Need that extra edge for competitive hill-climb competition or other? Carl’s Performance 685 big bore kit is the next step up from our popular 660 kit. By installing this kit you will gain 1 to 2 sled lengths over our 660 kit by adding more off the bottom. It’s just what the doctor ordered when hill climb racing—more acceleration out of the hole.

For the 685 kit, along with ported big bore cylinders, Carl’s bores and ports the cases and utilizes Pro-X pistons. The kit runs on pump gas, although a race version using race fuel can be built for competition only use. If you’re searching for that extra advantage on the competition, the 685 kit is the answer.

The 685 kit includes boring and porting your cylinders and cases, head and power valve modifications, new piston kits and all necessary gaskets.

Price listed applies to approved cylinder exchange only. This requires sending us your cylinders for approval. We then substitute pre-done kit cylinders from our inventory for your kit. Price is higher if you plan to purchase new cylinders for use in your kit.