which dual quad intake for the street
 

Hi all,
looking to put 2X4's on the old girl.... looking for some input on the differences between the 5450 Edelbrock (p65) and the Offenhouser 5499.
also, whats the difference between the 180 design Vs. the 360. Keep in mind, this is mostly street use.
FYI... my combo...
.060 428
455 crank/rods 10.2 CR
KRE D ports 290 port
Crane .041 clone
Rhoads V Max lifters
HS 1.5 rockers
M-23W 4 speed
3.31 12 bolt.
I have 2 Edelbrock dual quad carbs with linkage, fuel line etc already.

Thanks, Jeff

You will want the Edelbrock without question especially in light of your rear gearing in the car along with the slower port velocity of the 290 cfm heads below 3000 rpm.

In the mid to late 70s I had picked up a Offy 360 2- 4 bbl Q- jet Manifold and put it on my 3.55 rear geared stock 1970 400 in my GTO and within a weeks time I took it off and re- installed the iron stocker back on!!!

The Offy is way better than the E intake.It has the same carb spacing as the factory SD intakes.The factory air cleaners will fit.Try to avoid the E carbs.Early 60s AFBs are the best.For 625s The 3012s and as I remember the 2964 Buick’s are good.Maybe 61-63 on this site will confirm.For 750s the single quad 409s and the 3705s are great.Best of all are the real Pontiac SD AFBs.Tom

I am with Tom on this one. The Edelbrock intake jams the two carbs. together in the center of the manifold and makes it nearly impossible to get an air cleaner on it. Unless you use their own, goofy cheap looking junk. The Offenhauser manifold looks lousy at first glance and with it's tiny runners you would swear it couldn't support 400 HP. But you would be wrong. I am building an engine for a 62 Catalina right now and expect to make no less than 525 HP with one of these manifolds and a pair of clone SD-421 Carbs. The best possible manifold IMO will be the replica bathtub intake Tom is working on right now. I will switch to it when available and expect to gain another 20 HP or so with it. Plus the looks are nearly priceless. What are you putting your set-up on?

Opinion:

The Offy manifold is superior to the Edelbrock.

Neither one is going to work well on a Pontiac with the imitation carbs you mentioned, unless you REALLY modify the crap out of them!

Jon.

Tom's and mgarblik's comments are correct re the differences in carb spacing on the edelbrock vs offy intakes, and real afb carbs vs the edelbrock copies. Any late 50s-mid 60s Buick application afb is a better carb that the modern edelbrocks. Or you can use two Pontiac application AFBs. The offy intake places the carbs only 3/8" closer together than the real sd intake and you can thus make a setup look almost identical to the real sd setup with it, where the edelbrock intake jams them together.

But since you already have edelbrock carbs and linkage you can make a good performing setup that, way plenty of people have done it.

Here are two pictures of an offy setup using Pontiac application AFBs, with real sd air cleaners. The linkage is custom made.

I came back and edited this after I saw Jon's (carbking) comment. He was apparently typing his as I was typing mine. The edelbrocks CAN work and work well. You can walk down the pits at Norwalk and you will see dual quad setups on race cars with the edelbrock carbs on them and they go like stink. However, you can also get those carbs and never get them to work right no matter what you try to do. It is kind of a crap shoot with them. So if you already have them by all means try them. If you can't get them to work right you can always sell them and get a pair of Buick or Pontiac application AFBs. I will look at my notes and come back and share what jetting and metering rods I've put in sets I've done for people with your size engine.

For a 462 cubic inch engine start with .092 primary jets, .073 secondary jets, and .050x..060 metering rods, or .094 primary jets, .073 secondary jets, and .062x.068 metering rods. Actually you can use any size metering rods and use piRsquare to determine primary jet size, just have an 8-10 size difference between the small and large diameters on the metering rods.

I flowed all of the Pontiac Intakes produced from the early dual quad days, Edelbrock, Offy, etc on a Super Flow 1200 flow bench (lots of Flow bench flow capability and very accurate) and the stock Dual Quad Offy intake flowed quite a bit better vs the Edelbrock dual quad intake. Memory says the offy was over 20 cfm better per intake runner.

Joe C. ran one on his altered early tempest race car and picked up over the normal Pontiac Dual quad intakes. Well over a tenth if I remember correctly. Offy is better. Loren Budzinski posted the flow data at one time on the PY Board.

Tom V.

E clones race better than they street drive IMO.Tom

The E clones on my 409 have only seen dyno time so I can't say how the transition circuits are yet-maybe in the next year if I find a paint shop that won't put it in "paint jail". My 470/409 liked the 600s over the 750s. The Edelbrock intake flows way better than even the hi perf aluminum 409 dual quad and single quad intakes. I never flowed the Edelbrock dual quad Pontiac intake when I had one. M/T Pontiac cross ram does not flow as good as a single plane intake, but looks cooler!

