Custom, Performance Carb Intake Manifolds ( 2bbl / 4bbl )

[A20A1]

Most manifold vacuum lines pull about 24" hg. @ idle

Do you have a vacuum gauge?

Not all vacuum lines will have vacuum all the time... it will depend on the valve or solenoid they are connected to... and also if they are connected to throttle port vacuum, venturi vacuum, or manifold vacuum.

[87AccordLXsdn]

ok cool thanks man...also this may be a stupid thing to do...but how hard do you think it will be to go from weber back to stock. because i think that my carb is pretty fucked right now and i can just go grab out a keihn for like 5 bucks.

[A20A1]

By your post I thought you had a stock carb.

Whats wrong with the weber? have you tried replacing the gaskets... I found out later that too thick of a gasket can cause the plates and even the carburetor to warp causing vaccum leaks.


Also check the float level settings... there are plenty of diagrams online to adjust the float level... there are two adjustments... one is the maximum and the other is minimum amount of travel in the float.

Make sure that the float valve (the part that screws into the roof of the carb) is actually still screwed into the carb. They sometimes will work their way loose and begin to choke the fuel flow by putting pressure on the float needle.

[accord upset]

ok thanks a20a1 sorry if i was annoying u with pms im just trying to put my stuff to gether as quick as i can(gota get back to work so i can spend more money) and u have alot of knowledge that i dont.

[A20A1]

www.carbs.net sells the adapter plate, so does www.redlineweber.com

it's $50 for the plates.

https://www.3geez.com/forum/showthread.php?t=38161

[2oodoor]

ok cool thanks man...also this may be a stupid thing to do...but how hard do you think it will be to go from weber back to stock. because i think that my carb is pretty fucked right now and i can just go grab out a keihn for like 5 bucks.

Believe me brother you do not want to go back. Once you go weber you go forever.
That five bucks will turn into fifty into a hunnerd ...and so on

[A20A1]

Also check that the jets are all secure...


I went back to a keihin... but I had made some major adjustments to it.

I can't wait to try out the 4bbl.

[2oodoor]

A20A1 are you going to use the four barrel intake you made?
That is one nice piece of work. I thought maybe you sold it, by some thread I was reading a while back.
I wonder what you would use, rochester quadrajet? Like those myself
street demon, thermoquad, ..... that wierd motorcraft 4bbl they put on an AMX.Javlin??

[A20A1]

the predator

hehe


no not really.

the 390 holey is okay for cfm but I don't like it... and the edelbrock 500 might not be what I want either though.

The rochester has tiny primaries and fat secondaries. This design isn't as good for performance, I need something where the primaries and secondaries are close to the same size but the cfm needs to be low. 500 would be the max I would go. I kinda wished that demon would put out a 350 cfm or 400 cfm carb. The smallest I found was the road demon jr. with 500.

here is the carb throttle style I want.

http://www.mustangandfords.com/techa.../photo_22.html

it's an Autolite 4100 ... 480 cfm with the 1.08 venturi

It uses annular boosters so:

...an annular booster creates a stronger fuel signal, generally requiring smaller jet sizes. There are exceptions to this rule, but adding annular-discharge boosters requires smaller main jets and larger high-speed air bleeds...

[2oodoor]

Yes I dont think the rochester would work for that app, metering rods would be hard to deal with on a four banger, trying to sych with the power band rpm.
That is funny I was kind of joking about the motorcraft (autolite) four barrel, but I think that is the one you say you like. There are not a whole lot of those around. I rebuilt one several years ago for a guy, it was on about a 74 Javelin 401 motor OEM.

[A20A1]

If the annular booster is good then it should help even a small engine run a large carb once jetted right. Again you could set up the secondary to run on venturi vaccum or something instead of being a manual. I would have needed a vaccum secondary because I was automatic.

[2oodoor]

the rochester four barrel has stationary boosters intergral to the casting, it would take some intricate biomedical type tooling to muck with those and a box full of cores. Actually the rochester 2 jet two barrel offers a booster that is more likely to tinker with , those are not really too bad a carburatorfor racing, well kept secret for dirt track I suppose. There is a good roch. book at books a million I got one.
I do know a few tricks with the q jet, probably changing the spring below the step piston would get a 2.0 to get a good drink when slippping the clutch. Come to think, it may be worth lookng into a 2 jet for a replacement performance carb for stock LX , it would have to be modified for sure. I saw mention of a motorcraft 2bbl in the forum but it never really got interesting, the holley weber pinto carb would have been betta.
the autolite still looks interesting if you can get some cores, I just wanna see yours set up and running with a 4bll, that is the ulitmate illness, right up there with big block airboats, and that turbo vw bug on pinks with the holley 750 sticking up outta the eng. compartment...

[A20A1]

http://store.summitracing.com/partde...0+4294821996+0

wow I might want to look into a holley and the percy metering block.





I used the exhaust flow calculator and applied it to our intake manifold runner where is narrows to 1.5". If we take the 1.5" and we times it by 115, we get about 172 CFM, if the most our motor demands is 190 at 6,500 rpm... then the intake manifold is a restriction, however it will help the low end by having that added velocity.

