Well, it's getting close to time to fire up my 455 Olds/Offy dual quad combo in my Disaster 64 pickup, and I've realized I have a few questions. Here's the specs: -1969 Toronado 455, stock. -Redlines 4500rpm (torque monster, not a high revving machine) -Ran great last year with a single Edelbrock 1405 600CFM carb right out of the box (manual choke, Metering Jets - Primary .100, Secondary .095; Metering Rods - .070 x .047; Step-Up Spring - orange (5" Hg) -Last year was stock Toronado intake with a 2" carb adapter/spacer to clear the edelbrock linkage This years combo is: -Offy 360 intake -Two Carter AFB 500cfm carbs (4 1/2" neck style, front carb is a true secondary with no choke or idle parts) The pedal is rediculous stiff (14ft lokar cable) and from my figuring it will run pig rich with no real performance advantage, so I'm at a stand-still. What would I run for jets/rods, etc, to make it run as good as it did and as economically as it did with the single? The pedal stiffness isn't a huge concern, but the carb calibration is. Any help would be great, thanks!
Don't know about your Carters. I got Edelbrocks which came with metering rods for a BBC. Interesting note, I ran my linkage 1:1 because using just the rear carb created a lean condition in the front cylinders. My buddy ran progressive, then 1:1 and dropped his temp 15 degrees.
I suppose if I jet and meter them down, 1:1 could work too, and still be economical, streetable and powerful. I wonder how far down I could go, as it ran great with an edelbrock 600, and ran the same with a 750 but got worse fuel mileage.
You should be OK with the stock jets and rods... I run dual 600's on my Olds 455... I am running the stock jets and rods but the first year I ran 1-1 linkage... bit rich at idle... and I got 10-12 mpg. Next year ran a progressive linkage with the front carb idle mixtures only slightly opened to keep it cool... went from 10-12 mpg to 14-16 mpg. Popped a 700R4 in it and am up to 18-20 mpg! I plan on messing with the jets and rods this summer!
You might try here. Pick out your carb (500 CFM= 1404), and check out "Owners Manual"... especially the "Calibration Reference Charts"... http://www.edelbrock.com/automotive_new/misc/tech_center/install/1000.shtml
You didn't specify WHICH Carter AFB's you are using, and this would make a huge difference as far as applicability to your engine. In the absense of other data (like a dyno sheet on an identical engine), ALWAYS build the carb(s) absolutely stock. This way you have a repeatable baseline. If you picked carbs which are applicable to your engine, you should be very close. If not, you may (or may not) be able to recalibrate for your engine. Always useful if one can look at a factory specification sheet for the original carb used on a similiar engine. As Olds used Rochesters, this is not possible in this case. However Olds fuel curves are similiar to Pontiac and Buick (totally different from Chevrolet); thus if you used Chevy carbs you will have some tuning issues. Jon.
I don't know whole lot about Carters, but I do know they came with the intake, have been rebuilt as a matched pair, and are said to be "set up" to run on a 455. I guess my main concern was it ran off 600cfm last year and now I have 1000cfm. I may be overthinking it, and should probably try and run it and then worry about it from there. I can always test and record some mixture screw settings and see if that helps or hurts anything. How do I know which Carters I have? Are there numbers or a way of telling on them somewhere?
Do your Carters look like these? 500 cfm Carters in the pics. Not the best pics, but the carbs are identical to Edelbrocks. If so, do as Wingnutz suggests and use the Edelbrock manual to jet/rod back to the original level. 345 Desoto posted an address. Check or replace metering rod springs so it's back to original level. You won't need to make spring changes until you pop a bigger than stock cam in the engine and if you choose a mild cam, you probably won't need any changes. The dual quad setup will run fine on a stock engine with the factory carb setup. Only fly in the ointment will be if you live at al***ude. I moved from 350' al***ude to 3300' al***ude and went two stages lean on my 750 Edelbrock that's on my 462 Buick engine with mild cam. Runs great. Edelbrock went to a lot of trouble with their manual and you may as well take advantage....
