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?

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.

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.
Click to view attachment

Run a compression test
I’ve seen carbs with different idles.. even mains
That owners have compensated for a low cylinder

The altitude will mess with me here...

For Texas (600ft altitude) I'd use basic carb size of 40, venturis of 32, main jet of 130-140, air jet of 180-210, and idle jet of 50 or 55.

Due to the 7k plus altitude I'd expect that to need jets a bit smaller than what I listed above and maybe a venturis size of 30.

Whatever I did I'd be checking the actual mixture with a properly placed wideband O2 set up.

The 7k altitude has lowered the available oxygen by a significant amount.

Cars run like CRAP in Denver Colorado 6k versus Texas (600ft).
A 10 second 1/4 mile pass in Dallas is a 12.5 pass at Bandimere in Colo.

Less oxygen should require less fuel and equal LESS FUN!


Your main jets are way, way, off! I bet you're running 10.5/1 AFRs, and you will end up wiping the motor out via oil dilution with fuel.

Get a wideband and main jets that are a shitload smaller!

That car will benefit greatly from smaller vents. Really wake up your throttle response. And re jetting accordingly.

I've seen that as well...
Every time I've seen intentionally staggered jets it's been on a weird application and a SHITLOAD of testing has been done with individual EGT probes to accurize the jets.
It's never been on idles however, always mains and airs.

I'm guessing this is not a 100+ hours of professionally tuned engine...

I solved a weird one over the phone with a friend of mine who operates a race preparation shop.
He had a "Legends" car that was a heat winner for the first couple of races that gradually fell off during the evening. This class of racing has many very short heats in a normal evening. By the end run this was which led the pack on the first heat was the caboose by the last heat.

Marty is knowledgeable and did multiple compression test and leak down during one evening. Leak downs were perfect all evening long where compression fell off in the rear cylinders quite dramatically over the evening...

Let the puppy cool down for an hour and all is well!

I had Marty stagger the valve adjustments .001 looser for each cylinder past the right outer one. Cylinder #4 had a valve adjustment .003 looser than cyl #1.
The air-cooled motorcycle engine was turned 90 degrees from normal installation and the rear cylinders heated up more than the fronts...

Fixed it right up!
Heat winner all night long now...

I'm betting someone, who didn't know what they are doing, decided to go ahead and use the jets they found. Maybe they didn't even check (or know to check!).
Having 3 different sizes is damn strange though.
The carbs would have come with identical jets, and someone had to add those at one time.
Got to be a back story there somewhere.

Now, doing a compression and leak down test should be THE FIRST thing you do when you're setting up carbs. If compression is screwed up it's going to be much, much harder to get the carbs right.
Maybe impossible...

They would all be the same..They may have been drilled?
Do you have a way of checking the hole sizes?

+1 on the possibility that they have been drilled. Need to start with known jet sizes or measure them. You can't always go by the size indicated on the jets. They can even be soldered and smaller than indicated on the jets after redrilling.

What size are the Dells ?,36mm come with #52 idles for example or atleast that was what the last set I used had with 28mm vents.
Cheers.