Toronado Intake Manifold Exhaust Crossover Problem
Posted: Tue Sep 28, 2021 3:45 pm
Over the last several years I've had a recurring "vapor lock" problem. After driving, even short distances, and parking the car, It would fail to restart after sitting for more than 20 minutes or so. If it did start it would conk out within a minute or so and not restart.
After replacing virtually the entire fuel system, including a carburetor rebuild and changing the rubber tipped needle and seat for a steel one, I finally isolated the problem to heat buildup in the intake manifold after shutdown.
The manifold and carburetor were getting so hot after the engine was shut off, the fuel was boiling before it could make it to the cylinders. It would even vaporize out of the fuel bowl.
Anyway, I removed the intake manifold with the intention of blocking the exhaust crossover passages that heat up the carburetor to aid in cold starts and cold weather. I live in Atlanta so I'm not worried about that.
The intake manifold gasket is a one piece valley pan type. Unfortunately, no one makes those with the crossover ports blocked. Two piece gaskets are available without the valley pan but I like how neat and clean the valley pan keeps the underside of the intake as you can see in the photos. As you can see, the inside of my engine looks really nice. No coke or crud anywhere. That black goop is melted RTV sealant and its only in the center where the exhaust crossover is.
Mondello makes an aluminum intake manifold without the crossover passage but it costs about $900. $1500 if you want it polished and ported. They also make crossover blocking plates but they can only be used with their proprietary gaskets which, of course, do not have a valley pan. You have to buy a valley pan from them separately.
I decided to take a different approach.
I purchased a tub of refractory cement. It's used for patching cast iron furnaces and sealing firebrick in chimneys, etc. It withstands temperatures of 3000 F and is guaranteed not to stretch, crack, shrink, pull away, etc. Bonds to any surface.
I stuffed the passageway with stainless steel wool to act as "rebar" for the cement. I packed the passageway as much as I could using plastic knives and whatever I could push the cement in with. I think a grout bag would be a good way to do this but I didn't think of it in time.
I let the stuff harden and dry for a couple weeks before assembling the car.
So far it's working perfectly. The car has never failed to start. The carb base is much cooler than it was prior to blocking the passages.
After replacing virtually the entire fuel system, including a carburetor rebuild and changing the rubber tipped needle and seat for a steel one, I finally isolated the problem to heat buildup in the intake manifold after shutdown.
The manifold and carburetor were getting so hot after the engine was shut off, the fuel was boiling before it could make it to the cylinders. It would even vaporize out of the fuel bowl.
Anyway, I removed the intake manifold with the intention of blocking the exhaust crossover passages that heat up the carburetor to aid in cold starts and cold weather. I live in Atlanta so I'm not worried about that.
The intake manifold gasket is a one piece valley pan type. Unfortunately, no one makes those with the crossover ports blocked. Two piece gaskets are available without the valley pan but I like how neat and clean the valley pan keeps the underside of the intake as you can see in the photos. As you can see, the inside of my engine looks really nice. No coke or crud anywhere. That black goop is melted RTV sealant and its only in the center where the exhaust crossover is.
Mondello makes an aluminum intake manifold without the crossover passage but it costs about $900. $1500 if you want it polished and ported. They also make crossover blocking plates but they can only be used with their proprietary gaskets which, of course, do not have a valley pan. You have to buy a valley pan from them separately.
I decided to take a different approach.
I purchased a tub of refractory cement. It's used for patching cast iron furnaces and sealing firebrick in chimneys, etc. It withstands temperatures of 3000 F and is guaranteed not to stretch, crack, shrink, pull away, etc. Bonds to any surface.
I stuffed the passageway with stainless steel wool to act as "rebar" for the cement. I packed the passageway as much as I could using plastic knives and whatever I could push the cement in with. I think a grout bag would be a good way to do this but I didn't think of it in time.
I let the stuff harden and dry for a couple weeks before assembling the car.
So far it's working perfectly. The car has never failed to start. The carb base is much cooler than it was prior to blocking the passages.