well engine is running kinda, is anyone out there willing to help me out setting up a set of 40 IDF's with jet doctors ...got all my timing n such sorted out but be dammed if I can sync or tune these webers.Iit's running and idles ok but I seem to be getting some backfiring thru the muffler (unburnt gas,correct?) when its under load.
I have set timing at around 28 deg @3000 (009 dizzy) points are gapped correctly, no air leaks and everything is new.
Could this also be fuel psi related?

willing to pay in beers or similar.....

Cheers Binner

What size engine with what size jets & venturi's ??? You sure no exhaust leaks ???

Backfiring often means lean, which suggests you're not at a good starting point with the jets rather than just balance issues.

Once you are at a good starting point, things I'd be doing in order are:
1. Fuel pressure (3.5 psi MAX).
2. Bench set carbs, balance & adjust linkage
3. Timing and point gap
4. Balance while running
5. Idle speed while running
6. Idle mix adjustment while running (lean best idle)
7 Repeat 4 through to 6 until a nice stable idle

Otherwise happy to take a few of those beers in a week or two if you're still having probs !!!

Give us engine and carb details i.e. capacity, cam, compression, exhaust (just as an idea what kind of motor it is) and carb details of venturis, idles, mains, emulsions etc.

If it is a "bang" through the exhaust - my guess is rich

A "snap" or "sneeze" out the carbs - indicates lean

Idles I would start with 50's
vents are what they are - assuming you have a 2L or something, I would be expecting 32's
mains - 4.2X the vent = 135's
Airs - 180's
Mixture screws - 3 turns out

have a read here
http://www.aircooled.net/vw-carburetors-jetting-102/ 

and here

http://www.aircooled.net/synchronize-dual-vw-carburetors-103/ 

2027cc
C35 cam
los panchito heads
40 idf webers, rebuilt, floats set as per weber specs
fuel is running at around 3psi
no leaks that i can find

i have installed the CB perf weber upgrade kit which includes the below

34 Venturis
1.80 Air Correction Jets
1.60 Main Jets


thanks for all the responses, I do appreaciate it

Cheers binner

Ring me whilst your in front off your engine, if you'd like my help Ian.

No probs

Idle jets??
Mains seam large to me.
Matt's offer is good

160 is too large for 34's in my opinion and would be causing the backfire

140 or 145 would be better

Quote:

Originally posted by vassy66T1 Matt's offer is good

does the upgrade kit have a spray bar instead of the normal set up??

cause that mucks things up for opinions on jetting - well it certainly did on my dells
you run a fatter main - so my opinion above may mean jack

No worries, sounds like it could be rich with the 160's if it's not ignition

ok, so I swapped the coil for a 3 ohm standard coil and B A M ! it runs perky!!!!! (yeah I'm a crack head) I bought all this gear so long ago I can't remember whats what, so I just went ahead and shoved in the master blaster coil for electronic ig only which I was going to purchase but instead for some dumb reason I bought a points dizzy and just installed it without thinking and hence it was running like shit!!!.
So all I need now is to actually sync the carbs and I'm there. Been tearing round the neighbour hood all arvo and its running nice, just fine tuning now.

also had TACH BOUNCE so I installed a 1 amp diode inline and now it reads fuggin perfect!!! i likr it when things work

Thanks for all the replies and I'm just glad it's almost ready for rego

Nice man!

good to hear mate

n matt your mood script is gay.. xxx

ok ,so now a step further...pulled out the EMPI fuel pump (noisy) and bought one of these http://www.fuelflow.co.nz/FF_cms_03/eshop?page=shop.product_details&flypa... and one of these http://www.ebay.com.au/itm/Mallory-Ignition-4309-Aluminum-Fuel-Pressure-Regul...

3 year warranty, super quiet pump, mallory reg with bypass getting bang on 3.5 psi and able to adjust up to around 4 if needed. So after all that it finally runs nice and now just gotta get some help on the fine tuning and synching. Is it really worth buying a snail sync to tune or is a piece of pipe and good ears just as good?

cheers Binner

i don't ecommend a snail, thee is usually no gasket between the elocity stack and ai-ilte bottom plate so it is meaningless imO. Just get each cylinde esponding the same to idle mixtue adjustment and you'll be in sync.

^^ yep, my version

2a. 1/2 turn on idle stop screw
b. 1 3/4 turn for the mixture
3 adjust carbs using mixture screws to also help with balance, as you said, screw that makes most difference down idle speed or up other carb depending on where the speed is at first.
8 Bundy not SJ