This site is not affiliated with AGCO Inc., Duluth GA., Allis-Chalmers Co., Milwaukee, WI., or any surviving or related corporate entity. All trademarks remain the property of their respective owners. All information presented herein should be considered the result of an un-moderated public forum with no responsibility for its accuracy or usability assumed by the users and sponsors of this site or any corporate entity.
The Forum Parts and Services Unofficial Allis Store Tractor Shows Serial Numbers History
Forum Home Forum Home > Other Topics > Pulling Forum
  New Posts New Posts
  FAQ FAQ  Forum Search   Events   Register Register  Login Login


Tuning with a Vacuum Gauge

 Post Reply Post Reply
Author
Message
wrightk20 View Drop Down
Bronze Level
Bronze Level
Avatar

Joined: 04 Jul 2010
Location: wisconsin
Points: 52
Post Options Post Options   Thanks (0) Thanks(0)   Quote wrightk20 Quote  Post ReplyReply Direct Link To This Post Topic: Tuning with a Vacuum Gauge
    Posted: 27 Dec 2012 at 11:18pm
I have heard about tuning with a vacuum gauge and i'm wondering what the procedure is. I understand tuning in the idle mixture with the gauge to try and get the highest vacuum, but are you guys using the vacuum gauge to tune wide open throttle under load as well? I would think that at wide open throttle under load there would be 0 on the gauge with a properly sized carburetor, so i would assume tuning would not work with a vacuum gauge. I could very much so be wrong. Just wondering if anyone would enlighten me with the proper procedure. Thanks, Kevin.
Back to Top
Sponsored Links


Back to Top
D-17_Dave View Drop Down
Orange Level
Orange Level


Joined: 11 Sep 2009
Location: Mocksville NC
Points: 990
Post Options Post Options   Thanks (0) Thanks(0)   Quote D-17_Dave Quote  Post ReplyReply Direct Link To This Post Posted: 28 Dec 2012 at 2:06am
Your spot on. As soon as you open the throttle the vacuum drops. Automotive carbs have a port that comes off the venturi, this will give you 0 on idle and increase as you open the butterfly. But this does you no good for tuning, it;s an accesory port for selected attachments on the engine like the EGR valve.
Yea, I can fix that.....
Back to Top
CTuckerNWIL View Drop Down
Orange Level
Orange Level
Avatar

Joined: 11 Sep 2009
Location: NW Illinois
Points: 22807
Post Options Post Options   Thanks (0) Thanks(0)   Quote CTuckerNWIL Quote  Post ReplyReply Direct Link To This Post Posted: 28 Dec 2012 at 6:20am
How could the vacuum drop to 0? If it did, the engine wouldn't be able to draw air or fuel in to keep running.
http://www.ae-ta.com
Lena 1935 WC12xxx, Willie 1951 CA6xx Dad bought new, 1954WD45 PS, 1960 D17 NF
Back to Top
mlpankey View Drop Down
Orange Level
Orange Level


Joined: 13 Sep 2009
Location: Vols country
Points: 4580
Post Options Post Options   Thanks (0) Thanks(0)   Quote mlpankey Quote  Post ReplyReply Direct Link To This Post Posted: 28 Dec 2012 at 7:39am
you have to be reading actual manifold vacuum and no ported vacuum. Ported vacuum as already stated rises with butterfly opening. warm engine adjust idle mixture for the highest reading then adjust timming to highest reading then pull it back 1/2 to 1 inch to keep from detonating.    Ctucker the answere is venturi effect . I dont adjust timming this way . Any time you advance timing the idle comes up.  I adjust timing by sound and timming tape and light.

Edited by mlpankey - 28 Dec 2012 at 7:46am
Back to Top
cotncrzy View Drop Down
Orange Level
Orange Level


Joined: 07 Oct 2009
Location: TENNESSEE
Points: 599
Post Options Post Options   Thanks (0) Thanks(0)   Quote cotncrzy Quote  Post ReplyReply Direct Link To This Post Posted: 28 Dec 2012 at 7:48am
At an idle for both?
C, WD45,WD puller, 185, 200, 7060 Red Belly, 7060 Black Belly,8010, and a R52 Gleaner, AND PROUD OF THEM!
Back to Top
mlpankey View Drop Down
Orange Level
Orange Level


Joined: 13 Sep 2009
Location: Vols country
Points: 4580
Post Options Post Options   Thanks (0) Thanks(0)   Quote mlpankey Quote  Post ReplyReply Direct Link To This Post Posted: 28 Dec 2012 at 8:02am
Originally posted by cotncrzy cotncrzy wrote:

At an idle for both?
at idle sorry should have said it but forgot to.
Back to Top
Mrgoodwrench View Drop Down
Orange Level
Orange Level
Avatar

Joined: 03 Apr 2011
Location: CHICORA PA
Points: 2077
Post Options Post Options   Thanks (0) Thanks(0)   Quote Mrgoodwrench Quote  Post ReplyReply Direct Link To This Post Posted: 28 Dec 2012 at 8:23am
i've used timing tape on v8's but where do you install it in a tractor 4cyl like a 226...also what kind of timing you running, obviously it will be different with every set up just looking for a guide line
 
one other question when you say pull it bact 1/2 to1 inch i assume you mean retard the timing?


