Hey 573,

Must be something wrong inside your 53 , 16000 rpm sad !!!!

I turn a 8.8x8.75 at 19200 rpm on the ground, my viper is good for 150+ mph.

You got to lift the exhaust timing - open the exhaust all the way- then stick a Jett pylon/racing short pipe with adapter, you may want to consider smoothing the exhaust transition in the adapter as I did on mine.

Next thing is get a 45 head and swap out the 53 , the 45 head has higher compresion, ( I have many rossi parts to mix and match )

Now get a carby off Jett with the largest ventury possible , I think mine was a 12 mm from memory, this will let the air in and still give you a good idle.

Plug is a siggp002 tuned pipe , sigg products and they are $6 bucks or so,

Fuel is 5% coolpower,

All this will wake your rossi up , I've been playing with these things for years and are a powerhouse engine if worked over.

My viper is for fun only , gave up racing due to the politics - that takes all the fun out of things.

Have fun .