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914World.com _ 914World Garage _ Am I Over Carbed?
Posted by: 7TPorsh Aug 25 2014, 10:52 AM
I have been trying to drive my car comfortably but I am running across issues. Mainly after the car warms up it starts acting weird.
Coming to a stop and revs dropping. it just dies. Then I have to wait a minute or two to get started again. Then it runs a little rough, pops, backfires.
Just did the valves, points, timing but runs like crap when hot.
The engine is a 1.7 block with 1.7 heads and dual 40s. I don;t know if there was any work done internally but the block is a 71 and car is a 70.
It has been suggested that I am way overcarbed and running rich. i have no plans of building out this motor to match the carburation.
Am I better off selling off this dual weber set and putting on a single Weber 32/36?
I have my eye on this: http://www.ebay.com/itm/310953732343?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649
I am thinking the weber and hex setup should be worth around $450?
What say you?
Posted by: rhodyguy Aug 25 2014, 11:01 AM
look down one of the venturis and see if a number is on the top. a 28, 32, 36? using just one of the idle speed adj screws, increase the idle a bit. what happens? more investigation and info is somewhat important. take pictures of what you have and post them. linkage, fuel pump, etc. if you think you're rich take a look at the plugs. that single carb ebay package prob isn't going to be the solution to your issues.
Posted by: Alapone Aug 25 2014, 11:03 AM
I have been trying to drive my car comfortably but I am running across issues. Mainly after the car warms up it starts acting weird.
Coming to a stop and revs dropping. it just dies. Then I have to wait a minute or two to get started again. Then it runs a little rough, pops, backfires.
Just did the valves, points, timing but runs like crap when hot.
The engine is a 1.7 block with 1.7 heads and dual 40s. I don;t know if there was any work done internally but the block is a 71 and car is a 70.
It has been suggested that I am way overcarbed and running rich. i have no plans of building out this motor to match the carburation.
Am I better off selling off this dual weber set and putting on a single Weber 32/36?
I have my eye on this: http://www.ebay.com/itm/310953732343?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649
I am thinking the weber and hex setup should be worth around $450?
What say you?
For dual 40s with hex (and linkage?) you are probably right on with your value from what I remember (3months ago). I have heard that a single carb setup on the type IV is a road you don't want to go down (so to speak). Many unhappy comments were read by me on this forum related to cornering and fuel starvation and assorted other not good stuff regarding single carb. Maybe get to the root of the cause with the current set up?>
Posted by: stugray Aug 25 2014, 11:03 AM
The carb bodies should be fine.
What size venturis do you have?
You should be running the smallest you can find.
Someone on here makes them with their 3D printer.
If you could get a set to try out, you would know if that was your problem before spedning the cash on a complete set of permanent ones.
Posted by: 7TPorsh Aug 25 2014, 12:14 PM
I am a total novice when it comes to fuel delivery. It starves now on left corners and turns...dies out and I have to wait to start. Running a Carter rotary pump up front, steady 4psi.
I though the venturis were the carb bodies, thus the size being 40; and I thought the jets are what the variables parts are.
I am told these are 40 IDFs. Would the number on the inside be the venturi be body size? Have to take a closer look. Here is a pic I have handy.
Posted by: stugray Aug 25 2014, 12:21 PM
you have to remove the air filters.
Then look down into the throats.
The venturis are where the bore begins to restrict the flow before reaching the butterflies.
There will be a number imprinted on the venturi that can typically be seen from there.
Google some Weber 40 IDF venturis for examples.
Posted by: rhodyguy Aug 25 2014, 12:26 PM
for your reference. the venturis look like this. this one happens to be a 36. they are held into the carb bodies with a set screw.
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Posted by: rhodyguy Aug 25 2014, 01:12 PM
where does the pass side line from the bb terminate? just stuck thru the tin and spewing under the car?
Posted by: 7TPorsh Aug 25 2014, 02:23 PM
where does the pass side line from the bb terminate? just stuck thru the tin and spewing under the car?
