Our Mission: At Mark Sullens E85 Carburetors, we build more than carburetors and E85 conversions. We build trust, relationships, and community. Our work is driven by real world racing experience and a deep passion for E85 performance.

Because focus wins races. We do not split our attention between methanal, gas, and E85.. By building E85 carburetors exclusively, every calibration, modification, and improvement is based on years of E85-only testing, racing, and customer feedback. That depth matters. 

Every carburetor is built one at a time. We are custom builders, we tailor each aspect of the carburetor to fit your needs. While we start from proven base calibrations, final setup is tailored to your engine combination, vehicle weight, gearing, and intended use. No two builds are exactly the same.

Yes. We offer E85 conversions for compatible carburetors. Conversions include internal modifications, calibration changes, and flow adjustments required for proper E85 operation. Not all carbs are good candidates. If it is not right, we will tell you 

Our calibrations are built from real racing data, not theory. They come from our own research and development plus years of feedback from customers winning at local tracks, national events, and world championships. We refine constantly. If E85 teaches us something new, we apply it.

Yes, when the carburetor is designed and calibrated correctly. E85 offers excellent charge cooling, detonation resistance, and repeatability. Many racers choose MSE85 for its performance advantages and long-term reliability. All E85 builders are not the  same. 

You get real support from real people. This is a family business, and our customers are part of that family. We stand behind our work, answer questions, and help you dial things in based on real-world results, not guesswork. We answer the phone when your at that track and need a answer ASAP.

 I began building gas carburetors in my teens, and our team has the skill, experience, and technology to do so. We have successfully built gas carburetors in the past; and will continue, however, our primary expertise and livelihood are centered around E85.   

Due to our ongoing and ever-evolving research and development, we recommend sending your carburetor to us every few years for a refresh and update. That said, if your carburetor is functioning properly and you are satisfied with its performance, there is no need to send it in. We do not want to change anything if it is already doing exactly what you want it to do 

No problem. Fill out the spec sheet with what you know and mark anything you do not know as UNKNOWN. If you are unsure, do not guess. Guessing wastes time and can send the tune in the wrong direction. We would rather start clean with accurate info.  Then send it to us for a refresh or update.

Yes, if anything has changed since the last time we built or serviced your carb. Even small changes can affect tune and drivability. The fastest way to avoid delays is to submit a refreshed spec sheet so we are working with accurate addresses and info.

If anything changes after you submit the spec sheet, new cam, heads, compression, converter, gearing, fuel system, or even a major weather or altitude change, you need to refresh your spec sheet and tell us before you ship or before we start work. Our calibrations are built off your current combo, not last season’s.