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Topic: How to defeat vacuum advance and upgrade the mechanical (Read 18791 times) previous topic - next topic

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  • Bigrob26
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Re: How to defeat vacuum advance and upgrade the mechanical
Reply #20
my sidekick is a 1990 so it must be a crossover year like surly said. i took it apart just to be sure before i buy s/b chevy springs, sure enough it was exactly the same as the distributor used by beekiller in the pictures
now just to order a set of springs. id like to get one of the sets of different spring rates
any body try them??
-bobby

  • Surly
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  • All good things...
Re: How to defeat vacuum advance and upgrade the mechanical
Reply #21

It just dawned on me what Surly is referring to.  The early models had a carb. 


Nope. The earliest EFI systems only controlled the TBI, not the timing. The distributors used in those systems were garden variety vacuum advance types.

  • beekiller
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  • Krew Krawlers, Mountain Division
Re: How to defeat vacuum advance and upgrade the mechanical
Reply #22
So the early models didn't have carbs?   ???
All I want from tomorrow is to get it better than today.

Claiming you are offended is essentially saying you are incapable of controlling and managing your emotions, so everyone else should do it for you.


  • Bigrob26
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Re: How to defeat vacuum advance and upgrade the mechanical
Reply #24
how do i know how much to grind off of the centrifugal advance weights. i have an idea of how to do it but im not sure.
also how much maximum advance would you reccomend
i also ordered a set of springs, the same as listed by ScotY

if any body has done this before and has any input it would be appreciated  ;D
-bobby

  • ZUKIMON
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  • Krew Krawlers
  • Krew Krawlers
Re: How to defeat vacuum advance and upgrade the mechanical
Reply #25
Easiest way to tell if you have vacuum advance, and if this mod will work for you is to know if you have a vacuum hose going to your dizzy. ;)  If you don't, then you won't have the need for this mod. :D




I have a great wife. ;)

  • Bigrob26
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Re: How to defeat vacuum advance and upgrade the mechanical
Reply #26
i do have the right dizzy to do this i just dont know how much i can SAFELY advance the timing.
and how much do i grind off of the weights to allow them to advance more?
-bobby

  • beekiller
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  • Krew Krawlers, Mountain Division
Re: How to defeat vacuum advance and upgrade the mechanical
Reply #27
I didn't grind any off the weights.  You're just increasing the slot where the stop tab travels.  If you really wanna get technical with how much advance, mic the stock distance, then do the math to figure how much needs to be ground to produce the desired advance.  But it isn't going to be a linear function....probably more like a log function.   ;)
All I want from tomorrow is to get it better than today.

Claiming you are offended is essentially saying you are incapable of controlling and managing your emotions, so everyone else should do it for you.

  • jsoluna
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Re: How to defeat vacuum advance and upgrade the mechanical
Reply #28
Great writeup, great pics!


Some questions, though.  I'd be doing this mod on a daily driver, with the CV carb setup and a header with free-flowing exhaust.  I'm not sure what kind of advance I'm really looking for here, that is, I'm not sure how much to grind off that tab.  I'm wanting to get the engine running as efficiently as possible for high mpg's.  Any recommendations?  I've never messed with distributor timing advance systems in depth.

My other question:  are most of the people running a CV carb setup not even worrying about having the correct amount of timing advance?  I didn't find many posts on this issue, but it seems like a ton of people are starting to use the CV carb setup over the Weber...

  • beekiller
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  • Krew Krawlers, Mountain Division
Re: How to defeat vacuum advance and upgrade the mechanical
Reply #29
Going from everything I've read (here), it seems mid 30s total advance is the target.  Say 34-35 degrees.  Obviously this isn't an exact science unless you have a lot of time and patience along with a good micrometer to measure the gap and relate it to the changes made.  However, adding approx 50% to the existing gap will get you close.  I should have written down my measurements but I was more concerned with getting the procedure and pix nailed down.    :-[   If anything, shoot for not quite enough as opposed to too much.   ;)


Timing advance has been in several tech discussions here.  You may be able to find more info on CV carbs and timing in the tech section.  One of those threads is where the idea for this originated.   :)
All I want from tomorrow is to get it better than today.

Claiming you are offended is essentially saying you are incapable of controlling and managing your emotions, so everyone else should do it for you.

  • augeter
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Re: How to defeat vacuum advance and upgrade the mechanical
Reply #30
When I first did the Harley conversion on my 1.6 I set the timing stock and it was a little hard to start. ran very well. Backed up the timing and now it started great but, 3000 and it was running out of steam. After the DIST MOD it now starts easy and pulls strong past 5500. I try to limitmy shifts to 5000 max, most of the time 4000 works. I try to keep the revs down, this is a 1.6 after all and I am pushing 200K miles. I can't believe anyone with a Harley hasn't done this MOD. Like night and day. With my set up my peak torque seems to be 2900-3300. I need to play around and see if I can't lower that.

