3rd progression hole in IDAs

[67worshipper]

i know the reasoning for the 3rd progression hole being put in IDAs but my question is why not open up the holes that are already there instead of putting in more?

[rick m]

Several small holes will pull less fuel at idle than two big ones.  Dellorto's have 5 small progression holes.  What the holes do is allow enough fuel to pull into the motor as the throttle plates open and you transition from the idle circut to the main jets.  IDAs have a big flat spot in them and are notorious for their bog when you stab them.  When you put more transition holes in, it smooths out the bottom end.

If you get a chance to look inside a Dellorto, turn it upside down and look at the 5 small holes that are visible.  If two big holes were the way to do it,  the factories would have.  However, the volume of two big holes would most likely make it way to rich at the bottom. Go with the proven method of adding the third small hole that is the same size as what is there, or even one step smaller.

This process has smoothed out every set of IDAs I have owned and run.

Rick M

[Jim Ratto]

67w:

I know the "3rd hole" procedure is popular for the 48 Weber, but honestly, I think it isn't necessary, at least on 1800cc and up.

I've run 48's on my car for 18 years, and have only had driveability issues in low-to-mid rpm when "something's wrong" (intake leak, idle air holder has come unscrewed, fuel pressure fluke, float setting off, etc.). When all the tuning variables are where they should be, there is NO flat spot, or hesitation. I've set up 48 Webers on a few motors in the last 20 years, and only one had the dreaded "flat spot" that so many are afraid of, and I never got that one quite right, but didn't spend enough time with it either. It was John Bates' 1776. I think if we would have experimented more with ignition advance and idle air hoders, we could have gotten it to run like a kitten.

The hesitation is often due to idle/progression curve that is too lean. You'd be surprised how rich the curve is on a 48IDA, at idle and progression, to get the engine to pull seamlessly.

[67worshipper]

thanks for the replys guys.informative as usual

[rick m]

Ratto...try the third hole and you won't have to spend so much time on all the other crap.  It smooths them out nicely, makes them much more driveable and fun. Art Thaen (ACE VW in SLC) had a set on Chris Larsen's oval in Salt Lake City that drove like stock carbs.  The tunability of the carb becomes so much better with the third hole.  That is one of the secrets of the Dellorto's being so smooth throughout their whole progression range.

Gary Berg started doing it years ago too.  He actually did a set of my IDAs in the early 90's for me to put on the 2110 I had in my 67.  After having owned IDAs and spent a lot of time on tuning and jetting to get them to be more driveable,  I will never run a set again without the progression hole mods.  Just some food for thought.  It is a huge improvement on making them a more streetable and driveable carburetor.

True, you do not have to make the mods but you will never have a set without the mods once you've done it. It is a vast improvement for driveability.

RM

[deano]

You might find that engines with 9.0 or better compression do not need the extra progression hole(s).

[John Rayburn]

Third hole is unnecessary. "ALL that other crap " takes a fraction of the amount of time compared to tearing down a set of perfectly good carbs to drill holes in them. Mine have always run as smooth as my old 48 Dells and it took little tuning to get them that way. Perfectly smooth, perfectly driveable, and a lot of fun. Anybody that's ever gone for a ride in my car in either it's IDA or Dell state can attest to the smooth transition.

[rick m]

Thats the beauty of diversity and the freedom to express an opinion. For some of us who use IDAs for longer drives or have motors running less compression, as DEANO has suggested,  the application works well with these type driver motors.  There is no one application fits all.  It is just like motor building.  You could have 10 guys build a motor with the same parts, same displacement, even cam, carburetion and compression, and the tune and knowledge of engine building and preparation would be the big seperator.

Application will always be a variable for how people develop their motor, their tune and their use of a motor and all the ancillary parts.  Again John, your motor and what you are doing probably works well.  My perspective is coming from a different angle and application. There are a lot of great tuners in the hobby and around the world.

Rick M

[Jim Ratto]

Mine are staying as Weber made them. I'm 100% convinced my car runs exactly how I want it to. I'd be really surprised if a third hole would ever cover up "crap" like misadjusted float, fuel pressure, intake leaks or wrong jets. I drive it 1000-1200 miles a month too.
John, will you work on my Long Distance Flight T shirt 

[John Rayburn]

I'm on it!

[Bruce]

Mine are staying as Weber made them.

For a very short time, some of the last Italian made IDAs came with the 3rd hole from Weber.  I think that's why the modification is so popular.

[Zach Gomulka]

Mine are staying as Weber made them.

For a very short time, some of the last Italian made IDAs came with the 3rd hole from Weber.  I think that's why the modification is so popular.

Ohh snap

Why wouldn't you drill the third hole? Say you already have the carbs apart for a rebuild, what is the harm? Go ahead and enlarge the float bowl while you're at it...

[Harry/FDK]

I'm on it!

