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Heyas - How do I go about picking the right carb for my motor? I'm looking at upgrades for my 1970 Ford Torino and I'm going over the specs of the engine and it appears that the stock Autolite 2100 is too small for this application. The venturi stamp on the side of the carb shows 1.08 indicating its a 287 cfm. But the specs of the motor have it running 220hp @ 4600 rpm. If I do the back-of-napkin math (4600 x 302 / 3500) gives me a requirement of 396 cfm. Is this right? The car is a 3-speed manual that i'll be upgrading to a 5- or 6-speed manual and will eventually get to building the engine with new headers, a bigger cam, etc. It'll be built for street with a little extra under the hood for kicks. So I'm considering a 450cfm, electric choke, vacuum secondary carb like the Holley 4160. I'm new at this so can y'all check/challenge my thinking here?
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Aug 10, 2023 16:55
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| # ? May 3, 2024 20:15 |
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My carb knowledge is pretty basic so hopefully a smarter gearhead will chime in. It looks like you want to go from a 2 barrel to a 4 barrel if I'm understanding you correctly, I believe you'll need a new intake manifold to support a 4bbl. I honestly don't know what brand carbs are good or bad these days but companies like Edelbrock will sell carb+manifold combinations so you know the parts will fit together. A cursory Google search seems to recommend no more than 500cfm for a stock 302. I do know sometimes people throw the biggest, highest cfm carbs they can on engines because bigger number better, but it's actually detrimental. I bet someplace like a classic mustang forum will probably have tons of people that know all about carbies and 302's.
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Aug 12, 2023 17:22
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Quad downdraught webers E: the real answer is that it never made 220hp, that's basically what the 5.0 in late fox bodies made with better heads and efi. Pre net hp is basically just vibes. I have never owned a carbied car because efi is just better but all the car people I know generally say that oversized carbs are just fine but make it harder to tune. I would keep the two barrel and then hot it up and use the immortal 650 holley double pumper when the engine has a cam/zorst/gt40p heads. Save the money and the tuning headache. If you want to spend a bit more money, once the engine is built I hear great things about those efi systems that are on the market from holley. big dong wanter fucked around with this message at 19:06 on Aug 12, 2023 |
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Aug 12, 2023 18:57
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I'd be looking at one of those efi kits, some of them have or work with an ignition controller so you can upgrade that while you're at it. Keeps things looking mostly original and if the reviews are to be believed going efi makes it easier to start and run when cold and gives a little boost to mpg. A few years ago I had all my parts picked out waiting to find the right car (something huge from the 70s) and I ended up with something completely different. So try this and keep the thread updated so I can see how well it works.
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Aug 12, 2023 19:52
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Yeah those Holley Sniper kits look so cool. I think they just need a signal from a wideband 02 and tach and then they'll basically program themselves on their little touch displays while asking you things like "how many cylinders is your engine? What is the displacement?..."
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Aug 12, 2023 20:09
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Agrikk posted:So I'm considering a 450cfm, electric choke, vacuum secondary carb like the Holley 4160. 4160 would be pretty close to the OEM 4 barrel - in fact if memory serves correctly, I think Ford actually authorized the 4160 to be used as a service part to replace Autolite carbs, and it should bolt up to a factory 4 bbl manifold with just a spacer. No clue on CFM.
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Aug 12, 2023 22:48
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I have been considering a Holley Sniper kit because I think they’re really cool. I have heard from a classic car mechanic that they had nothing but problems in the one attempt they tried to use it so they don’t use them anymore. But that’s a survey sample of one and I really, really want to believe. But carb keeps the car simple and mechanical instead of computerized and it’s the draw I have to classic cars. But I also need to admit that I won’t be tuning my carb myself so it makes zero difference if a third party is tuning my carb or installing an EFI kit.  So many options. What I really need to do is create an actual upgrades plan so I can see what the end result might look like and then make decisions accordingly.
