2015 Challenge Series rules are published

[johngeorge]

The 2015 rules are out: https://nasa-assets.s3.amazonaws.com/document/document/345/FFR_2015_final.pdf

And the dyno form: https://nasaproracing.com/rules/factory_five_challenge_dyno_form.pdf

[Mark Dougherty]

Thanks
John

[FFRSpec72]

Some subtle but very nice changes, the crankshaft is a nice change as I'm just redoing my short block and will go with a 28 oz imbalance. Also nice to see we have a alternative new block we can use that should be pretty strong.

[Mark Dougherty]

That new block comes with a price
added weight.

[Steve Powell]

Tony, why do you want to go with 28 oz? Don't be going to a longer stroke and cheating on me ;) .

[FFRSpec72]

Tony, why do you want to go with 28 oz? Don't be going to a longer stroke and cheating on me ;) .

One reason is that the rules now allow for any crank as long as it meets the metal type and weight and most of the forged cranks are 28oz imbalance, so easy to go to a forged crank now. The issue is that these engines are running 4-6K most of the time and the stock crank has some flex at those RPMs, so no stroking. I still can't find a reason why Ford switched between the 50 and 28oz imbalance on the same engine block

[Scargo]

Could you please explain this. Why would you want to run an imbalanced crank? What does 28oz have to do with it? This is puzzling to me.

[FFRSpec72]

Could you please explain this. Why would you want to run an imbalanced crank? What does 28oz have to do with it? This is puzzling to me.

Moving from 50oz to 28oz, the early 302 had a 28oz imbalance crank, they then moved to 50oz imbalance cranks, there is no advantage with the 28oz imbalance, I just had some parts that made the rebuild easier