Guys, thanks for all the great info.
I'll start looking for the Offy intake
61-63, I believe the carbs I have are the 1803s(500 CFM ,IIRC)
The jets/ metering you suggested would be good in those carbs, or should I get larger CFM carbs, then jet/meter accordingly.
Also, this is in a '65 GTO.

At least a pair of 625s

The jets and rods I stated are for 600 cfm carbs. I've never done any 500 cfm sets so will have to calculate the calibration for those. It you were doing a race car you could go a 750 cfm set for your 462 but for street I'd say 600 cfm would be best. Once you decide for sure what cfm carbs you will use put it on here and I will give you a calibration for them.

I ran an Offy with matched 63 Pontiac AFB's with carbking's kits on a 65 GTO for almost 10 years. (and rebuilt them per carbking's specs) After a short dial in period that ran like stink with no problems starting and running. Way easier than the tri-power that was on it.

How do the pre edelbrock Carter aftermarket stack up, i have a pair of 625 cfm carbs. I know this is the street section,but could they be made to support 469 at 6400 rpm for a race applkcation. Sorry for the hijack

My 462" liked the Offy intake with Carter 9605s (600cfm) AFB carbs. Gotta use the adapter plates for the large base carbs since the intakes were made for small base carbs.

Jeff Chmura Stray Cat makes a good point. If you go looking on ebay, craigslist, and other places for a used offy intake be sure to get one with the adapters already on it. You will see them offered without the adapters and you don't want that because the adapters will cost you almost as much as the intake new and they are almost impossible to find used. Just keep looking and one with adapters will turn up.

Bill I've only done sets using the original AFBs so can't help with your question. Perhaps carbking can.

I have used them both on everything from mild street to much more serious combinations. I like them both, but I give the Offy the performance edge. (although I have ZERO head to head dyno experience to back it up.)

Here is a pretty nasty 462 I build for my '40 coupe.

https://hosting.photobucket.com/albu...pskr1ezw1g.jpg

And, a healthy 389 for my 51 Merc. I made my own air cleaner base to get around the goofy carb spacing.

https://hosting.photobucket.com/albu.../merc11282.jpg

-Abone.

Holy huge picture, Batman.

Sorry about that.

-Abone.

I ran dual edelbrock 500s initally on my 432. Was just choking it. I ended up finding a pair of edelbrock avs2 650s and am now running these. Took some time and tuning but it runs like a raped ape!

I was running an edelbrock 2-4 intake on my previous 400 and can say that it has a lower carb mounting height so keep that in mind if hood clearance may be an issue. I swapped to offy 5499 and have way less hood cleance with the same air cleaners. I am now running 3.25" tall air filters on 6.375" diameter bases and I had to make custom bases cause my air cleaner lids are about 1/4" away from the hood.

The Offy dual quad intakes had two different carb height pads for the intakes.
Sometimes the lower height pad will package better under some hoods.

Tom V.

I'm running the offy right now there the best of the two
And i've run 600-Holleys and 600 edelbrock carbs and they work good two
right outa the box but I run them where there both hooked together.
Don't try and run on for cruising and the other comes in later.
I also run 750 carters to but it was a little fat for the street.
I also get decent mileage too even with both carbs hooked direct.

GT

I don't have access to a dyno, which is why I normally post in the "street" section. My "dyno" is happy customers.

So I cannot tell you from experience if (2) genuine Carter 625's will support 469 HP, but Carter literature suggests they will.

Far easier to make any carb race well (WOT consideration only) than perform well on the street (idle, off-idle, various values of vacuum, transition, etc., as well as WOT).

Personal experience, with a LOT of testing:

I currently have two vehicles with performance engines: (1) Pontiac 350 with 850 CFM single spread-bore Carter carb, and (2) Ford modified 390 with two heavily modified Carter aftermarket 625 AFB's (similarity to Bill's question).

When I first put the two 625's on the 390, as always, I built them bone stock. They ran, actually pretty good, and many would have been happy. I wasn't satisfied. So I found a pair of 430 Lincoln AFB's, and transferred primary clusters, secondary clusters, auxiliary air valves, primary jets, secondary jets, step-up rods, and vacuum springs. MUCH BETTER, but still not happy. Changed the mid-range vacuum step on both step-up rods to eliminate a mild surge at cruise. Now it runs the way a carbureted engine should run; and a youngster (then about 25) insulted me by asking what fuel injection unit I was using!:gag:

Tom S. made the comment that the imitation AFB's race better than street use. The aftermarket Carters with which I started fit that description, because Carter calibrated them for Chevrolet. The calibration curve for Chevrolet is totally different than the curve for Ford, or Pontiac. If fact, the Ford curve is very close to the one for Pontiac (the Chrysler curve is even closer to Pontiac).

