vacuum gauge test - Cherokee SRT8 Forum
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post #1 of 40 (permalink) Old 11-30-2012, 04:30 PM Thread Starter
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Exclamation vacuum gauge test

I did some searching and could find much on here about doing this test. this test can tell us more then what we read on a trinity perhaps. it seems easy to read but the issue is what should our readings be if all is ok?? I bought a vacuum gauge because I feel like my engine sounds strange at idle and im not getting any codes. ill finally be pulling the trigger on a Prochager setup and wanna make sure im at top notch shape before installing some real power. I did some google search but the numbers they say u should see i dont think pertains to our engines. perhaps the experts can chime in hear and maybee give some insite so us wanna be gearheads can 1) learn and become gearheads lol and 2) do out own tests and watch to see how our engines are running. so what numbers should we be seeing at idle?? I did a quick hook up and only did a test at idle and it was reading pretty much at 15inhg with very little wobble. are there different readings when ur cammed? blown? stock? heads? tuned? what rpms should we be reving to and reading at to do a full tes? 4,000 5,000 6,000??? experts please chime in

2010 silver Jeep SRT8 W/ opts 1 and 2 W/ performance audio and nav

72mm FOGLIGHT TWIN TURBO
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post #2 of 40 (permalink) Old 11-30-2012, 04:52 PM
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I've had good experience using a leakdown test, it doesn't give much information about crank and rod bearing wear.

http://www.carcraft.com/techarticles...r/viewall.html

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post #3 of 40 (permalink) Old 11-30-2012, 04:53 PM
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With my cam at idle, I usually see around -15". Stock cam is around -18' to -20"

Chad (06 Inferno Red GC SRT8) PWR 6.3L, PWR Apache Heads, Stage6 76 mm Turbo, Stage6 Fuel Pump, SHR NAG1-HTCr, PI 2400 TQ Converter, ATI Flex Plate, BC Coil Overs, Wilwood TC6R calipers, Kooks Headers, Mopar exhaust, MM 85mm T-body, Jerseyboy CMR, Bwoody Sway Links, R1 Concepts F Slot & Dimp, R StopTech Pads, Earls Trans Cooler, TLS Rear Fog Harness

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post #4 of 40 (permalink) Old 11-30-2012, 04:58 PM Thread Starter
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chad thats what i saw at idle. but i dont see a minus sign on my gauge is it the same reading? and what about when u test at a higher rpm?
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post #5 of 40 (permalink) Old 11-30-2012, 05:00 PM Thread Starter
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Quote:
Originally Posted by SRT8-DOUGLAS SR View Post
I've had good experience using a leakdown test, it doesn't give much information about crank and rod bearing wear.

http://www.carcraft.com/techarticles...r/viewall.html

Guy
wouldnt crank and bearin wear give you a lower reading?
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post #6 of 40 (permalink) Old 11-30-2012, 05:01 PM
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inhg is negative so , yes. While driving it will get closer to 0, add boost and it goes positive. Not sure what happens when idling and higher RPMs Haven't really looked at it. The key is the idle.
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post #7 of 40 (permalink) Old 11-30-2012, 05:10 PM Thread Starter
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i only ask about the higher rpms because of a chart i waqs reading on goodle and about how the needle moves and where it moves to.. but as long as at idle we are sitting at the same measurement there should be no problems as far as bad rings.valves etc etc...?
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post #8 of 40 (permalink) Old 11-30-2012, 05:13 PM
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Mine is very similar to chad at idle I think it was 16. I will double check when I get home, make sure I'm not telling you lies.

PWR 393, Procharged D-1 @ 6 psi.
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post #9 of 40 (permalink) Old 11-30-2012, 05:19 PM Thread Starter
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im gonna do some more testing at higher rpms tomorrow just to investigate.lol. i will post back what i see and try to find what the readings should be for the rigs with a cam as i cant test a stocker unless jose srtateu2 lets me run a test on his at higher rpms
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post #10 of 40 (permalink) Old 11-30-2012, 07:07 PM Thread Starter
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U guys who ran the test with a cam in, is ur needle sitting still when testing or is it shaking back and forth in a very very small span like 15-15 1/4??? Got any video? If so please post um up for some to see


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