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67rustavenger Samba Member
Joined: February 24, 2015 Posts: 9762 Location: Oregon
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Posted: Sat Jul 31, 2021 2:23 pm Post subject: Interesting quote from Ohio Tom, Distributor Mod. |
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ivkings4 wrote: |
Ohio Tom wrote: |
So much wrong here, I'm not sure where to start...
idle mixture screws affect idle mixture. Not much else.
once you open past the first progression hole, fuel is metered by the idle jet size.
Mixture screws are way beyond affecting anything once you start the transition to mains.
My method for setting the screws. Dial it IN until that cyl drops out. Back it out slowly until it comes back. Add an 1/8 turn to 1/4 turn. Done.
Nothing magic about that.
Most effective if you have your idle rpm nice and low.
Many times folks think there is a problem with screws not working because they have the idle speed screws so fast, the throttle plates are above the first progression hole.
They have the speed screws cranked up because the base idle spark advance is at 5deg BTDC. So they have to turn up the speed screws to get it to idle. So much so, they are into the first progression hole.
This consumes lots of fuel for no dang reason. It's still burning on the way out the exhaust and will light exh valves on fire.
I modify most every distributor so that it idles at least 12deg BTDC. This speeds up the idle all by itself. thus allowing the butterflys to be more closed and mixture screws more responsive. Things fall into place real fast when you have 15deg base timing at idle.
This all I'm going to say on this subject.
Folks have their own ideas and opinions.
Mine come from setting up more IDF, HPMX, DRLA, IDA, DCNF's than I care to count. |
Couldn't agree more on the Timing being 14 to 15 at Idle. Especially if you have a bigger Cam. |
I saw this quote from Tom in another thread. I found it interesting. But didn't want to hijack the thread with off topic questions.
In the bold text above. Tom say's he modifies most distributors to 12° advance.
Is this as simple as setting the distributor to 12° advanced?
Or is Tom actually modifying the distributor? If the distributor is modified. What is being changed/modified to achieve the 12° advance at idle?
I'm curious about this. I do like the content of the quote. It makes sense and I plan on trying advancing my Magna Spark II, to 12° advance and adjusting the carbs from that timing setting.
So what's the story? _________________ I have learned over the years.
Cheap parts are gonna disappoint you.
Buy Once, Cry Once!
There's never enough time to do it right the first time. But there's always enough time to do it thrice.
GFY's Xevin and VW_Jimbo! |
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Glenn Mr. 010
Joined: December 25, 2001 Posts: 76912 Location: Sneaking up behind you
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Posted: Sat Jul 31, 2021 3:08 pm Post subject: Re: Interesting quote from Ohio Tom, Distributor Mod. |
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The 019 has 17° so ha I guess the idle at 12° yields a total of 29°. _________________ Glenn
74 Beetle Specs | 74 Beetle Restoration | 2180cc Engine
"You may not get what you pay for, but you always pay for what you get"
Member #1009
#BlueSquare |
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evanfrucht Samba Member
Joined: July 24, 2016 Posts: 2180 Location: Laurel Canyon, CA
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Posted: Sat Jul 31, 2021 3:14 pm Post subject: Re: Interesting quote from Ohio Tom, Distributor Mod. |
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Not positive but there might be a tab that can be bent to adjust the stop postion for where the advance starts?
I'm pretty sure there is a tab on 009's which can be bent to increase (or decrease) the amount of total advance. So without having one apart in front of me I gather there might be second tab to adjust the initial advance... speculating here. _________________ 1967 Bug ( the daily rod )
1964 Fury Wagon ( the pavement shredder ) |
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AlteWagen Troll
Joined: February 23, 2007 Posts: 8501 Location: PNW
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Posted: Sat Jul 31, 2021 3:16 pm Post subject: Re: Interesting quote from Ohio Tom, Distributor Mod. |
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Ive set tons of 009s to 30* total and they fall between 7-12 at idle. If really bad I just bend the tabs for the weight stops to dial in what the engine likes.
Ever wondered what that little oval plug is for? Popping it out gives you easy access so can adjust the weight stop without pulling the distributor!!! _________________ Grapes of Wrath $200 Engine Rebuild
Official Dual Carb Thread
Cylinder Head Quick Reference Sheet |
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Glenn Mr. 010
Joined: December 25, 2001 Posts: 76912 Location: Sneaking up behind you
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Posted: Sat Jul 31, 2021 4:07 pm Post subject: Re: Interesting quote from Ohio Tom, Distributor Mod. |
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The tabs can limit the advance, but not alter where it starts. _________________ Glenn
74 Beetle Specs | 74 Beetle Restoration | 2180cc Engine
"You may not get what you pay for, but you always pay for what you get"
Member #1009
#BlueSquare |
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Vanapplebomb Samba Member
Joined: November 03, 2010 Posts: 5410 Location: Holland, MI
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Posted: Sat Jul 31, 2021 4:21 pm Post subject: Re: Interesting quote from Ohio Tom, Distributor Mod. |
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Unless running a 34 PICT, 34PDSIT, Bosch Djet or Ljet that really need the late timing to behave properly, I really like the 12 degrees of initial advance at idle. It makes for nice snappy response off idle.
