16 replies to this topic

[grahama]

Hi all,

I have rebuilt my engine a while ago and have been rotating it without plugs in by hand to keep it free. It is indoors so should be fine but doing it just in case. I could feel an expected rush of air from the plug holes on compression when doing this. I put the plugs in to stop crud getting down there and have been rotating again on and off.

Now I know the air can not get past the plugs as before but I hear a hissing sound which I am sure is the ait making it's way through the gaps in the rings to the crank area.

Is this hissing sound all expected as the force on the air on compression, is a lot ???

Graham

[mike.]

I assume if you've got the head on that the rest of the engine is built up with the cam etc

So its probably just hissing as the valves open and release the compressed air in the cylinder. Nothing to worry about.

[087dave]

you have good compressionn lad

[grahama]

Yes all the head and valves in, all built up, and building up the courage to test start it lol. Will be interested in the compression figures when it's going if the hissing is a good indicator of that.

Thanks as always.

[Artful Dodger]

It will do that:P some of it is the air escaping past the piston rings, as they have not beded in yet. Also air going past the valves as they are not opening fast.

[grahama]

I can hear some hissing in the the gearbox as the bell housing isn't on but also when I put my hand over the ports on the back of the head the air 'farts' past my hand so quite good pressure. Sounds like you all know what you are talking about, unlike me lol !

thanks again

[BritishRacingGreen]

I had the exact same thing when I built my new engine up, hissing sound from lower engine.

Was told it should be okay, so chucked it in the car, did a compression test and it was perfect, hopefully it stays that way...

[tiger99]

The piston ring gaps hiss on all engines, everywhere, not just Rover, so absolutely nothing to worry about.

[Artful Dodger]

...until they have been run in. If air is escaping past the rings then, you have a problem!

[tiger99]

I did say ring GAPS. There is a gap in every piston ring. If it was not so, it would sieze. They always hiss, even in a fully run-in engine, which is why there is always residual pressure in the crankcase, so you need a breather. It is not always noticeable, because there are few occasions when a modern engine needs to be turned over slowly and carefully by hand, but if you listen, the hiss is always there. Sometimes you need to take the oil filler cap off to hear it.

[Artful Dodger]

I did say ring GAPS. There is a gap in every piston ring. If it was not so, it would sieze. They always hiss, even in a fully run-in engine, which is why there is always residual pressure in the crankcase, so you need a breather. It is not always noticeable, because there are few occasions when a modern engine needs to be turned over slowly and carefully by hand, but if you listen, the hiss is always there. Sometimes you need to take the oil filler cap off to hear it.

if that is so why are motorsport orientated companys making gapless rings? advertising the fact that it is a complete seal?
8)

[dklawson]

Gapless rings? Please post a link to information on that. How do you install them? Are they a spiral design?

Regardless, even after your new (regular) rings bed in, you will have compression blow by the rings when the engine is turned over by hand. It is normal and to be expected.

[midridge2]

_{http://www.totalseal.com/TechPage.aspx there we go.}

[sonikk4]

It looks interesting but is this purely for high power drag engines. I see it does say street and strip but in the states what they mean as street includes street racing not every day drivers or am i interpreting it wrong??

[Artful Dodger]

I can't see why it couldn't be used in an every day situation. The head gasket would have to be uprated to take the extra pressure but I can't see any other issues