Tech Questions/Advice
22494 My poorly running Fiat 125, and carb settings [s.spiers] (Wed Sep  1  6:31:00 1999)
   22524 Re: My poorly running Fiat 125, and carb settings [Campbell] (Wed Sep  1 11:58:37 1999)
   22537 Re: My poorly running Fiat 125, and carb settings [paultunley] (Wed Sep  1 15:15:32 1999)
      22539 Re: My poorly running Fiat 125, and carb settings [s.spiers] (Wed Sep  1 16:21:59 1999)

Here is the official update on my Fiat 125

If you are new to the thread, My 125 with a 1608 misses at high 
revs.

Well its been an interesting week. The dellortos that I was going 
to install turned out to be a bit too much hassle to install. On 
a 
125T manifold it is designed that the rear two inlet runners are 
not offset too much and the front two are offset more (because 
of the dizzy) this means that the two carbs are very close 
together. The linkage system on the dellortos then did not fit 
between 
the carbs and the ones off the webbers are different. So guess 
thats the end of the easy fix. One idea would be to try a single 
carb.

After discovering this, we decided to give the webers another 
once over and record all the jet sizes.

This is what we found, apparently thes carbs were set up for this 
engine!

Weber 40 DCOE on 125T angled manifold

Choke size: 27mm    (I know, they are small)
Emulsion tube:    F16
Air Correctors: 145
Main Jet: 115
Idle Jet: F11/50
Starter Jet: F565
Pump Jet: 35
Needle and seat: 150

Anyway, we did find some interesting features. The accelerator 
pumps in the two carbs were different, one was longer. So 
another was temporarly found out of a 45mm DCOE of the shorter 
type, then installed. Also 3 out of the 4 of the little ball 
bearings from the pump jet non return valve assembly were found 
to be missing. After all this we were sure of a good result, but 
not likely.

What do you think of the jetting? what is the difference in the 
accelerator pump sizes? what do you think the little ball 
bearings 
do?

Two days later

When I tried to block off the front two ram tubes, the engine was 
unaffected, when I block off the rear two, It stalled. So there 
could be a leak somewhere, I disconnected the booster line and 
pluged it up, tightened up the carb to manifold bolts, gave it a 
quick crude balance, and took it for a blat.

Wow - definate improvement, it's still not fixed, but it's the 
first good sign Ive had.
The engine will now rev right out in first gear, and sometimes 
second, in second it sometimes gives a little miss around 4500 
rpm but the comes right up to 7000.
third has more problems and 4th gear is terrible. This sounds 
like the carbs are not getting enough fuel?

I had a look at the fuel flow rate from the line to the 
carbs, it just dribbled out, anyone know what the flow 
rate should be? I decided to change the faset fuel pump in the 
car with one from the back of my mates 128 race car (so 
presumeably its good) now the flow was better, but not what I'd 
expect. maybe there is a blockage in the line?

So the saga continues, ill keep at it

what do you think, any more suggestions?

Steve

70 Fiat 125 (road/race car, daily driven)
73 Fiat 124CC (will be finished, sometime)
73 Fiat 124CC (parts car)

Stephen Spiers wrote:

: I had a look at the fuel flow rate from the line to the 
: carbs, it just dribbled out, anyone know what the flow 
: rate should be? I decided to change the faset fuel pump in the 
: car with one from the back of my mates 128 race car (so 
: presumeably its good) now the flow was better, but not what I'd 
: expect. maybe there is a blockage in the line?
: So the saga continues, ill keep at it
: what do you think, any more suggestions?

Steve,
The cards on the Lotus Elan we used in the Targa last year
required 2 litres a minute for a 1592 Lotus Twin Cam. Give
Murray Johnson a ring at Weber Specialities in Auckaland. He
knows his carbs inside out, and has owned Fiats in the past.
Ciao,
Campbell
1968 124 Coupe ('Cos We Love It)
197? Lancia Fulvia 3 Coupe
1975 124 Spider (Racecar)
1984 Uno 70S (Son's Club Car)
1986 Uno 70S (Wife's Daily Driver)
1989 Lancia Thema ie Turbo (Tow Car)
http://homepages.ihug.co.nz/~robbos

The original Weber jetting on 125Ts is ...
Main venturi choke   34mm
Main jet             130
Air corrector jet    185
Auxillary venturi    45
Idle jet             45F8
Accl pump jet        35
Needle valve seat    175
Float level setting  8.5mm
Accl pump pickup jet 60
Emulsion tube        F16        
Note however that the exact internals on your engine will effect 
these as will the type of fuel being used and also air cleaners.
Also, with your high rev miss being narowed down further, have 
you checked that the gaskets/sealing rings between your manifold 
and carb are not pinched and leaking?
Cheers ... Paul
1972 FIAT 125T (race car)
1986 Holden Commodore (tow car)
ps: try http://www.geocities.com/MotorCity/Shop/3342/albumidx.htm

 Also, with your high rev miss being narowed down further, have 
: you checked that the gaskets/sealing rings between your 
manifold 
: and carb are not pinched and leaking?
: Cheers ... Paul

I suspect that they might be, I might take off the carbs and have 
a look

Steve
 
70 Fiat 125 (road/race car, daily driven)
73 Fiat 124CC (will be finished, sometime)
73 Fiat 124CC (parts car)

dauber