The hose from the breather? It's down through the tin and plugged...no oil makes it down there. I am hoping at some point to vent the valve covers.
So on the venturi, I need to check later.
If these vary then I guess there are sizes up to 40? I can use?
What's the normal setup for a 1.7 or over-bored 1.7? I guess jet size is the next factor?
Posted by: Kansas 914 Aug 25 2014, 02:44 PM
where does the pass side line from the bb terminate? just stuck thru the tin and spewing under the car?
The hose from the breather? It's down through the tin and plugged...no oil makes it down there. I am hoping at some point to vent the valve covers.
So on the venturi, I need to check later.
If these vary then I guess there are sizes up to 40? I can use?
What's the normal setup for a 1.7 or over-bored 1.7? I guess jet size is the next factor?
1.7L heads have a tube just above the engine tin on each side for that hose from the breather puke can. Look at the left side in this picture of the intake just below the mounting nut. The passenger side would be towards the rear of the car.
Posted by: 7TPorsh Aug 25 2014, 02:53 PM
wow, I haven't noticed anything like that on my car. I sure do have to look close tonight.
Posted by: Rand Aug 25 2014, 02:58 PM
Hopefully you've heard feedback that says NEVER on that note. Never single carb a flat4.
Posted by: ThePaintedMan Aug 25 2014, 02:58 PM
Not all 1.7s had head vents - it's only the early or later ones (I can't remember which).
Posted by: rhodyguy Aug 25 2014, 02:58 PM
if you have those head tubes…one line from the pvc, center one on the box, and the sides to the tubes. the little filter on the box is not needed. there are usually little venting stand-offs on the lid and a piece of foam on the inside to help contain/control the vapors. oil builds up on the foam and becomes a part of regular maintenance. the plugged line is just going to fill up over time.
Posted by: Kansas 914 Aug 25 2014, 03:05 PM
Not all 1.7s had head vents - it's only the early or later ones (I can't remember which).
George,
Now that you mention it a friend called me the other day and said his 1.7 was puking oil. I asked him about the tubes in the head and he said he didn't see any.
Posted by: Kansas 914 Aug 25 2014, 03:08 PM
Not all 1.7s had head vents - it's only the early or later ones (I can't remember which).
George,
Now that you mention it a friend called me the other day and said his 1.7 was puking oil. I asked him about the tubes in the head and he said he didn't see any. I think his is a 1970 model.
Posted by: wndsnd Aug 25 2014, 06:16 PM
I do not think you are over carbed at all. You just need the right venturies and jets.
I am running 44IDF's set up by Tangerine Racing on my 1.7 and it screams. Sometimes it bogs in transition but that is very rare. So I am sure you could get your 40's to run well with the expert guidance of the the knowledgeable ones here.
Once set up correctly, you will have a blast... 
John
Posted by: Mblizzard Aug 25 2014, 06:27 PM
I think you may need to check your float level settings.
Posted by: 7TPorsh Aug 27 2014, 09:44 AM
Ok I checked one of the throats...assuming all four are the same. Couldn't see down there but camera got it.
28...what next?
Posted by: stugray Aug 27 2014, 10:22 AM
Next check all of the jets and write down the numbers while you do it.
Dont just blow through them. Inspect them FIRST then clear them.
Dont use any wire or anything to clear the passages.
The mains come out the top on the tall brass tubes.
Write down the numbers on the tall brass tubes as well.
The idle jets are on the outside of the carbs near the top and are kind of hard to get to.
Use a mirror and verify the o-rings stay in place on the carb body ( and that they are there in the first place). They are usually green.
Clear the idle jets, write down the number and screw them back in gently (do not over tighten).
Use the mirror to make sure they are all seated to the same depth.
Report back with the numbers and if clearing them all makes a difference.
