Weber Tuning Rif Raf

[Cerbin]

i Still have not got my 1970 2.2L 911 w/ dual weber setup to idle, or to quit "spitting" at low RPM, also the engine races and won't come back down to idle range for like 20 seconds! I currently am borrowing a synchrometer but im lost at this point of wht to do next. haha. i've done enough "****ing" around. lol i need some help...

...Like a step by comprehensive step list of the complete tuning procedure.
All help appreciated.

Patrick
1970 911 T/S

P.s. My ignition timing is pretty darn good.

[Zendalar]

You sure the carbs have clean jets and such?

[Cerbin]

nope ... but i think they are clean b/c the car runs fairly well at higher RPM 3-4000. IM pretty sure it all tuning.

More advice appreciated

Patrick
1970 911 T/S

[Superman]

The experienced Porsche guys I know seem to look through their jets pretty frequently. And sometimes they look in there and say "Ah ha!"

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'83 SC

[J Richard]

Its been a long time but tuning webers is not too hard, just takes some patience, once they are set up they will run without too much fuss. This assumes that the timing and ignition are all in order:

1.They GOTTA be clean!
2.Fuel pressure has to be correct 4-5lbs and the float level must be checked with a sight glass.
3.Disconnect the linkages from the carbs. You can't do this with them connected.
4.Turn the idle stop screws (both sides) in an even number until you have +-1200rpm.
5.Put the guage on the left rear throat, The round cone shaped gauge works better.
6.Adjust to about half way up. Check each throat, if it's different it needs adjustment.
7.Adjust the air bleed screw on the side until you get consistent measurements at each throat. Recheck each throat.
8.Back both sides down evenly to 900rpm.
9.Tighten each mixture screw in until the motor slows, then back out until it runs smooth, each engine is different, I used to back out a quarter turn more, try up to 1/2 turn in or out and see what runs smoothest. Once you have gone around once, go around again. Note that each throat will not be exactly the same number of turns in or out.
10.After mixture, recheck the sync. Then mixture again.
11.Now, and this is important, adjust the throttle linkage so it starts to lift the throttle plates equally on both sides, otherwise you will be opening one side too soon and the car will run poorly and spit.
12.Double check the throttle valve compensator, I think this is why your engine races. It is a sort of bell shaped thing adjacent to the base of the carb.
13.Loosen the locknut at the top and screw the adjusting screw in all the way.
14.Rev the motor to 3-3500rpm and release, it should drop to +/-2,000rpm.
15.If it is higher, lengthen the rod (this sounds like your problem)by screwing the ball end longer (It's best to have your girfriend or wife present to assist here...)
16.Adjust the screw on the top for 900rpm.
17.Burp the throttle, If it takes too long to return to idle screw the it in, if it hunts and tries to die back it out. If you can't get this adjustment I think you need a new compensator.

I hope this helps. Once you've mastered this you will get your Weber merit badge and impress your friends with your automotive prowess...




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93RSA

[Cerbin]

Thanx Richard! That's the ticket...I'll post tonite to tell how i did.

Patrick
911 T/s

[Reg]

Thanks here too! Very comprehensive and appreciated.

My problem is different though. My car will idle all day, but loses RPM's while cruising every few miles. The car sat for 4 yrs. I flushed all the fuel out, ran cleaner through the carbs, new filters and plugs, set the timing which is close. Put in a pressure regulater and (was told 4.5 psi max and 3.5 was ideal) that did not make much difference to the 8psi we were running at.

The car pops once and a while holding at mid rpms, and will backfire if you let off the throttle. The timing is much closer than it was.

It's like Its choking itself out I think. I didnt want to frigg with the carbs. I do not have probs with idle, and the car runs and revs quite smooth with no load on it, but cuts out while driving.

Any insights/suggestions on my situation would also be appreciated.

The car is a 2.2 T with SSI exchangers.

[clevy70911T]

I have a nearly indentical problem with my 2.2 Zeniths. I cleaned the idle jets, but no resolve with the popping or racing. I have to use the hand throttle to get the car back to idle. I'm starting a Techron treatment this week. I have seen some inquire about the Marelli distributor's centrifigal advance being a factor in the engine racing and not returning to idle. I used to have the instructions to tune the Zeniths, but I have lost them. I am needing to know about the 2 adjustments near the middle of the carbs around the accelerator pump distribution block. One is like a throttle compensator. I'm sure this is causing my engine racing, but I can't remember how to adjust them. Anybody?????

