Had the tops off both carbs the other day and they looked good but the jets sizing was all over the place. One carb had 3 different size jets in it! uzzled: So I've asked my local carb shop if they have jets and they said they do but have no idea where to start with recomendations uzzled: They gave me a list of jet and metering rods to choose from. My 401 Nailhead is stock so I'll be needing the smallest size I can get but just in case someone can make a recommendation I'll list what is available and you tell me what I should get. My 'restorer guy' has a set of jet drills so I can increase the size when I get the headers and Cam installed (at a later date) so this is just to get the motor running to see what happens (I'm dying to bolt them on - as you can imagine). Main jets: 383, 386, 389, 392, 398, 401, 404, 407, 410. Metering Rods: 16-5749 16-6337 16-6347 16-6537 16-6552 16-6755 16-6842 16-6847 16-6852 16-6857 16-7042 16-7047 16-7052 16-7057 16-7147 16-7337 16-7342 16-7537 16-7542 16-7547 How do I decipher these numbers anyway? What do they mean? The numbers on my current rods are not readable and I can only read half of the jet sizes either so I just want to start from a baseline and work up from there. Obviously 2 750's on a stock 401 is a "little" overkill so I expect that the smallest jets would be best but is there a way to choose a jet and Rod combo? For example do I use a set of rods to suit a set of jets? Also, are these 'main' jet sizes primary or secondary? I know that the primaries should be bigger than the secondaries but you'll have to excuse my ignorance. I'm having too much fun to let my lack of knowledge get in the way - if you know what I mean?
Bill: The early AFBs had a "dog's breakfast" method of number identification on metering rods. Newer rods such as yours are easier to tell the size...a 16-7047 rod would have a large diameter (economy) of .070 and small diameter (power) of .047. The jet size is the actual diameter plus .300... why I don't know...120-398 jet will be .098 diameter. A new Carter 600 cfm usually has .098 (or .400) primary jet with a 7047 (or 7147) rod and .095 secondary jet. Don't forget that Edelbrock AFBs use the same jets/rods and metering rod spring assortment. Hope this helps, Frank (Buford) :beer
Thanks Frank. That helps a lot. At least now I know what the sizes mean and where to start. I wonder how a 750 will go with the 600 size jets and rods? Edit: Would I be safe in getting the smallest jets and the fatest rods? Your guess will do. Or, does anyone know what the 750's would have come with stock?
Boy I sure do wish I had your problem Bill, Since your jetting is all over the place, what I would do is return the carbs to stock-out-of-the-box jetting. Somewhere around here I have Edelbrock's info on how their 750's come jetted, and I also have the Tech Info phone number to Federal Mogul, maker of the Carter AFB. I called them once, and they were able to look up the factory stock jetting for the 9635 on my Nailhead. I can dig this out tomorrow, it's really late here tonight. I can call them for you, since its an expensive call from Oz. After restoring to factory original, I'd read plug color and evaluate drivability and miles per gallon to see if the part throttle normal is OK before proceeding to wide open. Since this is an engineering project, I might even weld in oxygen sensor bungs in the exhaust, or pay for chassis dyno time. The really good AFB expert on this BB is Casey Marks, he posts in the Pure Stock forum. You might try to PM him as well. He's an Oldsmobile W-31 guy.
Thanks John, I don't know what the stock specs are for the 4760 Competition Series 750's are so I might have to ask for your help if you can find the book. There is no real hurry as I don't want to get these on until I am fairly comfortable with my baseline. Dyno time is available but oxygen sensors aren't. So I'll log back on tommorrow and see what info has been dug up. Go and get some sleep, thanks for your help.
Don't go with the smallest jets / largest rods... it will be super lean. The new Carter 750s have .113 primary and .107 secondary jets. Metering rods are .071 x .047...16-7147. I've found that the factory sizes tend to be on the rich side for near stock engines, but it would give you a starting point. Changing the rods is easy and quick for tuning the primary side, but you reach a point where you have to open the carb and change jets. If you change the rods with the "carby" on the engine, be careful as the metering rod springs can stick in the little piston then drop out, possibly down the carburetor! :stmad: Happy motoring Bill, Frank (Buford):beer
Frank, those jet numbers are different to what I can buy but I'm guessing that they translate to... 113=413 107=407 Would I be correct in assuming this? The rod sizes are the same numbering (16-7147). Thanks.
OK Bill, found my Edelbrock stuff first, we'll list that now. Carters and Edelbrocks are both made by Weber, and the jets and rods are the same. Might be easier for you to buy Edelbrock. Edelbrock 1407 (Calibrated for maximum performance): Primaries .113 and .071 x .047; Secondaries .107 Edelbrock 1411 (Calibrated for maximum fuel economy): Primaries .110 and .075 x .047; Secondaries .107 Both are 750 cfm, at least one is a match for the Carter given earlier. Now to dig up my Carter stuff.
