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Re: C1 heat riser disabling
Use a fuel injection spacer instead of the heat riser. That's the neatest way to solve the problem. Others wire the butterfly valve open. You might also block off the heat cross-over in the manifold with metal plugs in both intake gaskets.
Dale. -
Re: C1 heat riser disabling
you can also just disconnect the spring on one end of the heat riser valve and the weight will hold it open.Comment
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Re: C1 heat riser disabling
Donna, If originality is an issue, I just cut the valve plate off the shaft with a cutoff wheel and the assembly looks completely original externally. Without a valve in the system, the exhaust will take the path of least resistance and virtually no exhaust and the related heat will pass through the manifold. Good Luck, SteveComment
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Re: C1 heat riser disabling
The heat riser valve has a butterfly inside that is designed to restrict the exhaust flow out the back of the passenger side exhaust manifold when the engine is cold. The exhaust flow from the passenger side is then directed to flow through a passage in the cylinder head up under the intake manifold and back down the drivers side head passage to the drivers side exhaust manifold. This hot exhaust gas will rapidly heat up the intake manifold and carburetor for better cold engine drivabillity. The bi-metalic heat sensor coil spring on the reat riser valve senses the temperature rise over time and opens the rear of the exhaust manifold once the engine is warm.
This setup can be troublesome if the valve were to freeze in the closed poition which is not uncommon without regular maintenance.
Many people will experience drivabillity and other issues with the factory system and choose to disable it one way or another. For Judging, we want it to be original but there are other popular ways of modifying the setup.
I have found that I had excess heat flowing through my intake manifold heat riser passages causing idle instabillity and fuel percolation issues on my slightly modified SHP engine. The solution for me was to fabricate a very thin piece of stainless steel sheet metal to insert between the intake manifold and the cylinder head to block the flow of exhaust gasses. It was about 1-3/4" wide by 2" tall with an additional 1/4" bend at the top to give it a bit of stiffness. Slide that in between the 2 centermost drivers side intake manifold bolts and it works great. I left the passenger side open but installed the restrictor insert that comes with the gasket kit. The restrictor has a hole to allow some amount of heat flow to migrate up to the choke coil and operate the choke but not enough to cause the percolation and idle instabillity. This modification works well on aluminum intakes but for a cast iron intake it will cause extended warm ups and the associated cold engine drivabillity issues so perhaps a different solution would be better if you have a cast iron intake. This does cause a few extra minutes of warm up time on an aluminum intake engine but the drivabillity improvement is well worth it IMHO. It is a small compromise.
If you need a source for the thin stainless steel shim stock you can look no further than your kitchen cabinet to find a spare stainless steel mixing bowl with a bottom large enough to yield the required amount of shim stock. Be sure to procure this while your wife is out of the house and remember to deny any involvement in the disapearance. Alternately, you could order a cheap set of stainless bowls from Harbour Freight for about $5.00 or so but they will be manufactured from imported stainless steel materials so there is some trade-off here. Once again, it is all about compromise.
-Mark.Comment
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Re: C1 heat riser disabling
The intake block off plates are $4 through most catalogs.
They come four to a package. You'll have two extra as I
do. Do you need em? RobComment
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Mark Ring: Email me! *NM*
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