As long as you can really choke off the amount of air flowing with the throttles fully closed, it works great.
This can be problematic for the crowd that over-carbs there engine, or FI with large throttle bodies because it can be tough to get the idle speed down with that much air bypass and that much initial advance. But with sane carburetion or FI throttle bodies, it’s awesome. _________________ 1800 Type 4 Berrien 295
http://www.thesamba.com/vw/forum/viewtopic.php?t=487021 |
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74 Thing Samba Member
Joined: September 02, 2004 Posts: 7391
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Posted: Sat Jul 31, 2021 4:29 pm Post subject: Re: Interesting quote from Ohio Tom, Distributor Mod. |
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It is the stop tabs and spring perches. You can bend then to limit total advance and to have the timing come in faster or slower. |
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beetlenut Samba Member
Joined: May 27, 2009 Posts: 2983 Location: RI
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Posted: Sat Jul 31, 2021 8:02 pm Post subject: Re: Interesting quote from Ohio Tom, Distributor Mod. |
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I asked Tom about that in a PM, and he told me about bending the spring perches in about 5 degrees. I just did that tonight, and am going to check my timing tomorrow before I adjust my carb and take a test ride. _________________ scrapyards are for quitters
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Wetstuff wrote: |
... I spend more time shaking it than directing it?! I get a pretty decent blast for 8sec. then have to shake it again. |
- Words to live by right there!
My 74 Super rebuild thread: http://www.thesamba.com/vw/forum/viewtopic.php?p=6507104#6507104 |
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raygreenwood Samba Member
Joined: November 24, 2008 Posts: 21513 Location: Oklahoma City
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Posted: Sat Jul 31, 2021 8:09 pm Post subject: Re: Interesting quote from Ohio Tom, Distributor Mod. |
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Vanapplebomb wrote: |
Unless running a 34 PICT, 34PDSIT, Bosch Djet or Ljet that really need the late timing to behave properly, I really like the 12 degrees of initial advance at idle. It makes for nice snappy response off idle.
As long as you can really choke off the amount of air flowing with the throttles fully closed, it works great.
This can be problematic for the crowd that over-carbs there engine, or FI with large throttle bodies because it can be tough to get the idle speed down with that much air bypass and that much initial advance. But with sane carburetion or FI throttle bodies, it’s awesome. |
Late running ?...you mean ATDC? None of the D-jet runs retarded. Bus L-jet sure.
If you meant BTDC....
Agree....especially on D-jet...10-12 BTDC is exactly what it runs best at (your results may vary with cam).
Also...with regard to timing....and what Ohio Tom said....I would figure he is talking about "initial" advance set at idle. Meaning...if you want it advanced 12*...turn the distributor body. Set it vacuum hoses off and set idle to stay out of mechanical.
Everything else is "advance". Ray |
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ccowx Samba Member
Joined: May 15, 2015 Posts: 661 Location: Whitehorse Yukon
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Posted: Sat Jul 31, 2021 8:18 pm Post subject: Re: Interesting quote from Ohio Tom, Distributor Mod. |
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If you bend the tabs to limit the travel, it has the effect of shortening the advance curve. Since the distributor will have say, 18 degrees advance instead of 23 or so for a standard 009, you can set idle timing around 12-14 BTDC. Basically, the total timing is the initial plus the total advance. You want that number to land around 28-32, depending on many factors. If you make the dissy have less mechanical advance, you can set the initial higher without ending up at a huge number of total advance and destroying your engine.
Another thing to consider is that by bending the stop tabs, you are effectively cutting off the top bit of advance. This means that if you make the total mechanical advance stop at 18, you are probably achieving full advance at around 2400-2500 or so, instead of 2800-3000 like most 009's. Basically you are chopping around 20% of the travel, so it ends sooner. This might be a good thing, but just be aware of it.
Thanks!
Chris |
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Zed999 Samba Member
Joined: March 04, 2018 Posts: 1245 Location: UK
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Posted: Sun Aug 01, 2021 4:06 am Post subject: Re: Interesting quote from Ohio Tom, Distributor Mod. |
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There is a disconnect for cammy engines. I see the power/torque graphs often posted here showing engines that "do" almost nothing under 3-4,000 rpm so these guys surely don't care about where the curve ends up as their engines operate at full advance, or they are idling?
