Engine Compression very low, options

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If the throttle was closed, the engine could not suck in air to compress, and the numbers will be false lows. The throttle has to be held open somehow or the test is invalid. I hope the mechanic knew better.
 
no, the engine can suck enough air thru a throttle body that will idle....a leak down test can tell you much more about the condition of the inside of the motor than a comp. test.
 
no, the engine can suck enough air thru a throttle body that will idle....a leak down test can tell you much more about the condition of the inside of the motor than a comp. test.
It also pulls a vacuum at idle. Holding the carb open was a step that came with Dad’s compression gauge. I do not know why that would be different now.
 
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no, the engine can suck enough air thru a throttle body that will idle....a leak down test can tell you much more about the condition of the inside of the motor than a comp. test.
I agree about the leak down test. You can tell where the air is going.

The online steps do not seem to include holding the throttle open anymore. WTH? I guess If the other plugs are out, it is sucking air around the throttle butterfly only for that one cylinder, plus past whatever intake valves are partly open.
 
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Either way can detect the problem aside from valve overlap and ring gap that I think can effect result, remember, he may not know the engine history. If all the cylinders are within what? 15-20% of each other send it, at this point you're looking for possibly zero or very little compression one one or two cylinders, there is also the possibility of the SC pushing air through where under normal conditions would be hardly noticeable but not with the added boost. Then I'd do a leak down test, I'm just spit balling here and in no way claim to know anything about anything. This is the beginning path I would take.
 
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Well. Here is an update. My SC looks like it’s needs a lot of love. Do this look like stock lower intake?
 

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Like the General said, it is an explorer or Cobra/GT40 lower. The Cobra, GT40 and explorer all are very similar. Same bolt pattern and you can bolt any upper (Cobra, explorer/gt40) to any lower (Cobra, explorer/gt40). Mix and match wouldn't matter.