Help on tuning V6

[rob07]

I am trying to tune my fiat dino engine and cant eliminate some popping from the exhaust.this happens on light throttle and overun,not harder acceleration and higher revs.The only thing Ive got left to do is to better map the timing advance curve and fine tune the idle mixture screws on the webers.Ive put a Gunsons co meter on the exhausts and am getting about 2.65 on one pipe and 3.3 on the other.Its got an ansa freeflow exhaust which may be the cause.Would welcome any advice.

[davepoth]

Triple Weber DCOEs on these? The way to tune these is to swap out the jets and unless you have a collection, know exactly what you are doing or get it exactly right, you'll be buying aimlessly. That's even if the ignition is set up properly.

I really would recommend sending it to someone with a rolling road and experience of the engine and carbs. It won't be cheap but it'll be done properly.

[rob07]

triple weber 40 dcnf`s on this.I would like to tune myself, but why would I need to change the jets.

[85Carrera]

Can't help with your query but any pics you can share with us

[Slidingpillar]

rob07 said:

triple weber 40 dcnf`s on this.I would like to tune myself, but why would I need to change the jets.

Because at anything over idle, the secondary and the main jets will determine the mixture strength. The one adjustment screw is for the idle mixture.

[V8 Fettler]

Not specifically Dino, but exhaust popping can be air leaks.

[rob07]

If it was air leaks why is popping only on lower throttle.Regarding the jets,the question is still why do I need to change them.I understood the Idle mixture screws are not only for idle but effective up to about 3,000 revs.

[boyse7en]

As above. Get it rolling-roaded. the exhaust may be making it run lean.

I had my kit car's modified Pinto with twin Dellorto's done, and the guy went through about five sets of jets to find the best ones.

Cost me about £120 (about 10 years ago mind) for the parts and labour, but the car then ran properly without stalling, popping, backfiring etc.

[V8 Fettler]

rob07 said:

If it was air leaks why is popping only on lower throttle.Regarding the jets,the question is still why do I need to change them.I understood the Idle mixture screws are not only for idle but effective up to about 3,000 revs.

Increased gas flow perhaps? Fuel flow from main jets overwhelming any additional air introduced by leaks? Idle screws certainly affect transition. For DCOE there is a recognised and well trodden path for fettling, must be something similar available for your install. I have a Dave Andrews' print-out for DCOE nailed onto the lock-up wall