Engine diagnostics using engine vacuum - ZR-1 Net Registry Forums

Hog · 02-06-2015

Interesting site about using engine vacuum to find out what's wrong with your engine.

http://www.dennysgettogether.com/den...roject_018.htm

XfireZ51 · 02-06-2015

Good stuff.

mike100 · 02-06-2015

Nice! vacuum gauge reading and ignition analyzers (o'scopes) are kind of a lost art.

XfireZ51 · 02-06-2015

Quote:

Originally Posted by mike100

Nice! vacuum gauge reading and ignition analyzers (o'scopes) are kind of a lost art.

Mike,

A vacuum gauge and a tach were the first tools used by tuners of the early ECMs.

mike100 · 02-06-2015

I especially liked the flash animation as some descriptions in books (remember those) were a little difficult to imagine. Most interesting were the worn ring ones that could be a quick way to assess the health of an engine without taking the trouble to do a compression test.

gbrtng · 02-06-2015

Does anybody need a dwell meter and timing light? Mine are unused these days.

XfireZ51 · 02-06-2015

Quote:

Originally Posted by gbrtng

Does anybody need a dwell meter and timing light? Mine are unused these days.

That's funny. I just gave my nephew a Sears adjustable timing light which I have not used in 8 years. He was rebuilding an old Yamaha 70's 650 cafe racer and was timing the motor. That and setting points is a lost art.

Paul Workman · 02-07-2015

Yeah, that's why we keep Ami's ol' 69 C3 vert around - soze I can remember what a PIA tuning is/was before modern ECMs (and the like). I have a couple drawers in my hi-boy tool chest, dedicated to that car.

It's amazing how much art about engine analysis has been lost since the computers took over tho. But, it is good to have known it once, cuz every now and then (especially with OBD-I) a problem occurs that the ECM/sensors won't display - e.g., the leaking exhaust valve my Z developed (as result of a bad injector(?).

nelson007 · 02-07-2015

I use dwell meters and timing lights all the time. All my older Corvetts require tuning all the time, specially the old Rochester fuel injections. The vacumm guage also comes in handy. My c2s and my c3s, the head lights, the a/c, the windshield wipers and distributors are all controlled by vacuum. Something always seem to be leaking.
Nelson007

9T1 Red ZR1 · 02-07-2015

How much vacuum should you read on a stock 1991 at idle?

02-06-2015	#1
Hog Join Date: Jul 2010 Location: Woodstock, Ontario, Canada Posts: 1,275	Engine diagnostics using engine vacuum Interesting site about using engine vacuum to find out what's wrong with your engine. http://www.dennysgettogether.com/den...roject_018.htm __________________ peace Paul ZR-1 Net Registry Member #1494

02-06-2015	#2
XfireZ51 Join Date: May 2007 Location: Chicagoland, IL Posts: 9,708	Re: Engine diagnostics using engine vacuum Good stuff. __________________ [SIGPIC][/SIGPIC]Former Membership Chairman Former ZR-1 Registry - BOD 1972 Corvette 4speed base Coupe SOLD long time ago 1984 Corvette Z-51/4+3 SOLD 1992 Corvette ZR-1 Aqua/Gray #474 SOLD 1992 Corvette ZR-1 Black Rose/Cognac #458 2014 Honda VFR Interceptor DX

02-06-2015	#3
mike100 Join Date: Feb 2011 Location: San Marcos CA Posts: 1,802	Re: Engine diagnostics using engine vacuum Nice! vacuum gauge reading and ignition analyzers (o'scopes) are kind of a lost art.

02-06-2015	#5
mike100 Join Date: Feb 2011 Location: San Marcos CA Posts: 1,802	Re: Engine diagnostics using engine vacuum I especially liked the flash animation as some descriptions in books (remember those) were a little difficult to imagine. Most interesting were the worn ring ones that could be a quick way to assess the health of an engine without taking the trouble to do a compression test.

02-06-2015	#6
gbrtng Join Date: Feb 2006 Location: San Antonio area Posts: 1,179	Re: Engine diagnostics using engine vacuum Does anybody need a dwell meter and timing light? Mine are unused these days. __________________ “Buy the best example of what you want, and pay whatever it takes. That way, you cry only once.” ~ Bruce Meyer

02-07-2015	#8
Paul Workman Join Date: Nov 2007 Location: Squires (near Ava MO in the Mark Twain N'tl Forest) - Missouri Posts: 6,493	Re: Engine diagnostics using engine vacuum Yeah, that's why we keep Ami's ol' 69 C3 vert around - soze I can remember what a PIA tuning is/was before modern ECMs (and the like). I have a couple drawers in my hi-boy tool chest, dedicated to that car. It's amazing how much art about engine analysis has been lost since the computers took over tho. But, it is good to have known it once, cuz every now and then (especially with OBD-I) a problem occurs that the ECM/sensors won't display - e.g., the leaking exhaust valve my Z developed (as result of a bad injector(?). __________________ Good carz, good food, good friendz = the best of timez! 90 #1202 "FBI" top end ported & relieved Cam timing by "Pete the Greek" Sans secondaries Chip & dyno tuning by Haibeck Automotive SW headers, X-pipe, MF muffs Former Secretary, ZR-1 Net Registry

02-07-2015	#9
nelson007 Join Date: Sep 2012 Location: Westminster, Md. Posts: 436	Re: Engine diagnostics using engine vacuum I use dwell meters and timing lights all the time. All my older Corvetts require tuning all the time, specially the old Rochester fuel injections. The vacumm guage also comes in handy. My c2s and my c3s, the head lights, the a/c, the windshield wipers and distributors are all controlled by vacuum. Something always seem to be leaking. Nelson007 __________________ WAZOO MEMBER 1993 #124 Ruby 1994 #??? Red/Black 1995 #061 Black/Red 2012 ZR1 Preproduction

02-07-2015	#10
9T1 Red ZR1 Join Date: Jun 2013 Location: Warminster, PA Posts: 78	Re: Engine diagnostics using engine vacuum How much vacuum should you read on a stock 1991 at idle? __________________ LT5 Red/Red