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Compression Test Issue M440

I figure those thousands of Chrysler engineers put the passages there for a proper warm up and fuel atomization but don't really know for sure. Clean them out with anything, I don't think you can hurt the manifold.
I was reading earlier about your elbow gasket questions and just wanted to say that the system works fine with the OSC121 gasket that is used at both ends of the manifold. You know that water doesn't pass directly from the manifold to the riser? It goes via the short 1" hose, make sure there are no kinks in that hose.

Dan
 
Be sure not to use silicone on the gasket in the intake runner port area. Gasoline disolves silicone and will give you a vacuum leak if you do. Use something like Permatex HiTac in the brush can or spray can. I'm an old Big Block Mopar head and learned that one the hard way.

That passage in the intake manifold is to pre-heat the manifold in cold weather operation and heat the old well style chokes. If you have the well style choke, it needs to be heated, but electric chokes eliminate that requirement. Besides, I don't ever recall seeing a butterfly valve in one exhaust manifold, which forces hot exhaust thru the manifold. In auto version, the butterfly has a spring on outside of manifold that opens it when it gets hot. When hot rodding the BB Chrysler, since we always installled headers, eliminating the butterfly, the first thing we did was blank off that passage in the manifold so the fuel mixture would be a cool as possible, since the BB Chrysler is a dry manifold, and use an electric choke. Cold weather / cold engine performance suffered some until engine warmed up. Once warm, it helped performance.
 
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I have ALWAYS pulled all plugs doing compression tests for the following reasons:
1. So that engine spins freely
2. There is no chance of an engine start while cranking. Don't forget, if there is a ballast resistor, you have a bypass and can start while
spinning starter.
3. Less strain on starter
4. Adjacent cylinders can not influance reading if there is a head gasket leak.

Just make sure all cylinders are within the maual specs for compression readings. If 2 adjacent cylinders are low and very close to each other, then figure on replacing head gasket. If 1 or more cylinders are low, add a teaspoon of oil into plug hole of each and test again. If pressure jumps up, it's rings. If pressure doesn't jump up, it's a valve problem or gasket leaking into somewhere other than adjacent cylinder, in either case, time to pull the head (s). Never do a valve job on just 1 head. And, if the engine is old and somewhat tired, a new valve job will usually make engine start burning oil in a short time, due to the renewed compression forcing blowby on the tired old rings.
 
04fxdwgi said:
Be sure not to use silicone on the gasket in the intake runner port area. Gasoline disolves silicone and will give you a vacuum leak if you do. Use something like Permatex HiTac in the brush can or spray can. I'm an old Big Block Mopar head and learned that one the hard way.

That passage in the intake manifold is to pre-heat the manifold in cold weather operation and heat the old well style chokes. If you have the well style choke, it needs to be heated, but electric chokes eliminate that requirement. Besides, I don't ever recall seeing a butterfly valve in one exhaust manifold, which forces hot exhaust thru the manifold. In auto version, the butterfly has a spring on outside of manifold that opens it when it gets hot. When hot rodding the BB Chrysler, since we always installled headers, eliminating the butterfly, the first thing we did was blank off that passage in the manifold so the fuel mixture would be a cool as possible, since the BB Chrysler is a dry manifold, and use an electric choke. Cold weather / cold engine performance suffered some until engine warmed up. Once warm, it helped performance.
Click to expand...

The 440 carbs use the well style choke and need the pasage operational.

Dan
 
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