2 Please, To get me motivated and get my rear end driving this Winter.

[Jim Ratto]

no harm unless you call throwing the tune of my carbs out the window and starting over because "somebody said so." I've driven engines with 3rd hole, and in one instance, it was the worst running 48IDA engine I have ever driven, until it got up 5K and up. FYI it was built and dynoed and tuned by Gary Berg and it had an annoying dead hole, the worst I have ever driven (48IDA) and it was delivered as such from them. The owner asked me to get involved in fixing the flat spot, and it took a 70 idle and a custom drilled 140 air holder to "lessen" it. I'd say alot more time and frustration was involved with those 3 holes than any stock 2 hold 48 I've tuned. Before that experience, I had no opinion. My carbs ran well when the sum of all parts was in order. After driving this 2213 nose-diver, there's no way.
Ever drive a 34PICT-3 stocker with a 009? Imagine that flat spot squared.

[Harry/FDK]

Then i think (and knew) i made a big mistake.

[Sarge]

I've had them both ways and can't say one way is better then the other.  Carefully thought out engine combos and tuning make all the difference in a nice driving street car. 

[louisb]

no harm unless you call throwing the tune of my carbs out the window and starting over because "somebody said so." I've driven engines with 3rd hole, and in one instance, it was the worst running 48IDA engine I have ever driven, until it got up 5K and up. FYI it was built and dynoed and tuned by Gary Berg and it had an annoying dead hole, the worst I have ever driven (48IDA) and it was delivered as such from them. The owner asked me to get involved in fixing the flat spot, and it took a 70 idle and a custom drilled 140 air holder to "lessen" it. I'd say alot more time and frustration was involved with those 3 holes than any stock 2 hold 48 I've tuned. Before that experience, I had no opinion. My carbs ran well when the sum of all parts was in order. After driving this 2213 nose-diver, there's no way.
Ever drive a 34PICT-3 stocker with a 009? Imagine that flat spot squared.

Not really taking a side here. Just pointing out that if it was built by a Berg, it probably had low compression.

--louis

[Jim Ratto]

This one didn't
It was 90.5 x 86, Carillo 5.5, FK87, 11.0:1, Berg 872's, yada yada yada. Lived on a diet of C12

[Zach Gomulka]

Ever drive a 34PICT-3 stocker with a 009? Imagine that flat spot squared.

I have driven my car with a 34PICT and a 010... that was nasty!

I've only driven two IDA powered VWs. One was my buddies '68, 2276, blah blah blah. It had the third hole and drove very well. The other was my IDA's on my buddies 1915 '67 sedan. It drove well with only 2 holes, but he said it needed a little tuning to make up for the high elevation we were at.

[rick m]

To each his own on this subject. The paradigm of continuous improvement comes to mind here. Tune has everything to do with any application but if I can enhance something and improve it, I will. For those of us who have tried the third hole and know full well how to tune our motors for all applications, we've found the third hole a value-added move.  I can drive my engine with IDAs at any elevation (altitude) and in any combination of weather circumstances and not have to make constant tuning mods, jet changes or timing changes on a motor that has had this done.  Our use of IDAs has been varied enough that we find the third hole an enhancement...not a cureall.

Art Thraen is very dialed in on this and I think everyone who knows him, his work and the IDAs he turns out, is equally as pleased with the modification. There is no mandate by anyone to perform the mods but I assure you it does not ruin a set of IDAs as Ratto has suggested.  That is purely his opinion but not held as accurate by those with years more experience in many applications running IDAs.  Like any subject, study it out and don't listen to one or two perspectives.

Everyone has an opinion.  We purely go by what we find improves and enhances the performance of a VW motor with IDAs on it. For anyone who wants to do the modification and discuss it with a guy who is a well respected tuner who is dialed in on the process, give Art Thraen of ACE VW in SLC Utah a call. Whereas some have limited experience with this, he has done more IDA mods than anyone I know.  Gary Berg has also done this for years. It is an enhancement.

The modification is not the end of all performance mods.  Tuning, including jetting, venturi size, float levels, etc, etc, all play a part in the tuning. This is simply a mod that makes them very driveable from 1,000rpms and up, along with the idle jet mods too.

RM

[andy M.]

personally I like the IDA flat spot, it's a good reminder that I'm driving something that wants to kill me if i don't pay attention,

andy

[dougmische]

I wonder if the V8 guys running quad 48IDA's on Cobra replicas and such have anything on their forums about progression circuitry mods

[Jim Ratto]

I wonder if the V8 guys running quad 48IDA's on Cobra replicas and such have anything on their forums about progression circuitry mods

Hi Doug 

check this out... http://www.clubcobra.com/forums/archive/index.php/index.php?t-74594.html

see ya next month

[Bruce]

The few V8 guys I've talked to hate the way we "mess-up" IDAs by drilling the 3rd hole.  I think it's fear of what they don't know.  IMO, they aren't brave enough to try.  Look at Jim's link.  Those guys fear 42mm vents in a 7 liter engine.  They're too big!

