MonkeyDunk
New Member
About 3 years ago when I graduated tech school, I decided that I needed a fun vehicle to enjoy with my new found income. I originally wanted a motorcycle, but after deciding that it was just too dangerous, and after one two many episodes of Roadkill, I decided on a classic car. I wasn't looking for anything special, but I happened upon a 1972 Plymouth Duster loaded with the 225 Slant six and A904. I instantly fell in love with it based on the paint and body, and I had a bit of familiarity with the engine as I had driven a classic aircraft tug run by the slant six.
For the first few months of owning this Duster, I was driving it everywhere. I really should not have been as every piece of suspension rubber you care to think of was nonexistent, but I was hooked. I found that I could drive it for a while until the engine got hot and it began to bog down and shut off. I researched the problem and discovered what would be the bane of my existence. VAPOR LOCK.
Over the course of the next three years, I replaced, removed, adjusted and modified just about everything people said to do to a Slant that is experiencing this issue.
New V8 radiator, hoses, water pump, thermostat, coolant flush
Valve lash, corrected timing, vacuum advance check, new distributor, HEI ignition mod, new coil, new spark plug wires.
New carburetor, new fuel pump, new fuel tank, the SlantSixDan fuel line mod with extra heat shielding on everything, Custom aluminum carb heat shield, thick phenolic carb spacer.
Inspected brakes and wheels for dragging, new disc brakes, new bearings.
All of this work over the years never fully fixed the fuel boiling and subsequent vapor lock. Around year two I decided that I hated the Slant Six engine, and that I rue the day that I ever decided to get one. I vowed to replace this leaning piece of junk with a 318 the soonest chance I got. Even so I continued to work on it. The shame of it was, all of these new parts and modifications had the car running and driving fantastic, but only for a short period of time. During all of this engine work, I had also managed to completely overhaul the suspension, power steering, and convert it to disc brakes. All the time and money spent on this car and it couldn't ever be fully enjoyed.
Last night I finished installing the new distributor and HEI mod. So this evening I decided to see if at long last it wasn't boiling fuel anymore. I had found a broken ground wire in the old distributor, so the engine was running like never before. I had never felt so much power come from my slant. But of course, as always, I made it to the first light out of my neighborhood, and I could already feel the vapor lock setting in. I drove it home, opened the hood and just stared.
Why did this engine act this way, what had I done to deserve this fate. But then I glanced at something I had never payed much attention to, the heat riser. I don't know why I had never looked at it before, but I started examining this rust pile hanging off my intake a little closer. I could see that a rod with a clock spring on it was rusted shut. After a brief forum surf I discovered that my heat riser had failed in the open position and had been directing heat directly onto the intake where the carb sits at all times. I got a pair of pliers and cranked it shut and took it for a drive.
Just like that, after three long years, my chronic vapor lock issue ended. I now have an almost mechanically brand new '72 duster and Slant Six to do with whatever I want, no longer limited to 4 miles before falling on its face.
I write all this to say, if you have endless fuel boil issues, please check your heat riser. I still cant believe how much time and money I wasted before looking at that common cause.
For the first few months of owning this Duster, I was driving it everywhere. I really should not have been as every piece of suspension rubber you care to think of was nonexistent, but I was hooked. I found that I could drive it for a while until the engine got hot and it began to bog down and shut off. I researched the problem and discovered what would be the bane of my existence. VAPOR LOCK.
Over the course of the next three years, I replaced, removed, adjusted and modified just about everything people said to do to a Slant that is experiencing this issue.
New V8 radiator, hoses, water pump, thermostat, coolant flush
Valve lash, corrected timing, vacuum advance check, new distributor, HEI ignition mod, new coil, new spark plug wires.
New carburetor, new fuel pump, new fuel tank, the SlantSixDan fuel line mod with extra heat shielding on everything, Custom aluminum carb heat shield, thick phenolic carb spacer.
Inspected brakes and wheels for dragging, new disc brakes, new bearings.
All of this work over the years never fully fixed the fuel boiling and subsequent vapor lock. Around year two I decided that I hated the Slant Six engine, and that I rue the day that I ever decided to get one. I vowed to replace this leaning piece of junk with a 318 the soonest chance I got. Even so I continued to work on it. The shame of it was, all of these new parts and modifications had the car running and driving fantastic, but only for a short period of time. During all of this engine work, I had also managed to completely overhaul the suspension, power steering, and convert it to disc brakes. All the time and money spent on this car and it couldn't ever be fully enjoyed.
Last night I finished installing the new distributor and HEI mod. So this evening I decided to see if at long last it wasn't boiling fuel anymore. I had found a broken ground wire in the old distributor, so the engine was running like never before. I had never felt so much power come from my slant. But of course, as always, I made it to the first light out of my neighborhood, and I could already feel the vapor lock setting in. I drove it home, opened the hood and just stared.
Why did this engine act this way, what had I done to deserve this fate. But then I glanced at something I had never payed much attention to, the heat riser. I don't know why I had never looked at it before, but I started examining this rust pile hanging off my intake a little closer. I could see that a rod with a clock spring on it was rusted shut. After a brief forum surf I discovered that my heat riser had failed in the open position and had been directing heat directly onto the intake where the carb sits at all times. I got a pair of pliers and cranked it shut and took it for a drive.
Just like that, after three long years, my chronic vapor lock issue ended. I now have an almost mechanically brand new '72 duster and Slant Six to do with whatever I want, no longer limited to 4 miles before falling on its face.
I write all this to say, if you have endless fuel boil issues, please check your heat riser. I still cant believe how much time and money I wasted before looking at that common cause.
