Okay I just got done torquing down my new heads and I seem to notice after I rotate the engine that there is a hissing noise. It kind of sounds like the piston is sucking in air. I can't make out where and which cylinder but is this normal after installing new heads and gaskets?

 

are the plugs out?

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89 Iroc-Z LB9 305 TPI auto 2.73 posi:
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Nope, all plugs are torqued down to spec. Could it be that the air is just being sucked through the valves (I havn't put the rocker arms on yet)? I didn't here this hissing noise when i rotated the motor with the old heads/gaskets.

 

Try some mild soapy water around the head gaskets and check for bubbles. To check if the valves are sealing take some wide thin making tape and tape over the ports. If there is a seal problem you will see the tape move. I am assuming that you have the rockers and intake off. I would do one cyl at a time with all pulgs out except the cyl you are testing. Also rotate both directions.

 

Its probably air pushing past the rings. Its normal. If you are sure the gasket is on right, don't worry about it.

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I'm pretty sure I put the gaskets and torqued the heads down(in the correct order) correctly. I'm probably just paranoid and just worrying too much. Anyways, thanks guys for your info.

 

Yep, I agree that it's normal. If you are relatively confident that you installed the heads correctly, what you're hearing is air escaping past the rings on the compression stroke. This is perfectly normal.

Anyone's who's changed bearings with the engine in the car will recognize that hissing sound when the engine is turned over by hand in order to reach the different bearings.

Hope this reassures you.

Jake


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