Also while looking down the barrels, turn the throttle linkage and verify that you see a squirt down each barrel and that they are approximately the same. These are the acceleration pumps (the phallic shaped thing directly in front of the number in your pic above)
Finally after all that, you should check the float levels ( as mentioned above), but that requires you to take the linkage off and remove the tops of the carbs. I never do that unless I already have a spare set of carb-top gaskets.
There is a chance you will tear one especially if it is your first time.
Posted by: rhodyguy Aug 27 2014, 11:24 AM
if you haven't done so, order or go to a vw parts store and buy one of these. then, everything we tell you will make sense and you'll know what we're talking about. i think they are cheaper from amazon than cb performance.
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Posted by: maf914 Aug 28 2014, 06:22 AM
Along with the Tomlison Webber Manual above, you might try the following three from Amazon or AbeBooks.
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Posted by: Mike Bellis Aug 28 2014, 07:33 AM
I have been trying to drive my car comfortably but I am running across issues. Mainly after the car warms up it starts acting weird.
Coming to a stop and revs dropping. it just dies. Then I have to wait a minute or two to get started again. Then it runs a little rough, pops, backfires.
Just did the valves, points, timing but runs like crap when hot.
The engine is a 1.7 block with 1.7 heads and dual 40s. I don;t know if there was any work done internally but the block is a 71 and car is a 70.
It has been suggested that I am way overcarbed and running rich. i have no plans of building out this motor to match the carburation.
Am I better off selling off this dual weber set and putting on a single Weber 32/36?
I have my eye on this: http://www.ebay.com/itm/310953732343?ssPageName=STRK:MEWAX:IT&_trksid=p3984.m1423.l2649
I am thinking the weber and hex setup should be worth around $450?
What say you?
If you buy that single webber, you will be kicking yourself in the ass until you buy another pair of 40's. The single webber will run like shit.
Posted by: 7TPorsh Aug 28 2014, 09:24 AM
I haven't had a chance to look at the jets yet. I do know they are clean since I cleaned them all and the tubes a few months ago.
The number 12 sticks in my head...jet size?
Assuming all is setup near correct, what adjustments should I be looking at? Float level sounds like it may be an issue. Idle mixture?
These books are great I am sure but honestly don't have the money and patience to go that route. Just want to get the car running somewhat smoothly.
Posted by: rhodyguy Aug 28 2014, 10:32 AM
the tomlinson book is $20. stating 'idle mixture" can refer to (1) idle jet sizing, (2) plugged idle jets, (3) idle air mixture screws…the trouble shooting guide is helpful to say the least. you will save yourself countless hours knowing precisely what is being referred to in the responses. much more direct rather than 'try this and then try that' which will get you nowhere and frustrated.
Posted by: ThePaintedMan Aug 28 2014, 10:38 AM
Gary,
Kevin and Stu have given you great tools to point you in the right direction. It's completely understandable to be frustrated with carbs - we've all been there. But keep in mind, this is a very simple system and can be fixed, but only with the proper understanding/knowledge. Part of that knowledge can be easily gained through the Tomlinson book. It's $20 that is well spent and you can always resell if it you don't use it again (which I highly doubt).
The rest is basically effort on your part. We're here to help. You need to get the jet sizes by pulling at minimum, one main jet and one idle jet. Otherwise we're just wandering around in the dark. The 28 mm venturis are a decent match, so the hard part is done.
Posted by: rhodyguy Aug 28 2014, 10:52 AM
george has travel the path you're on. to the point where provides a rebuild service. in addition, examine your JETS (all of them) one carb at a time and note what you have. it's not all that uncommon to have different sized jets on different carbs trying to cure some ill. you still need to know what jet does what and when.
Posted by: AE354803 Aug 28 2014, 12:30 PM
Am I the only one that is impressed by how clear that picture of the venturi inside the carb came out?
Writeup on carb rebuild is linked below, should give you a better understanding of what you're working with, all credit to George for the good writeup
http://www.914world.com/bbs2/index.php?showtopic=207017&hl=weber+rebuild
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