Good Evening,
Fairly new to the forum, but a long time Porsche/Audi tech. Last spring a bought a very rust free 72 914 with a 2.0L and a side shifter transplant. The engine is fairly fresh and was built by a local guy who still builds approx 40 type 4 bus engines a year. It has a web 86b cam, large valves ported heads and twin 44idf's (i know too big).
So I have chased poor low speed manners since I got it, I rebuilt the carbs and replaced all of the intake gaskets and carb gaskets, no change. So after farting with it yesterday I came to realize that at low speed >2500 rpm it was a little lean. I pulled the idle jets and inspected, they were 60's. So I decided I would open them up to 65's. I borrowed a set of numbered drills from 61-80 and checked them. For more info a 60 jet is .6mm or 0.0246" The results are as follows.
.0210
.0220
.0220
.0245
What the hell! Over a 10% variance over four OE weber jets that have never been messed with. So I drilled them all to 0.0245" cleaned them and reinstalled. Fired up the car and set idle mixture, all four landed at approx 3/4 turns out. The best part is it runs AWESOME! it will pull cleanly from 1000 rpm in 3rd gear, no fluff, just clean and smooth. Idle is rock solid at 850 rpm.
So the moral of the story is, just because the parts in a car may be OE and new does not mean they are "right", I encourage if others have low speed driveability issues with webers, check the idle jets and make sure that they are all the same.
Have a great day,
Dan
Full Version: I hate webers
Sounds like you 'like' (I won't say love) Webers now that you have it dialed. 
You should try MFI 
I good friend of mine who really does LOVE Webers does exactly as you did for every set he has and when changing from the parts bin; uses numbered drills to check every jet. Always need to start with a quantiative known point.
Good on you and have fun.
You should try MFI I good friend of mine who really does LOVE Webers does exactly as you did for every set he has and when changing from the parts bin; uses numbered drills to check every jet. Always need to start with a quantiative known point.
Good on you and have fun.
QUOTE(FJ1200 @ Jun 15 2020, 04:50 PM) 
Good Evening,
Fairly new to the forum, but a long time Porsche/Audi tech. Last spring a bought a very rust free 72 914 with a 2.0L and a side shifter transplant. The engine is fairly fresh and was built by a local guy who still builds approx 40 type 4 bus engines a year. It has a web 86b cam, large valves ported heads and twin 44idf's (i know too big).
So I have chased poor low speed manners since I got it, I rebuilt the carbs and replaced all of the intake gaskets and carb gaskets, no change. So after farting with it yesterday I came to realize that at low speed >2500 rpm it was a little lean. I pulled the idle jets and inspected, they were 60's. So I decided I would open them up to 65's. I borrowed a set of numbered drills from 61-80 and checked them. For more info a 60 jet is .6mm or 0.0246" The results are as follows.
.0210
.0220
.0220
.0245
What the hell! Over a 10% variance over four OE weber jets that have never been messed with. So I drilled them all to 0.0245" cleaned them and reinstalled. Fired up the car and set idle mixture, all four landed at approx 3/4 turns out. The best part is it runs AWESOME! it will pull cleanly from 1000 rpm in 3rd gear, no fluff, just clean and smooth. Idle is rock solid at 850 rpm.
So the moral of the story is, just because the parts in a car may be OE and new does not mean they are "right", I encourage if others have low speed driveability issues with webers, check the idle jets and make sure that they are all the same.
Have a great day,
Dan
I get this but..... Let me know when you get a issue at wot wide open throttle. Their pretty good there
FJ -
I had read elsewhere that even the best jets can vary a lot, but had no idea that they could vary so much.
I have a stock 2.0 (no cam, etc.) and IDF-44's - and it was only when I went from 50 idle jets to 60's that I got great idle to low-end to mid-range performance. I know, you can't do that with a stock engine. Yes you can.
As engine is down, carbs are off - and I'm going to check the size of those idle jets.....
Will report back on what I find.....
GN
Oh - I added drill sizes in in red below:
Good Evening,
Fairly new to the forum, but a long time Porsche/Audi tech. Last spring a bought a very rust free 72 914 with a 2.0L and a side shifter transplant. The engine is fairly fresh and was built by a local guy who still builds approx 40 type 4 bus engines a year. It has a web 86b cam, large valves ported heads and twin 44idf's (i know too big).
So I have chased poor low speed manners since I got it, I rebuilt the carbs and replaced all of the intake gaskets and carb gaskets, no change. So after farting with it yesterday I came to realize that at low speed >2500 rpm it was a little lean. I pulled the idle jets and inspected, they were 60's. So I decided I would open them up to 65's. I borrowed a set of numbered drills from 61-80 and checked them. For more info a 60 jet is .6mm or 0.0246" The results are as follows.
