Cam Cover Hissing Inside

[waxer52]

Well after trying to sort out all my vacume leaks I think I may have found a bad problem.

While pressuring the inlet manifold I could hear a leak but it sounded like it was in the head. So I removed the oil filler cap and put it under pressure again only to hear a louder hiss and if you got close enough you could feel the air leaking out.

Next job is to do a leak down test.

Would anyone have an idea as to whats gone, or has this happened to anyone before.

Thanks for looking.

[blitzxtr]

Well after trying to sort out all my vacume leaks I think I may have found a bad problem.

While pressuring the inlet manifold I could hear a leak but it sounded like it was in the head. So I removed the oil filler cap and put it under pressure again only to hear a louder hiss and if you got close enough you could feel the air leaking out.

Next job is to do a leak down test.

Would anyone have an idea as to whats gone, or has this happened to anyone before.

Thanks for looking.

let me guess, were the cams still in the engine? Id say it was air entering the engine as some of the inlet valves were open.

Edited July 30, 2010 by blitzxtr

[waxer52]

Yes the cams are still in the engine, but I dont understand why it wont hold any pressure in the inlet manifold. The air seems to go in through the manifold and out through the oil filler cap.

The reason I am doing this, is that I am leaking air some where and im running lean. I need to find this problem and fix it once and for all.

[Moodles2]

Just an idea, maybe the rocker cover gasket (the one big piece one, 1 on intake side and 1 on exhaust side) is shot

[Adriano]

If you are worried, pull the cams out and the plugs and try again, should rule out the inlet valves. However you say there is a leak making it run lean. Pretty much a leak will always make it run rich, unless it is on the inlet manifold, and even then only under vacuum, boost it will still run rich

[waxer52]

ok so if I remove the two cams and leave the plugs in to seal the cylinders, the only place it can leak is at the plenum (if that is where the leak is).

[Adriano]

Yes, but if you remove the plugs, you can see if the inlet valves are leaking. How do you know it is running lean?

[waxer52]

I have a lc-1 wideband and datalogit installed.

Will also remove the cams later and see what happens.

Edited July 30, 2010 by waxer52

[Adriano]

Hwt ecu, could it be in the tune?

[waxer52]

Power fc is still on the standard map. i am about to tune it so I have to make it some bit right.

My mods are:

rb30/25det with vvt

holset hx35/40 turbo

power fc and datalogit

550cc high flow injectors

greddy copy plenum

external wastegate

avcr boost controller

z32 maf

It cant be in the tune as it still has the standard map and things only went lean after the plenum install. I cant find a leak where it seals against the head but I have the inlet cam cover off and I can hear strong hissing when pressuring the plenum.

[blind_elk]

Air pressure is coming from the plenum through the inlet valves into the cylinder, and out into the rocker covers through the valve stems and valve stem seals. Maybe the ex valves aren't closed at the particular postion the engine is at, or the they aren't sealing properly.

Or it could be blowing by the rings into the sump and up into the rocker covers.

Try rotating the engine a bit so that a different cylinder has its inlet valves open, then check again.

[waxer52]

I have tried rotating the engine and it has made no difference to the leak, it is still hissing the same.

My compression test showed up ok. 10% difference was the most between each cylinder.

[blitzxtr]

Or it could be blowing by the rings into the sump and up into the rocker covers.

spot on my friend, the rings are not a perfect seal.

Edited July 30, 2010 by blitzxtr

[waxer52]

Ok so if it blowing through the rings and up into the cam cover and out through the oil filler hole,

then why does my engine run lean with this leak?

[The Dan]

The hissing you are hearing is probably the PCV valve. They all hiss when running.

if you don't know how to do comp or leakdown tests, take it to someone who can.

+ lol at Greddy Copy plenum. You probably sucked a large chunk of cast into your engine. I've never seen a good one yet.