Twin carb problem --- FIXED

[FbSTDwagon]

Heya Knuckleheads!

I have been on the 'chasing my tail' roundabout for while now in regards to the grey motor not running right.
The problems were apparent on 91 fuel, when I changed 98 the engine has given me nothing but major problems.

SYMPTOMS...

-engine was misfiring on early acceleration ie first 10% of pedal travel then would act normally for the remaining 90%
-revs not returning to base idle without a few taps of the pedal, on return the base rpm was inconsistent- linkages checked out OK
-major misfiring, popping, flat spots, farting and generally the engine was sounding a pop corn making machine
-spark plugs were totally fouled on 1-3 cylinders, 4 was an average foul and cylinders 5-6 totally lean
-spark (on clean plugs) was strong and adjustment of timing had NIL effect on symptoms
-changing out to new plugs seen them have same symptoms within minutes of running the car
-both carbs base idle revs set via vacuum bubble sync tool, front idle rev screw hardly on, rear was 1.5 turns in
-setting base idle revs both at 1.5 turns in on front cab had vacuum to outer space, rear carb wouldn't even register
-carby idle air mix needles not working as they should, front carb air mix needle not really doing anything, rear seemed to be working correctly

Diagnosis at this point was as follows

Engine health - Excellent. No oil usage, no knock, no blow by and compression 150psi perfectly even across the board
Ignition health - OK. My auto electrician mate checked everything over and dismissed ignition as the issue.
Carby health - ABSOLUTE RAT SHIT

Then focussing on carbs I ensured my base rev idle and air mix settings were correct - I had always followed correct procedure so I eliminated operator error in carb tuning as the fault.

Pic below of the spark plug readings at this point......

[FbSTDwagon]

These plugs were looking this way with both idle air mix needle 1.5 turns out evenly.

At this point I leaned the front carb progressively, fitted cleaned plugs and ran the car on the same route.
This cycle is did at least 8 times - God freaking damn it I make more work for myself than required.

Eventually I got all plugs running evenly, clean and lean.....

Front carb idle air mix needle fully closed... rear still at 1.5 turns out. Houston we had a problem!

I investigated everything my brain could imagine including mis matched carbs, faulty idle mix needles and cracked throttle plates.

That's when I swallowed my pride and called Michael Bresnehan who built the carbs, after many phone calls and following his lead I still had no result.
I then called old mate BS for a chat and as much as we both agreed that the carbs shouldn't be acting like this we were both a bit stumped.

BS asked..."Have you read Harvs Stromberg bible".... ahhh errr ummm... 'Ahh nah mate I haven't"
Nek minit in my email is the book that the should be taught in every religious primary school in the junior years... Harvs Stromberg Bible.

I then retired for the night for some whole some reading under to romantic light of my bed side lamp and awoke the next morning like I had been awoken from the dead. My vision was clear and I was talking in tongues.

The devil had spoken to me and he said... Go forward my son and check the idle secondary ports on the front carby...

In a jiffy the carbs were on the workbench for a bit molestation.....

[FbSTDwagon]

With the carbs throttle bases plates removed and side by side for comparison this what stood out like dogs balls..

Can you see it?

Rear carb base on right - butterfly closing nicely past the idle ports
Front carb on left - butterfly not closing fully and idle ports partially covered.

Diagnosis - Front carb butterfly not closing fully, creating extra vacuum which activated idle secondary ports.
Constantly pissing fuel into the intake aka over fuelling at idle - hence running super rich on the front cylinders.

[FbSTDwagon]

Both butterfly were then removed for a 'check & measure' which shown there front butterfly was larger in dimension about about '.005.
Checking the fit of the front butterfly back into the base shown it was an interference fit and was sticking in the throat of the base.

[FbSTDwagon]

The directive was then to reduce the size of the outside dimensions of the butterfly so it seats in the same manner as the good carb.
I wanted the front throttle to close in the same manner as the rear

Process was delicate but simple... some fine filing, sanding and rubbing with scotchbrite pads.

I checked the butterfly fit for high spots with a torch shining underneath to show any high / low spots on the and I adjusted the plate accordingly.

After taking the phot below I realised I had removed too much material so I raided 'EKmart" as Blacky would say, found another plate and started again.
Taking more care than the first time I got it perfect, way better than the photo below.

[FbSTDwagon]

After a lot of fecking around I got the throttle plate to close which matched the good throttle plate position of the rear carb.

[FbSTDwagon]

While I was there I found a worm accelerator plunger arm with a elongated "d clip' hole which was giving me un-even plunger depth.

Again raided 'EKmart', found a good one and got the plungers et at same height and to factory spec.

BTW the hand model got fired, she won't be visiting again...

[FbSTDwagon]

From there I reassembled the carbs and threw them back in.

Tuning was then a breeze, the carbs synced perfectly as expected when following the procedure.

The 219 was then terrorising the neighbour hood, driver waving at grandmas, kissing babies and patting single mums on the bum.

Got home removed the plugs and this what I found!!!

[FbSTDwagon]

Totally happy with the result I then knew I could fine tune it and get the plugs 100 percent perfect...

Happy days...lots of WOT action coming to a neighbourhood near me!!!!

[Blacky]

Awesome - Harv's bibles should be declared a national treasure

I admire your patience, I would just spit the chewy, have a tantrum and ship it off to somebody to sort out for me ......

[briby]

Well done Drew, had to be something common to the front 3, makes ya warm & fuzzy when something works out.
But i'd probs follow the Blacky route & then grumble about the labor rate.

[Harv]

Can't weld, but I know my way around a carby-retta. Glad you got it sorted.

One of these days I'll publish the next version of that Stromberg Guide. I've got all the info to update it to include the WWs, but never seem to get around to finishing it.

Cheers,
Harv

[FireKraka]

Hey Drew fantastic outcome for your ‘fuel make it happeners’ now I know why I go EFI