SPITTING CARB - 914-6 all stock, 917 Update (Date not Car) Options

[ctc911ctc]

1970 - 914-6 All stock

Got the car off the rack after a 1 year clean up documented here:

http://www.914world.com/bbs2/index.php?sho...3371&st=100

- tightened the lugs, check one more time for leaks.......

Car started first try, backed out of the driveway and went around the block

Drive strong.....very strong......

#2 cyl-carb is still 'spitting' definitely not backfiring. Chasing this through my trusty guide:

https://www.performanceoriented.com/special-procedures-1

See "notes" section

Seems that when I performed the Lean Best Idle procedure #2 failed during the procedure......the diagnosis within the document states that either the path in that carb #2 is blocked or the jet is the wrong size - my bet is a clog......though the carbs were very clean when I got the car.

There is a little noise from the right side, that in a 914-2L 4Cyl would be considered quiet, my hope is that it is not valve noise and may be exhaust leaking......did I tighten the heater manifold small nuts????? dry.gif

Carb advice sought from those that have chased a SPITTING Carb

[rgalla9146]

Don't trust the marking on jets.
Get a jet measurement tool to verify they have not been reamed.

[ctc911ctc]

*******UPDATE*********

I was getting pretty frustrated - ready to send the engine out to an expert and have it completely rebuilt.

AND HERE IS THE PART ABOUT 911WORLD's power

I received a message from a member stating he had a pair of original carbs and that he had them tuned and operating on an an engine stand with a 2.0 '70 914-6 engine running perfectly and that he would sell them to me. I bought them and put them on the car.

Double checked all of the connections, turn the key and.....battery dead??? Huh, must of left the interior light on.......got the charger and got some lunch.......looked for fertilizer for the lawn......must be around here somewhere....answered the phone, my son wanted to work on a project, bringing his car over......neighbor stopped by to ask me why his TOYO was doing something ridiculous..........and then I stepped on the gas 2 times and turned the key.

The car started on the first turn and purred........ (IMG:style_emoticons/default/beerchug.gif)

Did not even have the idle advance handle in postion....... (IMG:style_emoticons/default/cheer.gif)

One or two minor pops and then just silky idle.........

I could not run the car too much since it is Easter weekend - more to come!

[porschetub]

*******UPDATE*********

I was getting pretty frustrated - ready to send the engine out to an expert and have it completely rebuilt.

AND HERE IS THE PART ABOUT 911WORLD's power

I received a message from a member stating he had a pair of original carbs and that he had them tuned and operating on an an engine stand with a 2.0 '70 914-6 engine running perfectly and that he would sell them to me. I bought them and put them on the car.

Double checked all of the connections, turn the key and.....battery dead??? Huh, must of left the interior light on.......got the charger and got some lunch.......looked for fertilizer for the lawn......must be around here somewhere....answered the phone, my son wanted to work on a project, bringing his car over......neighbor stopped by to ask me why his TOYO was doing something ridiculous..........and then I stepped on the gas 2 times and turned the key.

The car started on the first turn and purred........ (IMG:style_emoticons/default/beerchug.gif)

Did not even have the idle advance handle in postion....... (IMG:style_emoticons/default/cheer.gif)

One or two minor pops and then just silky idle.........

I could not run the car too much since it is Easter weekend - more to come!

Wow great result ,well pleased you are sorted ,carbs you bought must be healthy ,yes if they are good just a few pumps on the loud peddle, I don't use my hand throttle much more than to warm the engine for a few minutes and it's also handy when I balance carbs.
I remember a while ago you were going to check vents, jets etc ,what did you find ? ,I suspect as others said your old carbs were setup wrong for a stock application 2.0 litre 914/6 motor.
All you need to finish up is to balance the airflow for YOUR engine , cheers.

[930cabman]

All is well that ends well. but what could have been the culprit? clogged passages/jets?

we may never know but at the least you can drive the car (IMG:style_emoticons/default/piratenanner.gif)

Happy Easter and happy motoring

[brant]

They need a full high end rebuild. Possibly butter flys.

Which cost thousands

[930cabman]

They need a full high end rebuild. Possibly butter flys.

Which cost thousands

Curious: I have heard/read of the throttle shaft air leakage, but if these IDA, IDT, 3V carbs can be dialed in at idle where air leakage should show up, how can this be an issue off idle?

small teflon pieces are the actual bushes?

[brant]

An air leak is unmetered air and effects mixture always

[Superhawk996]

They need a full high end rebuild. Possibly butter flys.