So your 625 Carters will probably race well as is, better with minor tweaking, but will require surgery to run well on the street. But "running well" is a subjective term, different folks will have different tolerances.

For street use, we generally suggest using a couple of original Pontiac single AFB's as the calibration curve is close, and only minor tweaking is generally necessary. Doesn't really matter which Pontiac AFB, as long as the two are the same. We generally suggest either 3300s or 3326s (these two MAY be mixed or matched), as they are relatively easy to find, and relatively inexpensive.

Jon.

My 409 I jetted the E 600s one step leaner than stock and made 600 HP

With the exception of the Grocery Getter Guys does anyone have any experience with track testing the Offy manifold??

Maybe I'm missing something but I've ran them several times on different applications, all three square bore versions and a low rise dual Q-jet and never noticed any kind of gain over a single four barrel other than the Offy liked to RPM a bit more. The best set up was welding the rear halves of two manifolds together to get rid of the big bend in the front runners.

Back in the day my buddy went back and fourth between the Offy 2x4 and his tri-power and they seemed very close in performance. The tri-pwr seemed to have more mid-range and the 2x4 rpm'd a little higher.

A guy that works for me runs one on his Olds because they look cool but pretty sure his four barrel set up is faster.

Can't answer your question re track testing but I've had more than one person tell me they could get rubber in third gear after installing the offy dual quad setup, where they couldn't with the tripower setup they replaced with it.

Paul,did not do any back to back on the Dport engine but did do a RA V engine with a factory dual plane,a single plane and a dual quad low tunnel ram.Results are on this site somewhere and I think Stan posted it also.Prostocks run duals for a reason!Tom

I can get a couple 3651 AFB also, from a 64 421. How does the Doug Nash measure up to the Offy intake?

There is nothing wrong with the Carter Competition AFB carbs that start with a 9000 number. I have heard for years they are junk. My experience says different. Even the E carbs are not bad. I run the Carter Competition 9755 AFBS on my 66 since 2005. SMALL CID stock block with a Wenzler intake. Car weighs 3750 with me in it, Stock suspension, full exhaust and has been the best of 9.79 in the 1/4. I also street drive this car and have never had a problem with idle. Drove it 30 miles to eat lunch with my daughter the other day. 60 miles round trip with quite a few red lights. No issues, no rich exhaust fumes etc. ANY carb needs tuned to the combo.

The Offy intake was .4 tenths faster than the Edelbrock P65 on my car. The Wenzler was .3 tenths faster than the Offy. Both intakes were ported to a 1233 gasket.

As far a carbs go, I have run the Carter Comp 750's and the E-800's back to back. Only .04 difference. The E-600's were bout .15 slower.

Guys...all good info...
I'm 98% sure I have 2 '65 GTO AFB's. One for sure.
Just an FYI....
I'm running a Brawler 850 on a performer RPM right now and I can't get the carb set up right
I'm rich at idle,lean at cruise, and I'm so disgusted that I'm either going with the 2x4 setup (mainly for the cool factor, plus I already have carbs,),or EFI, which it going to be more $$$.
Damn hobby......lol

The 2- 65 carbs should work really well with that set-up.

This is great information from everybody. I'm reading through it trying to figure out what to do with my set up. I have a new 467 stroker with the Edelbrock P65 manifold and two 600 cfm edelbrock carburetors on it. It runs OK, but I'm having a hard time getting it dialed in for optimal performance. It sounds like I need to go more lean than stock settings since I'm running two carburetors. Is that generally correct?

And as far as the original question goes, I opted for the Edelbrock P65 because of the dual plane design and I was looking for more low end torque than high RPMs. I wish it looked more factory original but it is what it is.

Thanks in advance.

You can pull the tops off of your carbs, with the carbs on the engine, and use pin gauges or small drill bits to determine jet sizes, and a dial micrometer to determine the diameters of the metering rod steps, and go from there. It may be that you can reach the calibrations I suggested for the primary jets by changing your metering rods alone? I don't know what you consider "optimum performance" or why you feel you don't have it but the best way to check for it is by using a wide band air/fuel ratio gauge, and after that just reading your plugs. If your engine is falling on it's nose shortly after you put your foot all the way into it your problem is most likely float level.

Thanks for your reply.

What is in there now is more rich than the original settings I believe. The front carburetor has .100 jets in the primaries and .098 jets in the secondaries. The metering rods are 075 x 047 with orange springs.

