I'm looking for info on some carter carbs, mainly 4758S and 4761S - they are 500cfm competition carbs. im looking for info on what the std primary and secondary jets are and std metering rods. I'm also looking for info on what other metering rods would fit? i.e. what was in the strip kit 10-101. i've got a blown SBC and its running a bit too rich but i think the metering rods are the wrong size so looking for info on what would fit them to lean in out a bit.
Standard Edelbrock stuff should work, I use it in my Carter carbs, I do have some of those 500's though, all looks the same inside
Last year I pains takingly restored two 4761S. https://www.jalopyjournal.com/forum/threads/my-crazy-dual-quad-carter-afb-restoration.1270168/ From my research the following parts were standard. These parts are what I found in both of my carbs. The 4758 and 4761 parts are: Primary Jets:#120-395 (.095") Secondary Jets:#120-371 (.071") Metering Rods: #16-136 (.071" x .061") Needle & Seat: #25-860 I have info on what was in the 10-201 strip kit. I can't remember exactly, but this kit may have superseded the 10-101 kit. It is very easy to end up with the wrong metering rods as there were lots of them. Beware not all of the later Federal Mogul and then Edelbrock parts will work properly. Carbking on here is by far the most knowledgeable, so maybe he can chime in. What meter rods and jet do you have now? The standard parts are probably going to run too lean on a supercharger. I would verify the correct float level first.
I have the same metering rods as you have quoted - #16-136. I think i remember reading these were the biggest rods supplied for these carbs? I can't find anything about what was in strip kit 10-101. I bought 2 10-201 strip kits but i didnt think i could use the metering rods from this kit in my carbs? I think i've got #92 jets in the primaries and #89 in the secondaries. I would need to check though. the quote level is all good, carbs were rebuilt using carb kits from Jon (Carbking). I don't believe i've got any jets below the 89's. I might need to get some and do some testing.
Your post is a little confusing. You say you have the same metering rods and then refer to them as jets. You should be able to use the parts from the 10-201 strip kits. They have jets as small as .071" and as large as 110". In your original post you say it's running a bit rich but you don't say where in the fuel curve? Is it fat at idle, part throttle, or full throttle? Does it bog and if so at what RPM? Black smoke when you hammer it? What do the spark plugs look like? Remember changing the A/F ratio on these is a result of the combination of both the metering rod and the jet. When the rods get lifted is important and a result of the piston spring pressure vs the vacuum signal which obviously changes with rpm but is going to be different with a blower. From what I understand (and I can always be wrong) tuning these carbs for a blower applications can also involve playing with the secondary air door weights.
Strip kit 10-101 has primary jets from .092~.104, secondary jets from .068~ .089, and is the correct kit to use for 4758s and 4761s. The jets in the 10-201 kits are about the same, and may be used. The step-up rods in kit 10-201 will physically fit, but the sizes (other than 1 rod which was renumbered) are less than useful. This same renumbered rod is in strip kit 10-102, but is the only rod from that kit that is useful. The jets in 10-102 may be used. If you really want the good information on these carburetors, check the classifieds; I listed the actual Carter prints a few days ago. Expensive, but try to find the information elsewhere! I personally bought the prints directly from Carter in about 1980 when we were Carter distributors. Here is an article from my website discussing both the first and second series strip kits. https://www.thecarburetorshop.com/Perfparts.htm Should you attempt to use the modern rods which some say will interchange, don't call me if you have issues! Jon
In the post above, I listed the sizes of both primary and secondary jets in Strip Kit 10-101. I listed them in this manner as this is the way Carter listed them on the original print. It should be noted that the physical dimensions of these jets, other than orifice size, are identical. So, just because Carter listed a 120-383 (0.083) jet as a secondary jet does NOT mean that it cannot be used as a primary. Because the metering area of the primary is the AREA of the primary metering jet minus the dynamic AREA of the step-up rod in the jet at any time, very few will ever have a need for a primary jet IN THESE CARBURETORS smaller than maybe 0.089. The comment in the two paragraph preceding this one is NOT TRUE for many Chrysler AFB's and MOST Carter AVS carburetors which use the high step primary jet, and the normal secondary jet. Jon
I certainly didn't get small jets like .071 in the kits i bought but it did have the larger jets. Maybe i need to invest in some smaller jets. The metering rods i have in the carbs are .071 x .061 - they were in both carbs when i bought them. tbh it didnt make much difference when we changed them with other rods in the set so i eventually put them back in as i knew they were the correct rods for the carbs. The engine is a newly built 350 and has only run on a dyno but it was rich throughout the whole rpm range, it wasn't bogging but the plugs are a little black.
thanks for the info Jon. I seen the ad's but they are too expensive for me, would love to have them though.
I re-read your earlier post and you listed Strip Kit 10-102 not 10-201. Kit 10-102 is for Carters 4760 & 4762 which are 750 cfm. That may explain why you did not get the smaller jets. Your ignition timing curve will have a big affect the A/F ratio as well. Even changes in the weather can affect it as will the heat range of the spark plugs. The good news is your starting on the rich side. Sounds like you need to drive it with the correct timing and some fresh plugs and see how it does then maybe start down sizing the jets in small increments until you get good color on the plugs. I would have thought a .092 primary jet would actually be too small with the blower but we really don't know the specifics of your camshaft, heads, blower type and size or even the drive ratio. You could also install oxygen sensors and an A/F ratio meter to aid in tuning. Good luck and have fun!
@tomcat11 cam is a lunati, spec is Advertised Duration (Int/Exh): 303/313 Duration @ .050 (Int/Exh): 234/244 Gross Valve Lift (Int/Exh): .488/.509 LSA/ICL: 112/107 Valve Lash (Int/Exh): Hyd/Hyd RPM Range: 2200-6000 heads are AFR Eliminators 195cc, street head Blower is a GM 4/71 and is running about 3% boost.
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