[2oodoor]

that is great idea.I see that on your car...taransula dude.....but really these carb gurus still around need to be figuring this stuff out so they can have advantage over those nitrious runners who dont know what the heck they are doing by counting on a large, too large percentage of secondary and heck primary too being much counting on bottle. then when it comes when times that the bottle malfunckeds , they have no motor to run , its a joke. agree?

[A20A1]

Hey Shepherd79 what was the alumaloy like soldering stick you found that was better than alumaloy?

I need to finish the dividing wall in my manifold, that way I keep power in the low end by having a smaller plenum on each side, dividing the carb, and keeping the runners the small diameter that they are.

I really want this manifold to look nice, with black textured BBQ like paint and brass barbed vacuum fittings and colored brake fluid lines converted to vacuum hard lines for PCV, Distributor, and Brake Booster Vacuum.

At least I can finish it all up and sell this manifold and hopefully the header too, I don't think I can find another 3G and do the 4bbl conversion any time soon.

[shepherd79]

i got it from this webpage.
https://weldingsupply.securesites.co...ogs.pl?SIGNOUT
the stuff called WELCO 52. if you do a search for it, it is the first thing that comes up on that page.

make sure you get your hands on this http://www.bernzomatic.com/bernzomat...rnzoProd100044
or at least mapp torch, it burns hotter than propane.

this product is easy to work with.
just make sure you clean the area very good, ruff it up, and heat it up.

[A20A1]

Thank you .


awe I searched but it says it's for galvanized steel? Was that what you used it for or did I search wrong?

EDIT: nevermind I found it


So I can use straight mapp? I'd like not to mix gas if all possible.

[A20A1]

Yay, I ordered the 1/4" sticks time to rock and roll. I got two orders... i hope it's enough.

$27.10


I was going to buy their aluminum cleaner but figured I could find something locally.

Maybe I'll make a totally custom manifold as well with my other intake flange, or weld 4 keihin base plates together to make a progressive 8-BARREL M-ITB setup.

well I bit the bullet, I'm getting the Rochester Quadrajet
ROCHESTER QUADRAJET
Looks like I can play with it and get it to work.

nice article on the Q-Jet
http://www.carcraft.com/howto/57178/

Might think I'm crazy because it's a 750-800 cfm carb.

Numbers are aproximate

Primary 226 CFM

Primary + Secondary 1060 CFM

divided carb

Primary 112 CFM

Primary + Secondary 530 CFM






I could actually run the carb with just the secondaries and it'll be enough CFM , 418 CFM to each side

I should be able to get it to work with the jets and passages set right and the vacuum secondary set right.

Just need me a tunning book... and a 3G


Really I just got it cause my manifold has been so lonely.

[shepherd79]

it is not that hard to find another 3G on the island, is it?
i am not sure how much money you want to spend.
just look here
http://honolulu.craigslist.org/oah/car/281571046.html
http://honolulu.craigslist.org/oah/car/281517917.html
http://honolulu.craigslist.org/oah/car/281255851.html
http://honolulu.craigslist.org/oah/car/281251511.html


autotrader.com has some car also.

[A20A1]

Actualy there is one outside my house that is abandoned... it has a broken upper ball joint for the rear knuckle and slashed up tires... and tickets on the windshield. I wanted to save it. It even had a muffler, but that worried me cause I dunno how they treated it.
5 hours to go on the ebay auction for the carb.
I was looking at the base gasket for the Q-Jet, I'll have to shave my universal manifold flange even more to fit the throttle plates.
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27 minuets to go. I'm getting worried, another Q-Jet that i was watching was just bid on. I swear the same guy is buying all the cheap carbs... what a.....
Woohoo! I won
I broke out the manifold just to get a picture of things. This is going to be neato.

Here is the link if you want to see it... I may need to scrap my 4bbl adapter and put on a q-jet one because it looks like the throttle plates will hit outside the mounting area.

http://cgi.ebay.com/ebaymotors/ws/eB...m=160085298528

What about this mod for the Gasket? I might have to build support under the gasket though just to be sure the gasket wont tear and reopen the area I'm trying to reduce.

Anyways it should cut the effective area of the throttle to about %60 of it's maximum.

This is in case the vacuum secondary doesn't work out on it's own.



Then there are the mods to turbo a Q-Jet
http://www.wallaceracing.com/TFProjectUpdate1b.html


Might get this book as well

http://www.amazon.com/exec/obidos/AS.../wallaceracing

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[A20A1]

Interesting experience...

http://www.bob2000.com/carb.htm
Scroll down to the first paragraph under "BASIC THEORY"

He also confirms for me that with vacuum secondaries, big carbs could be made to open just right for the engine so size isn't that much of an issue.
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[A20A1]

All you carb guys can appreciate just how big theses secondaries are

I just love the person who designed the Q-Jet... just as crazy as I am.



Dual throttle bodies anyone?

[shepherd79]

good lord that is huge.
i hope you can tune that SOB.

[A20A1]

lol, those two secondary barrels combined could swallow our entire keihin.


I got another picture that compares the secondary on the keihin to the primary on the Q-Jet.

The opening up top is the same as on bottom which is the throttle port size on the secondary.

[A20A1]

I will see how big the chokes and venturies are when I get the carb... then I'll get a better idea about what to do.