I wrapped my headers all the way to the flange last year. The main idea was to control underhood heat but it felt like a nice little pickup in power.
Maybe to really boost your combination you should build yourself a 1.25 inch diameter, single, pea-shooter exhaust.
true there is way more combo's than an average pipe bender can accomplish and back in the 80's it was cool to take the hot rod down for its final big bill and listen to it rumble with true duels who knew or cared of x verses y and stepped up diameters for a couple ponies , I was with alec we were building it by the dozens but great research Gary I will never overlook that finishing touch again :TU:
Here is a non-sarcastic, legitimate response. To quote myself from another thread: A large base Rochester 2g will peak around that RPM (with the use of an earlier stock cam OEM replica). A bit further up for a modded 2g or a 500 CFM Holley 2 barrel. As far as what the engine needs, it depends on VE, RPM, and scavenging, though the Buick 350 is special in this regard with its intake and head runner design. In this regard, bigger is generally better, up to a point. This is why the large base 2g (or other large throttle blade 2 barrel) does well on it. It works well with a 350-500 CFM 2 barrel or a 600-650 CFM 4 barrel (non-Qjet) in stock form. Others will say to overcarb it for the reasons mentioned previously, not realizing that the Qjet doesn't give the full 750 (or 800) CFM potential on engines with less air/fuel demand. If you can afford it, a Holley 650 double pumper would suit a stocker nicely, or a Holley 500 CFM 2 barrel, particularly with the exhaust mods suggested earlier. Another advantage a 2 barrel has is the even fuel/air distribution, since the carb sits centralized on the intake, unlike any 4 barrel's primaries, for better fuel distribution from partial to full throttle. I've nothing against a good ole Qjet either, and is an excellent choice for cruising around and having some punch when you need it. More control over your power is had with a large 2 barrel, however. Imagine how you'll drive it and choose accordingly. Gary
I can't say for sure but I think the torque come up on the 2 barrel for another few reasons beside as Gary mentioned. The carb barrels are centrally located above intake track and the 2 barrel Venturi sits higher in carb with a larger float bowl and as can be found the the Buick like carb spacers and the 2 barrel sits higher giving more straight down fuel mixing time . I'm sure Gary has a thought on this. Also the secondary's are huge and direct fuel toward rear slightly. So I assume location of carb means a lot. And with the 2 barrel you don't need 50% or more opening to engage a secondary system which itself drops velocity of air flow some so you have greater control over the throttle opening . Just thoughts no facts but again I'm sure Gary might have something
That's a pretty good description. Before anyone knocks the 2 barrel's potential, check out what one can do on a racing engine: [video=youtube;u2H1vSn7Jcc]https://www.youtube.com/watch?v=u2H1vSn7Jcc[/video]
And with the bigger 2 barrel carbs they have been tricked by some carb builders to flow 600 cfm. That more then enough to feed a 4500 rpm purpose built low rpm torque monster easily .
More 2 barrel info: http://www.camcraftcams.com/index.php?page=cam-failures To quote a bit from it in terms of understanding CFM flow: "Now is a good time to understand carb flow ratings. 2 barrel carbs are rated at 3 inches of vacuum and 4 bbl carbs are rated at 1.5 inches. A 650 carb on a 358 cubic inch engine will seldom see 1.5 inches but a 350 carb on the same engine will frequently see 5 to 8 inches. At 7 inches of vacuum the 350 carb is really flowing about 430-440 cfm." Unless you're going all-out racing, I don't think you need any more than 350-500 CFM 2 barrel carb. Gary
Here's a 1970, bone stock 2 barrel engine (according to the poster). These were rated at 260 hp 360 ft. lbs. from the factory. [video=youtube;pvMrc1aciNQ]https://www.youtube.com/watch?v=pvMrc1aciNQ[/video]
Well yeah on a larger opening, 4 barrel intake. The engine pulls harder on a 2 barrel, which will have higher vacuum, so yeah the CFM ratings will vary. A 2 barrel engine is not a max effort piece. It's designed for good (even great) power within a low-mid range (1500-4500 RPM) powerband and a wider powerband between the peaks, making it ideal for street use and taller gearing (on the Buick 350). You know, the fun stuff. For max effort 2 barrel setups, opening up the carb (CFM mods) as much as possible for slower velocity is desirable. This goes against the 4 barrel mindset, I know. The 2 barrel moves air so fast it needs to slow down a little as you get into higher RPMs and larger cams/heads/headers etc. This will give lower vacuum and put it closer to the lower vacuum rating. For a stocker or mild street engine, it seems 350-500 CFM wet flow rating is the sweet spot on a 350 CID engine. Google is your friend. Tons of info on this kind of thing with circle track racing. Look how wide the powerband is on that 2 barrel racing engine video I posted earlier. From about 3300 RPM to 8100 RPM, on a 320 CID engine producing over 520 hp. Don't forget about partial throttle performance either, where you spend the majority of your time. Gary
For max hp / top end Max torque will alway be lower in rpm so cfm isn't so important but hi velocity air flow and mixing of fuel will create more torque.
Correct, I know this thread was concerning maximizing low end tq, but im sorry if you take two identical 71 skylarks with 350 engines of equal health one with whatever exhaust pipe science you wish and a two barrel carb and one with a 4bl and 2.5 duals, ole 4bl car is gonna run off and hide from the other
Not many people are familiar with 2 barrel performance (outside the choked off stocker they replaced), and so in their ignorance will always claim their experience with 4 barrel engines to always be superior. If you don't understand simple math and science, then the information in this thread will appear alien and impossible to you. Look at the videos and do some research for yourself. It's easy to poke fun at things you don't understand. It's simpler. You don't have to do any real thinking. Take the same '71 engines (assuming one works equally well with a 2 barrel as it does a 4 barrel, and are equally tuned properly. THIS is important for this comparison) and assume they both have factory gearing (somewhere between 3.08 and 2.73 let's say) with a factory stall. Which one do you think would perform best at partial throttle? Or even at wide open throttle, which one do you suppose would take off faster? My Skylark with a 350-2 walked away from a Mopar 383-4 up to half way through second gear, then the 383 finally passed me and ended with him about one car length ahead, and that isn't even comparing two SIMILAR engines. According to the specs and the paradigm, he should have blew me away from the start. But he didn't... Through an obstacle course where many speed-ups and slow-downs occur (and partial throttle curves), the 350-2 ate the 383-4 alive. Remember there's more to driving than 1/4 mile straight line full throttle runs. Past 4500 RPM the 4 barrel engine would shine vs the 2 barrel of course. But on a stock engine, the cam won't have much life left to it to matter. Gary
And performance is measured by et and speed in ALL motor sports , no events I know off that give trophies for almost winning or who has better part throttle pull from 30 to 70
Using a 350 2bl for anything other mundane transportation, is my mind pointless, I understand you gotta start somewhere, we all did, but trying to devise complex procedures and theories for scientifically optimum performance on a 200hp engine in a 3500lb car confuses me a little
As far as 2bl performance goes im familiar with it , and have seen more clapped together dirt cars than one can stir with a stick run quite well as well as a certain 351 mustang that runs the FAST series stock appearing and made over 675hp I believe with a 2bl, but ive owned and driven more Buicks than most anyone my age and have done quite a few 2 to 4bl swaps. And yea the idle to 25mph performance is snappier with the 2hole but after that is out of breath. Just my experience
