Vacuum Gauge in center console

[drock87]

Hi all.  I guess considering AMC is the only car I know with a vacuum gauge....I would like to know more about it.  I have a Sport Wagon with a factory gauge package.

-What (and where) vacuum is it actually measuring?  What should it be doing under normal driving (and where at?)

Thanks nest

[Budwisr]

Vacuum gauges are actually very useful. They are more common on cars from the sixties. They simply measure manifold vaccum. Here is a chart that shows how to read a vacuum gauge for troubleshooting. Also they can tell you when the engine is operating at the engine's highest efficiency (highest vaccum).

[drock87]

Thank you! Great help.  Makes me think I have a timing issue..... I'm still new...once I'm at 15 posts I'll be back with an egg 

[eagleman]

Good info.Should be useful to a lot of folks.

[carnuck]

My old Bird ('66 Firebird convertible with OHC 6 cyl and 4 speed with O/D) had the factory gauge as did many higher performance and even my Mitsubishi Montero had one (and level/yaw/pitch gauges)

[AMCKen]

A 258 with lots of advance and idling will have near 20" vacuum. My 232 74 Gremlin cruises on the highway with about 10" vacuum, the 401 80 AMX is at about 15". Poor old J10 with 258 and 2.72 diffs is more near 5" and the engine is getting pretty tired of working so hard all the time.

[carnuck]

Did you do a MC2100 swap on the J10 yet? Water trickle decarburizing? Did the cat clog up (mine "fell" off and power perked up considerably, even with 220,000 miles on it. Napa 15W50 synthetic took care of a LOT of it's blowby and exhaust smoke too0)

[AMCKen]

The BBD works fine so I'm leaving it on. With those differentials the highway rpm is just 1900 at 60mph. I have a set of 3.31s to swap in one day that should help the engine get to a more comfortable rpm. I haven't fiddle with the jets and needles it it yet.

[carnuck]

Swap the rear first and make sure you like the way it feels highway cruising before doing the front.

[AMCKen]

Math says rpm should be about 2300 with the 3.31s and that's fine.

[standup650]

Did you do a MC2100 swap on the J10 yet? Water trickle decarburizing? Did the cat clog up (mine "fell" off and power perked up considerably, even with 220,000 miles on it. Napa 15W50 synthetic took care of a LOT of it's blowby and exhaust smoke too0)

i hope your adding a zinc additive. if not then say goodbye to your cam and tappets.

[carnuck]

Hasn't bothered the cam and tappets in 230,000 of the 375,000 on my MJ

[standup650]

yup and zinc only went away in the last ten years topps. dont take my word for it ask an engine builder. or just google it. newer engines dont need it so they cut it way back in the oil our engines do!

[carnuck]

I've put all those miles on just since '99. Motor is due for a rewind now (still original rings. I've been waiting for it to wear out so I could put my stroker 6 in))

[standup650]

I'm not trying to be an :censored:head just in case you think I am. I'm just looking out for fellow AMCer's. if you google "flat tappet engine oil" there is hours of reading. and everyone i have talked to from engine builders to hotroder's say the same thing. at least read this article this covers it pretty good:
http://www.hotrod.com/techarticles/engine/flat_tappet_cam_tech/viewall.html
I just run a additive every oil change. the valve train is a little quieter now and the oil seams to stay golden longer.