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How much vacuum at idle

Posted: Sun Jan 25, 2015 4:08 pm
by Charlescrown
Just a quick question for loggers and tuners. I have a VR V8 and when logging its got 104Kpa key on eng off. Out by 3 yes I know. When idling it reads 37/38 Kpa. This to me equates to around 18 inches of Hg a scale I have used for engine diagnosis for a long time. To me it seems a little low. The engine did go through a very serious overheat a few years ago but has always run extremely well. My concern is not the rings but what would the cam lobes look like at 180000kms. Am I getting overly concerned?

Re: How much vacuum at idle

Posted: Sun Jan 25, 2015 4:34 pm
by delcowizzid
in the 30's is perfectly normal area for stock its around 20.67 inches mercury i run cammed ones at 70kpa idle LOL.the last 304 i rebuilt the valvesprings measured at 40Lb seat pressure but it reved out fine went bloody good bearings were all touching copper 9psi idle oil pressure like they have LOL .totally different engine after a freshen up with new cam and springs and slight skim and port bowl tidy up though.

Re: How much vacuum at idle

Posted: Sun Jan 25, 2015 5:45 pm
by Holden202T
hahahah yeah its very rare i see a motor with 30's at idle!!

Re: How much vacuum at idle

Posted: Sun Jan 25, 2015 5:57 pm
by Dylan
Mine has 85kpa idles fine. (worked motor though)
What does stock V6 idle at?

Re: How much vacuum at idle

Posted: Sun Jan 25, 2015 7:09 pm
by The1
my vs ecotec is around 30

Re: How much vacuum at idle

Posted: Sun Jan 25, 2015 8:01 pm
by vlad01
my VR idles around 20Kpa from memory.

Re: How much vacuum at idle

Posted: Sun Jan 25, 2015 8:03 pm
by vlad01
delcowizzid wrote:in the 30's is perfectly normal area for stock its around 20.67 inches mercury i run cammed ones at 70kpa idle LOL.the last 304 i rebuilt the valvesprings measured at 40Lb seat pressure but it reved out fine went bloody good bearings were all touching copper 9psi idle oil pressure like they have LOL .totally different engine after a freshen up with new cam and springs and slight skim and port bowl tidy up though.
So I suppose its normal for 304 used oil to be like liquid metal like everyone I have changed the oil on?

Re: How much vacuum at idle

Posted: Sun Jan 25, 2015 10:40 pm
by delcowizzid
not really LOL they do sludge up good and proper over the years.i had one i did inlet gaskets and dizzy on for a guy you couldnt see the lifters it just had pushrods coming up out of dirt LOL

Re: How much vacuum at idle

Posted: Sun Jan 25, 2015 11:01 pm
by vlad01
every holden v8 I took apart were clean but heavily worn. bearings, cam and lifters, bores too. 308 and 253 were the worst of the ones but plenty of 304s with what id class as low Ks. Most I have come across were done by 200k.
Been disappointed in them longevity/reliability wise. Maybe I been spoiled with the V6s being tough engines lol

here is a 304 with 304k lol. I have never ever seen V6 develop a bore lip even with 500k. In all my engines I pull the piston out the top with no hesitation.

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Re: How much vacuum at idle

Posted: Sun Jan 25, 2015 11:11 pm
by krusty
If you have in the 30s vac she's good. Try adding idle timing to see if it pulls more vac but you'd probably only get even more on the stock cam