I'm trying to figure out the differences between the C3B, C4B and C3BX intakes, and I THOUGHT I had it figured out. Until this C3BX popped up in the classified ads. Here's what I thought: C4B: Chevrolet, 4BBL C3B: Chevrolet, Holley 3BBL carb. It has a notch in the plenum divider to clear the rear throttle blade of the unique Holley. C3BX: I thought it was also for the Holley 3BBL carb, and it has a boss for the mechanical choke that my C3B doesn't have, and an extra port on the water cross-over. On the C4B, the carb pad is a 4-hole, and the divided intake plenum has the raised floor on the driver's side, which makes for two very long runners, and two very short runners on top, same on the bottom. My C3B and C3BX both have the raised floor on the passenger side, which makes the two long runners exit from the other side of the plenum, making the loooong runners a bit shorter, and lengthening the two shorter runners, for what I'll guess is more even fuel distribution. Then I see a 3CBX in the classified with divided plenum, NO notch to clear the 3BBL Holley, the original C4B long/short runner lay out, the choke boss and the extra water port. Additionally, I've seen that these intakes were available with the thermostat housing on either side of the oil fill tube--driver's or passenger side of the intake. I've seen all three versions of the intake with the t-stat housing on either side. So what's the deal? Does anyone have any vintage catalogs with the different versions of the intakes, and maybe a description of why they changed things? I'd love to know the difference between C3B and C3BX, especially now that I've seen this other C3BX that looks just like an early C4B, but with a divided plenum and choke, rather than 4-hole carb base. Here's the one from the classified, with the raise plenum floor on the driver's side, two looong runners, two short stubby runners. As I said, for the other C3B and C3BX I have, the raised portion of the floor is on the passenger side, so the runners exit on the passenger side of the plenum divider, which shortens to long runners, and lengthens the short ones. -Brad
hey brad...i just came in from the garage. i bought a c3bx with a holley 3110 on it for $65 like a month ago. while researching the parts, i found many sources stating that the c3bx will not clear an hei distributor. since i have an hei distributor, i bought another setup. so, back to today. today i began taking my engine apart to put on the new setup. i wanted to see how badly the hei hit the c3bx, since my distributor was out and the c3bx was just sitting there. it came very close to the rear runner, but didn't hit it. the distributor seemed to completely seat in the hole. my distributor is from a 1977 impala, which i believe is the largest diameter hei that exists. this is annoying and confusing, since i spent a lot more than $65 on the new parts. is there any hamb enlightenment offered in this dilemma?
Brad, I just bought a c3bx with no notch (from here)...I have couple of others and will get them on a table and post some pics. Bill
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