Where that curve lies / revs had a huge effect on my stump pulling type engine that operates mostly somewhere on the curve. In fact unless I'm giving it all I'm always somewhere on that curve. Bending the advance stops then rotating the distributor for a higher idle advance messed it up. I would have liked to adjust at the start end but gave up hope of that and bought a programmable 123 which seemed the easiest way to get what I wanted. Not recommending them, I read they are pretty rubbish at higher revs... higher than I ever get to. |
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Vanapplebomb Samba Member
Joined: November 03, 2010 Posts: 5410 Location: Holland, MI
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Posted: Sun Aug 01, 2021 6:51 am Post subject: Re: Interesting quote from Ohio Tom, Distributor Mod. |
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If you want to stay mechanical advance, the VJU 4 BR 8 (019 with adjustable vacuum advance) from a 36hp bus should work well. They had about 16 degrees mechanical, so with 38 degrees all in mechanical advance, initial timing would fall back to around 12 degrees.
I plan on using one of these on my next 66x103mm T4 build. I have never used an old cast iron distributor on a T4 before, but it looks ideal for someone who wants to stay mechanical and be able to fix it on a trail 50 miles from the nearest road with nothing more than a flathead screw driver.
For more flexibility, the 123 Bluetooth fully programmable distributors are a really nice option. _________________ 1800 Type 4 Berrien 295
http://www.thesamba.com/vw/forum/viewtopic.php?t=487021 |
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Casting Timmy Samba Member
Joined: August 04, 2012 Posts: 1221 Location: Kansas City, Kansas
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Posted: Sun Aug 01, 2021 7:56 am Post subject: Re: Interesting quote from Ohio Tom, Distributor Mod. |
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AlteWagen wrote: |
Ive set tons of 009s to 30* total and they fall between 7-12 at idle. If really bad I just bend the tabs for the weight stops to dial in what the engine likes.
Ever wondered what that little oval plug is for? Popping it out gives you easy access so can adjust the weight stop without pulling the distributor!!! |
That sounds like a good topic expansion as well, good thread everyone is doing here. _________________ T1 IRS Rebuild Book on Lulu.com
http://www.lulu.com/shop/tim-marshall/t1-irs-transaxle-book/paperback/product-24055997.html
As seen in Volks America Issue 14 Page 11 (Full page review) |
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raygreenwood Samba Member
Joined: November 24, 2008 Posts: 21513 Location: Oklahoma City
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Posted: Sun Aug 01, 2021 9:17 am Post subject: Re: Interesting quote from Ohio Tom, Distributor Mod. |
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Casting Timmy wrote: |
AlteWagen wrote: |
Ive set tons of 009s to 30* total and they fall between 7-12 at idle. If really bad I just bend the tabs for the weight stops to dial in what the engine likes.
Ever wondered what that little oval plug is for? Popping it out gives you easy access so can adjust the weight stop without pulling the distributor!!! |
That sounds like a good topic expansion as well, good thread everyone is doing here. |
I think so as well.....but everyone also needs to bear in mind in this discussion.....what each persons APPLICATION is that may post.
I say that because just in this thread already.....we have people speaking of "stockish" engines.....and people speaking of higher performance builds with totally different cams and different driveability. It can make a big difference in how you proceed in this adjustment.
Example:
Back to Ohio Tom's quoted comment:
" I adjust most every distributor so that it idles at least 12° BTDC. This speeds up the idle all by itsel, thus allowing the butterflys to be more closed and mixture screws to be more responsive"
So.....that is one particular method for one particular result.
So..... is he turning the distributor body to achieve more initial timing at idle? Because that WILL increase idle...and combustion efficiency by starting the ignition process when the piston is farther down in the bore. Classic ignition advance concept.....right?
But.....since nothing internal on the distributor was tweaked.....it does not increase or change the total amount of mechanical advance available......from the weights and springs.
But it does increase the total cumulative advance (12° from distributor position + X amount by mechanical system). So....is he limiting that by springs and tabs.....and if so.....does tightening springs affect the RATE or SPEED of the remaining advance?
As I noted and I think a little of what Vanapplebomb was pointing out.....other types of engines and fuel systems use various methods.
For instance .....with D-jet .....the throttle plate must always be 100% closed all the way when you are at idle. And.....while and idle setting if alightly higher than the stock listing is good.....it needs to be controlled. Excessive idle speed by just the ignition advance alone is detrimental to fuel control.
And.....the mechanical advance total RANGE needs to stay the same....so tweaking springs and tabs to get that 12° at idle is not ideal......which is why we move the distributor body.