[Jim Ratto]

To each his own on this subject. The paradigm of continuous improvement comes to mind here. Tune has everything to do with any application but if I can enhance something and improve it, I will. For those of us who have tried the third hole and know full well how to tune our motors for all applications, we've found the third hole a value-added move.  I can drive my engine with IDAs at any elevation (altitude) and in any combination of weather circumstances and not have to make constant tuning mods, jet changes or timing changes on a motor that has had this done.  Our use of IDAs has been varied enough that we find the third hole an enhancement...not a cureall.

Art Thraen is very dialed in on this and I think everyone who knows him, his work and the IDAs he turns out, is equally as pleased with the modification. There is no mandate by anyone to perform the mods but I assure you it does not ruin a set of IDAs as Ratto has suggested.  That is purely his opinion but not held as accurate by those with years more experience in many applications running IDAs.  Like any subject, study it out and don't listen to one or two perspectives.

Everyone has an opinion.  We purely go by what we find improves and enhances the performance of a VW motor with IDAs on it. For anyone who wants to do the modification and discuss it with a guy who is a well respected tuner who is dialed in on the process, give Art Thraen of ACE VW in SLC Utah a call. Whereas some have limited experience with this, he has done more IDA mods than anyone I know.  Gary Berg has also done this for years. It is an enhancement.

The modification is not the end of all performance mods.  Tuning, including jetting, venturi size, float levels, etc, etc, all play a part in the tuning. This is simply a mod that makes them very driveable from 1,000rpms and up, along with the idle jet mods too.

RM

Wow, I guess my "opinion" is really misunderstood here. Where, exactly, did I use the word "ruin", Rick? I'm not saying anyone is wrong here at all. I am aware that Art Thraen does fantastic work, and if I felt my abilities were inadequate to get my car and other cars to run as well as my standards allow (which you can ask anyone that knows me are very high, probably to a fault). I'm not here to beat my chest and profess that others have no or little experience. I don't doubt that the work you have had done on your cars has been top notch or that your 48's run like tops. I'm only saying that it isn't correct that all, most, whatever, 48IDA Webers are going to bog and have flat spots unless you poke more holes in them. If you don't agree, or believe me, that's fine, Rick. Anytime you want to find the flat spot in my car, come on out and go for it. But please don't beat me up for my opinion, which is based on experience I have encountered, and don't discount my abilities or my experience. If I had posted that the real way to make your 48 Webers to run perfect was to bolt them on upside down, then fine, bash me.
If I had a flat spot I couldn't tune out then I would look into a 3rd hole mod. But why dick with something that isn't broken?

[Bruce]

I recall talking to Doug about the 3rd hole.  He had an idea I've never heard from anyone else.  Like a Dellorto DRLA, he drills his 3rd hole much larger than the lower ones.  His reasoning is that the signal that pulls through the holes deminishes as the throttle opens up, so by drilling them bigger, you make them even more effective.  If you are going to do this, open the top one to 1.1mm.  Then try 1.2mm.  I think he said he's done 1.3mm on the top one.

I've only used my IDAs with the 3rd hole.  I've had it run really well, and even passed the smog numbers for 1975 model year once.  I've had no driveabilty problems either.
However, having driven Bill's car with only the stock holes, I've vowed to try IDAs that way.  To me, it is impressive if you can make a 60 idle jet work at sea level with only 2 progression holes.  Any IDA will run well with a 70 idle jet.  Just don't stand behind it when it idles.

[Sarge]

....  Any IDA will run well with a 70 idle jet.  Just don't stand behind it when it idles.

Truer words have yet to be spoken .  Back in the old days, it was only the main and air jets that we messed with it seemed.  You never wanted to spend much time idling at a stop light lest you be overcome by the fumes.  I like Deano's idea about compression ratio playing a part in the puzzle, too. 

[Steve D.]

We drilled the 3rd hole on my brothers 2276 and it seemed to help a little, but not a night and day difference.  On the other hand, once I ditched the twist linkage with 30 bends on the PS linkage arm and went with a normal tayco crossbar linkage, my last motor drove buttery smooth- even with 45mm vents (granted, the motor was FOKKEN huge!)

If you want to drill them, fine.  I just wouldn't pay somebody money to do it- a simple 1mm jet drill and run it in by hand.  Other than that, I just don't really see it being an absolute necessity for a smooth driving IDA motor.

[67worshipper]

this seems to be a big topic lots of people on each side of the fence.its interesting that the V8 guys think we,re nuts doing what we do.perhaps the amount of carbs they use make a difference in the transition?

[dougmische]

I wonder if the V8 guys running quad 48IDA's on Cobra replicas and such have anything on their forums about progression circuitry mods

Hi Doug 

check this out... http://www.clubcobra.com/forums/archive/index.php/index.php?t-74594.html

see ya next month

Thanks Jim!  Interesting info there...

Really looking forward to seeing you next month too.  I want as many VW's in front of my house as I can get.

But drive slow in the 'hood.  Lots of little kids around.