[schuga]

Hello,

I have noticed over the last week that my '67 Duetto would have a bit of hesitation (very slightly) and it went away as quickly as it began.

This week when starting the vehicle, it backfired and after running I could tell I was not running on all 4-cylinders (story of my life, ha). Changed spark plugs and that seemed to work as I the car ran great and I ran her hard to see if the problem would come back.

The car sat for a bit and then I went to go somewhere else, and the car started idle rough (not all cylinders firing). So I cleaned the spark plugs and tried again but the same problem persisted and seemed to have an intermittent no spark or hesitation. Hard to describe.

Here are some specs:
1600 engine with 32 DCOE 27 webers
weber specs:
-venturi: 30
-main jet: 120
-Air corrector: 180
-emulsion tube: f-16
-Idle jet 50F11
-Starting jet: 65f5
Early alfa manifold with a screw in thermostat
AR carb support installed
using Duetto airbox with homemade filter attachment
123 ignition
bosch red coil 222 119 030 and tests good
sparkplug wires test good
running a variety of spark plugs so I can have fresh plugs available.
-LODGE Golden Lodge HL
-Lodge B7ES
-Bosch plugs WR7DC+

This is what I have done:
-checked timing (with cam cover off) and it is good (No 1 point up and not to specified direction)
-check power to coil + side and is 12.6
-check for spark with inline spark tester and all cylinders have spark
-checked compression on warm engine with WOT
1. 170 170 170 165
2. 170 170 160 155
3. 160 160 150 155
4. 170 170 170 160
-replaced 123 distributor with a new one, same problem and changed back to original 123 dizzy and set up as described by 123
-changed cap and rotor
-changed spark plug wires (even though ones I using tested good)
-installed new bosch red coil and test good
-replaced mech fuel pump
-changed fispa fuel filter and cleaned out bowl
-took weber carbs off and cleaned the carbs, jets and replaced gaskets. set-up as described in this post
Ridiculously fast "idle" on weber converted S2... post #13

I DID NOT change the rubber mounts as I am just trying to get the car to my winter warehouse where I can do more work. Mounts look ok but could be changed this winter.

Now the car starts and getting a rough idle, it seems like it is missing and backfiring. It bogs down when given gas.

Any help and guidance would be greatly appreciated as I have no idea what else could be wrong or the issue as I need to move the car in the next few days.

Thank you,
Chip

 

[spiderserie4]

"This is what I have done:
-checked timing (with cam cover off) and it is good (No 1 point up and not to specified direction)"

you mean at TDC on cylinder #1, the front cam lobes point UP?
that is not right....

...or am I mis-understanding something.....?

 

[schuga]

Sorry, I see the confusion.

Verified timing on the car with cam cover off. Lobes are pointing out and cams are on the timing marks and the pointer is on 'P'.

Meant that the dizzy is pointing UP to about 12h30 as I thought it was to be at 15h00. But that is no big deal as the car is in proper timing as per the attached from spiderserie4 and the points above.

Chip

 

[spiderserie4]

well I am not so sure....if the rotor points at 12 o clock or just past, is that where you have put no#1 lead?
(I thought the rotor always points forward on TDC......well, unless the dizzy/pump has been put in 180° out, but then it would face backwards!)
but you seem to be between the two! ...your distributor is properly pushed down to locate the offset drive I presume.....

 

[tom shewchuk]

Is your hesitation around 2500 to 3000 RPM? Mine is doing the same thing. Runs kinda rough. Seems like there's a misfire when driving around town, but seems good on the highway.
Gordon Raymond suggested that I go one idle jet richer to a 55F11. It runs better. I had the idle screws out 3/4 of a turn, and I turned them in to a 1/2 turn.

 

[Gordon Raymond]

Have you checked fuel pressure? Neither the diaphragm or bow seal on the FISPA FRB 11 or your FISPA fuel pump were designed for todays fuel. Fuel pump, pressure regulator or both could be on the way out.

 

[schuga]

Thanks all. Problem solved! Went to a hotter spark plug and increased gap to .040" and the Duetto runs great!

All that work and I did not consider changing plugs.