DCOE Jet's - 240z

General Discussion about the 510 Club of BC
HuD_91gt
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Joined: 27 Jul 2015 09:26
Location: Vancouver, BC

DCOE Jet's - 240z

Postby HuD_91gt » 25 May 2016 09:36

Hello Everyone,

I'm picking up a set of triple webers. Previous posts suggest the most cost effective solution to tuning these is bring it to a shop with a dyno and a large selection of jets! The DIY, would buy a bunch of jets and read their plugs when in different ranges of driving.

I have a wideband 02 and would like to go about trying this on my own. The only issue with this, is these jets can add up quick going from trial and error. Does anyone know of someone who has a good selection of jets who would rent, borrow, trade or sell to a nice enthusiastic young fella(In the lower mainland). I think the issue that may arise is I have 3 of these webers, on a 510 forum. Oddball one might say.

I'm in no hurry, as rebuilding the carbs is on the list of projects but i'm just trying to look ahead a bit. I now have a warmed up L28, and despite how much I want to get out there and start thinning out my SU needles, I think it's time to move to the next level.

Colten
Crush - 1971 240z

twistin
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Joined: 26 Oct 2015 14:29

Re: DCOE Jet's - 240z

Postby twistin » 27 May 2016 20:26

If you have to go larger you can always drill them out.
My other car is an unfinished project.

HuD_91gt
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Joined: 27 Jul 2015 09:26
Location: Vancouver, BC

Re: DCOE Jet's - 240z

Postby HuD_91gt » 29 May 2016 15:38

Oh really. I will most likely need larger. The carbs were previously on an L24, and now into my cammed L28.
Crush - 1971 240z

Chickenman
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Location: Coquitlam

Re: DCOE Jet's - 240z

Postby Chickenman » 30 May 2016 08:25

OverSeas Auto in Vancouver stocks Weber Jets. They aren't that expensive. A set of number drills ( and that is what you should be using ) is going to cost you more than a couple of sets of jets. You can also buy them Online from E-Bay stores for very reasonable prices.

Drilling is OK on Air jets, but Iffy on main fuel jets. Carburator jets are very susceptible to any microscopic irregularities and drilling introduces swirl which can alter the flow characteristics.( Source David Vizard, Doug Roe ). Drilling is OK to get you " in the Ballpark " for sizing, but just as a test. Once you figure out where you need to be, then go out and buy the correct size. And don't forget to mark the drilled jets so you don't mix them up with " undrilled " jets.

Any one who runs Webers, Mikuni's, Holleys etc, usually ends up with more than a few hundred dollars invested just in jets....

Chickenman
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Re: DCOE Jet's - 240z

Postby Chickenman » 30 May 2016 08:44

Until you get the carbs rebuilt, adjusted and running on the car, I wouldn't go changing a lot of things. Mark down all the sizes of Main jets, Emulsion tubes, Air correctors, Low speed jets, pump jets, and Choke sizes.

Get some books on Weber rebuilding and tuning. Two excellent technical books ( Bibles ) are by John Passini:

1: Weber Carburettors Book #1 " Theory ". ISBN 0-903-192-40-3

2: Weber Carburettors Book #2 " Tuning and Maintenance " . ISBN 0-851-130-60-7

It's very difficult to use someone else's setup, because every engine is a little bit different. Unless the engine specs are EXACTLY the same, the fuel is the same and the carburators are EXACTLY the same, just one variable can alter the whole fuel curve. Ball park numbers are the best you can hope from the Internet.

Idoxlr8
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Location: Burnaby

Re: DCOE Jet's - 240z

Postby Idoxlr8 » 30 May 2016 14:06

Agree with everything Chickenman says with the following additions.

Balancing the three carbs is critical. If you don't have a synchronizing tool, get one. Any differences in airflow between the carbs results in backfiring and rough running.

Choosing the right idle jets is as important the high speed. They control fuel from idle to mid range throttle and make all the difference in the world to a streetable motor that won't balk and stumble every time you try and accelerate.

I found this web site very helpful.
http://datsunzgarage.com/weber/

It takes time and patience but it's not brain surgery...you can do it with a little background and educating yourself how the carbs work.

Hope that helps a little bit.

Dean
260z owner
510 wannabe

HuD_91gt
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Joined: 27 Jul 2015 09:26
Location: Vancouver, BC

Re: DCOE Jet's - 240z

Postby HuD_91gt » 31 May 2016 16:41

Great tips. Those books are certainly making their way to my bookshelf. I was hoping someone with a few hundred dollars in jets hanging around may want to get rid of their stash, or lend it out. For now i'm researching DIY home zinc plating as the carbs are pretty rough. They should be a fun project either way! Thanks again for the tips.