.0210 Drill 75
.0220 Drill 74
.0220
.0245 Drill 73 is .024" or .61mm
What the hell! Over a 10% variance over four OE weber jets that have never been messed with. So I drilled them all to 0.0245" cleaned them and reinstalled. Fired up the car and set idle mixture, all four landed at approx 3/4 turns out. The best part is it runs AWESOME! it will pull cleanly from 1000 rpm in 3rd gear, no fluff, just clean and smooth. Idle is rock solid at 850 rpm.
So the moral of the story is, just because the parts in a car may be OE and new does not mean they are "right", I encourage if others have low speed driveability issues with webers, check the idle jets and make sure that they are all the same.
Have a great day,
Dan
I had read elsewhere that even the best jets can vary a lot, but had no idea that they could vary so much.
I have a stock 2.0 (no cam, etc.) and IDF-44's - and it was only when I went from 50 idle jets to 60's that I got great idle to low-end to mid-range performance. I know, you can't do that with a stock engine. Yes you can.
As engine is down, carbs are off - and I'm going to check the size of those idle jets.....
Will report back on what I find.....
GN
Oh - I added drill sizes in in red below:
QUOTE(FJ1200 @ Jun 15 2020, 05:50 PM)
Good Evening,
Fairly new to the forum, but a long time Porsche/Audi tech. Last spring a bought a very rust free 72 914 with a 2.0L and a side shifter transplant. The engine is fairly fresh and was built by a local guy who still builds approx 40 type 4 bus engines a year. It has a web 86b cam, large valves ported heads and twin 44idf's (i know too big).
So I have chased poor low speed manners since I got it, I rebuilt the carbs and replaced all of the intake gaskets and carb gaskets, no change. So after farting with it yesterday I came to realize that at low speed >2500 rpm it was a little lean. I pulled the idle jets and inspected, they were 60's. So I decided I would open them up to 65's. I borrowed a set of numbered drills from 61-80 and checked them. For more info a 60 jet is .6mm or 0.0246" The results are as follows.
.0210 Drill 75
.0220 Drill 74
.0220
.0245 Drill 73 is .024" or .61mm
What the hell! Over a 10% variance over four OE weber jets that have never been messed with. So I drilled them all to 0.0245" cleaned them and reinstalled. Fired up the car and set idle mixture, all four landed at approx 3/4 turns out. The best part is it runs AWESOME! it will pull cleanly from 1000 rpm in 3rd gear, no fluff, just clean and smooth. Idle is rock solid at 850 rpm.
So the moral of the story is, just because the parts in a car may be OE and new does not mean they are "right", I encourage if others have low speed driveability issues with webers, check the idle jets and make sure that they are all the same.
Have a great day,
Dan
QUOTE(FJ1200 @ Jun 15 2020, 04:50 PM)
twin 44idf's (i know too big)
You can choke them down with smaller venturis (btdt).
The increased air speed will help with the off-idle transition.
QUOTE(FJ1200 @ Jun 16 2020, 11:50 AM)
Good Evening,
Fairly new to the forum, but a long time Porsche/Audi tech. Last spring a bought a very rust free 72 914 with a 2.0L and a side shifter transplant. The engine is fairly fresh and was built by a local guy who still builds approx 40 type 4 bus engines a year. It has a web 86b cam, large valves ported heads and twin 44idf's (i know too big).
So I have chased poor low speed manners since I got it, I rebuilt the carbs and replaced all of the intake gaskets and carb gaskets, no change. So after farting with it yesterday I came to realize that at low speed >2500 rpm it was a little lean. I pulled the idle jets and inspected, they were 60's. So I decided I would open them up to 65's. I borrowed a set of numbered drills from 61-80 and checked them. For more info a 60 jet is .6mm or 0.0246" The results are as follows.
.0210
.0220
.0220
.0245
What the hell! Over a 10% variance over four OE weber jets that have never been messed with. So I drilled them all to 0.0245" cleaned them and reinstalled. Fired up the car and set idle mixture, all four landed at approx 3/4 turns out. The best part is it runs AWESOME! it will pull cleanly from 1000 rpm in 3rd gear, no fluff, just clean and smooth. Idle is rock solid at 850 rpm.
So the moral of the story is, just because the parts in a car may be OE and new does not mean they are "right", I encourage if others have low speed driveability issues with webers, check the idle jets and make sure that they are all the same.
