Hiss over 3000rpm ?

[redtvr]

Dear all
I would like some advice... I had the wadding removed out of the back box and it sound like it should (which is a good thing). However, when I floor it above 3000rpm (regardless of which gear) there is a hissing sound, as if the engine is sucking in sea-gulls. I put it up on the lift the other day, on tick over and blocked the exhausts but there was NO sound of the exhaust blowing....
Any advice would be good.

[the dodger]

Inlet manifold leak - although I wouldn't think you'd hear it at 3k rpm - more at tick-over. Some vac pipe leak? Fuel breather? Dunno really

[jamesuk28]

Yes sounds like an induction leak, assuming you do not have a sports airfilter fitted, my k&N whistles a bit.

Do a quick check along your intake hose past the air flow meter to plenum. However the leak is almost certainly going to be within the engine itself, valley gasket etc.

[2 sheds]

Intake air leak could "hiss" this would happen as you back off the throttle (when vacuum is created within the inlet manifold & plenum) although this is more of a squeel, sounds to me that it's the exhaust flow /harmonics.
Tim

[redtvr]

Thanks for the replies,
There is also a small amount of power loss, which makes me think about the induction area. If I get no joy I'll take it to the fixers and let them sort it.
However, the exhaust is Monsterously throaty and is well worth the 60 pounds.

RAGARDS

[_topcat]

If you fancy checking for an induction leak yourself, get a squirty bottle, window cleaner bottle, and fill with water, on tickover squirt small amounts round any suspect seals on inlet manifold. I fhtere is a leak you will hear the engine cough a little. this should point out any leaks.

[old64er]

Aerosol brake cleaner squirted around the plenum and inlet faces will show any leak (engine usually revs up).
In my experience if the inlet is leaking and you can hear it, then it will tick over like an old Ford tractor.

[philr]

I have a possible simple answer to this problem. A few years ago I had something similar under hard acceleration only, a "suckuing air through a straw" type noise + tail off of power right where it should have kept going.

It turned out to be the air intak pipe that runs the length of the engine bay. It has a slight depression/kink in it and when the engine sucked hard the pipe would collapse in on itself at this point. Possibly this wasn't helped by the high temperatures under the bonnect making the pipe more "malible".

In the end, a bit of fiddling and rearranging managed to remove the kink + I then wrapped the pipe in heat reflective material to help stiffen and keep the pipe cool.

Since then I've had no problems at all...in that area anyway.

Phil

[redtvr]

that is exactly what is happening... i'll check it and report back.

thanks for that... you described much better then I.

[redtvr]

I have found out what the whistling is...!
It is the air passing through the exhaust system.
Since having the wadding taken out of the exhaust the whistling has been noticeable... and on closer inspection concluded that is the cause.

What I want to know now is how to stop the whistle...?

[only me]

when the wadding was removed did you get the pipes through the box sleeved , i believe the whistle is caused by the air rushing through the holes and can only be cured by sleeving the holes

[redtvr]

No.. I just had the wadding removed.. you think I should get the pipe sleeved.. ?