But.....total cumulative advance needs to be limited at the top end. Its also worth it to keep in mind that the system I am describing.....also needs and uses vacuum advance.
In some of the higher performance versions (Porsche 914 1.7 and 2.0 and VW 412 with manual trans).....this is done with a set screw on the vacuum advance unit.
Ray |
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UK Luke 72 Samba Member
Joined: September 07, 2011 Posts: 2867 Location: Little Britain
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chrisflstf Samba Member
Joined: February 10, 2004 Posts: 3439 Location: San Diego
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Posted: Sun Aug 01, 2021 10:17 am Post subject: Re: Interesting quote from Ohio Tom, Distributor Mod. |
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Pics or videos doing advance mods to distributors would be helpful |
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beetlenut Samba Member
Joined: May 27, 2009 Posts: 2983 Location: RI
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Posted: Sun Aug 01, 2021 6:34 pm Post subject: Re: Interesting quote from Ohio Tom, Distributor Mod. |
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beetlenut wrote: |
I asked Tom about that in a PM, and he told me about bending the spring perches in about 5 degrees. I just did that tonight, and am going to check my timing tomorrow before I adjust my carb and take a test ride. |
OK, responding to my earlier post, I reset my timing to 32 degrees. 34 PICT 3 with a 28mm venturi and an 034 SVDA, vacuum hose off and plugged, 3k rpms. My idle timing went up to 12 degrees from 10 degrees. Re adjusted my carb slightly, and I have to say I've gotten rid of that a slight bog off idle. The extra idle timing helped! _________________ scrapyards are for quitters
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Wetstuff wrote: |
... I spend more time shaking it than directing it?! I get a pretty decent blast for 8sec. then have to shake it again. |
- Words to live by right there!
My 74 Super rebuild thread: http://www.thesamba.com/vw/forum/viewtopic.php?p=6507104#6507104 |
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j-dub Samba Member
Joined: November 09, 2003 Posts: 865 Location: Phoenix, AZ
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Posted: Sun Aug 01, 2021 6:59 pm Post subject: Re: Interesting quote from Ohio Tom, Distributor Mod. |
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I like Ray's point that the timing needs of the engine is very specific to application. I also like that the main point of this thread is that many of the common distributors we use do have some degree of adjust-ability if the user is willing to do some work and accept that it will be trial and error. I assume Tom's statement above was focusing on performance engines likely using dual carbs.
Some general rules regarding timing:
As RPM goes up the timing should go up, as load goes up the timing should come down.
More overlap and aggressive the cam, the sooner you can start to ramp in timing and often will want more initial timing.
The higher the cylinder pressure and high cylinder fill the less timing you need. This is why at a light cruise you can use 40-45 degrees(including the vacuum advance of an SVDA) but with a turbo on boost at wide open throttle you may only need 20-24 degrees.
Larger piston size needs more timing as the flame front has more distance to travel
Idle is a funny area where we are purposely NOT trying to maximize torque so we have torque in reserve as soon as we hit the throttle. If using carburetors it also needs to be set so that the butterflies are positioned right before the progression ports. _________________ 1957 Oval rag
"POLICE STATION TOILET STOLEN ... Cops have nothing to go on." |
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Janne71 Samba Member
Joined: September 29, 2015 Posts: 127 Location: Sweden
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Posted: Sun Aug 01, 2021 11:07 pm Post subject: Re: Interesting quote from Ohio Tom, Distributor Mod. |
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beetlenut wrote: |
beetlenut wrote: |
I asked Tom about that in a PM, and he told me about bending the spring perches in about 5 degrees. I just did that tonight, and am going to check my timing tomorrow before I adjust my carb and take a test ride. |
OK, responding to my earlier post, I reset my timing to 32 degrees. 34 PICT 3 with a 28mm venturi and an 034 SVDA, vacuum hose off and plugged, 3k rpms. My idle timing went up to 12 degrees from 10 degrees. Re adjusted my carb slightly, and I have to say I've gotten rid of that a slight bog off idle. The extra idle timing helped! |
Doesn’t that get to much advanced timings. The 034 advance max at 3800rpm if you put it on 32 degree at 3k? |
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Ohio Tom Samba Member
Joined: February 09, 2006 Posts: 1660 Location: Marshallville Ohio
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Posted: Mon Aug 02, 2021 4:51 am Post subject: Re: Interesting quote from Ohio Tom, Distributor Mod. |
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AlteWagen wrote: |
Ive set tons of 009s to 30* total and they fall between 7-12 at idle. If really bad I just bend the tabs for the weight stops to dial in what the engine likes.
Ever wondered what that little oval plug is for? Popping it out gives you easy access so can adjust the weight stop without pulling the distributor!!! |
Giving away secrets now...
I'm flattered by this post... |
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