What we have here, fellas, is the ACE Fireball 535 Royal Enfield high performance engine kit. You take your stock, single cylinder Royal Enfield Bullet and with the addition of this kit, turn it into a real, … well, fireball. No, you’re not going to challenge any of the boy racers out there, but compared to any stock Royal Enfield, you’ll be the man to beat, seriously. This thing is fast. A video showing an impromptu drag race between the ACE prototype and another modified Bullet makes it clear what a jump in horsepower and performance these modifications deliver, the ACE Fireball simply runs away from the other bike.
This package was developed over the last 5 years to overcome the shortcomings of some other Royal Enfield modifications that were very race oriented, which meant lousy street manners and questionable reliability. RE owners wanted more performance but good manners and something that would last.
So, what exactly is the ACE Fireball 535? The primary piece is the modified cylinder head. The development and engineering was done under the supervision of Joe Mondello, one of the most famous names in cylinder head modification. In fact, each head is hand signed by Joe Mondello himself, and individually serial-numbered, they’ve even created a registry for documentation.
Tom Lyons, one of the partners (along with Sumanth Janardhan aka “Chummaji”) behind the ACE, sent me a virtual truckload of information on the kit (I think he’s very proud of it!) and it’s taken me quite a while to digest it all.
The work begins when the customer’s cylinder head arrives. It is stripped and pressure cleaned. The head gets new valve seats, the intake and exhaust ports are treated to a full Mondello high-velocity, high-flow porting job, and the seats get a new multi angle valve job. Custom stainless steel Manley Racing valves with narrower stems are installed in new valve guides with modern keepers holding the PAC Racing stress-relieved competition beehive springs. The springs sit on hardened precision-ground spring shims with custom-made titanium upper valve spring retainers on the other end. There are also precision-ground hardened-steel lash caps over the tips of the valve stems and Viton valve stem seals control oil flow. This entire valve spring system is seated into a machined recess which is cut into the head casting for the purposes of making room for this very different valve spring set-up. It is NOT a “drop-in” package, and there is considerable machine work needed to get this valve gear system into the head.
The combustion chamber is coated with a silver-gray Thermal Barrier coating of the CER-MET(ceramic/metallic) type. This slows the heat transfer from the combustion chamber into the head casting, so the head runs cooler, and more heat is retained in the chamber to make more power. It also provides resistance to detonation because the surfaces cool quickly and do not retain heat as much as the metal substrate. The faces of both valves also receive this same coating to keep them running cooler.
The exhaust port is also coated in a black Thermal Barrier coating that is mostly ceramic material. The purpose of this coating is to insulate the alloy head casting from soaking up unwanted heat from the exhaust gas stream as it exits the head through the port.
The result is a completely modern, high performance cylinder head for the Royal Enfield Bullet, something to awaken the giant within.
But wait, … there’s more!
There’s also the ACE Magnum Cams. I could go into all of the detailed specs but basically, the Ace cams are designed to be a “hot street,” NOT a “full race” cam set. They are targeted at a reasonably higher rpm range for power production, while not going higher than reliable piston speeds would allow with the improved bottom-end parts. The engine remains manageable and “street-mannered” so it idles well and has torque available in the lower and mid rpm range. You can have fun without having to wind it tight.
Wait, what was that about “improved bottom-end parts?” Those are made up of the ACE piston, 3mm larger than stock diameter and forged from 2618 alloy, using Total Seal piston rings and connected to a steel Carrillo connecting rod. As an option, you can get the Thermal Barrier “CerMet” coating on the crown, which keeps the piston running cooler, and the skirt is coated with a Moly Dri-Lube coating.
They also have custom torque plates for keeping the Bullet barrels distortion free during boring and honing plus there is a Mikuni TM32 flatslide carb, a Barnett clutch and a nice exhaust system to top it all off.
Here’s ACE number 1 on the dyno, hitting the rev limiter at 6200 rpm:
ACE Fireball number one has about 16,000 miles on the piston and bottom end and 4000 miles on the Mondello head and everything is running great. It also clocked 103 mph on the GPS speedometer, with the bags on! For those of you who have ever ridden a Bullet, you know that’s definitely quite a bit over stock. It’s ridden every day on the highways between New York and Philadelphia.
Tom sums it up this way:
In essence, the results are a vintage 500 single that rides with the authority and performance of most 650-750 vintage twins like the Triumph Bonneville T120. Torque is available in great quantity from just off idle, all the way to the 6000rpm redline, with a torque peak of 38 ft-lbs @ about 3700rpm. Horsepower peaks at 37.1 at the rear wheel, at about 5700rpm (We’ve doubled the rear-wheel hp of the stock bike). A very wide and useful powerband. Very easy kickstarting, great idle stability, great riding around town and in the city, and can really burn up the road on the twisties, and hits 103mph. Cruises on the highway at 80mph without problems.
It’s a niche-bike that is aimed at the real-world riders who need to “have it all”, and not just a race bike. This bike delivers in spades, in every category, including 70-75mpg fuel economy.
Here’s Fireball number 1 with the drag race toward the end of the video. Sounds great!
Before anyone asks, yes, Tom has already had discussions with Aniket Vardhan about installing the ACE Fireball kit in Aniket’s 1000cc Musket currently in development. Sweet!
OK, what is the price of entry?
Ace Mondello head mods (on customer’s head casting) $1000.
Custom hand-matched intake manifold (pinned and flowed), $100
Ace 535 Forged Piston with pin and rings $295. Coated add $50.
Ace Magnum Cams $350/set.
Barrel and bottom end work, Carrillo rods, Alpha bearings, main bearings Mikuni carbs, exhaust systems, etc, P.O.R.
I hope a lot of Bullet owners take a serious look at this kit. It could surprise the heck out of some vintage bikers out there as they get dusted by an unassuming Royal Enfield.
Very, very nice looking kit with lots of development behind it. I like this a lot.
You can find Tom on the Yahoo group for the ACE