As for balancing the carbs, I have a sync tool i've used on my SU's. I believe it's mad by holley, but it is the standard type your adjust the screw to the amount of airflow required, and the ball in the tube rise or lowers dependant on the vacuum created. I believe it's called a "Unisync" tool? Is this suitable, or are the more expensive "colour tune"s required?
Crush - 1971 240z

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Byron510
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Re: DCOE Jet's - 240z

Postby Byron510 » 31 May 2016 17:14

Chickenman wrote:Drilling is OK on Air jets, but Iffy on main fuel jets. Carburator jets are very susceptible to any microscopic irregularities and drilling introduces swirl which can alter the flow characteristics.( Source David Vizard, Doug Roe ). Drilling is OK to get you " in the Ballpark " for sizing, but just as a test. Once you figure out where you need to be, then go out and buy the correct size. And don't forget to mark the drilled jets so you don't mix them up with " undrilled " jets.

.


I have never personally drilled jets - I guess the crown I have hung around with always shy'd me away from such tactics.

But there is a guy here in Vancouver by the name of Paul Silva - he is a master tuner, and he loves twin choke carbs of all sorts. He has worked on my cars, and he certainly has the magic touch - there is no doubt. Do he have a wonderful fancy shop - no. But he has the knowledge and patience that guys with fancy shops wish they had!
When Paul was working on my car one time, I inquired about a piece of equipment that looked like an old tuning tool, but had been obviously modified. He said it was a jet flow bench....

Suddenly the piece all fit together. Paul actually flows all of the jets in his cars as a final tune. He stated that there are differences at times, and it could drive you nuts. So he simply flows all air and fuel jets as part of the job! Very cool, and goes right along with what Richard stated above.

BTW - if you are in Vancouver and want a cool Portuguese guy to just hand you your car back running as good as it possibly can - go see Paul Silva. Not only is he good, he's a great guy as well.

Byron
Love people and use things,
because the opposite never works.

Chickenman
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Re: DCOE Jet's - 240z

Postby Chickenman » 31 May 2016 19:00

Paul Silva.... why is that name familiar?

Interesting information from Holley Tech. They have a line of close tolerance jets that have much finer tolerances than the regular jets. All Holley Jets are numbered by flow ( not hole drill size ) , within a certain tolerance. Standard Holley jets can have a flow variance of up to 4.5%. So a low side #83, may flow exactly the same as a high side #82. The close tolerance jets are reputably held to within 1% of rated flow number.

Comp Cams makes ( or did make ) a line of Max Jets for Holley's that goes even further. Jets can be ordered in half steps IE #82 < #82.5 and some of the more popular sizes apparently come in one quarter steps.

Chickenman
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Re: DCOE Jet's - 240z

Postby Chickenman » 31 May 2016 19:18

A Uni-Syn tool works OK. May bounce a bit a bit on Independent Runner carbs, but you get used to them. Picture of Uni-Syn below.

Image

There is another type called an SK Synchrometer that is supposedly better than a Uni-Syn. I've never actually used one of these so I can't comment. Perhaps others can chime in.

Personally, I've had very good results in the field with a length of heater hose and a sharply tuned ear. IE: When no Sync Tool was available. YEMV ( Your Ear May Vary )

Image

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defdes
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Re: DCOE Jet's - 240z

Postby defdes » 31 May 2016 19:37

I have both of the above, I really only have the Uni-Syn (top model) for when I had my race car and I couldn't fit the SK style between the #4 and the BMC. The SK unit is much nicer and much more sensitive.

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Re: DCOE Jet's - 240z

Postby 510rob » 31 May 2016 22:56


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Byron510
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Re: DCOE Jet's - 240z

Postby Byron510 » 01 Jun 2016 05:50

Thanks Rob, cool book.

Page 57 shows a set up similar to what Paul uses - utilizing a vaccume signal to balance the carbs. His gauge is a four meter unit that is much more compact than shown in the book in Robs link, but works very well. The trick is aquiring the fittings needed to utilize those vaccume ports in the carbs.

Thanks Rob for posting that.

Byron
Love people and use things,
because the opposite never works.

bigjim5551212
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Re: DCOE Jet's - 240z

Postby bigjim5551212 » 20 Jun 2016 17:01

The syncrometer is way better than the old unisyn. We have a good selection of jets at overseas auto.
"He forgot more than what i know about a Datsun"


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