1978 L-82 Vacuum Reading
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1978 L-82 Vacuum Reading
Guys I was wondering if yaw'l could look at my vacuum readings and make some recommendations. Vacuum system is tight. Intake gasket replaced. Distributor restored and recurved by Mark Saunders Paramount Distributors in Michigan. Quadrajet restored by Cliff Ruggles. A.I.R. pump belt removed and vac lined plugged. Heat riser removed. It was annoying! Proper dual exhaust by Allen Stainless.
AC off
AC On
Known issue: Carbon build up in intake valves. I noticed this when I replaced the intake gasket.
AC off
AC On
Known issue: Carbon build up in intake valves. I noticed this when I replaced the intake gasket.
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From: Bridgewater nj
If you have a performance cam, that is about right for vac but if its stock, you're a little low. A tight valve would have it bouncing around and a vac leak in the intake gaskets would make idling very difficult. It does sound like it's working hard. That's why I suggested advancing the timing and it should bump the vac up 1 or 2 points.
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As far as I know the cam is stock. I'm the third owner. Bought the car in 1997 with only 9,859 miles on it. Yes I remember that number well. It now has 49,000 miles.
I have often wondered whether or not the original owner installed a little beefier cam.
I have the timing set to the factory recommendation on the emissions sticker. 12 degrees at 900 rpm with vac advance disconnected.
My advance curve is not stock it was optimized by Paramount Distributors. I assume an extra 3 degrees would not hurt. I can set it to 15 and see what happens. I will post some full throttle blips. The vac reading shoots to somewhere between 26 and 30 on deceleration.
I have often wondered whether or not the original owner installed a little beefier cam.
I have the timing set to the factory recommendation on the emissions sticker. 12 degrees at 900 rpm with vac advance disconnected.
My advance curve is not stock it was optimized by Paramount Distributors. I assume an extra 3 degrees would not hurt. I can set it to 15 and see what happens. I will post some full throttle blips. The vac reading shoots to somewhere between 26 and 30 on deceleration.
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The restored carb has been back in service about a year. I recall adjusting the idle mixture when I reinstalled it. I can check it again for max vac. I'll do that this weekend.
PCV was connected and working as it should I assume. Further thoughts there?
I advanced the timing 3 degrees JUST NOW. It seemed to increase the vac by 1/2 to 1 inch of Hg. It is hovering more over the 17 inch Hg line on the gauge now than it was. I certainly would like for it to be up around 20.
I fear this car needs a valve job. The carb had all the typical Quadrajet issues. (Leaky bowls, leaky air horn, etc...) That is why I sent it to Cliff.
When I changed the intake gasket I did notice that the EGR passages were completely clogged. I cleaned it up really good before reinstalling it.
I assume the carb issues lead to all the carbon build up.
I've run Sea Foam through the carb a couple of times and I ran a little water through it too.
My whole goal is a nice strong idle while the AC is on in hot weather.
I replaced the OEM timing set for an all metal one about 3 years ago.
Another test drive tomorrow after advancing the timing may tell a new story.
Melting Slicks
Joined: Apr 2009
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From: Great Plains Iowa
16" Hg is about normal for a stock engine so I would recommend doing absolutely NOTHING. Its not unusual for a vacuum gauge to slowly fluctuate a Hg or so because changing rpm will also change the Hg. Close the hood and enjoy your ride..................
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From: Bridgewater nj
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