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south65ss 04-30-2012 10:09 PM

How to tune dual Strombergs??
H everyone!
I just acquired an Offenhauser intake for my 51 Mercury flathead and I already have a pair of old Stromberg 97s. Should I modify one or both of them to work in pairs? Whats the deal tuning this things? Any tip or trick will be very appreciated!

Thanks in advance!

timothale 05-01-2012 08:05 AM

usually both
usually both open at the same rate. years ago my brother had 3 on his merc. they used a device over the carb to match-tune them, I was 11 or 12 and just watched. there are a lot of guys on the HAMB web forums that run flatheads, here chevy V8's are most popular.

AutoGear 05-01-2012 08:24 AM

Get a Uni-syn and make friends with a guy in his 70s.

Irelands child 05-01-2012 08:50 AM

First of all - make sure those ancient Strombergs (97's? 81's?) are any good. They do wear out, leak air and/or gas and can be a general PITA to make work right at~75 years old. Once you are sure they are in good shape, with a good neoprene or other space age material instead of steel-on-steel inlet needle and seat, a neoprene accelerator pump instead of the leather originally used, the throttle shaft not leaking air, identical jets (you need a special wrench for them), you are ready. While that Uni-syn is a nice tool, it really isn't needed for a dual set up. Adjust the idle screws to seat, then back off 3/4 to 1 turn then start the engine. Use a vacuum gauge and work those idle screws to the best at idle setting - you are then done - go for a ride. Enjoy.

A couple of points - if you have an original distributor, that vacuum advance will not work correctly** - there is no mechanical advance. Next, those two Strombergs together might not be much if any bigger then that screwy looking original "back draft" carb used on Merc's, hence no real performance improvement. The Holley's used '49-'53 and a variation '55-'56 are a bit bigger, more readily available, cheaper and with parts easier to find.

BUT - it sure will look nicer


John long 05-01-2012 06:35 PM

All good information from IC. One other thing to consider. All the old Stromberg and Holly 2 barrels ford used on the flatheads were bad to leak fuel. They can not stand much fuel pressure. Running a fuel pressure regulated at about 3 1/2 pounds will save some grief as well as a fuel stained intake.

Flatheads for ever! :)
John L

John long 05-01-2012 07:04 PM

I know I am getting a little off subject here but since you are asking about improved carburation let me throw something else out. You can buy a centrifugal advance electronic distributor fairly reasonably priced from Speedway motors or similar supplier. Also it is fairly simple to modify an early Chevy distributor to fit a late flat head. I am running a Chevy distributor, Holly 390 cfm 4 barrel carb combination. This solves both the fuel and vacuum advance issues. The Holly supplies the correct vacuum the Chevy distributor is looking for. The distributor obviously must be recurved. I think I originally found the information for this conversion on the Ford Barn Forum.

John L

timothale 05-01-2012 08:13 PM

hammered carbs
I used to carry a small hammer and when I would smell gas I would stop and raise the hood and tap until the leak stopped. I'v seen a lot of hammered carbs at the swap meets. In the old days the old timer said to carry a hammer.

south65ss 05-01-2012 09:26 PM

Ok people, will try and post results. Thanks a lot!

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