Rod and Jet Trivia Bill, Sizes are in thousandths of an inch. Enjoy. There are many other sizes listed in both my Carter and Edelbrock stuff, here's the ones you listed, with a couple of larger jets thrown in for good measure. I've seen pictures of how you drive. Metering Rods: Size: Carter: Edelbrock: .057 x .049 16-5749 1437 .063 x .037 16-6337 1442 .063 x .047 16-6347 1443 .065 x .037 16-6537 1444 .065 x .052 16-6552 1460 .067 x .055 16-6755 1463 .067 x .042 16-6842 ---- .068 x .047 16-6847 1447 .068 x .052 16-6852 1448 .068 x .057 16-6857 1436 .070 x .042 16-7042 1450 .070 x .047 16-7047 1451 .070 x .052 16-7052 1452 .070 x .057 16-7057 1418 .071 x .047 16-7147 1453 .073 x .037 16-7337 1454 .073 x .042 16-7342 1455 .075 x .037 16-7537 1458 .075 x .042 16-7542 1419 .075 x .047 16-7547 1459 Main jets: Size: Carter: Edelbrock: .083 120-383 1422 .086 120-386 1423 .089 120-389 1424 .092 120-392 1425 .098 120-398 1427 .101 120-401 1429 .104 120-404 1430 .107 120-407 1431 .110 120-410 1432 .113 120-413 1433 .116 120-416 1434 Edit: this damn thing took out the nice formatting of the table
Ok, now where geting down to it... :TU: I can work with those numbers. At least enough to use as a baseline to at least get it driveable down to the dyno where I can check air/fuel mixture levels at different throttle positions. I'd still like to come up with factory settings for the 4760S's but I think that's a great start. Yep, I certainly don't believe in wasting any available power. Vroom is good therefore more vroom is better... in my books anyway. Thanks also for the cross reference to the Edelbrock numbers, that will certainly be helpful in ordering. While we are at it. I'll have a look at my power valve spring and see what color I have. Though it's essentially stock now, I plan to add a mild cam and a set of headers by the end of the year which will help everything breathe much better. I wish I had them now. Also, please don't break your back getting this information to me immediately. I'd rather wait a few extra weekends to get the right combination from the start than rush through with what I've got just to get it on the road and find it runs like crap. So, 'at your leisure' will be fine. I'm collecting all this information and printing it out as it comes through and discussing it with my 'restorer dude' as we go along. Once again I appreciate the effort.
I'll call Federal Mogul (Carter) technical info for you on Monday, and post the answer. Do you have an Edelbrock catalog, and are their parts readily available in Oz? I'd like to see you get this setup going, I was considering going dual quads myself, until a QJet manifold became available. I've heard the QJet will edge out an Offy dual quad, but the dual quad has an undeniable "WOW" factor going for it. I'm going to wander over to the Yahoo Nailhead group and see if Russ Martin or Tom Telesco have posted anything print-worthy.
I have reasonable access to parts down here and if they are not in South Australia then they are available from the east (Sydney, Melbourne...etc). We actually have a Fedearl Mogul warehouse right here in Adelaide but I doubt that they would know anything about this setup. Might be worth a try on Monday too. I really appreciate all the effort you are going to John. Russ has sent some specs through but Tom hasn't replied yet. Today I'm going to my friends garage where the carbs are and see if I can get the exact sizes of everything. I was tempted to just throw them and see what happens but when I came across three different jet sizes in one carb I was kind of stopped dead in my tracks and decided to investigate a little further. I haven't even started to discuss my air cleaner setup yet but I've come up with a solution I think might work with the 1.5 inch clearance my hood gives me uzzled: .
Carter Carbs Are No More Well Bill, I remembered to grab my Buick tech notebook today and bring it in to work with me. I called the Federal Mogul tech services hotline, and they told me that FM got out of the carb business at the first of the year, and they couldn't help me. So I guess that means that we'll see Carter AFBs and their parts start to disappear from the market??? That Buick tech notebook is a bunch of stuff I've printed out from the old GSCA board (here today gone tomorrow), the Yahoo Nailhead Buick group, and this board, and other places (I've got your Nailhead articles from your website). Sorry I wasn't more help.
Thanks John. Actually you have been a lot of help. I found this site that is selling Edelbrock AFB's and it conveniently lists the jet and rod sizes. I think my black step springs are wrong though because they all seem to be using orange springs which tells me something. http://shop.store.yahoo.com/gofast/percar.html What I don't know is how this all translates to an over carbed dual quad setup like mine will be. There is a guy who is familiar with AFB and owns a Dyno who said that he can adjust everything for me but the entire carb section of his workshop went up in flames and he lost all the small (carb) spares he had. He said if I can bring in a range of jets and rods he will be able to tune it and said that it "should run well with a fair amount of response by the time we're finished". Great, now I have to by a stock of jets and rods...sigh. I suppose you must "pay to play".
Howdy, I have a simular question. I have the new 600 performers on my 65 Riviera GS but the carbs are set up for Chicago and I live in Colorado Springs, CO. To make matters worse I'll be going to TX, MI, and finally settling in Ohio this summer so its not like I can pay someone at each spot to retune this thing. First order of business is to get the car drivable here in Colorado. Does anyone have any suggestions for a stock 425 with the 2x4s at approximately 7000 ft? I'd like to do this myself, it would be a useful skill to be able to tune dual quads, something you don't see many people doing anymore. Oh.... I do still have the orginal numbers matching Carters but I'll stick to the performers since its an everyday driver. Thanks,
