Norm Schenck at Competition Fuel Systems has been dyno testing Stromberg 97 and BIG97 carburetors for us for year. In fact he had a major hand in developing the BIG97 from scratch.
We set up a dedicated dyno motor at Norm’s facility in Vassar, Michigan and we’ve been watching intently as horsepower has grown with small tweaks to the carburetion and heads. This set up is with the cast iron vortec heads, that Norm ported himself. We have a set of AFR CNC ported heads waiting in the wings and they would probably make more power, but Norm suspects that the limitations of the Edelbrock tri-power intake would not have allowed for much more flow than was achieved with the vortec heads.
Want to know the numbers? This is a GM 330 horse crate motor and the best we got this time (by taking off the mufflers) was 404 ft-lbs of torque at 4300rpm and 386HP at 5400rpm. We still made over 400/380 with the mufflers on. This was on 89 octane gas with top end A/F ratios all in the 13s ! The dyno can now read separate A/F ratios per cylinder.
What this motor will do once someone (ie us) develops a new intake for the BIG97s is anyone’s guess. But it will be impressive, you can be sure of that…
We have been testing our BIG97 carbs recently to see how much cfm we can get out of a modified carburetor, with our consultant Norm Schenck at Competition Fuel Systems in Michigan. The vertical manometer shows the vacuum pulling air through the carb – 20.4″ H2O, which is 1.5″Hg. The handle on the front of the flowbench, below the carb, is set on the 400cfm scale. The inclined manometer shows the volume of air going through the carb as a percentage of that 400cfm scale. In this case, 77% of 400 is 308 cfm. There is a probe inside the 5″ cylinder below the carb, with a small correction factor that makes the airflow correct in term of the Superflow flow calibration plate. Applying that correction factor brings the flow to 300.5 cfm, though what looks like a regular Stromberg 97!!
If you’re planning a big engine build and want some serious cfm capability, contact Norm at Competition Fuel Systems – email email@example.com
Watching a BIG97 equipped Cadillac 331inch race engine (out of an Allard) on the dyno is not something you want to miss. So off we went to Connaught Competition Engines in Kent, UK, to watch and help with jetting and tuning. The way the driver wanted to go was with three BIG97 Primary carbs for this engine, on a direct linkage. The old Edelbrock intake was opened up to take the bigger throttle bores. And the final results? Not bad for an old Cad motor!!
405lb ft torque at 3500rpm and over 350hp at around 5500rpm where these old intakes max out. Best of all, the BIG97 added some 40hp over the regular 97s, even with that old style early intake manifold. We didn’t even have to change the Primary stock jetting (0.56inch main jets). And there were no issues with residual fuel pressure on shutdown, either.
Big thanks to Phil at Connaught Competition Engines for driving the dyno, and Gus Gingell who built the engine.
Want to know more about BIG97 Tri-Power installation? Watch Bob ‘Bleed’ Merkt modify his Chevy intake manifold and install the carburetors, linkage and fuel line on his 1932 Ford Panel. The Stromberg BIG97 Tri-Power base castings may have the same external dimensions as a regular 97, but on the inside you’ll find bigger, offset throttle bores with flared exit cones to increase airflow capability and improve air pressure recovery. The intake manifold modifications recommended here (click this link for a print-out) enhance that effect, adding even more potential to your BIG97 Tri-power. Another great video, awesomely directed and filmed by Piero DeLuca.
Stromberg 97 carburetors ( regular and BIG97 ) have gained some superb coverage in a major feature in January 2016 Street Rodder. It’s all about flathead Ford intake manifolds. Navarro, Edelbrock, Sharp, Offenhauser and more (all of which can work with the BIG97, of course). Written by Ron Ceridono with help from Kev Elliott and Mike Herman from H&H Flatheads, it’s also available online. You might find the online version a little easier to read. Click here to check it out! Here’s a couple of excerpts:
“Thanks to Mike Herman we were able to gather photos of the most popular intake options H&H currently offers for early (1932 to 1948) and late (1949 to 1953) Flatheads. While the manifolds look similar there are significant differences. The positions of the carburetors on two-two manifolds vary and as a result some require moving the generator, others don’t (manifolds that accommodate the generator are often called regular dual, while those with the carbs further apart are usually referred as super dual). By spreading the carburetors further apart they have a straighter shot into the ports and fuel distribution is improved but relocating the generator requires a head-mounted bracket. Some manifolds are equipped with exhaust heat, others aren’t. In cool locales with today’s fuel exhaust heat can help driveability, in hot climates it’s not normally necessary. All the manifolds shown here accept the stock-style fuel pump stand and the oil filler/road draft tube for 1949 to 1953 applications. Another difference is the number of bolts used to secure the manifold. Due to the shape of the runners, in some cases, the number of bolts has been reduced. On the other hand, in some cases, there are more holes in the manifold in the block, but in either case it’s not a problem.
Although all the manifolds shown are good, some manifolds may perform better than others with a given engine combination. The best bet to resolve that issue is to deal with an expert on the subject like Mike Herman.
Stromberg now offers a larger version of the 97. Completely reworked internally, they flow 250 cfm, compared to the original’s 165 cfm.”