1) Actually, you don't have 1000 CFM. CFM is NOT additive. Without doing a flow test of the manifold system, a good guess would be 700~750. 2) The link below will explain the several locations to find ID numbers: http://www.thecarburetorshop.com/Carburetor_ID.htm Jon.
I run two Carter 600's on a 350 just fine, put your setup on and see where it's at, like was said start from stock baseline and go from there.
Jon, you always come up with something educational and interesting. Where do think a couple of 750's would end up at using the same intake manifold? Reason I ask is, Kenne-Bell recommended 750's for my dual quad 462" Buick engine and I opted for 500's so as to end up with a good, crisp responding street engine. Worked well and it idled at 600 rpm with a fairly big cam. The Carter/Edelbrock carbs are pretty forgiving. Couple weeks back my pal's 46 Ford sedan with 600 cfm Edelbrock, moderately cammed 302 Ford drowned a float. We stuck one of my 750's on it (Carter) so we could finish that part of a three day rod run and the car show that followed. Ran great, had good throttle response even though it was set up for 350' al***ude and a 462" engine. We were at about 3500' where the pic was shot. I live at 3300' and he lives at 4100'. Not a bad day to wait for rescue....
Wow do you guys have information, this is great! Here's some more info, including pictures. -Al***ude 1800ft -Carbs have inlet in the front, not the side -Front carb has no mixture adjusting screws, a true secondary Both have the number "C 1565" cast into the body on the driver side Both have the number "6-1743" cast into the top on the p***enger side The front carb (secondary) has "930-94" cast into the top on the driver side, on the very side edge of the lip. They look unlike a lot of Carters I've ever seen before. They have a different size air cleaner neck than an Edelbrock, virtually no vacuum ports and the fuel inlet in the front instead of the side. Inside, they look like any Carter/Edelbrock. If I could get this setup working on this truck, that would be excellent, as it looks just awesome sticking out the top of the bed. Thanks guys, this is amazing!
Kinda look like a pair from a Buick 425. Look at the front of the carbs; there may be a number stamped in the front of the p***enger side right below the mounting hole. It would read something like 3645S.
Pontiac also had front fuel inlets. The numbers you're looking for would be stamped onto the edge of the base at the back of the carburetor. If these are a "matched" Factory set for most any car, according to the numbers, they could be worth a lot of money...
"Wow do you guys have information, this is great! Here's some more info. -Al***ude 1800ft" Youll probably be ok with the original jetting, but it wont hurt to lean it down one step per the Edelbrock manual. The 750 Edelbrock I'm running is jetted two steps lean as noted previously, but it runs just fine down at the river with its 500' al***ude. 　 "-Carbs have inlet in the front, not the side" One of my 750's has the outlet on the right side and the other on the left. (Ones a Carter and the other an Edelbrock, but identical and parts interchange.) There are kits to run an inlet on both sides of a single carb install. Ill probably have to make up a round, flat fuel block, install it near the front mounted coil mount then run long lines to the carb fuel bibs. Similar to the one on the bench, but with a different mounting setup. "-Front carb has no mixture adjusting screws, a true secondary Both have the number "C 1565" cast into the body on the driver side Both have the number "6-1743" cast into the top on the p***enger side The front carb (secondary) has "930-94" cast into the top on the driver side, on the very side edge of the lip. They look unlike a lot of Carters I've ever seen before. They have a different size air cleaner neck than an Edelbrock, virtually no vacuum ports and the fuel inlet in the front instead of the side. Inside, they look like any Carter/Edelbrock." That shouldnt create a problem. Tap your vacuum lines for whatever you need from a manifold - full time vacuum - source. Maybe a larger block with two fittings at the rear for trans and power brakes if applicable. And one in a separate area of the manifold. This isnt critical, more of a convenience since it doesnt take too much vacuum to run trans and brakes. "If I could get this setup working on this truck, that would be excellent, as it looks just awesome sticking out the top of the bed. Thanks guys, this is amazing!" Is that one big screw sticking out of the front of the carb? Little brother and I fooled around with an AFB with big screw on the front and it was an air adjustment. There are some AFB books out there and some of the Carter aftermarket books cover adjusting these as does most any of the blue Motors Manuals - from the proper era. Fwiw, I like straight linkage. Food for thought.
