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Author Topic:   CARB - JET CHANGE
copper
Member
posted May 10, 2004 09:52 PM
I SAW IN SPEEDWAY MAGAZINE THEY PUT HOLLEY JETS IN ROCHESTER CARBS CAN A PERSON DO THIS AT HOME? IF SO--HOW? OTHERWISE WHERE CAN A PERSON FIND JETS FOR ROCHESTER 2BBL CARBS. HAD A GUY TELL ME HE JUST TOOK HOLLEY JETS AND WORKED THEM IN AND OUT OF THREADS SLOWLY BACK AND FORTH WITH ANTI-SEIZE ON IT TILL HE MADE NEW THREADS. ANYONE DID THIS? SOUNDS LIKE A SCARY WAY OF DOING IT TO ME. ANY ADVISE WOULD BE HELPFUL. I NEED TO FATTEN UP MY JETTING MORE. THANKS.


madmodshoe
Member
posted May 10, 2004 09:55 PM
yep, thats how you do it, in and out!
The jets are a much harder material than the cast body. Be careful to get the alignment correct though!


racer17j
Member
posted May 10, 2004 10:08 PM
go to your local hobby shop that sells rc cars and get a tap for a gas r/c motor spark plug if i rember right it's like a 1/4 24


KPLugnut
Member
posted May 11, 2004 07:06 AM
The jet threads for the Holley jets are 1/4 x 32 NEF thread.
The taps are available at R/C suppliers, as well as about any tool supply house
We buy ours from www.mscdirect.com

We also stock Rochester jets if you'd prefer not to change over to Holley jets.


KP

[This message has been edited by KPLugnut (edited May 11, 2004).]

whiterabbit
Member
posted May 12, 2004 02:21 AM
Holley jets can be used Roch. 2G's one of two ways,one by tapping out thread in float bowl assembly or by rethreading holley jet. Rethreading jet is my preferred method, one because you don't disturb thread in float bowl. Threads are very similar and if you thread bowl with holley tap it is very easy to cross thread when changing jets. Also you don't have to buy expensive tap aprox. 30 dollars. Roch jet thread is the common 1/4-28". I start by putting die in die handle with it in correct postion so as to start jet into die from correct and normal side, don't be concerned with squeaking noise this process will make as brass alloys are difficult to thread because they seem to 'gall when threading (I belive actual thread enterferance). After i screw jet until it almost hits the shoulder on jet I remove jet and start jet into die from the other side of die so to be able thread jet in entirity. By rethreading jet, thread in bowl is left alone because, when thread in bowl is stripped you either s**** bowl or have install a expensive thread insert of some kind.
Good luck
whiterabbit


KPLugnut
Member
posted May 12, 2004 08:33 AM
Interesting process there.
But taps are available for $7.16 plus shipping thru MSC, and it takes about 60 seconds to tap the jet holes in a body properly with a bottoming tap.
And rethreading jets would require each jet in each size to be rethreaded, thereby making the racer have to "create" a custom jet kit of numerous sizes just for use in the 2G carb. Then, if a jet change were ever required at the track, the racer would then have to be re-threading jets in the pits assuming the parts trailer/truck had the jets he needed in the first place.
And if a racer was having to go thru THAT much hassle just to do a jet change, I'd probably send him either an assortment of Rochester OEM jets in the right sizes, or send him a jet tap for free, just out of pity. :-)

It is always nice to hear how others "skin a cat", tho. :-)

KP

[This message has been edited by KPLugnut (edited May 12, 2004).]

whiterabbit
Member
posted May 12, 2004 03:35 PM
Any racer that goes to the track without a assortment of jets and required tools to make a jet change in a orderly fashion is surely aback of the pack kinda guy! For those of you that have'nt retapped the float bowl, just try it. I guarantee that in short time the jet thread's will be dicked up. For those of us fortunate to read spark plugs, different engine comb. and changing weather condititons make jet changes more frequent.
Good luck
whiterabbit


copper
Member
posted May 13, 2004 09:01 PM
KP SENT YOU AN E-MAIL ON KINETIC PERFORMANCE E-MAIL.


KPLugnut
Member
posted May 14, 2004 07:59 AM
Got it.
Sent ya a reply...

KP

BIGG C
Member
posted May 15, 2004 06:38 PM
How much trouble to put holley jets in a ford 2300 carb? Holley jets are quite a bit smaller than ford jets. Thanks BIGG C


KPLugnut
Member
posted May 15, 2004 07:28 PM
We do it all the time. I assume you're talking about the Motorcraft/Autolite 2bbl and not the Holley/Weber 5200 series progressive 2bbl found stock on Mustangs, etc?
There's much that can be done to that carb too, but we typically don't put the std Holley jets in those.
The M'craft 2bbl found on Fords does have large jets (5/16x28 thread). We convert them to the 1/4x32 NEF thread used in standard Holley jets by using the thread portion of the old jets as sleeves or mock-helicoils. It's tricky tho...

KP


Bob0092
Member
posted May 16, 2004 07:42 AM
KP , do you drill and tap the jets first and then screw them into the carb? How do the jet sizes(numbers) relate between the Holley and the Ford(Autolite,Motorcraft) jets? Do you seal the jets(Ford jet sleeves) to the carb? Please explain. Power valve or block-off? Ford 2300 stock lower end with .150 off-of head. Zero deck block .480 cam with 106 lobe center. Running 1.23 carb with efi intake with one inch spacer. Any help appreciated. BIGG C

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KPLugnut
Member
posted May 16, 2004 06:44 PM
Hold the Motorcraft jet in a soft-jaw'd vise, carefully drill and tap it (tap very slowly or it'll break in half) and use tapping fluid to lubricate.
Once you have that done, then coat the outside threads of the M'craft jet with either red high strength Loctite or the ultra-strong white sleeve lock stuff. Just a drop will do. Quickly screw in the jet into the carb and just as you get it seated, you'll find that the head of the OEM jet snaps neatly right off and leaves nothing but the threaded "sleeve" insert which is permanently installed once the sealer dries.
As for the jet sizes, the numbering system does NOT correspond. We do not calibrate by any other numbering system than the Holley jets (unless we're talking Rochester jets, but that's a different subject).
There are jet size vs. orifice diameter charts for Holley jets on the internet. Earl Parker has a chart on his website, too.

The typical starting setup for your situation, BiggC would be to start with a 4.5 power valve (I NEVER block off the power valve), and tune from there.

Hope that helps,
KP


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