The rear carburetor has .101 jets in primaries and .098 jets in secondaries. The metering rods are 075 x 047 with orange springs.

I did check and reset float levels last week. They were a little off but not much. It is not falling on it's nose at WOT, but just not what I imagine should happen with all the extra air/fuel flow that is available when I get into it. I had a couple of single four barrel 400s over the years that would really pull strong, so my expectations are relative to those days. I'm expecting a bit more out of a stroked 467 with head work done. I was previously running stock 62 heads.

This is strictly "seat of the pants" judgment of performance. I don't have access to a dyno. I have considered a wide band AFR but I believe to get meaningful information out of it, that would need to be a permanent installation rather than the kind you hang in your exhaust pipe while not driving. Is that correct?

I think you would be way rich with those jets and rods when you get into it. I would have to do the math and see your net flow area to make a comment re cruising on only the front holes of the rear carb. Is your linkage progressive? What color are your plugs? Here are some calibrations I did for people years ago who have engines close to your cubic inches, and they never changed their calibrations. 462cu .094/.073 jets .062x.068 rods, 472cu .097/.074 jets .058x.068 rods, 480cu .095/.069 jets .058x.069 rods.

We're kind of stealing jeff chmura's thread here.

Yes, I'm sorry about that. Hopefully it is helpful information for him and everyone else who reads it.

I'm running as non-progressive linkage, they are opening up together. Plugs are dark but not wet or fouling (yet). Thank you for the recommendations. I will try those soon.

I would agree with 61-63 about way too rich with those numbers.

But even if you get the numbers dialed in, EXPECT hesitations on the street at various RPM's with the imitation carbs when the secondary(2) try to engage because of the wrong auxiliary air valves for Pontiac use. If drag racing and you leave the line at 6000 RPM, the air valves won't be a problem ;)

Jon.

I have driven my 64 GTO with a couple of single 4 BBL PONTIAC AFBs.
What I mean by that is one carb on the engine but two different physical carbs.

In BOTH cases, the Pontiac AFB carb was seamless in acceleration performance once I had it dialed it. None of that TRI-POWER sudden secondary acceleration.

But I have driven a Tri-Power Car/Engine for over 50 years. So it is what it is.

Pontiac & the Carter OEM Engineers really had their act together on the Pontiac AFB carbs.

Just my opinion on the subject of a dual quad street AFB application.

Tom V.

Guys, I'm following along with all the great info.
I'm sure that after I get the manifold squared away, I'll need some carb info also.
Thanks. jeff

John Reeder wrote an excellent 2 part article in Smoke Signals magazine. On how to clone SD Carter carbs for a dual quad. The article is actually available on their web site now. It is very in depth with both text and photos.

Thanks for that tip, should be an interesting read. you can find the document here: https://secure.poci.org/Docs/291.PDF

And just in case someone is interested.. these might be from someone on the board here or not (they aren't mine) but https://www.ebay.com/itm/AFB-Dual-Qu...e/193775590100

Absolutely great article!

Adding a bit of history:

Carter 3433s and 3435s were released on 13 November 1961 and discontinued 29 January 1968.

The drawings were for "low production tooling". Basically, when an order was received, the folks at Carter would pull a pair of Carter 3012s (Chevrolet) carbs from the shelf, grind off the "3012s", and build using the Pontiac throttle shafts, and internal Pontiac calibrations.

For identification, the air horns were marked with an India ink stamp, and tags were placed on the air horn to body screw along the back of the carburetors on the pump side (I use Carter designations of pump side and choke side, rather than driver's side/passenger side; remember driver's side depends on where you drive ;) .

As the Chevrolet 3012s underwent a number of changes over the years, casting numbers on the bodies will depend on exactly when the 3433s and 3435s were ordered and built. Somewhere, I have the list of casting numbers used, but don't remember where it is, and don't want to look for it. Memory (not as good as it once was) says 4 different body castings were used over the range of production.

The Chevrolet 3012s was the only donor that Carter used, but many folks use the Buicks today, as John mentioned, because of costs.

During the production run, 33 changes were made to these carburetors for various reasons. Those that are totally anal about appearance will have a difficult time because the shape of plugs, the design of the "S" link, and other external changes were made.

For those looking for specification pages in the big Carter master parts books, good luck! As these were low production carburetors, Carter did not print the normal specification pages for these carburetors.

For low production units, Carter issued (T)emporary (F)ield (N)otices, referred to as TFN's, on a need-to-know basis only. Should one have access to the Carter TFN's, the original TFN covering these units was TFN-622. TFN-622 was superseded by TFN-686, TFN-694, TFN-696 and TFN-696A which was the final release. The later releases, in addition to the 3433s and 3435s, also cover the later SD carbs.

Jon.