4Afc Project Questions And Problems

[smaccas1411]

I recently purchaced a 1990 Holden nova sedan with the 4afc motor. It had a blown head gasket as a result of a faulty thermostat. The auto choke was also seized. I replaced the head gasket, intake manifold gasket, exhaust manifold gasket as well as the dizzy, ignition leads and thermostat. Full oil change and tune up. Having a few problems with a shutter or surge at low reves when driving. Any suggestions.

 

While the head was off i cleaned the pistin heads and the carbon buildup on the top edge of the cylenders was removed and pollished. Valves also cleaned.

 

 

[altezzaclub]

Any clues on the stutter? Do you reckon lean or rich when it does it? Does the carb have a window for fuel level??

 

Does it idle fine?

 

What sort of rpm or what speed in which gear when it plays up?

 

Slight throttle on or slight throttle off, or over-run with no throttle?

 

It might pay to start by pull the top off the carb and clean out the jets and drillings in there.

[smaccas1411]

Blown head gasket and leaking thermo housing so i pulled her to bits and put in a full new gasket kit. She runs like a dream now but there is a slight shutter at low revs like its not getting enough fuel. Its in every gear at revs around 1200. Everything on the electrical side is new so I'm guessing its carb related. Any experts on the carb.

 

Put a few pics of the build just for interest sake.

 

Under the rocker cover

 

Carby looked like she had copped a heap of oil from the pvc valve and the auto choke is seized

 

Pistins were built up with carbon

 

 

The head off and cams out.

 

Cleaned the mating aurface on the block and the pistins. To really shine up the mating surfaces i used a flapper pad with a super fine grit on a drill to pollish them up nice

 

 

Edited July 9, 2016 by smaccas1411

[smaccas1411]

Cheers mate ill give the carb a good cleanout. Ats at about 1500rpm just on the throttle accelerating or holding speed at low revs in 1st 2nd and 3rd

[altezzaclub]

Yeah, that's the hardest time for a carb. The motor is off idle and has to produce power, but the throttle is hardly open to give any flow. The idle jet is still doing most of the work then, so take it out, take out the adjusting soeed screw and hose petrol or carb cleaner through the drillings.

 

I use a syringe full of petrol, but an aerosol with a tube on will do it. If you've got a compresor follow it up with a blast of air.

 

My twin SUs struggle with the same thing, although the surge is only when I lift off at those revs.

 

If that doesn't fix it, the timing is also difficult at those revs as it is the steep part of the timing curve. Any slop in the advance weights or dizzy gears might be the problem.

[LittleRedSpirit]

Ive merged your two threads and FYI, we love to help, but if you sully up the forums with multiple threads for your same single problem then you will get deleted and banned, as above all else its counter productive to finding a solution and spreads the info people may need to reference over more threads for no reason other than you are impatient.

[smaccas1411]

Sweet as. I was using the mobile ap and though the first didnt upload. Cheers for that. I'm putting a catch can in after the pvc to keep out the oil after the carby clean clean. Ill let you know how it goes.