[stormcrow]

It is possible that you may have some contanimants in the gas tank, which could be causing a restriction when you are calling for more fuel.

I had a similar problem with a 55 chevy that sat for about a year. Varnish deposits from the fuel sitting in the tank collected in the screen for the line going to the fuel pump. When the engine was at idle or not moving, everything was fine. The car would even run but every now and then it would quit, like it was being starved for gas.

You may want to check it out.

Steve

[Zendalar]

I had that situation too, well still do. There are still rust particles in the tank and I have to change the fuel filter now and then.

[joehahn]

Fear no more I have the answer.

Get paper towel or rag and stick it under the connection of the line from tank to fuel pump. Make sure car is off. Undo line and let the few drips of fuel fall into the paper towel and then throw that out. Unscrew gas cap and set aside. Now scrunch your head down into engine bay (this is tricky but possible, you will see) and blow the SHHIT outta that line back to the tank until you can hear bubbles gurgling in the tank. Problem solved! HOWEVER, this is a temporary solution. The intervals in which you must do it gradually decrease until it is almost a daily practice. Mine has gotten so bad that I now have no choice but to yank the tank and get it boiled. I will posting that question a little bit later!

Good luck, and you are describing EXACTLY what I have had in the past so I hope this fixes it.

Joe 68L

...I forgot to add, the block is purportedly the screen at the outlet of the tank not your filters. That was what was killing me, filters looked o.k. but still wouldn't work!

[This message has been edited by joehahn (edited 08-21-2001).]

[SteveStromberg]

For a rusty tank take a large magnet and place it on the bottom of the tank. I use old speaker magnets. Steve

[Reg]

I couldnt take out the line that goes from the tank to the fuel filter. I did though remove the botoom line (I guess the overflow) line and drained all the gas out of the tank, after all , it is below the pick up line.

I wanted to remove the pick up line , but it was harder to get at with the tank installed on the car as it is higher up on the tank.

I have chevron techron in the tank now. I really do not want to mess with these carbs and am hoping it cure itself.

Am I dreaming?
and thanks for all of the info!




[This message has been edited by Reg (edited 08-21-2001).]

[fred hannah]

i have done the blowing back through fuel line many times myself, i even went as far as having a seperate 2 foot lenth of hose tucked away in the engine compartment that i could quickly attatch to hard fuel line coming into the engine compartment. the idea of the maggnet works real well also. eventually you will end up doing these things less frequently, but you will probably never get it all, atleast i havent and ive been doing it for about 3 years now, on and off, good luck

[J Richard]

On the sides of the zeniths there is a large pair of screws, the Aux. Mixture control and the flow rate adjustment (the big one in the middle) these two settings will affect the driveablility of the car. And need to be set from side to side much like individual throats on the webers. On both types check your accelerator pump delivery shot, they need to be consistent or you will get some running fat while some are lean during accel which=popping. I have seen backfires and over rich conditions actually burn (melt) the bottom of the emulsion tubes. The car popped and stumbled, only repair was to replace the tubes. Throttle shaft wear can wreak havoc with these carbs as well, try some carb cleaner at the shafts while the car is running to see if you have a leak.

On the tank you could drain it with the drain at the bottom. run compressed air through it to dry it out. Blow through the main back into the tank. Once you are convinced it is dry and NO vapors, stick a shop vac with a plastic tube taped to the end into the tank. with it running blow into every hole you can find to stir the debris while moving the tube around the tank. If you pull the sensor out it gives you a big hole to work through and you don't have to worry about damage. Then get a big, clear fuel filter to act as a pre filter to your main filter.

Anyway just my .02

Happy wrenching...

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93RSA

[Reg]

I have a few questions as to J Richard's list above.

2.Fuel pressure has to be correct 4-5lbs and the float level must be checked with a sight glass.

Ok, checking I have a brass screwed fitting that has a level guage on it. I assume this is what I use to check the float level. Where should it be on this guage? It has two sets of double lines.. is it correct to assume it needs to be within these limits?

If this is the proper way to check the level, how does one adjust?

3.Disconnect the linkages from the carbs. You can't do this with them connected.

I am just wondering why they need to be disconnected, and is there a better way of doing it?

6.Adjust to about half way up. Check each throat, if it's different it needs adjustment.

I have the cone type guage that pelican sells in this catalog. Half way up ? My scale reads 0 to 30 pounds, but half way on the scale forgetting the numbers is about 5 pounds, whereas 15 pounds would be 3/4's up the scale. Just a clarification here please.

