I have a 364 Buick Nailhead that I intend to use in a street rod project. I am not looking for performance and just want it to run good and look cool. It is a factory 2 barrel Stromberg which runs like crap. Kits are over $70 and I really don't intend on keeping that carb anyway. I have a Rochester here, that from the numbers, appears to be a 62 Chevy 283. The butterflies measure 1 3/8" just like the Stromberg. I doubt if this actually relates to actual CFM, but I would like to use a Rochester carb like that. Does anyone know the actual CFM ratings for those 2 carbs? I might get scolded for this, but future plan is to try to make a "fake" tri power setup and that is another reason for the Rochester vs the Stromberg. The Rochester physically bolts onto the 364 but it is just a parts carb for test fitting. I will be running stock cam, A.T. and highway gears. Low budget geezer type project so buying an expensive manifold/new carbs is not in the plan. Any suggestions appreciated as usual. Thanks.
Don't know anything about those carbs, but the best carb is usually the one you can tune perfectly for the engine. So how available jets etc. are is important, possibly the price of the jets in case you back off buying all you need for trial & error testing because it gets expensive, you need knowlege about tuning the carb and while there are books about some models others have no accessible information at all. Doesn't matter how good, cheap or expensive a carb is, if you can't tune it all it's good for is sitting on a shelf looking pretty.
The large base Rochester 2G used in oval track racing is about 500 cfm on the flow bench. The Venturi is bored out and it would lose some responsiveness down low. Normally the 2G is rated between 225 cfm [small base] up to 425 cfm depending on OEM application Your 283 2G would be a small base and 225 cfm. For a Tri-power centre carb you would need a 2G with the side inlet for the fuel line or there is no room for outer carbs. I used a side inlet 2G on my 57 [which is incorrect] but I wanted to convert to Tri-power later. I also added electric choke which is more reliable. The 2G is very responsive down low on my 283 [it has diesel like manners] but cam and compression choice is important.
My neighbor had a few of the Rochester 2 bbls and he let me borrow 3 of them. 2 were the bigger base with front inlet. The 3rd was the small base which fit my Buick manifold and it has the side inlet. It looks just like the one you show here except for the choke. Mine actually has a crack in the bowl and it is pretty much junk and good for mock up only. I figured that would have to be my choice to be able to fit 2 more on it. The front inlets just wouldn't leave room. I ordered a new Chevy carb base gasket that I am going to use to compare to my Buick manifold to make sure it will seal up. The Stromberg that is on it now is bulky looking and the Rochesters should be more plentiful and cheaper. Thanks for the tips.
If doing a fake tri power, why not one Stromberg, one Rochester & one Carter? You might be the first on your block...
Interesting. I've never played with the Rochester 2G, but am keen to learn. What differences occur in the various OEM 2G variants that make them capable of flowing 100% more? Is it just venturi size (the BX Strombergs were like this... lots of different venturis in the same type of carb = lots of different CFM ranges, albeit not 100% more)? Cheers, Harv
For best results, measure the large venturi on your Stromberg, and look for a Rochester with the same venturi diameter. Many of the WW's used on the 364 used a 1.281 main venturi. In the FWIW category, the Stromberg WW as used by Buick is an excellent carb. They do have one issue: the aluminum throttle body. Just like the Rochester Q-Jet, higher mileage Stromberg throttle bodies need to be bushed. Occasionally, one will require replacement of the throttle shaft. As to CFM, don't recall any factory ratings on Strombergs, but they did make a few that flowed pretty well Note the EE-1 (marked "97") on the right. Jon.
The small base and the large base 2G's are different animals with different manifold bolt patterns. The small base 2G flows 225 to 278 cfm The large base 2G's came in four sizes 352, 381, 423 and 435 cfm Venturi sizes were 1-3/16", 1-1/4", 1-5/16", 1-3/8" respectively, The 1-3/8" can be easily bored out in a lathe to flow 500+ cfm but these carbs are "flat as a turd" down low. Which is why they are only suitable for oval track racing [where rules require a 2 barrel] For a street application a quadrajet is the ideal carb with small primaries and large secondaries. Some Tri-powers used a small 2G as the centre carb and 2 large 2G's as the outer carbs with a progressive linkage. [basically a spreadbore tri-power] A large 500 cfm 2G as a fake tri-power would be worse than 3 x 225 cfm 2G's for street manners. I was playing around with Dellorto side drafts on my Lotus Cortina [I had a pair of 40mm's and a pair of borrowed 45mm's] Both carbs combinations made the same Hp with the same size chokes [34mm] BUT the larger carbs had more power down low than the smaller carbs. The reason was the 40mm Carbs with 34mm chokes had almost no venturi whereas the 45's with 34mm chokes did. Above 4000 RPM both were the same, so we used a 5.0:1 rear end and a close ratio "rocket" gearbox to cure this.[rev it to the stratosphere ] there was massive gasoline "wash" on the inner fenders at low rpm I am not a fan of boring out venturi's unless the rules dictate this sort of innovation .[sometimes called cheating] Just get a bigger carb. We normally do "reverse calculations" when using a control carb for racing. A race engine needs 1.67 cfm per horsepower at wide open throttle [this can be fudged to 1.43 with unlimited compression and cams] So a 500 cfm carb can feed a 299 hp engine [up to 350 hp with a 13:1 + engine] If the 300 hp engine was 350 cu inch , it could rev to 4937 rpm before it's volumetric efficiency drops off [with a 500 cfm carb] So peak torque needs to be at or under 4937 rpm. To get 300 hp at this RPM the engine needs 319 ft/lbs torque @ 4937 To get a flat torque curve we would want the torque to be a lot higher below this rpm [380 ft/lbs @ 3800 rpm] This ^^^ would net 275 hp @ 3800 and 300 hp at approx 5000. So the cam profile would need to match this. Horsepower is the size of the bang multiplied by the number of bangs per minute [Keith Duckworth]
The Jalopy Journal
