Anybody have any ideas as to what rods/jets would be about right for a 318 w/ a mild cam and exhaust? How can you check what size you have, are they marked somehow?
fourspeed
09-06-2006, 05:42 PM
I can't tell you what combo to run. Too bad, I just rebuilt my AFB on Monday too. Here's a chart that at least has the jets/rods listed. When I get the 318 in the Great Pumpkin dialed in, I'll have to make note of the carb setup.
http://cars.rasoenterprises.com/Carbs-CarterAFB_Jetting.htm
mlauk
09-07-2006, 09:59 PM
It's been 5 years since I adjusted mine, but I wrote down what I changed to tune it in. If you tell me which carb. no. you have, I can tell you what rods and jets came stock. I've got a 400 motor with a 600 cfm carter afb, stock exhaust, edelbrock manifold and RV cam. It was running rich (tested by revving the motor and a little black smoke came out, it also did not pass the emmisions test). I changed the metering rod from 16-1747 to 16-388 and the primary metering jet from 120-400 to 120-398 to lean the mixture out. It runs great and passed the emmisions test.
To check the metering rods, slowly remove the spring loaded retaining plates so they don't fly out. Pull out the piston, spring and metering rod. The number is stamped on the side of the metering rod. The metering jet is removed with a flat blade screwdriver and the number is stamped on it. It's been a while, but it didn't seem difficult. I also have a book, so if you have any questions, I can look it up.
Speed Dragon
09-07-2006, 10:13 PM
Cool, thanks mlauk. I get the # off the carb tomorrow. I got it running pretty good tonight, apparently this engine is super cold natured :/ I have a Carter book somewhere too, although I don't think it lists all the rod/jet sizes.
Speed Dragon
09-10-2006, 01:48 PM
Only #'s I see on it is 2312 on the top and 0-1862 on the side of the main body.
mlauk
09-11-2006, 07:02 PM
The carb numbers I have on my chart are:
9502-9504 500 cfm
9605-9607 600 cfm
9635-9638 625 cfm
9755-9758 750 cfm
Do you know what cfm your carb is?
fourspeed
09-11-2006, 11:35 PM
Only #'s I see on it is 2312 on the top and 0-1862 on the side of the main body.
Well, 2312 comes up as a 1956 BBD two-barrel. I'll bet that is NOT what you have! :D
Can you post some pics, so we can get an idea what vintage it is?
Speed Dragon
09-12-2006, 11:42 PM
Well, 2312 comes up as a 1956 BBD two-barrel. I'll bet that is NOT what you have! :D
Can you post some pics, so we can get an idea what vintage it is?Lol nope definitely not what I have. I forgot that Ifound that same thing when I looked it up before I bought it. I got it from 75PowerWagon on here, he said he believed it was off a 340, but not sure.
I'll see if I can get a pic tomorrow.
Speed Dragon
09-12-2006, 11:45 PM
The carb numbers I have on my chart are:
9502-9504 500 cfm
9605-9607 600 cfm
9635-9638 625 cfm
9755-9758 750 cfm
Do you know what cfm your carb is?Not really, but I believe it's either a 625 or a 750. Not really sure though, there's not really any markings on it.
Speed Dragon
02-08-2007, 09:10 AM
Okay, found out that this thing is supposed to have a tag on it, but doesn't anymore, probably thrown away or lost when it was tuned or something at one time. Anyway, 75powerwagon said it was supposed to be off his 340 originally, which was out of a '68 Cuda. So it would seem that it is a '68 275hp 340 4-bbl carb, if that will help out any.
However, I think I'm gonna build my Eddy carb for it, so if anyone has a carb setting for Edelbrock 1400 carb, I'd apreciate that too. I'd still like to know a good setting for the old AFB though too, just to know :)
Edit: I have an Edelbrock owner's manual for the 1405-1411 carbs, would the info it it be applicable to the 1400 as well?
mlauk
02-08-2007, 01:39 PM
Just looking in the Summit catalogue, it lists the Edelbrock carbs as follows
I don't know what the difference is, but there was not a calibration kit available for the EDL-1400, while all the non-emmision carbs had a kit available.
