Ken Troutman of KT Engine...
Ken Troutman of KT Engine Development gives our multiple-fuel-burning Ford powerplant a quick visual inspection before beginning another dyno pull.
When engine builder Ken Troutman heard the request, he thought it sounded simple enough: One of his customers was sending an engine in for a rebuild. Would it be possible to rig it to run on either gasoline or alcohol? "I thought, 'Sure, it shouldn't be too much trouble,'" says Troutman. "And it wasn't-except we had to learn a few lessons the hard way. Other people can do it too, and hopefully, they can avoid our mistake."
Before we get to that mistake, let's set up the background. The engine in question is a Ford small-block that had been powering a Limited Dirt Late Model. It is a wet-sump with 13.2:1 compression and fully ported, cast-iron cylinder heads. It's nothing too exotic, but it's easily capable of producing in excess of 600 hp.
The engine's owner raced at a track that allowed gasoline- or alcohol-powered engines. He wanted the option of running either fuel, but he didn't have the budget for two full-on racing mills.
Too Hot to Handle
You can see the scuffing that...
You can see the scuffing that damaged this cylinder bore when the engine ran too lean in the first attempt at building an engine capable of burning either alcohol or gasoline.
"We thought we had the problem solved pretty easily," Troutman says. "We rebuilt the engine and used a high-volume fuel pump that we felt was capable of giving us the pressure we needed. To run effectively, an alcohol motor needs to burn approximately twice as much fuel as a gasoline motor. Unfortunately, the bypass in the pump simply wasn't large enough and couldn't handle the task of the extra flow.
"The engine ran well on the dyno at lower rpm, but on a full pull, it ran out of fuel and got too lean. We noticed it because the egt (exhaust gas temperatures) got too hot and we saw a sudden drop in power. Fortunately, we caught it pretty quickly and the only damage was a scuff in one of the cylinders and small cracks in two intake seats."
New hardened seats had to...
New hardened seats had to be pressed in to fix the two intake seats that cracked. All the exhaust ports already had hardened seats.
The damage was easy to fix, and this is where we came in on the buildup of the gas/alky convertible race engine. The cracks in the intake seats were in the front two combustion chambers, and the scuffed cylinder was also in the front of the block. The heads are Ford's N351 castings, which do not come with hardened valve seats. Troutman had already installed hardened seats for all the exhaust valves because alcohol race fuel lacks the lead that protects the exhaust seats when racing with gasoline. To fix the cracks, he simply cut out the two damaged intake seats-being careful not to cut into the water jacket-and installed hardened replacement seats for those two valves. The scuff in the cylinder bore was similarly easy to fix. It disappeared by simply rehoning the cylinder, which didn't even increase the bore size appreciably.
Since the point of this conversion was to keep the engine as standard as possible, we won't get bogged down in a blow-by-blow of every part installed. Instead, we'll just concentrate on what was done to help the engine run well on a diet of either gasoline or alcohol. The biggest obstacle, obviously, is the fuel pump. After much research, Troutman settled on a belt-driven pump sold by BLP Products that is a vast improvement-in terms of available flow-over any pushrod driven pump. To allow a variety of mounting options, BLP pumps are available with an adjustable mounting bracket and a mandrel that mounts to the harmonic balancer that allows several options for mounting drive pulleys. Our setup is underdriven by a small cog-belt pulley mounted to the mandrel. Troutman adjusted the pump to provide between 9 and 12 pounds of pressure at race speeds.
Because alcohol can easily contaminate the oil supply and potentially cause a bearing failure, Troutman switched from a low-tension to a standard racing ring package. The change can cost a little in terms of parasitic friction losses, but it does reduce piston blow-by and cuts down the opportunity for the alcohol fuel to enter the oil supply.