New Empi hpmx What are these things?

I don’t know, but my guess is that they’re picking up idle jet air from those tubes, rather than from down at the top of the carb. 

What is weird about it is there are no photos of this Empi carb online with these tubes attached, they mess up the cover plate  for the air cleaner, the gasket does not accommodate for them, and the original Webers have these threaded holes but no tubes attached.

Those look like Jet Doctors, but I no longer have my carbs to look at and verify.

I am guess a 'jet doctor' is a vent of some sort?

MotoCarlo posted:

I am guess a 'jet doctor' is a vent of some sort?

It’s exactly what I described above. 

Jet Dr. is the trade name of CB Performance extended vent tube for idle air drillings in the top cover of the carb- idle air is picked up in the "clean air" up high, rather than the air right at the carb tops.  Cuts down on clogging of idle jets.

OK, so a good idea of not?
Seems most simple let the plate gasket cover these holes and let her ride... I want the carbs to work their best, but life would certainly be easier to follow the usual and simply cover them. 
Another interesting thing about these Empis is , the choke pate is cast onto the body - meaning there is  no way to use the Weber cold start system. (unlike the photo of what I thought I was buying)
So ... I wonder if that is why these carbs have the Jet Doctors.
?

Thanks again for the help!

Rcosta - thanks.

You would want to add them if they were not already installed.

Thanks for the help guys.
Here is a link for others "in the dark" like me.

http://cbperformance.net/pdf/WeberJetDoctor.pdf

If you have clogged idle jets you can blow air into the top of the Jet Doctors and temporarily clean them. The debris will eventually clog the jet again but just maybe you can get home before it does.  Also,  I found that if I suspect a clogged idle jet is my problem, I blow air into the Jet Doctors one at a time. If the clogged idle symptoms go away on a particular cylinder when doing this , I know which carb and jet is the culprit.

Not an earthshaking little technique  but may be helpful sometime...........Bruce

It's really easy to isolate a dead cylinder, there are many techniques. Close the air to a throat at a time by covering the velocity stack with your hand. Close the idle mixture screw. Pull a plug wire(my least favorite). Anyway, the cylinder with no rpm dip is your winner.

I don't use compressed air in the carbs. But, I'll pull the jet AND the mixture screw and squirt carb cleaner both ways through the circuit.

Those "threaded holes" on your old Webers, are they really threaded? There are no factory holes in that spot on the top plate of Spanish or Italian Webers. Those are drilled specifically for the aftermarket Jet doctors. Do you see the oval hole in the middle of the top cover? That is where the air intake is for the idle circuit normally. Honestly plugged idle jets come from dirt falling into that oval hole every time you take the air filters off. Or dirty fuel, or disintegrating floats. Putting the idle air intake over by the velocity stacks gives you a better chance of dirt NOT falling into the idle circuit.

You also have to drill through the base plate and make a hole in the gasket.

Please take the tops off the carbs and completely disassemble and clean them, then set the float height. EVERY NEW CARB NEEDS THIS! No exceptions, unless you got some already set up by Blackline......

If you don't have it, get the CB Weber book and also download and print my synch instructions.

Honestly I can't figure out why you bought these carbs @MotoCarlo. I'll wager you're still going to have problems. But keep at it, you'll eventually figure it out.

DannyP posted:

 I can't figure out why you bought these carbs @MotoCarlo. I'll wager you're still going to have problems. But keep at it, you'll eventually figure it out.

I'm really curious about this as well. EMPI carbs are wildcards, as you are finding (the parts not matching the pictures), and are the cheaper Asian copies of the carburetors you already have (Weber IDFs). Unless there is a problem with your Weber castings (throttle shaft play, etc.), what you moved out of (IDFs) have a far better reputation that the new ones (EMPI clones).

I wish you success, but worry you might have moved out of the frying pan and into the fire.

DannyP posted:

Do you see the oval hole in the middle of the top cover? That is where the air intake is for the idle circuit normally. Honestly plugged idle jets come from dirt falling into that oval hole every time you take the air filters off. Or dirty fuel, or disintegrating floats. Putting the idle air intake over by the velocity stacks gives you a better chance of dirt NOT falling into the idle circuit.

Danny, The carbs on my Spyder were extensively modified ( not by me). The builder had made risers from 3/8" round tube with one end swagged to fit the oval opening. They were about the same height as the stacks. Jet doctors were not installed. I still was constantly cleaning the idle jets and float bowl. I finally get it all sorted out just before selling the car.

On the Speedster, I found that the jet doctors helped a great deal. Not a 100% cure, but a really big help.

Motocarlo,

As Danny said, the Weber Carburetors book is an absolute necessity. Redline also has really good information free. These are the Old and New Testaments. It's in there.

www.redlineweber.com/html/tech...ustment_controls.htm

The IDF's should have been made to work. Close reading and re-reading is required. If you do the steps EXACTLY per instructions, the carburetors will work as designed. You must know what jets and venturi you have before turning a screw. If they are not properly matched to your engine size there will always be problems.

One tripping point, that took me a while to figure out, is that the idle speed screw is NEVER more than 1/2 turn opened. The manual does tell you that, but was confusing to me. Once the best idle is determined the idle will be above 900 rpm. Probably 11-1200. You will have to back out the isle speed screws to get idle down.

This is my experience. Others may be different.

Thanks Jim. Big "Amen" from this camp.
My old Weber book is worn out .(I have had Porsches for many decades.) And I certainly understand the 1/2 MAX on the idle speed. More than that it opens a small port in the venturi , and that changes everything. Also what each jet does, sizes, and what rpm it effects, etc etc etc... And of course the float height setting - least we forget, the needle and seats, and the return valve size in the bottom of the bowl...
Jezz these blasted carbs! 
 I am a meticulous guy and  have a good basic understanding of the idf. And have had luck over the years getting them to work properly.
So thanks. And thanks for the Redline link. It has been awhile since I read that, probably time to refresh my mind.

