manifold leak test

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FL58
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manifold leak test

#1

Post by FL58 »

Hi,

my 58 engine is completely rebuild now and I was doing a manifold leak test before re-installing the linkers carb.
There is no leak at the manifold area but all the air is coming out by the rear intake guide.
Guides and valves are new and are HD NOS.
Is this a problem and if so what do I have to do before putting back the engine in the frame ?
thanks for your help

sincerely
hogboy52
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Re: manifold leak test

#2

Post by hogboy52 »

Ignore this
blewcrab
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Re: manifold leak test

#3

Post by blewcrab »

before you pressurize the manifold , you have to rotate the engine to a position where all the valves are closed . Lift off the pushrod covers , then you can see when all the valves are closed . this can easily done with the plugs out ,re install the plugs before pressurizing .
FL58
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Re: manifold leak test

#4

Post by FL58 »

Thank's guys you for your answers.
Blewcrab, the valves are closed and the air is not going in the combustion chamber but through the rear intake valve guide.

Hogboy ok I'll ignore.

sincerely
Mark44
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Re: manifold leak test

#5

Post by Mark44 »

FL58 wrote:Thank's guys you for your answers.
Blewcrab, the valves are closed and the air is not going in the combustion chamber but through the rear intake valve guide.
How much air pressure are you applying? For a manifold leak test, all you need is 10 to 12 psi. Are you hearing air coming through the valve guide into the pushrod tube? I've seen quite a few threads where people ask about doing a manifold leak test, but no one has mentioned a problem of air coming past the intake valve guides.
FL58
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Re: manifold leak test

#6

Post by FL58 »

The engine is still on my workbench and the rocker covers are open, so I can hear and feel air coming out by the intake valve guide.
I may have applied too much air pressure.
I may be wrong but once air has passed through the intake manifold where can it goes ?
1/ down in the combustion chamber (between the valve and the seat)
2/ up by the valve guides (between the guide and the valve rod)
3/ or by a rocker cover screw hole that has been drilled too long.

sincerely
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Re: manifold leak test

#7

Post by blewcrab »

FL58 wrote:The engine is still on my workbench and the rocker covers are open, so I can hear and feel air coming out by the intake valve guide.
I may have applied too much air pressure.
I may be wrong but once air has passed through the intake manifold where can it goes ?
1/ down in the combustion chamber (between the valve and the seat)
2/ up by the valve guides (between the guide and the valve rod)
3/ or by a rocker cover screw hole that has been drilled too long.

sincerely
you don't want the pressure to pass thru anywhere .....you want the manifold to hold the pressure , with no air blowing out from anywhere . if you have air escaping , that is where the problem is ! Don't pump it up over 10 or 12 pounds !
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