Is it typical practice to drill out jets to size correctly?

[mbrobe]

Hey all,

My 48 IDAs were jetted with what I thought were 150 main jets. I have had a heck of a time getting it tuned and dialed in perfect. After pulling the emulsion tubes out I notice one of the jets is marked 135 and the builder had drilled it out to make it work. Looks a little too big to me but who am I to judge.

Is this typical practice to drill out the jets? Do you all just drill these things out to make them work or do you all spend the $7 bucks to get the right ones?

Cheers and thanks for any insight.
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[modok]

If you are blueprinting carburetors it is typical to find some jets and passages are not the correct size.
For anybody getting into that I recommend to buy a set of machinists pin gauges so you can measure the jets accurately.

Drilling jets to a different size can work well. There is nothing fundamentally wrong with the practice if done right, but.....if YOU cannot check the size then you will have to trust somebody else to do that for you.

[Dale M.]

Maybe....

https://www.piercemanifolds.com/JET_DRILL_SET_2_05MM_3_0MM_98_0169_00_p/98.0169.00.htm

https://www.piercemanifolds.com/JET_REAM_SET_98_0181_05_p/98.0181.05.htm

https://www.piercemanifolds.com/JET_GAUGE_045MM_TO_1_50MM_98_0135_00_p/98.0135.00.htm
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[vwracerdave]

Some say yes and some say no. You are not going drill 4 holes exactly the same size with a drill bit. Reamers are more accurate than a drill bit.

Personally, I might drill out jets to get to the size I need for testing, then I would buy 4 jets accurately sized for final use.
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[modok]

I do not use tapered reamers but some do and I guess that's ok, in any case they should all match.

[mbrobe]

Would you expect it in an $8000 engine build for a customer to have three 150's and one 135 drilled out?
_________________
'72 Standard Bug

[gt1953]

I would like to have some smaller jets for my type three dual solex carbs. the main jets 127 125 possible 121. Living at elevation need smaller mains. Prefer stock ones...look at my adds may be we could barter something.
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[Wreck]

idle jet no , too small and critical to flow differences . Also get idles from one source or you will chase your tail (dellorto jets I get from Alfa 1750 on eBay)Mains and airs , yes . I drill them and solder them up and re drill them when needed . I keep my jets in a small compartmented storage box with the drill bit and the size written down , small jets, I use a bit of balsa wood with the size written on it .

when you are chasing a tune and going up and down on mains and airs , it can get very expensive to say even have 5 sets of mains and airs .

[rugblaster]

I have a set of genuine Weber jet drills and a pin vice. So, yes you can drill even an idle jet. Mic the bit, and drill the shit out of it.
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[modok]

[modok]

I don't believe what is written in an engine part has anything to do with how it runs, and I don't make prices either.

IMO if you want all the right numbers written on your engine parts you would request that and you should get it.
And nothing is free.
But I don't have a problem with it, seems like a good idea, but personally I'm not interesting in paying for it personally. A lot of cheap parts they stamp what size they wish it was on there instead of the real size it is, that's worse than nothing, wasting of time and effort.

Berg took all the numbers OFF half the parts he sold, and he isn't the only one.
You can see why he did that right? no numbers no complaints about numbers, also no low effort backdooring and copying his stuff.
I don't agree with that either, because again nothing is free, one guy putting numbers on and another taking them off seems like some commie BS.

You want genuine italian made weber jets that were flow tested and calibrated and marked for size that's great, of course, but it might cost extra.
Before there was competition weber parts were 2-4x what we pay now, and I'm very glad we now have cheap jets. When in doubt buy one or two size small and ream them to size yourself.

[earthquake]

Someone on Ebay used to sell a bulk pack of 110 main jets pretty cheap but I can't find them now, I thought about buying some to have on hand to ream for tuning.

eQ
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[mbrobe]

Alright, I guess it may be more common practice than I would have guessed. I guess I am just too anal about it and expect standards and consistency where they are not required.
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[BFB]

I think the main group of ppl that have issues with drilled jets are the ones who dont know how to check jets and also assume that jets are the size that their stamped.
Also, if OP spent $8000 on this engine did you not even get a spec sheet for the carbs?
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[Alstrup]

Yes, I see the frustration and risk of rejetting wrong if you go out from a set of jets that are reamed out to a larger size.
That said, if you are to stock all jets, acc. pump jets and E tubes for Solex, DCNF, IDF, Dellorto, Edelbrock Holley, Mikuni and Kehin carbs you could soon be set back some 3000 bucks. We have gathered most normal sizes, but it took some years to get there.
As for drilling or no drilling. The postulate is that a redrilled jet will not flow the same as a jet that is properly made to the given size. That is correct, BUT, if you drill 4 jets to the same size, THEY will flow equal. So if you later want to swop to a set of "proper and marked jets" you can´t expect the engine to still be in the same tune. Also, especially with IDF main jets. Some are "flat" in the bottom, and some are tapered. Do not mix those either as the flow characteristics vary greatly one model to the other.
When I redrill I usually tell the customer that I did it. Then at least he knows., but most have forgotten about it even before they leave the site.
I have to admit that I have also been taken for a spin a couple of times wrt redrilled jets by relying on the stamped number, but you´ll find out pretty soon.
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[mcdragracer]

Yes drilling or reaming is no problem, I do it quite a bit for my customer basis and it's saves them money as opposed to selling them jets, I would say over 50% of the carbs I receive have different size jetting and they all are stamped the same number, although If I end up sizing just 2 jets on a set of dual I will match the other 2 so they have the same profile and whether reaming or drilling I have seen no difference in performance.

[rugblaster]

I like drilling and reaming. As much as possible, I might add... Also, how in the hell did the holes get in the jets to start with?
_________________
'69 Karmy, '69 Camper, Meyers clone, '65 drag bug, 10.78 @ 128 (sold it) '51 Dodge farm truck,
'09 MB E350 '18 MB E400, '65 Plymouth Valiant convertible and a '19 Ford F250 King Ranch (nicer, but dirty, farm truck)

VWoA factory trained line tech 75 till 90 or so
ASE Master Certification
VWoA Assoc. of Quality Technicians inductee (One of 25 in the five state southwest region)
La Confrerie des Chevaliers du Tastevin (San Angelo Chapter)
TCU ......GO FROGS!!!!!!

[rayjay]

What I never hear VW people talk about is drilling out pump shooters. In my Holley days I drilled out pump shooters on a regular basis. Any drag race build needed big shooters. Even in the 90s they were relatively expensive so drilling out the useless small ones was a no brainer. I just drilled them out to my largest jet drill , .039", and then experimented with the pump cam to get the launch right and all was good.

Same for street cars with larger cams. They need a bigger pump shot.

The biggest headache for the accel pump was oval track engines with restrictor plates. You would need the large 50cc accel pump kit and the cam would neeed some mods. You needed pump shot coming off the turn even with the motor at 4000+ rpm and the throttle pedal about 1/2 way down at the apex. Sadly, you couldn't hide these mods so they got widely copied.

[modok]

I used the search and it looks like I talked about drilling the pump jets around 20 times in the last ten years.

[rayjay]