Have a great day,
Dan
The issue with carbs this large is the venturies supplied (usually 36mm) are simply too big,they require over sized idle jets to mask the poor vacuum and with big valve heads things are somewhat worse,transtion to main jets will be slower and not smooth in a street car this isn't much fun....in a race or competation car less important.
General comments are that these carbs are good for 2.2 litres and up ,if you reduce the venturies to 34mm you will notice a good improvement in bottom end power and better transition to main jets, which is great for a street car,the result may mean you will go back to around 57-60 idles and reduced main jet size due to improved vacuum.
You will lose a bit of top-end power but you don't drive in that range much so really little lost.
My experience is not gospel but has always worked based on experience,many on here know more than me will chime in, I hope they do ?.
Good luck.
With rebuilding my /6 Webers and then totally sorting my float levels, jetting, linkage, tuning, etc I must have at least 60+ hours into them, maybe 80.
SirAndy -
You know 100x what I know, and I'm just a dumb flunky, but I tried 32mm venturi's and engine had less than half the power from 1/3 throttle up and wouldn't even get out of its own way regardless of how I jetted it......but it did run nice.....another top 914 mechanic told me to try the 32's.
Happy with my 44's & 36mm venturi's........and runs just as nice now........maybe I've got a weird 2.0.
GN
You can choke them down with smaller venturis (btdt).
The increased air speed will help with the off-idle transition.
You know 100x what I know, and I'm just a dumb flunky, but I tried 32mm venturi's and engine had less than half the power from 1/3 throttle up and wouldn't even get out of its own way regardless of how I jetted it......but it did run nice.....another top 914 mechanic told me to try the 32's.
Happy with my 44's & 36mm venturi's........and runs just as nice now........maybe I've got a weird 2.0.
GN
QUOTE(SirAndy @ Jun 15 2020, 06:42 PM)
QUOTE(FJ1200 @ Jun 15 2020, 04:50 PM)
twin 44idf's (i know too big)
You can choke them down with smaller venturis (btdt).
The increased air speed will help with the off-idle transition.
Wow. That's a lot of hours just on carbs Mark. But then they are triple-barrel, right? 3 of everything.....
GN
With rebuilding my /6 Webers and then totally sorting my float levels, jetting, linkage, tuning, etc I must have at least 60+ hours into them, maybe 80.
GN
QUOTE(Mark Henry @ Jun 15 2020, 06:57 PM)
With rebuilding my /6 Webers and then totally sorting my float levels, jetting, linkage, tuning, etc I must have at least 60+ hours into them, maybe 80.
Thanks for the input guys, as far as downsizing the venturis. I see no point. The transition to the main jets is smooth and she pulls strong right up to 6000rpm. The low speed driveability is great, as a matter of fact I find myself in a higher gear now as it just that much easier to drive. And Gattornapper, thanks for adding the drill sizes I forgot to note them before returning the drill index to my friend.
Dan
Dan
As stated above, the smaller venturis (i also went down to 32) increase the air speed and significantly help with the vacuum.
As you said yourself, the 44s are too big for a 2.0L ...
As you said yourself, the 44s are too big for a 2.0L ...
Don't stop with the idle jets. Measure all the jets
QUOTE(SirAndy @ Jun 16 2020, 01:46 PM)
As stated above, the smaller venturis (i also went down to 32) increase the air speed and significantly help with the vacuum.
As you said yourself, the 44s are too big for a 2.0L ...
no amount of reading appears to have reached 
.This issue has been addressed time and time again with SO many members,many of these carb setups appear in the FS section because they can't get them to work with supplied vents and jetting.
Case it point with my 2.2 "six" I rebuilt the carbs and went to 32mm venturies because I hadn't researched enough and should have known better,jetting was in the ballpark but there was a horrible hole on transition to mains and they were very hard to balance/tune (reduced vacuum).
Swapped to 30mm vents and slightly smaller idles and mains and bingo ,lesson learnt,however great result in the end.
For folks that say these work great then drive a car with the right size carbs and jetting or go and research carb size to engine/carb calculators ,most ask for cubic capacity divided by 4,ventury size,max rpm ,these are good starting tools for setup
and nothing changed it's just simple engine theory and fact....rant over
When I got my 356 it had webers on it, I chased a flat spot for over a year, it would move here, and move there, but never went away. I finally got sick of it, had a friend build me a stock set of Zenith Supers, and put them on. That was over 10 years ago, haven't touched them since, bulletproof. I think Webers are great if you like to tinker, or are racing and need that extra 5-10% that you can squeeze out of them. But for you average guy who wants to drive around and grab a coffee, leave the Webers on the shelf.
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