10.After mixture, recheck the sync. Then mixture again

You mean after I do the adjustments , place my cone airflow guage on the stacks and see how close they are to being at the same level? If they guage is the same on all 6 throats , the carbs are set , aside from the even linkage?

Is it just the air mix screws I should be fooling with?


I hope to have it running good on the weekend, go for a first smooth drive is teh goal! Thanks so much

[J Richard]

Reg

2. The float level should be between the lines, depending on what year and model of webers you have the float adjusment varies from a small screw to a bendable tab. It's hard to say unless you look at the carb.

3. The throttle linkage must be disconnected (only at the ball joint, don't take the whole thing apart!) so that it is not holding one bank of throttle plates open due to it being tied to the other side. You want to adjust and balance the carbs and then hook up the linkage so they are both working from the same idle adjustment.

6. All the synchrometer is doing is giving you a relative flow rate, with the cone type you just put it on and read it, with the unysin type you have to adjust the guage to get the ball to read initially.

10. Yep, you're just going over it one more time. usually it requires two passes at least to get it all right. The thing is that adjusting the mixture on one throat can cause it to use more or less air due to a more or less efficient combustion cycle. So the first adjustment gets you in the ballpark, the fine tuning is the next pass.

Go back up and follow the process in my original post. After the air screws then mixture, then air screws, then mixture, then Idle compensator. (and then I usually went back and checked the air screws and mix again!) Everytime you change something in the system you affect everything else, you are working your way to a common state with each pass. And you can't skip a step or fuss with stuff out of sequence or you'll just be wasting your time over a hot motor.

Before you start you may want to just check a few things:

1.Is the timing right on? Including dynamic at 6000rpm? it really needs to be checked at 6000, or your advance could be sticking and messing you up. Pull the cap off and check the advance mech is operating and free. Suck on the advance hose and make sure the plate moves and you have no leak. If you have a marelli distributor, dump it and get a bosch.

2. Try the Sync on each of the throats before you disconnect the linkage. Are any way out? or all fairly consistent?

3. Rev the motor and see which throat is backfiring on release. Is it just one in particular? a burned valve can cause a backfire.

4. How was the compression? any cylinder low?
Valves adjusted?

5. On your orig post you said that the car idles but looses RPM while crusing. Is this an abrupt loss of power and stumble/backfire or a gradual reduction in power? I would be looking in two different places depending on whats going on. Sounds dumb but if it is slowly loosing power you may have a fuel tank venting problem or the wrong gas cap.

Anyway I hope some of this is helpful, It's really hard to do this without hearing the thing. I would spend the cash and get a weber tuning book there are several out there which will give more specific info.

Good luck, have patience, it will take some...


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93RSA

[Reg]

5. On your orig post you said that the car idles but looses RPM while crusing. Is this an abrupt loss of power and stumble/backfire or a gradual reduction in power? I would be looking in two different places depending on whats going on. Sounds dumb but if it is slowly loosing power you may have a fuel tank venting problem or the wrong gas cap.


It just starts to gasp really... you floor it as it is slowly loosing rpm's at highway speed. sputters , backfires some , pops.
It idles all day well, but seems a slight miss , very slight to me while at idle. It does not hesitate when you open up the throttle with your hand at the carbs.

If you sit the car for say 5 minutes, it starts right up and rev's freely. If you start the car too soon after this all hapens you play with the throttle and its rough for a bit , then breaks free and away you go.

Sad thing is a couple times it revved really nice, and pulled my neck back while adding a big smile to my face! I want that again!

My other friend suggested to t off the fuel line with a pressure meter in the cockpit and monitor the pressure at speed when the car dies out. We have it regulated at 3.5 psi, and can only regulated it to 4 psi, without going to 8 psi without this regulator installed.

BTW , the car ran the same way at 8 psi, but of course like now, it is not running correctly!

The car is a 70 t , 2.2 with SSI's and the 40 webers..not sure if anything other than stock inside the engine, but am assuming so.


Thanks again!

[This message has been edited by Reg (edited 08-31-2001).]

[This message has been edited by Reg (edited 08-31-2001).]

[Zendalar]

I had the same kind of problems.

I had fuel filters in my car that i did not know of, full of rust. Almost no gas came out at the carb end. Replaced the fuel lines +filters and has been working since (gotta change filter pretty often though

[joehahn]

I did por-15 tank sealer kit (Wayne, you guys should carry this, 50 bucks!) This is truly idiot proof. Once I put tank back in and whacked the side of carbs with screwdriver handle, car ran fine (and holding).