Club126UK
Fiat 126 Chat => Tuning & Customising 126 Models => Topic started by: Ray on October 02, 2013, 12:13:50 AM
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The engine Balancing is different from all other 2 cylinder I have seen and done the norm is a 50%to 90% over balance that is for a 50 % balance the weight of the big end plus half the weight of the small end plus half the weight of the piston and rings made into bob weight clamped to the big ends of the crank
I have a Steel billet Crank and light weight rods and this formula was not even close I set up the original 650 crank and rods I drove this car before pulling it apart and it was shaky at idle like normal but smooth through the rev range to as far as it would rev to I guess 6000 - 6500 rpm I had no tacho but up to valve bounce was smooth
The std fiat cranks are hollow and fill with oil when running so the weight of the oil needs to be factored in this is substantial amount and at least 50 to 50 grams I put a grease nipple into the plug in the crank and pumped it full of grease to simulate the weight of oil then added weight to the bob weights till i got balance the std engine is just a bit over only the weight of the big end on the rod just 15 grams more almost a a zero percentage balance I have never seen this before I read in the internet that people balance these engines at 37% 50% and 89% ..... 37% would be about right if no oil was factored as the extra 37% over std would be about the weight of the oil and would compensate almost for the oil I found that fiat actually use a nominal figure of a bob weight of 415 grams in the factory and this amount adds up to the weight of the oil plus the weight of the big end plus about 15 grams
The balance factor can vary if the revs increase but this balancing from the factory is unusual and I want my new engine to rev to at least 7500 rpm and the factory new what they were doing for sure and I am unsure which way to go I have contacted a few other balancing company's and they I am sure do not know what they are doing with the fiat 2 cylinder only one new to add the weight of the oil in and this is a huge amount a normal balance error for a race engine is less than 3 grams and the oil in the crank weights 50 -60 grams
Any idea of witch way to go
Regards Ray
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Hi Ray :welcome to the Forum Unfortunately most 126 owners don't get so involved in re-balancing engines the only person who maybe able to help answer your question is Steve who had his engine re-balanced before fitting the Turbo and Inter-cooler, You can PM him by clicking on his name "smallcox" Scroll down to his user name on this thread ;D
http://club126uk.co.uk/smf/index.php?topic=5006.0