Which cost thousands

Or . . . More likely just the proper Venturi and jetting. 32mm Venturis on a 2L six cylinder is craziness unless racing and top end power is the goal.

Guess we’ll never know (IMG:style_emoticons/default/laugh.gif)

Regardless, glad the carb swap helped it and maybe now it can get driven. (IMG:style_emoticons/default/smilie_pokal.gif)

[ctc911ctc]

****UPDATE*****

I have another thread that talks about Bucking - MY guess is that my carbs are getting closer - most of the problem is my on the job learning curve. (IMG:style_emoticons/default/dry.gif)

The car was idling perfectly but on occasion would tap. Uh-oh - valves? (IMG:style_emoticons/default/sad.gif)

NO! turns out the carb throttle plate rod is oscillating laterally. Literately Laterally!
(IMG:style_emoticons/default/WTF.gif)

https://youtube.com/shorts/KFZnitg3QZU?is=92xMfJZFT57ZZkvQ

In this video, when i hear the tapping I PRESS against the throttle plate rod which I can feel oscillating laterally. When pressed the sound ceases.

My guess is that the throttle rod HEX collars need to be adjusted? Has anyone seen this before?

Thoughts (IMG:style_emoticons/default/confused24.gif)

[Superhawk996]

(IMG:style_emoticons/default/popcorn[1].gif)

Video looks like you might have gone back to stock Venturis but is there a reason Venturi size is being kept a secret?

Idle seems sort of rough and that may be causing the throttle shaft to oscillate? (IMG:style_emoticons/default/idea.gif)

And yes you need to make sure you linkage joints don’t have excess slop in them too.

There really shouldn’t be much lateral play in the actual throttle shafts but there are a few springs and washers along with a coupler between the two throttle shafts that could be loose. But having said all that, the thing that ultimately dictates lateral play is the slight but necessary clearance between the throttle plates and the throttle body.

Before I’d even think of tearing down carbs, I think you need to focus on tuning basics and see if you can smooth the idle shake.

[rgalla9146]

If you hear a clacking noise at idle and it can be stopped by putting your finger
on the tip of the shaft, it is throttle shaft play.
This is often seen at #1 and #4 cyls.
How thorough was the rebuild on the purchased carbs ?

[ctc911ctc]

(IMG:style_emoticons/default/popcorn[1].gif)

Video looks like you might have gone back to stock Venturis but is there a reason Venturi size is being kept a secret?

Idle seems sort of rough and that may be causing the throttle shaft to oscillate? (IMG:style_emoticons/default/idea.gif)

And yes you need to make sure you linkage joints don’t have excess slop in them too.

There really shouldn’t be much lateral play in the actual throttle shafts but there are a few springs and washers along with a coupler between the two throttle shafts that could be loose. But having said all that, the thing that ultimately dictates lateral play is the slight but necessary clearance between the throttle plates and the throttle body.

Before I’d even think of tearing down carbs, I think you need to focus on tuning basics and see if you can smooth the idle shake.

Video looks like you might have gone back to stock Venturis but is there a reason Venturi size is being kept a secret?


Super Hawk! No Super Secrets here - I expected to see a number on the venturi, did not see one - no micrometer at this location.


Idle seems sort of rough and that may be causing the throttle shaft to oscillate? (IMG:style_emoticons/default/idea.gif)

Today I am attending to this again - i am starting over on the process. ALSO, I believe I may have a small ignition issue - have the devices to trouble shoot this today also.

And yes you need to make sure you linkage joints don’t have excess slop in them too.

;^}>


There really shouldn’t be much lateral play in the actual throttle shafts but there are a few springs and washers along with a coupler between the two throttle shafts that could be loose. But having said all that, the thing that ultimately dictates lateral play is the slight but necessary clearance between the throttle plates and the throttle body.

YES! this is my concern - if i remove the play will I introduce binding or prospect of wear.


Before I’d even think of tearing down carbs, I think you need to focus on tuning basics and see if you can smooth the idle shake.

Will Do!

[Superhawk996]

if i remove the play will I introduce binding or prospect of wear.

Yes - you don’t want the throttle shafts side loaded.

Based on your snail airflow numbers I’m not surprised you have idle shake with the bank to bank flow that far off.

When adjusting carbs you need to start by setting idle with all linkages disconnected. Linkages don’t even come into play until you have airflow from barrel to barrel balanced, best lean idle mixture, bank to bank airflow, and idle speed iterated.

