What is good engine vacume?

[rtviper]

I am trying to determine if my engine has a vacume leak. I can hear a loud whistle at idle. I have tried the smoke machines the stethoscope with no luck in finding it. I put a vacume guage on the engine and at idle I have 10-13 lbs vacume. I do notice when the whistle gets louder the vacume will fluctuate from 13 down to 10. The engine has a fairly healthy solid roller cam.
Is 10-13 too low?
Thanks

 

[aminga]

YOu have a leak

 

[sabersaw30]

Check your egr gasket.mine usually stays around 16 to 18.I had a egr gasket drive me crazy one time changed out the cam thinking it was the cam the car would not even run when the gasket come apart on me.Also only use a ac delco pcv valve.Whistle could also be a intercooler hose.

 

[Scooter3800]

Two questions:
1. What is a vacume?
2. When is this forum going to get a spell checker?

 

[gndoug]

Get yourself a can of carb cleaner and spray it into areas around the egr gasket, intake gasket, vacuum hoses, T.B. etc. When you hear the rpm's rise and the engine kinda smooth out you sprayed it in an area with the vacuum leak. It will help you find what needs to be fixed. Always works.

 

[rtviper]

Thanks everyone I tried all those methods with no result. I guess I have a leak on the inside of the intake manifold so the smoke doesnt show on the outside. I guess 10-13 lbs is low then?
Scooter vacume is the same as vacuum just spelled vacume if your from Ontario. You mean to tell me you have never had a vacume burnie?

 

[forcedfedv6]

Thanks everyone I tried all those methods with no result. I guess I have a leak on the inside of the intake manifold so the smoke doesnt show on the outside. I guess 10-13 lbs is low then?
Scooter vacume is the same as vacuum just spelled vacume if your from Ontario. You mean to tell me you have never had a vacume burnie?

10 to 13 is normal if you have a large cam and ported heads.. Mines reads 11 at idle and close to 14 while cruising and it goes up to 20 after i left off the throttle and just let it roll..

 

[TURBOPOWERED68]

My car

Warm in parking -20
Warm in gear -18-17

I would say 10-13 is low
Is your engine Stock?

 

[rtviper]

No its a twin turbo v8 in a GN. It has a Hogan manifold and the whistle is loud. I was hoping to find it without tearing it apart. I cant think of a way to check for leaks inside the motor from the manifold? Maybe take out the distributor and close all the valves and run the smoke detector?
Thanks Guys

 

[rtviper]

Forcefed it does have a large cam and ported heads? It has a motec so I dont know how to read the data to see if its lean from the leak?
Yours has the same vacume(vacuum) ? Maybe I will look some more or maybe throw it on a dyno and see how it runs?

 

[Martin U]

I guess I'll subscribe to this one also. I have been through 3/4 case of startind fluid/carb cleaner looking for the reason my BLM's are around 140-141. Every hoseis zip tied ect, but I am running a 208/208, GN1 heads,ATR headers & pipes. I cannot find any external reason foa a leak either.
Mart

 

[INTHEEIGHTS]

Are you sure its not the turbo making the noise.

 

[ronbuick]

RT, you could also verify with another gauge, but I would think that 11-13
for your set uo might just be OK

 

[TURBOPOWERED68]

If 10-13 is normal for a modded engine.
How does the -10-13 work with vacuum brakes?

 

[rtviper]

If it is the turbos or another part on the motor shouldn't you be able to place a stethoscope near the source and hear it louder? Also if it was leaking inside the motor at the intake shouldn't you be able to place the stethoscope at that location where it bolts to the heads and hear in through the manifold. The sheet metal intake is exposed all along the heads.

 

[TurboDave]

I guess I'll subscribe to this one also. I have been through 3/4 case of startind fluid/carb cleaner looking for the reason my BLM's are around 140-141. Every hoseis zip tied ect, but I am running a 208/208, GN1 heads,ATR headers & pipes. I cannot find any external reason foa a leak either.
Mart

Withh 140 BLM's I seriously doubt you're suffering from a vacuum leak. Vacuum leaks will usually always drive the BLM's to their upper limit 150 or 160 depending on the chip. You just need a bit more fuel. Usually a bit of a mis-match between the chip's idea of what your injectors are and what they actually are flowing.
A 140 idle BLM certainly isn't anything to be tearing your hair out over.

 

[Martin U]

Great,now I can stop looking for that new rug. Everytime I mention my BLM's I get "you have a vacuum leak". I have been doing every thing I can to keek from removing the intake to have a look see. Not all that easy on a hot air.
I'm at 43# FP, Should I add fuel at the TT chip? I have run up 25lbs boost like this just fine.

 

[TurboDave]

Great,now I can stop looking for that new rug. Everytime I mention my BLM's I get "you have a vacuum leak". I have been doing every thing I can to keek from removing the intake to have a look see. Not all that easy on a hot air.
I'm at 43# FP, Should I add fuel at the TT chip? I have run up 25lbs boost like this just fine.

I haven't studied on the TT chips much, but if you have a way to add some idle (low load) fuel, do that. I wouldn't mess with the fuel pressure much if your car likes it where it is. You could try 45# to see what happens, but the problem with messing with fuel pressure is, it affects the entire fuel curve, not just the area you want to correct.

 

[pajo]

low

how much of a lift does your cam have and do you have a vacoom conversion brakes on your car.?either way 12-13 psi indicates lift in the 500 which is normal ..just my 2 cents .

 

[rtviper]

Thanks I am sure the lift is at least 500. I might check other things out first.
Duttwieler put this motor together and I dont want to mess with his assembly. I am sure I could mess something up by taking it apart and back together?