what do you guys recomend for a stock banshee with toomie pipes and an open air box. crank is not welded. live at 3200 feet. my shop recomends the 19cc domes on pump gas. iwant to run pump gas only. thanx for any input

 

Peewee:

I have a ported/polished banshee with a coolhead. I run 18cc domes, but must use Race Gas.

I called Pro Design when I originally put the coolhead on. The owner of the company told me anything below 21cc requires Race Gas. At a minimum, 21cc to 19cc domes requires a 50-50 mix of Race Gas and Premium pump gas. Anything below 19cc domes takes Race Gas only.

I run Sunoco Purple (leaded 110 octane).

Without the high octane of Race Gas, the high compression created by the domes will cause the engine to detonate early, thereby increasing the chances of burning a hole in your piston.

I would go with the 22cc domes if I were running Pump gas only. The little bit of performance difference between the 21cc and 19cc domes wouldn't be worth the risk of burning up my engine.

Call Pro Design and ask to speak with the owner. He is very friendly and will provide you with all of the info you will need.

Good luck!

 

Pump gas works fine with the 19cc domes. Anything smaller, and you will need pump gas. The 19's will give you around 155lbs of compression. Your crank should be welded, but it isnt totaly necessary. Inwould however run the highest octane pump fuel available.

 

I just blew a hole in my piston. Was using the 19 domes. My compresion at 5000 ft. was 140 on a fresh rebuild. It blew up riding at 6000 ft. It had been running great for the first six hours with no indication of any problems. Was going wide open around a bowl when I heard a bang.
I would like to know why Pro Design doesn't include the compression info when they sell their product. CT Racing, Trinity Racing, and Yamaha of Arizona all sold me 19 domes without saying anything about race gas.

 

why would this engine blow up. was it to lean or was it because of the 19cc domes. i dont understand. a stock banshee at sealevel has 130 lbs comp. 10 more lbs shouldnt make it blow up should it. i put the 19cc domes in mine and have 139-137 lbs of comp. at 3200 feet. im scared to take it out though.

 

I defer to my above Thread reply. Free1seteven....sorry bout' the engine!

 

Your engine blew because of a lean condition, not because you were not running race fuel. There is absolutely no need to run race fuel with 140lbs of compression.