idle jets, mixed sizes Options

[Petepat]

Got a 1.7L engine with Dellorto Carbs which I took out the idle jets and notice on one side they are both 50 but on the other side they are marked 55 and 52 could there be a reason for this or a case of anything goes?

[technicalninja]

Check the venturis!

The Datsun Z 3X2 set up sometimes had a different sized venturi and corresponding different jets in the intake runner that they sourced the brake booster vacuum hose from.

They needed a better vacuum signal in that runner and dropping venturi size was the CHEAPEST route to this.

The above is a STUPID idea. On an ITB set up I ALWAYS delete the booster or give it an electric powered vacuum source which usually works kick ass.

Our 914s don't have this problem and the only real reason I can come up with for your jetting differences is incompetence...

If the venturis are all the same size (they should be) monkeys have been "molesting" it and EVERYTHING about the engine is suspect!!!!

I'd rebuild the carbs and investigate anything else that looked wonky...

I could make those idle jets work at idle. The needle adjustments on the cylinders with the larger jets in them would be farther in than the other cylinders.
They would work, just not well...

As these carbs run mostly on the progression holes the jetting difference WOULD make a difference off idle and during 70% of the normal street use driving.

For a track car the issues would be less prevalent as they are normally above 50% throttle opening.

I wouldn't let a 'customer" car return to service with mis-matched jets.

[CCE]

Check the venturis!

The Datsun Z 3X2 set up sometimes had a different sized venturi and corresponding different jets in the intake runner that they sourced the brake booster vacuum hose from.

They needed a better vacuum signal in that runner and dropping venturi size was the CHEAPEST route to this.

The above is a STUPID idea. On an ITB set up I ALWAYS delete the booster or give it an electric powered vacuum source which usually works kick ass.

Our 914s don't have this problem and the only real reason I can come up with for your jetting differences is incompetence...

If the venturis are all the same size (they should be) monkeys have been "molesting" it and EVERYTHING about the engine is suspect!!!!

I'd rebuild the carbs and investigate anything else that looked wonky...

The amount of gas burning, and the smell is terrible

I could make those idle jets work at idle. The needle adjustments on the cylinders with the larger jets in them would be farther in than the other cylinders.
They would work, just not well...

As these carbs run mostly on the progression holes the jetting difference WOULD make a difference off idle and during 70% of the normal street use driving.

For a track car the issues would be less prevalent as they are normally above 50% throttle opening.

I wouldn't let a 'customer" car return to service with mis-matched jets.

If you find out a method to identify, appropriate: gas, air, Venturi, size please let me know..
I have a 2.15L with twin 44mm weber, regular valves, mild cam, and live in an altitude of 7450ft. In Mexico City …
Jets is for me at the moment a big issue too.
There must be a chart or a formula to sort it. Without going trough every jet possible. At a cost…. Or having to go a tech school, to learn the procedures…

I am currently using 36mm Venturi’s, 2.0 air and 160gas… it runs fine but wasting big time in gas.