[ctc911ctc]

UPDATE

spent an hour

Warmed the engine - still spits and misses a bit - bucking, etc.

Dropped linkage
1 turn on each side after contact - idle adjust screw

Dialed into 950 rpm (timing light) with same airflow on cyl 1 and 4 ~5inches
set airflow on each cylinder to match ~5 inches

I believe that this is important:

ALL OF THE CYL WERE AIRFLOW ADJUSTABLE INCLUDING 2 AND 3

Minor idle change - higher - adjusted, watched airflow, results in a tad UNDER 5inches

Started least lean method

Cylinder 1 - 200-to-300 drop, backed out the screw until it came back
Cylinder 2 - NO DROP when moving the idle mixture screw........huh.....has no effect
Cylinder 3 - same as 2
Cylinder 4, 5, 6 all are adjustable, however, with 2&3 acting this way, I stopped the process.

I need to fix cyl 2 and 3 on the carb

Notes: Carbs were purchased rebuilt with receipts from a member on this board, my old carbs had another set of issues......hhhhmmmm

I noticed that there is play on the shaft of the throttle at the front where the throttle arms connect.

There is also play (not as much) at the back next to Cyl 3.

All ideas welcome

Thank you,

[brant]

Spray carb cleaner on the loose idle shafts

If the rpm changes at idle you know you are then getting unmetered air there

New throttle shafts are the solution for that

[Superhawk996]

I need to fix cyl 2 and 3 on the carb

(IMG:style_emoticons/default/agree.gif)

[ctc911ctc]

On my way to buy carb cleaner now -

Question - shaft wear or journal wear?

On my way................

I need to fix cyl 2 and 3 on the carb

(IMG:style_emoticons/default/agree.gif)

[ctc911ctc]

******NEW INFORMATION********

So, where we last left this puzzle is as follows.

1. Car came with Carbs - Not original but Weber Reproductions in very good shape
2. Could not get the carbs to tune
3. Bought a Set of originals, in very nice shape - recently rebuilt, receipts, etc.
4. Installed the new Carbs
5. Still had the same trouble.
6. Changed the Distro springs - they were not correct, too loose
7. verified timing, right on the money
8. Car started and spitted and popped
9. tried the least Lean method - could not get carbs 2 and 3 to react to the method
10. Clanking was heard from the accelerator shafts bouncing left to right and then back

https://youtube.com/shorts/KFZnitg3QZU?is=92xMfJZFT57ZZkvQ

Was told to spray carb cleaner around the shafts to detect air leaks - when I spray the car idles a bit better if I spray around the carbs 2 and 3, however, it is hard to detect change.

What type of idle change should one expect?


I ordered new teflon spacers and will install them

ALSO

Here are some pictures



Carb that came out of the car on the right, one that came with the car when I bought it is on the left



27mm is from the new carbs that I bought that are original Porsche Carbs.....I just pulled this from the car a few hours ago



32mm is from the carb that came with the car, had all of the original trouble that perhaps was attributable (somewhat) to timing trouble.


Next Step - install teflon on the shafts - measure the shafts for wear.

[Superhawk996]

27 mm Venturis (IMG:style_emoticons/default/wub.gif) these are your best shot at good street driveability.

Check those throttle plate screws - may just be the picture resolution but they don’t seem to be peened. Some people use red locktite so I don’t want to panic you but I by far prefer a mechanically peened screw.

Get the bottom of why cyl 2&3 weren’t responding to idle mixture screw adjustment and you should be on your way toward success.

Check idle jets as first on the list
Passages clear of debris
O-rings intact
Shine bright light into the hole for the idle mix screw adjustment and see that the needle seat area isn’t torn up / corroded / blocked

[ctc911ctc]

Was hoping you would be on line!

I watched aircooled consulting on this topic:

https://www.youtube.com/watch?v=jEvmk8VziPQ
Go to 25:40 as to peening vs. Red Locktite

I am concerned as to the different screw types, also I am more concerned as to the throttle shafts bouncing left to right and clicking the throttle plates against the walls.....

Is this a common issue?

Gets very loud - video hides the impact of the noise.

Thanks SuperH!

27 mm Venturis (IMG:style_emoticons/default/wub.gif)

Check those throttle plate screws - may just be the picture resolution but they don’t seem to be peened. Some people use red locktite so I don’t want to panic you but I by far prefer a mechanically peened screw.

Get the bottom of why cyl 2&3 weren’t responding to idle mixture screw adjustment and you should be on your way toward success.

Check idle jets as first on the list
Passages clear of debris
O-rings intact