These idle jet "snorkels" are new to me.
So ... live and learn and learn and learn...
You guys all have been a big help - again.

In the link the "t" in tech must be a capital letter "T".

sorry

Jim Gilbert - Madison, Mississippi posted:

In the link the "t" in tech must be a capital letter "T".

sorry

Here's the corrected link:

http://www.redlineweber.com/ht...ustment_controls.htm

"Honestly I can't figure out why you bought these carbs @MotoCarlo. I'll wager you're still going to have problems. But keep at it, you'll eventually figure it out."

I just now read Danny's post above. And again, appreciate the interest and help. So here is my long story.

I have been fighting the Webers for about 3 years. New floats, acc jets, every jet combo you can imagine: main, idle, ac jets, new float seats and needles, ... And again I have to say, I am not new to this. So it is getting a bit frustrating, because they are not adjusting out like one wants.

History: I got the car from a guy in Miami, where it sat unused for 10 years. Lots of little corrosion that I have had to take care of : electrical connections, pitted chrome, rings that were so dry I could not get compression out of the engine (even after soaking them in marvel mystery oil) - so I rebuilt the engine with new Mahler P&C set - bringing it up to 1835..  Now : good compression on all 4.

 I had the car running pretty well. But the carbs really never adjusted out like they should . 
Then I installed the Magnaspark II , and it lost a lot of power at 2k rpm, backfiring etc...
Of course , I took the MSII off and went back to the coil and distributor it had.
But that problem persisted.
This made me thing the hotter faster spark showed a problem  in the carbs, especially since they never did adjust perfectly .
(Remember the Miami corrosion I mentioned above,  the carbs had some corrosion in them when I first took them apart. So my thought is there is some little plugged channel or hole in the Weber bodies that I can not find...,  That is why I finally said FkIt and got some new carbs to try.)
So I threw some new carbs on to see how it goes. (Other post people say how much they like the Empis) 
Back to the carbs.
In adjusting the new Empis, idles, # 1 and 2 pretty good, #3 and 4 do not adjust out as you would expect - very little change in the idle via sending the screws in and out. (tried jet sizes 5, 5.5 or 6).

I will be able to get back to it this weekend and see. 
I did not check the floats (duh!) So I will have a look at those.
If the Empis do not solve my issue, I will no not doubt that I put the Webers back on and have a set of near new Empis for sale. 
:-)

Then I plan to do a fresh compression test to see if something is amiss deeper down.
Not a lot of fun in the garage these days .

Did you swap carbs side to side?  If so and non response to idle adjustment persists on 3/4 side, check for air leak where manifold attaches to head (Propane trick may have been discussed here on SOC; it has on spyderclub.com).  If non response follows carb from side to side, remove idle jets and idle screws and thoroughly back flush the idle circuit with carb cleaner.  Check and verify that all idle needle/screws are the same. reassemble and try again.

"Did you swap carbs side to side?" Huh?

I replaced both Webers with both Empis. So not sure what you mean. ?
I did take out the Empi jets and replace with my  jets. The Empi combo was pretty weird. But the floats ... now that is my #1 bonehead overlooked move. So I will check them asap.

I appreciate being reminded of the old motorcycle trick of using the propane to find an intake leak. I had not thought of it. I'll give it a try.

I swapped the carbs around on my car. It gives you reasonable access to all of the adjustments. Swapping the carbs lets you place the adjustments toward the middle rather than having them facing the wheel wells where you can't see the screws. You have to buy a different set of intake manifolds ($80) and rework the linkage. I wrote a detailed note concerning what was done about a year ago. Look at my post. This is well worth the time it takes to do.

I think RCosta was trying to say, swap carbs to see if the problem persists on the opposite banks - cyl 3, 4.

MotoCarlo posted:

"Did you swap carbs side to side?" Huh?

I replaced both Webers with both Empis. So not sure what you mean. ?
I did take out the Empi jets and replace with my  jets. The Empi combo was pretty weird. But the floats ... now that is my #1 bonehead overlooked move. So I will check them asap.

I appreciate being reminded of the old motorcycle trick of using the propane to find an intake leak. I had not thought of it. I'll give it a try.

Move the right side carb to left side of the car and vice versa. That will tell you if it is the carburetor itself.

Got it. Thanks.

Guess I didn't understand Rcosta's response either...

OK here is my update. Thanks to this thread , my attention was drawn to the intake manifolds. After putting the (adjusted) new Empis on , I had the same problems on the same cylinders as with the Webers. So moving down the line, I had a look at the intake manifolds. Sure enough on #3/4 there is a fitting and hose tapped in for a brake boost line. I had completely forgotten about it. (working on 4 cars, over 60 , did the new cylinders 3 years ago , etc... my excuses). That fitting was loose and the hoes easily pulled off. Those are the same cylinders I was having the major adjustment trouble with. Air leak.
So the webers will gp back on after getting completely cleaned and reassembled with new parts, new gaskets, and new gaskets for the manifolds (gonna delete that boost fitting for now).

All good info everyone. I forget who mentioned the propane test, but that headed me in the right direction.  Fingers crossed.

Take that fitting out and plug the hole with a threaded plug. Glad you found it.

Sheesh, at least this thread(and solution) was shorter than Mr. "Brass Thingy"!

Vacuum leaks are almost as good as bad grounds, in terms of ****ing you up.

Amen brother.  :-)

A lot of people have changed turbo's to find a simple hose was the culprit.