Edited by Mrgoodwrench - 28 Dec 2012 at 8:24am
There are 3 ways to do job GOOD, FAST, CHEAP. YOU MAY CHOOSE 2. If its FAST & CHEAP it won't be GOOD, if it's GOOD & CHEAP it won't be FAST, and if its GOOD & FAST it won't be CHEAP!!!!
Back to Top
mlpankey View Drop Down
Orange Level
Orange Level


Joined: 13 Sep 2009
Location: Vols country
Points: 4580
Post Options Post Options   Thanks (0) Thanks(0)   Quote mlpankey Quote  Post ReplyReply Direct Link To This Post Posted: 28 Dec 2012 at 8:34am
Originally posted by Mrgoodwrench Mrgoodwrench wrote:

i've used timing tape on v8's but where do you install it in a tractor 4cyl like a 226...also what kind of timing you running, obviously it will be different with every set up just looking for a guide line
 
one other question when you say pull it bact 1/2 to1 inch i assume you mean retard the timing?
  retard the timming so the vacuum falls.     with a degree wheel you can transpose degree marks with a hacksaw blade into the pulley  once you 0 then you have the base line for tape you also need o fabricate a good non moveable pointer . the degree of modification will depend on how much advance initial timming needed. ofcoarse my initial is also my total.

Edited by mlpankey - 28 Dec 2012 at 8:37am
Back to Top
wrightk20 View Drop Down
Bronze Level
Bronze Level
Avatar

Joined: 04 Jul 2010
Location: wisconsin
Points: 52
Post Options Post Options   Thanks (0) Thanks(0)   Quote wrightk20 Quote  Post ReplyReply Direct Link To This Post Posted: 28 Dec 2012 at 9:08am
So then this is only used to tune idle then?
Back to Top
mlpankey View Drop Down
Orange Level
Orange Level


Joined: 13 Sep 2009
Location: Vols country
Points: 4580
Post Options Post Options   Thanks (0) Thanks(0)   Quote mlpankey Quote  Post ReplyReply Direct Link To This Post Posted: 28 Dec 2012 at 9:15am
pretty much in my opinion
Back to Top
Hudsonator View Drop Down
Orange Level
Orange Level
Avatar

Joined: 21 Oct 2009
Location: Tennessee
Points: 2113
Post Options Post Options   Thanks (0) Thanks(0)   Quote Hudsonator Quote  Post ReplyReply Direct Link To This Post Posted: 28 Dec 2012 at 9:47am
About any method of tuning is futile these days if you are running "pump gas".  The ethanol content and/or additives are so inconsistent, as to drive a carbureted/distributor engine crazy.  Modern computer controlled engines don't have these problems, as they constantly "re-tune" themselves to accomodate the variable fuel quality.   Its dang near impossible to tune a carb/dist combo to an "optimum" state these days, as that "tune" is only as good as the particular tank of fuel being run.  At best, you can hit a happy medium, a low-medium at that.
 
As far as fuel goes, even if your pulling engine doesn't need it for octane reasons - find a good, high quality racing fuel.  For no other reason than consistency.  I don't pull anymore, but this fuel problem is driving me nuts with my gas-burning farm tractors, antique cars, and carbureted motorcycles.
 
A vacuum guage is great for tuning, particularly lean-best-idle and timing.  What it does for your timing is compensate for altitude and atmospheric pressure.  If you adjust your timing until maximum vacuum is reached, this is the best timing at idle for your altitude and weather conditions.  The generic backing off 1/2 to 1" mmHg is to compensate for crappy fuel and crappy advance curves.
 
Theoreticly, if your distributor is curved properly to your engine and fuel - the vacuum gauge is the quickest and best timing tool you have, simply adjust to max vacuum.  Even if your distributor is not curved so good, you can adjust your timing to get max power at whatever rpm you are running at max power, then back the engine down to idle and observe what your vacuum is - bingo - that's your vacuum setting at idle.
 
Lean-best-idle is simple as well.  Adjust your timing to max vacuum first (regardless of whatever your final desired mmHg is), then adjust the idle mixture screw lean until you notice a drop in vacuum.  Go rich until it reaches max again, then adjust your idle speed down.  Repeat.  You are looking for the highest vacuum reading you can get, as lean as your mixture screw will allow, at the lowest idle speed your engine can maintain.  Once this is done, return your idle speed to whatever you want and return your timing to whatever mmHg you want to run.
 
About the only time I use a timing light anymore, is to correlate vacuum readings to actual distributor timing or on a "first fire-up" after having the distributor out.
There isn't much a WC can't do.

WD's just do it better.
Back to Top
Larry(OH) View Drop Down
Orange Level
Orange Level
Avatar

Joined: 11 Sep 2009
Location: Shreve Ohio
Points: 1576
Post Options Post Options   Thanks (0) Thanks(0)   Quote Larry(OH) Quote  Post ReplyReply Direct Link To This Post Posted: 28 Dec 2012 at 3:02pm
I was using it in my Jeep in the manifold runner to get readings, then tuned the power valve in the holley off of it.  Also played with the timing some as stated, but not that much
'40 WC puller,'50 WD puller,'50 M puller '65 770 Ollie

*ALLIS EXPRESS contact*

I can explain it to you, BUT I cannot understand it for you!!
Back to Top
 Post Reply Post Reply
  Share Topic   

Forum Jump Forum Permissions View Drop Down

Forum Software by Web Wiz Forums® version 11.10
Copyright ©2001-2017 Web Wiz Ltd.

This page was generated in 0.047 seconds.


Help Support the
Unofficial Allis Forum