Speed Dragon
02-08-2007, 04:16 PM
Only difference I see is that the 1400 has a tube in the airhorn for the vapor line that runs to the charcoal canister. So probably it can be tuned the same as the 1405. I'm glad it's only a 600cfm too, I think that's about all I need for this engine. It's probably already jetted pretty close to right too, since it's obviously set for a stock engine w/ a 4-bbl swap. Just needs to be cleaned and rebuilt probably.
Anybody else have any idea what their 318 4bbl is jetted at?
Speed Dragon
02-11-2007, 03:59 PM
Pulled my Eddy 1400 apart today and cleaned it out. As far as I could tell (numbers weren't really easy to read) the jets have 120 and I think 398 on them. The rods have 7347 on them.
Speed Dragon
02-13-2007, 01:17 PM
Well, I think that carb is too rich, the truck doesn't seem to be pulling very hard at the top of third. It feels and sounds to me like it's too rich. Anybody what metering rods would lean it out some, like take it one step leaner? Again, the ones I have now have 7347 on them.
mlauk
02-14-2007, 09:54 PM
Speed Dragon,
The 120-398 jets have a diameter of .098. The 7347 rods have a .073 diameter cruise step and a .047 diameter power step. You can either go with a smaller jet (leaner) which comes in step of .003, ie
120-395 .095 diameter
120-392 .092 diameter
down to
120-371 .071 diameter
or you can change the rod with a bigger diameter (leaner) like 7652 which has a .076 diameter in the cruise step and .052 diameter in the power step.
Speed Dragon
02-15-2007, 07:26 AM
Cool, thanks man. My '68 AFB has 16-691 rods in it, they look thicker than the ones in the Edelbrock. I may see if I can swap those into the Eddy, they look like they should fit.
BTW, the Eddy has I think 120-385 secondary jets, where as the AFB has 120-398 on all four.
mlauk
02-15-2007, 08:40 PM
FYI, the 16-691 has a .076 cruise step and a .055 power step.
Speed Dragon
02-16-2007, 12:09 AM
That should lean it out some then, right? I'm kinda new to carb tuning, this is my first 4-bbl engine, always had 2bbl V8's (no tuning parts there lol) and EFI using an A/F gauge.
mlauk
02-16-2007, 12:17 PM
Yes, it would be equivalent to installing the next size smaller jet. .003 reduction in diameter. I don't know if it will be enough, but it's so easy to change out, you can find out real quick. I'm no expert either, but had to get mine to pass emmisions inspection a few years ago and it wouldn't pass because it was rich. I based my changes by revving the engine and looking for black smoke out of the exhaust. It passed inspection no problem and now that it is over 25 years old, it doesn't have to go through an emmisions test. Another method it to look at the spark plugs to see if it is too rich or lean.
Speed Dragon
02-16-2007, 09:19 PM
Well, I don't have any black smoke, but it feels and sounds rich, and last time I had the plugs out, they were pretty sooty, especially for only being a week old :0
Speed Dragon
02-19-2007, 05:21 PM
Well, I guess I was wrong. Put the leaner rods (16-691) in and it ran worse. Rather, it still ran good, but had less power and chugged pretty bad when I stepped on it. So I put the Eddy 7347's back in this afternoon, and it does a lott better. Still does seem to have much at WOT, though. On the highway today, I pulled it in 4th and floored it at about 65mph, and it barely was accelerating at all. Maybe I need to richen the secondary jets? I think it has 120-386 now.
mlauk
02-20-2007, 10:56 AM
I guess that explains why you didn't have any black smoke. You might want to baseline it with some timed runs, then play with the secondary jets and actually measure the differences versus seat of the pants feel.
Speed Dragon
02-20-2007, 03:04 PM
Yeah I need to, drag strip isn't open yet though, I don't think.
Speed Dragon
03-06-2007, 07:52 PM
Update:
Well, now I have the AFB, back on it, I put the accel pump and the pistons out of the Eddy into it, complete tore it down and sprayed everything out, and put the 16-691 rods back in it. Runs good now, cranks up good, no flooding. It feels a little less powerful w/ the 16-691 rods than with the Eddy 7347 rods. I need to get a strip kit for it, fiddle w/ it some more. I think the Eddy carb has some leaner secondary jets in it, I may swap them in and see how it does. I put the leaner rods in cause it was dumping fuel from the boosters when you just cracked the throttle a bit.
