Help! I have a Edelbrock 750 CFM carb with an electric choke on my 66 Skylark GS 401, automatic. If any of you guys have tuned this carb for this application could you please let me know what jets and metering rods you used? Also, does the stock intake manifold need to be enlarged to clear the primary or secondary throttle plates? Thanks
750 Edelbrock carb set up Steve, the stock calibration for an 750 Edelbrock is Part #1433 (.113) for the main jet and Part#1456 (071 x 0470) for the metering rod. 1 stage leaner(4%) would be Part#1433(.113) for the main jet and Part#1457 (073 x 052) for the metering rod. 1 stage richer (4%) would be Part#1434 (.116) for the main jet and Part#1456(073 x 047) for the metering rods. The part numbers are stamped on both the jets and metering rods, you may have to use a magnifying glass to read them. The idle mixture screws should be gently turned clockwise until they GENTLY seat at the bottom then turned counterclockwise 1/2 to 3/4 turns each. This will get you in the ballpark. I use a phenolic spacer under my carb, because the heat from the heat riser will warp the aluminum base of the carb. Also, I machined the intake manifold so that the holes in the manifold match that of the carb bore. The primary holes in the manifold are smaller than the primaries in the 750 carb. The machining can be done at any machine shop very inexpensively. The phenolic spacer I mentioned earlier should also have a dual bolt pattern like the edelbrock 750 so it will bolt to your manifold. The spacers are available through Jegs or Summit. Good Luck, I hope this helps, Jeff.
Thanks Jeff. Did you have to go 1 step richer or 1step leaner? I suspect that the stock 750 calibration is too rich? Also do both the primary and secondary holes need to be opened up? How large is the spacer? Will the spacer allow the use of the stock air cleaner? My stock air cleaner has been modified to mate to the larger edelbrock. thanks
Edelbrock 750 setup Steve, I went 1 step leaner (4%) because I live at 5100' elevation. You should be just fine with the stock calibration if you live say 2000' or less above sea level. If you want to try a different calibration, I would try the 1 step leaner because mine runs just fine when I drive down to 1200' elevation but it may not be necessary in your case. Only the primaries have to be opened up. You could scribe a line using an edelbrock gasket around the primary holes and use a die grinder(obviously after removing the manifold from the engine) to enlarge or radius the edges to make a smoother transition. I used my milling machine to open up the manifold into two large oval openings just like you see on the new edelbrock manifolds for a small or big block chevy in the ads. in Hot Rod magazine. Like I mentioned earlier this can be done at any machine shop inexpensively. As for the spacer, I used a 1 inch spacer and had no problems closing the hood on my 63 Wildcat. They do sell them in smaller heights or they also sell a heat insulator thats about 3/8 to 1/2 inch thick. If you do this at home with a die grinder just remember to wash the chips out of the manifold with hot water. I hope this helps, Jeff.
Thanks Jeff, I'll tackle that project later! I was also considering replaciong the stock intake manifold gaskets with the ones Poston sells that block off manifold heat to the carb.
Intake Gaskets I just ordered Intake Gaskets with the blocked heat riser from Carmen Faso in N.Y. $20 or $25 per pair I don't remember which.
Steve, I didn't know that anyone sold those manifold gaskets to block off the heat riser. I just used some very thin pieces of sheet metal and some non-hardening non-sylicone Permatex 2 to seal off my maniflold gaskets. Next time I'll order some of those gaskets from Poston or Carmon Faso. See ya!, Jeff.
