445||+8||1166||+8||-2 Both Ends|
I worked out the adjustments required as shown in the right hand column of the table above. For the Piston end adjustments I enarged the drilled holes in the bottom of the pistons and also ground a little off of the webs. The Big Ends were pretty easy to adjust – I ground metal off using an angle grinder.
Once all of the adjustments were made, I weighed everything again. I can’t believe that I actually got them this close, but here it is.
|Cylinder||Total||Big End||Piston End|
It is interesting that number 5 is heavy at the Big End. Number 5 Piston and Rod were untouched so this is as it left the factory. I will take a couple of grams off of the Big End of number 5 to improve its balance.