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Fri May 05, 2017 8:53 pm

Is there a chart somewhere of what bit sizes to use to drill out the jets for a Solex 34-3? I have some lying around that look to have been drilled already, so I am thinking no harm in drilling them out to use for tuning my new carb. At least then I will know what they are!

Thanks!

Chris

Fri May 05, 2017 9:18 pm

I couldn't say for actual drill bits, but I use a set of jet reamers to tweak my jets, and a set of jet gauges to measure what size they are. They're aren't the cheapest tools in the shed, but I consider both to be indispensable for carb tuning.

God luck, man.

Sat May 06, 2017 4:24 am

I opened my main jet to .062 with a pin vise.Worked for me.

Sat May 06, 2017 5:50 am

Precision drills, jet reamers, jet gauges...

http://www.piercemanifolds.com/category_s/327.htm

Dale

Sat May 06, 2017 6:33 am

The jet sizes are in decimal mm metric so you don't need a conversion chart assuming you have a metric drill set and pin vise. Which can be bought from all over eBay for under $10

But you are only going to find them in multiples of five so for a jet like an idle where you might need a half size more often this approach may not work as well.

But it can certainly get you in the ballpark

Sat May 06, 2017 8:14 am

There are metric pin vise drill bit sets available. The last place I got a set from lists them out of stock, but there are other sources if you google it. The jet sizes are metric, so a "55" idle jet is .55mm. And as mentioned, if you get a standard set, you would simply divide the metric amount by 25.4. So, .55mm divided by 25.4 would equal 0.0216 inches.

Sat May 06, 2017 9:30 pm

You should never use a drill on a jet, it can leave swirl marks in the bore which can decrease flow. you should always use a jet reamer. I think all the ones you buy nowadays are tapered, I had a set that were stepped like a Unibit but some one borrowed them from me and never brought them back.

Casey

Sat May 06, 2017 10:30 pm

I thought he was looking for info on what size the jets SHOULD be???

Beyond the info in the service manuals, i don't know.
You might ask on the late beetle forum, some of those guys apparently use stock carbs.

Sun May 07, 2017 6:10 am

A set of "number drills" can double as jet gauge...

Dale

Sun May 07, 2017 7:48 am

earthquake wrote: You should never use a drill on a jet, it can leave swirl marks in the bore which can decrease flow. you should always use a jet reamer. I think all the ones you buy nowadays are tapered, I had a set that were stepped like a Unibit but some one borrowed them from me and never brought them back.

Casey

Every time I've drilled jets or air bleeds the AF ratio on my wideband has changed in the direction it was supposed to. I.e. I've never seen a jet I've drilled result in less fuel flow

Sun May 07, 2017 7:56 am

earthquake wrote: You should never use a drill on a jet, it can leave swirl marks in the bore which can decrease flow. you should always use a jet reamer. I think all the ones you buy nowadays are tapered, I had a set that were stepped like a Unibit but some one borrowed them from me and never brought them back.

Casey

That's not too much of an issue with a main jet, but good luck trying to ream an idle jet from 55 to 60 with the portion of the ream that's .023 of an inch in diameter (thats actually about a .017 square) without breaking it on the first jet. As for not using a drill bit on a jet, how do they get the hole in them in the first place from the manufacturer?

Sun May 07, 2017 9:07 am

Another thing is you shouldn't need a shit load of jets to tune just one.solder up your jet until you are happy than buy the one you need.

Sun May 07, 2017 12:46 pm

Here is another question. I am looking through my jets and I am not sure what has been drilled and what has not. Specifically, I am wondering what is the relationship between the hole in the end of the idle jet and the four holes arranged radially around the body. I assume that the 4 holes are what is referred to with the "55" or "65", ie 5.5mm or whatever.

The end hole seems to be used mainly for allowing fuel into the jet, to be dispersed by the other holes. Am I correct and is there any critical measurement in this hole, or is it just to let fuel in and then it is metered by the 4 holes?

Chris

Sun May 07, 2017 1:05 pm

The fuel is metered by the hole on the tip. The holes on the side are just to let fuel through. The total area of the holes on the side is way greater than the metering hole, anyways.

Sun May 07, 2017 1:07 pm

So, I got it totally reversed? Story of my life!

Seriously, that is fair enough, now I know what the numbers mean and I can figure out where I am at.

Thanks!

Chris

Sun May 07, 2017 3:44 pm

idle jets should be changed in increments of "2-2.5" anyways, not 5. 5 is a huge change in size, way too big for one shot.

Sun May 07, 2017 4:06 pm

I am using a PICT 34-3 with a 28mm venturi in an 1835 with an Engle 100 cam and an svda dissy. It is going into a 1970 Westphalia.

I have been looking at old threads about tuning such a set up and it seems that the idle jets are usually falling in the 55-60 range and the main in the 140-150 range. This was in a thread that Alstrup and you were involved in, among others.

My thought was to start out with a 55 idle and a 140 main jet and see how that looks. I would think that the 45/127.5 combo would be lean. My goal is driveability and mileage, with any power gains a welcome side effect.

I am very open to any suggestions or advice on tuning this combo!

Thanks!

Chris

Sun May 07, 2017 4:16 pm

who said anything about using a 45 idle jet? Unless you are at 6k'+?

The jetting which works depends on your distributor, which you didn't mention.

Sun May 07, 2017 4:21 pm

ccowx wrote:

I am very open to any suggestions or advice on tuning this combo!

Thanks!

Chris
Put webers on it :P

Just kidding.
Just have to put it on and find out what happens.
If you tell us what it does, then we can brainstorm what to do about it.
That's kinda fun, and usually works, well, usually they don't follow directions :roll: , but when they do it works more often than not, which about is as good as it gets considering most carburetor problems aren't carburetor related

Sun May 07, 2017 4:24 pm

I thought the 45 was the stock idle jet in a 34-3?

The thread I was looking at is here:

https://www.thesamba.com/vw/forum/viewtopic.php?t=511245

The distributor is a 113 905 205 AJ that has been curved to come in at 2800-3000 rpms and has the SVDA vac can that I bought from you.

Thoughts appreciated!

Chris

PS: I know about the Webers thing. I am trying to save the oil bath aircleaner for driving in sand conditions and to have it look stock-ish. Webers all the way on my upcoming beetle project!!