Yep, they both have the big screw at the bottom where a PCV vacuum source would normally be. I have enough vac lines right now, so it's not a problem, I just found it weird as on my Edelbrock, I had a lot of ports capped off.
It may be no more than a marketing/merchandising rumor put out to help parts sales. I've had no probs with swapping electric chokes, jets, rods, gakets & springs. Needles and seats I have look the same. Both Carter and Edelbrock come off the Weber ***embly line....
i run two afb's on 327 chevy small block.it ran really rich untill i put on on fuel preasure adjustable regulator ,now it runs great
With due respect... Carter produced 505 different AFB carburetors PRIOR to the infamous hostile takeover of Carter by FM. FM redesigned the aftermarket AFB in the mid-1980's. These are the units that came off the Weber ***embly line. Prior to the takeover, there were many "interchangeable" parts that might physically "fit", but not work. Examples: (A) At least 2 different physical height fuel valves (B) At least 3 different length metering rods (C) At least 10 different physical profile metering rods (different step lengths). (D) 2 different main metering jet heights. (E) 5 different accelerator pump diameters (F) Many different accelerator pump lengths. (G) At least 5 different floats (H) At least 9 different airhorn gaskets Be careful with your "interchanges". Jon.
I should have clarified the statement to indicate the late Carter's that are identical on the outside to the Edelbrock's. My Carter 500's were purchased new circa 1985. New Carter 750 purchased new about 97 or so. And the Edelbrock 750 purchased about 2002. These last two are the ones I've swapped stuff into. The strip kit I bought for the 500's and a NOS strip kit for the 750's was purchased 2003. All the stuff in the strip kits looks to be interchangeable. I am careful and thanks for the additional info. It is appreciated.
The circa 1985 and newer aftermarket stuff probably is pretty much interchangeable, as it presumably all is of the FM redesign. Since we won't do anything with the FM redesigned stuff, I cannot offer any hard facts either way. Several of the original Carter carburetor numbers were retained by FM. These would include 9510, 9511, 9635, 9636, and 9637. The easy way to tell if one of the above is original or FM is to look at the number suffix. The original Carter suffix would be "S" as in (S)am. The FM suffix would be "SA". Example: 9635S is Carter, while 9635SA is an FM clone. FM also added some numbers, and of course the clones which are marked either Weber or Edelbrock have their own numbers. I have no knowledge of these. Jon.
Curious if when you set the idle mixture when using 2-4's, do you balance the mixture between the two carbs? I an running dual 4's and can't get my idle down without balancing the idle mixture between both carbs. In other words, if I'm open 1 1/2 turns on all idel mixture screws, I'm at 1200rpm's. If I balance the mixture, 3/4 turn per screw in both carbs, I get about 800rpm's, but the engine runs lean. Any ideas?
Running two fours, set the primary throttle plates on the front carb all the way closed, adjust curb idle speed with the rear carb primarys. I adjust idle mixture using both carbs. I have a pair of 600s on a 454, progressive linkage. The primary carb is jetted about 5 percent leaner than the secondary. Been working good since 89
Depends on if you are using "progressive" or solid linkage. As I tend to use solid linkage on virtually any street setup, I use the idle screws on both carbs. Of course, one must synchronize the carbs if using solid linkage. I have a pair of custom 625's on a 390 that does very well. Jon.
Agreed. I have a pair of 390 Holleys on a 302 Ford and tried using progressive linkage, but the design of the manifold pretty much insured the car would run like **** on only one carb. But with both carbs all the time, the car starts easier, idles better and the throttle response is like night and day. To try to help out the mileage somewhat I did adjust a bit of slack into the front carb's accel pump arm (about .015") and that helpd the milege without sacrificing throttle response.
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