only 12 hg of vacuum at idle???

N

noslow5_0

New Member

Nov 7, 2003

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dallas tx.

Apr 8, 2004

#1

• Apr 8, 2004

• #1

well i was trying to find out why my car was smoking... turned out to be my timing was WAY off, and caused it to smoke a little once i kicked it down some.... well in the process i got a vacuum guage on it, and it only read 12 hg at idle??? could the combination of my heads (world products windsor jr.'s) and e 303 cam cause that??? no vacuum leaks anywhere, the motor feels strong as hell, doesnt skip a beat, and was only has about 4500 miles on it.... also i dont have the vacuum canister in the passenger fenderwell right now.... could that be it too???

 

B

battyice

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Mar 7, 2004

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West Chazy, NY

Apr 8, 2004

#2

• Apr 8, 2004

• #2

You say your timing was way off...did you get your 12 hg before you adjusted the timing or after? Having little or no advance on your timing will cause low manifold vaccum readings. Some people actually adjust their ignition timing with a vaccum guage; you adjust the timing at an idle until your engine pulls the most vaccum.

 

Grn92LX

Fidanza Man!

Founding Member

Jan 14, 2001

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129

New York

Apr 8, 2004

#3

• Apr 8, 2004

• #3

What does your vac gauge read at WOT? Cold idle mine reads about 12-13, warm idle it reads about 15. My gauge might be broken. The last was definatly was because when I floored it, it went to 6, but the new one goes to 4 now when I floor it. Weird.

 

Michael Yount

Mustang Master

Apr 10, 2002

9,039

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79

Charlotte, NC

Apr 8, 2004

#4

• Apr 8, 2004

• #4

That vacuum reading is quite common with the E - I could only get 11" out of mine, and that was at 1050 rpm idle speed; it was even lower at 900. At w.o.t. there should be virtually no vacuum - it should read very close to zero.

 

N

noslow5_0

New Member

Nov 7, 2003

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dallas tx.

Apr 8, 2004

#5

• Apr 8, 2004

• #5

Michael Yount said:

That vacuum reading is quite common with the E - I could only get 11" out of mine, and that was at 1050 rpm idle speed; it was even lower at 900. At w.o.t. there should be virtually no vacuum - it should read very close to zero.

Click to expand...

well at idle with my timing at 10* the vacuum was 12 with it at about 20* it was 15.... when the idle speed was at about 1000, i got 20". I cant remeber off the top of my head, but when i hit WOT the guage maxed out??? cant remeber if it was 0 or 30??? ill check tonight an see what it is....

 

Michael Yount

Mustang Master

Apr 10, 2002

9,039

6

79

Charlotte, NC

Apr 8, 2004

#6

• Apr 8, 2004

• #6

WOT throttle reading will be close to zero. With no engine load (sitting still), the higher the idle speed, the higher the vacuum reading. With engine load (driving) the wider open the throttle, the less vacuum. Remember - atmospheric pressure (14.7 psia standard) PUSHES air into the engine; when the throttle plate isn't in the way - wide open throttle - you have atmospheric pressure conditions in the manifold. No vacuum.

I'd idle that thing up to 850-900, set the timing at 14-16 btdc, and you should have a good solid 15-17" of vacuum - perfectly acceptable for that cam.