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Aug 13, 2023 00:20
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probably anything 450-600 cfm would be about right for a 302. a 650 is perfect for 350-400 cid, so probably whatever's available in that range. summit's cfm calculator says 445 cfm, so i think you're already on the money. a 4160 is just a 4150 where you can't tune the secondary metering, which is probably fine if you don't need to gently caress with it. afaik any square-bore carb should work on any square-bore intake. my personal experience has been that holleys are more tunable and you can get a little more performance out of them that way, but edelbrocks run great out of the box on a mild street motor. ive heard good things about the AVS2 but haven't owned one. with a light car and a manual transmission, i think you'd want mechanical secondaries. vacuum secondaries come on kind of gradually, which maybe you want and maybe you don't. the torino is a midsize and iirc mid-weight, so could probably go either way depending on how you're going to drive it. to BDW's point, the later gt40 heads (available in junkyard explorers) might be a good upgrade, but 1970 was before smog laws choked everything out so maybe they're pretty good already. i don't know tons about windsor motors, but usually that happened around '72.
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Aug 13, 2023 00:38
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"Raluek" posted:to BDW's point, the later gt40 heads (available in junkyard explorers) might be a good upgrade, but 1970 was before smog laws choked everything out so maybe they're pretty good already. i don't know tons about windsor motors, but usually that happened around '72. it's less so smog and more that cfd is really hard and all pre computer normie heads flow like dogshit. The 6.0 in my car makes the same hp as a 426 hemi (net) with a little baby stock truck cam because cad is magic.
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Aug 13, 2023 02:16
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big dong wanter posted:it's less so smog and more that cfd is really hard and all pre computer normie heads flow like dogshit. The 6.0 in my car makes the same hp as a 426 hemi (net) with a little baby stock truck cam because cad is magic. sure but gen3 was a total redo. its more like comparing vortec heads to double humps. they're probably better, but not by the leaps and bounds that they would be if you were comparing them to the malaise era tbi heads or whatever
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Aug 13, 2023 02:38
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Raluek posted:sure but gen3 was a total redo. its more like comparing vortec heads to double humps. they're probably better, but not by the leaps and bounds that they would be if you were comparing them to the malaise era tbi heads or whatever Sure, but the double hump is a rare bird compared to whatever fomoco put in a 2 barrel family car. The double hump has its own issues with fragility and boomers hoarding them. I don't know the exact head that's on the torino but I got a tenner that says the gt40/p would be a huge upgrade for minimal dollarydoos. That said you won't really gain much without actually doing any supporting mods and the supporting mods won't do nearly as much with the stock heads.
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Aug 13, 2023 03:07
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Agrikk posted:Heyas - The other option I've heard chucked around for the 289 cars is an Autolite 4100 with the 1.08" venturi size. It's basically the 4-barrel version of your carb with vacuum operated secondaries. They're supposed to be set and forget, at least according to everything I've read online. The 1.08" venturi size is supposed to be in the 450 cfm range, which should be perfect for your application. This, combined with a Weiand Stealth intake, or similar, and some port work on your stock heads would really wake it up. The stock thermactor heads have *garbage* exhaust ports and really benefit from opening them up. This pdf shows exactly how awful they are (I know the link looks like aids, but it's real): https://cdn.website.thryv.com/7fc8b09813234ba0b3c5e3c0a1b8c109/files/uploaded/Port%20Matching.pdf If you're feeling really spicy you could get some AFR aluminum heads and long tube headers and a roller cam setup and then you'd truly be down the path to automotive insanity.
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Aug 21, 2023 18:36
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| # ? May 3, 2024 20:15 |
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Any 500 to 550cfm 4 barrel should be almost fine. A 289 with good heads, 10 to 1 compression, and a mild cam will make about 250 Net HP with a 500cfm carb and still have a bit of headroom at the top end.
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Aug 25, 2023 16:27
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