Weber bogs the engine when the secondary opens

[mfolsom]

I brought this info over from a previous thread I posted because there is another problem I need help with.

 

All the emissions stuff but the PCV is gone.

 

The wagon passed emissions today. It failed miserably the first time so I waited to put the Weber on before trying again.

 

Now I just gotta figure out why it bogs when the secondary opens. It starts and idles fine. There is no shaking like I experienced before. All the extra vacuum stuff is removed and capped.

 

Here is what I have, 85 GL Wagon, EA82, Weber.

 

I have spent 2 cans of brake cleaner finding the vacuum leaks and believe I have them all resolved.

 

It accelerates smoothly and gains RPM right up to the point the secondary opens. At WOT it gets loud and either slows or just barely maintains speed.

 

I have moved the timing from 8 deg to 12 deg and back.

I have moved the vacuum advance tube from the manifold to the port on the carb and will probably move it back.

 

There is a kit on the way and I will open the carb up and see which jets are actually in there.

 

I have spent hours looking at threads about the Weber and don't see anything about what I am experiencing. I am open to ideas if anyone would like to throw them at me.

 

Thanks

Mark

[chef_tim]

Here's a start for you to read through. My first guess would be to large a jet in the secondary. Tim

 

http://www.ultimatesubaru.org/forum/showthread.php?t=29778&highlight=official

[Truckerman666]

It sounds like the secondary barrel is open too soon. I am not familiar with Webers, but I have worked on Holley 4 barrels some. I once knew someone with the same problem with a Weber on a Datsun truck, it was simply too much carburation, on a small inch engine.

What I think is happening is that when the secondary opens, it flows too much air and overloads the engine temporarily.

I realize that a Holley is not Weber, and a GMC is not a Subaru, but the basic principles that carburetors and engines operate on do not change.

I learned how to tune Holleys on a 1969 GMC 3/4 ton camper special truck. It weighed 5200 lbs, and I really had to get the secondary opening point perfect, or it would bog down horribly. When I finally got it right, it was like night and day.

The smaller displacement of your engine and the heavier your car, the worse this problem gets. Using a manual transmission will make it easier, because you can get the rpm up faster, and get to the point where you actually need the extra airflow sooner.

A vacuum operated secondary will be much more forgiving and easier to tune than a manual one.

I know that there is a mathematical formula to choose the right size carburetor, but I could not find it on google, Holley prints it in their catalog, in the form of a chart. If I knew how to convert CC's to cubic inches, I would do it for you, sorry about being to much old school here.

You answer some basic questions, engine size, rpm, stall speed etc. A typical stock engine is about 80 % efficient concerning airflow, or volumetric efficiency (VE).

The chart will tell you how many cubic feet per minute (CFM), your engine can flow.

You then choose the next size smaller carburetor, trust me, you will be happier with smaller one instead of the bigger one every time, unless you are building a real fire breathing full race engine.

After all of this trivia, I have 2 suggestions:

1. adjust the secondary to open later, keep doing this until you begin to lose top end power, the go back a little.

This is not a high precision method, but it will get you reasonably close.

Weber probably makes a kit with springs, cams etc. to help you with this.

2. Check the accelerator pump:

A: to make sure it is functional.

B: to make sure it is injecting enough gas to to keep the mixture richened up until the mains jets start flowing.

Based on the symptoms you describe, It is almost certain that #2 is not your problem.

After you get the secondary adjusted properly, experiment with jets etc., and have real smooth running Subaru. You will be amazed how well a carbureted car can run.

I hope this helps.

[mfolsom]

Here's a start for you to read through. My first guess would be to large a jet in the secondary. Tim

 

http://www.ultimatesubaru.org/forum/showthread.php?t=29778&highlight=official

 

Thanks for the link but I have already been there and read all of them. None of the posts say much about the secondary circuit. In fact, there is not much at all on the internet about the subject that I have found yet. This weekend I'm taking the carb apart to see just what is in it for jets.

[mfolsom]

It sounds like the secondary barrel is open too soon. I am not familiar with Webers, but I have worked on Holley 4 barrels some.

.

.

.

I hope this helps.

 

Everyone on this board swears by Weber 32/36 on the EA82. From what I have read it is made to cover engines from 1600 and up.

 

There is a kit on the way so I will get in to the guts when that arrives.

 

It is a mechanical secondary and is set to open after the primary is fully open. The accelerator pump appears to squirt a good stream but that doesn't have anything to do with the secondary because it's action is already out of play just after partial throttle.

 

There is a power valve in this carb and I will be replacing that as well as checking on which jets are installed.

 

I do have a d/r 5 speed and even getting the rpm up by downshifting doesn't help.

 

Thanks for the suggestions

 

Mark

[desertsubaru]

Hows your exhaust flow? If its restricted it may not breath right.

[mfolsom]

Hows your exhaust flow? If its restricted it may not breath right.

 

No problems with exhaust that I'm aware of. The car will run out nicely until I hit the carbs secondary. With the Weber on the RPMs rise alot quicker than before and I can maintain flat and level highway speed just fine. I will specifically look at the flow this afternoon.

[Skip]

MF did you happen to see this picture

in your search?

Thanks to Pyro925 for the Pict and GD

for the list of jets

Gives you a good look at what you will be seeing

The post is also excellent

(GD tells all when it comes to Weber's, him and Big Jim

are your "go-to guys" )

Here is the post on the venturi problem and new gasket

http://www.ultimatesubaru.org/forum/showthread.php?t=84804&highlight=venturi

 

Here is the post on the jet sizes

http://www.ultimatesubaru.org/forum/showthread.php?t=85403&highlight=main+jet%2A

[mfolsom]

MF did you happen to see this picture

in your search?

 

Yes

Yes

and Yes

 

Thanks

[Skip]

You are most welcome, I doctored the pict

to show what GD lists and to get it to fit most

monitors.

 

Don't for get to check the venturi problem.

That may be an issue with your secondary problem.

Do not need the top off to see it.

 

 

 

 

I have opened up several of mine.

 

It's real simple not like taking the top off

a Carter AFB.

[mfolsom]

You are most welcome, I doctored the pict

to show what GD lists and to get it to fit most

monitors.

 

Don't for get to check the venturi problem.

That may be an issue with your secondary problem.

Do not need the top off to see it.

 

I have opened up several of mine.

 

It's real simple not like taking the top off

a Carter AFB.

 

I noticed the text was a little neater on the picture.

The venturis seem to be pointed the right direction. I just haven't taken the top off yet because I'm waiting for Big Jim to send me the kit. I'd probably mess up the gasket and have to let the car sit. I went so long with a sick motor that it's really fun to drive now with the fresh one, even with the carb problems.

 

And it's too cold and rainy to ride the Harley right now.

[mfolsom]

Friday driving to work everything worked fine. It was like the carburetor elf jumped in and made things work.

 

Saturday I took it apart anyway and found brass shavings in the jets, a 115 secondary main jet, a 190 secondary air jet and a 90 in the secondary idle. I also found a strip of metal attached inside th hole where the secondary air jet goes which I pulled out. It looked like a casting defect.

 

I drilled out the 115 secondary main to match the 135 primary main jet and cleaned the whole carb, installed the rest of the kit and put it back on the car. I did check a couple of local shops for jets but nobody carries Weber stuff and the jets for Holly are totally different. I must have misread somewhere that the Holly jets would fit the Weber.

 

With things the way they are now, the car runs fine and actually accelerates on the secondary circuit.

 

Thanks to all for the ideas and support.

 

Mark