1.6 in a 96 TT, pacesetter header, no cat, home made 2" exhaust with a Turbo Muffler, 93 springs on the suspension, Stock gears, 215/75R15 with stock rims, 25 MPG intown, 28 @75-80 highway.  I also have not done the final jetting on the carb. OK for now but it's lean on idle and very rich at cruise. Guess this will be my summer project.
"It seems common sense isn't very common anymore" Eustance 2012
Batteries not included, Your mileage will vary.

  • jsoluna
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Re: How to defeat vacuum advance and upgrade the mechanical
Reply #31
Thanks guys.  I guess I was surprised as well, that there weren't more mentions of the problem of not having that additional advance accounted for with the carb swap.  The 50 % more advance equates to probably a few milimeters being shaved off the stop?

I think I can actually see the difference between modified stop and original stop in the two pics, just looked at it more closely.  So you measured the distance between the stop and the metal piece, halved that value and shaved that value off the stop?
  • Last Edit: Monday, Dec 28, 2009, 01:59 AM by jsoluna

  • beekiller
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  • Krew Krawlers, Mountain Division
Re: How to defeat vacuum advance and upgrade the mechanical
Reply #32

Thanks guys.  I guess I was surprised as well, that there weren't more mentions of the problem of not having that additional advance accounted for with the carb swap.  The 50 % more advance equates to probably a few milimeters being shaved off the stop?

I think I can actually see the difference between modified stop and original stop in the two pics, just looked at it more closely.  So you measured the distance between the stop and the metal piece, halved that value and shaved that value off the stop?



You got it.  [thumbsup]  Perhaps I should be more specific about being so general.  The total timing as well as the advance curve desired will depend on many factors such as which engine you're running (1.3, 1.6), any mods done to it, it's condition, etc.  So it does involve some 'test and tune' to optimize it to your setup.   ;)






All I want from tomorrow is to get it better than today.

Claiming you are offended is essentially saying you are incapable of controlling and managing your emotions, so everyone else should do it for you.

  • jsoluna
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Re: How to defeat vacuum advance and upgrade the mechanical
Reply #33
Crystal clear.  Thanks man.

  • pacman99
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Re: How to defeat vacuum advance and upgrade the mechanical
Reply #34
Would this work for a propane setup.  I don't think I'm getting the timing I need and with no vacumn advance it seems a little sluggish?

Don
Just like a Polaris, goes anywhere, but with heat!!

  • beekiller
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  • Krew Krawlers, Mountain Division
Re: How to defeat vacuum advance and upgrade the mechanical
Reply #35

Would this work for a propane setup.  I don't think I'm getting the timing I need and with no vacumn advance it seems a little sluggish?

Don



Hey Don!  It should work fine, though I wouldn't have a clue how much more advance you'll need for prop compared to pump gas.   ;D 
All I want from tomorrow is to get it better than today.

Claiming you are offended is essentially saying you are incapable of controlling and managing your emotions, so everyone else should do it for you.

  • pacman99
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Re: How to defeat vacuum advance and upgrade the mechanical
Reply #36
When I get the bearings in the 1.6 I will have some time hopefully to try this.

Don
Just like a Polaris, goes anywhere, but with heat!!

  • beekiller
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  • Krew Krawlers, Mountain Division
Re: How to defeat vacuum advance and upgrade the mechanical
Reply #37

Crystal clear.  Thanks man.



It's time to expand on your question a little more.  For anyone who tries this mod, a good end point is to achieve around 35* of total timing.  Having a couple of dizzies around to compare notes and experiment, the added 50% was too much. 


With the dizzy disassembled, find the advance marking.  Some say 8.5, others 10.5.  If it's a 10.5, put the lighter springs in it and see where you get, tear down and trim if needed.  If it's an 8.5, trim about 25%.  Hope I haven't messed anyone up already.  Mentally I had tried adding the vac adv into the equation as well, and it just isn't necessary.   ;)  Yeah, I'm slow sometimes.....but trial and error got to this point.   :D
All I want from tomorrow is to get it better than today.

Claiming you are offended is essentially saying you are incapable of controlling and managing your emotions, so everyone else should do it for you.

  • beekiller
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  • Krew Krawlers, Mountain Division
Re: How to defeat vacuum advance and upgrade the mechanical
Reply #38
Here is more info:

Using the smallest (black) springs from the Mr. Gasket Advance Curve Kit produces a good curve.  Part number is #929G

http://www.oreillyauto.com/site/c/detail/MRG0/929G.oap?keyword=929g


Initial timing set around 12-14*.
All I want from tomorrow is to get it better than today.

Claiming you are offended is essentially saying you are incapable of controlling and managing your emotions, so everyone else should do it for you.

  • v-stone
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Re: How to defeat vacuum advance and upgrade the mechanical
Reply #39
THANK YOU!!!
I putting the CV carb on right now and was worried about the advance. Just finished this mod and it was pretty easy (hope I did it right).
3rd Zuk- 86 samurai 5" lift, 31" tires, side draft carb. I love my little micro machine!