Have you ever done it, or seen it done successfully? I'm making progress piecing together a blower set up for a 351W and am wondering if I can use a pair of 4g carbs that I have. If I don't have to go buy carbs, the project will come together sooner. I am planning on mild street motor with about 8 pounds of boost, maybe 450hp. I haven't torn into the carbs yet to see what it would take to boost reference them, but they are real simple carburetors, so I expect it shouldn't be too hard.
I'm sure it was done back in the day. The only thing I can see as a problem would be if you were running a big blower it may restrict it, the more you resrtict it the hotter your charge will be when it hits your intake.
The blower's pretty big, an 8v-71, but I plan to run it slowly, say 15% underdriven. I had looked up the CFM ratings for the carbs, but now I forgot. The're small, like 500 cfm
I was thinking that they weren't rwal big. If I was going to run 2 4s on one I might lean towards a pair of Carter AFBs. You may be alright with the 4gs but before I invested cash in them I would try and sell or trade them. Just my .02 They would be perfect for one of these fellas with a small displacement motor that wants to run 2 4s.
I'd look around for some old AFBs if I were you. or even a pair of Holley 1850s. Or some WCFBs or something
my Rochester book says some positive things about the 4GC they can be made to perform surprisingly well, although the reference is not specific to blown applications, and it looks like to performance tune they need surgery.. not just simple parts swapping like some of the more popular choices
"I'm making progress piecing together a blower set up for a 351W and am wondering if I can use a pair of 4g carbs that I have" Have you found a manifold for the 8V71 yet??
I've run them for years,,had to,as does all Stock/Super Stock 283/220 and 327/250 engine combos. I will say one thing,many SS guys run well in the 9,000 RPM range with little problems,,but boy,,they are really small. One good thing,they are a dual float design and hold a lot of fuel in the side bowls,,so running out of fuel or having to run massive pressures aren't a problem. The sharpest guy around on these carbs is Dean Oliver in Stuttgart Arkansas. He is who most of the Stock/ Super Stock guys go to for carb modifications,,within the rules of NHRA. He's a good guy and probably give you the best info if you chose to go this route. He is at [email protected]
If it is a pull-through, I don't see a lot of issues. If it is a blow-through, sealing the accelerator pump is going to be a challange; and depending on boost, you might have to fab baffles to fit inside the float pontoons. The standard "vacuum seal" could be machined for the throttle shafts. Sealing the idle screws would not be difficult. If you have the models with the idle air bypass design, sealing this would require some doing. As to ratings, while specific CFM ratings were not published; various 4-G series carbs were made from roughly 375 to 625 CFM. Jon.
Well, there is no such critter as a 8V71 intake for a 351w, or anything else. I bet you knew that. I have an EFI lower intake that I'm adapting. I cut one piece of plate to match to top of the intake, and another to match the bottom of the blower. They are pretty similar. When I have the distributor and pulley's mocked up, I will put the plates together.
As always, I appreciate everyone's thoughtful responses. The shortcomings I had seen for the 4g was that most of the one's I've come across have an odd ball bolt pattern and air cleaner size. They are also tall. The blower is already going to be sticking way up there. But the price is right, and they have a more vintage look than many carbs out there now.
Spyder look in our classifieds. There was a pair of AFBs not blower referenced yet but good runable shape complete with linkage for about 325 to 350. Sounds like a lot of cash but you would be in there like swimwear. they are real old AFBs also and not new Edelbrocks so you could even tell everyone that they are real old school carbs. Hell I'll see if I can find the link for ya. Ok here's a pair that Desoto has: http://www.jalopyjournal.com/forum/showthread.php?t=557454&highlight=afb This is the pair I was thinking about. http://www.jalopyjournal.com/forum/showthread.php?t=558031&highlight=carter
I thought there was something strange looking about them...thanks for the correction Early AFBs have the small air filter flange too don't they? but they're probably easier to put right next to each other than 4Gs.
The very early STANDARD bolt pattern was almost square (3 3/4 x 3 7/8). This bolt pattern was used on: Carter WCFB 1952 - approximately 1956 Holley 2140 (all) Holley 4000 (all) Rochester 4G 1952 - approximately 1956 Stromberg 4A (all) Of the above the Carter WCFB and the Stromberg 4A are the easiest to modify The others may be modified by those who know what they are doing, and don't mind fabricating parts. The "approximately" in the time line is due to the fact that not all makes switched to the newer 4 1/4 x 5 9/16 rectangular pattern at the same time. Jon.
Yes, and I'm not sure what determined whether AFBs got the 4 7/32 or 5 1/8 inch lid. Every factory Chevy AFB I've seen had the smaller opening, except for the 400hp 409 carb. Pontiac AFBs always had the smaller top, but Mercury and Lincoln AFBs used the larger top right from the start in '57.
Oldsmobile went to the larger bolt pattern in '54 while Cadillac, for some reason, stuck with the small pattern through '56.
Ok, I now have a set of AFB's as recommended. I had one, and just found another to match it. It was much cheaper than Holleys. Thanks
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