Hi all, Looking for some advice from the hive mind. I've been presented with the opportunity to buy a pair of Stromberg BIG97's at a very good price. Will two of these carbs prove too much for an 8BA engine? A regular 97 does 162CFM so a triple setup would be 486CFM. The BIG97 does 250CFM, so two would supply 500CFM. Also there are three types offered, want to make sure it's the right one for my engine. They have a standard one, a cable choke version, and a lz push throttle. Which would be best for an 8BA? Thanks
The first concern is what are you going to do about the distributor. An 8BA uses a proprietary advance system known as a "Load-a-Matic" The general consensus is that the distributor will only work properly with a strictly stock single carburetor. (The "Big 97" does not supply the proper vacuum signal to the distributor.) Also, we need to know more about the engine. How big is it (cubic inches); does it have a stock or aftermarket camshaft; have any other modifications been made to the engine? More information please.
Thanks Tubman that's good to know. The upgraded carbs will be part of a rebuild I'm planning. Currently the engine is a completely stock Merc 8ba, but it's a getting tired hence the rebuild. So sounds like I'll need to upgrade the distributor (any suggestions?), had already planned to upgrade the internals as part of the rebuild, and add aluminium heads. Already running 4" crank as standard. Any suggestions on the different types of BIG97? Thanks
As to distributors, you basically have 2 choices : an old Mallory dual-point or an SBC distributor converted to flathead use by someone like Charlie Schwendler in New York. I have Mallory dual points (mechanical advance only) on a couple of engines. and like them fine. The converted SBC units can be had with vacuum over mechanical advance, which may be a little better for fuel economy, but I prefer the old Mallory's on a "looks" basis. I'll volunteer a couple of upgrades you might want to consider. First, if you are going to replace the pistons, I would opt for a 1/8" overbore which will yield a 276 ci engine. The cost of pistons and machine work should be a "wash" between this and a smaller bore, and extra cubes are always welcome. Second, before you install the heads, you should blueprint them to come to a compression distance of .045 to .050" (quench). If you haven't been on "The Ford Barn" forum yet, I would go there and check out a thread by a gentleman named "GB Sisson" titled "A 276 flathead from 35 years of parts". It is quite long, which makes it quite comprehensive, and some of the most experienced flathead builders around have chimed in with tips and tricks. It's more of a "stock type" rebuild (no cam or carburetion changes), but shows the basics for a good running engine. As a matter of fact, the fired it for the first time yesterday and everything points to the engine being a real winner. As to what type of "Big 97" to use, I don't have a clue because I am not familiar with them. The type of choke would seem to be more dependent on the actuating linkage in the vehicle rather than the carburetor. Good luck with your build.
I run across statements like this from time to time, which mystify me. You do realize that you are running with no advance at all, don't you? Even Model "A"'s had an advance lever on the steering column. I think you would be well served to try mounting a distributor with a properly working advance and I think the term "works very well" will take on a whole new meaning for you.
Thanks for your help! Might go for the Stromberg e-fire distributor (sacrilege I know) but probably easier for me to get hold of in the UK than the options you suggested.
That will probably be fine. Just check that the distributor has a Ford advance curve (2 2to 24 degrees total advance). Some times, aftermarket distributors come with a SBC advance curve (36 degrees total), which can lead to problems, overheating among them. I had an MSD setup that had just this problem years ago.
The Big 97 was really made for OHV engines. It’s made for bigger engines running multiple set ups. A snotty 350 or a big Olds or Buick could really use the extra cfms that the Big 97 provides. In my opinion it could be run as a single on the right engine. A good example is a Ford Y block with a 3 Bolt intake. As Tubman said, the 97 has to run with a distributor with mechanical advance. In 1957 Ford went to a mechanical advance distributor on their V8s. In summary the big 97 would be a great consideration for an Y block running the 57-64 distributor. I think the Big 97 can be a candidate for the 8BA but only as a single and only with the distributor change.
Thanks for your reply. I've seen lots of people running triple carbs on Flatheads, why do you say it would only need one BIG97?
Because 97s are small. The big 97 is well...... big as far as CFM. It is similar to the large Y block 3 bolt 2100 in cfm size. 2 97s are great on a warmed over flathead. 2 Big 97s that’s really too much. Actually they make a Stromberg 97 that’s rated the same as the oldStromberg 81. The smaller 81 rated size would be great for triples or a single on a warm 4 banger. Last I checked...... They have small....81 rated Regular.......Original 97 Big.....Big 97.
I'm running an 8BA with dual 94's with progressive linkage and a stock distributor, I picked up the vacuum off the primary carb and it works great. I've put a timing light on it and it advances, didn't degree the crank pulley so don't know the actual degrees advance.
Ok now I’m confused. I have three 97s with the “97” in a circle and one carb that has a small “97” stamped on it. So what is a BIG 97? Is that the newer aftermarket carb?
Flatheads are just like any other engine, the more you build it, the more fuel it requires. A lot of guys like the look of three 97s on a "warm" flathead (when I hear that descriptor used the engine usually has aluminum heads and intake, some chrome covers on the head bolts and 2 of the carbs blocked off). You don't put a 850 CFM carb on a stock SBC (or a hot one for that matter) IMO. 500 CFM on any engine is right up there, whether or not it will run nice depends on what you do to it. A stock Merc with 500 CFM is a possible mismatch. Bore the merc open, up the CR, cam it, and run those carbs progressive (if the intake allows it) and you may be alright. You're in England, call Clive at Stromberg and have a chat with him since you talk the same language. He'll help you out. One of the nicest and most knowledgeable Stromberg guys in any country. I run three 97's on progressive linkage that I sourced from Clive. I have a merc 8BA, .125 over bore, 8.5:1 CR, ported, relieved, 471 blower (8pounds of boost), MSD ignition, no vacuum advance. I told him what I was building, he supplied the carbs. Regular 97's not big 97's. I am quite happy with it years later. I guess he was right.
Now this I can understand. At least the basic rudiments of the "Load-a-Matic" system are still in place. Whether it provides optimum performance or not is beyond the scope of this discussion. It might show up an a series of comparative dynamometer runs, but probably not in a "seat of the pants" comparison. I noticed you said "primary carb". If you are running a progressive linkage on a dual setup using what I call a "biased manifold" (where the front carb is being run as the primary), I have no doubt that this probably works excellently, as the primary is essentially in the same position as a stock manifold. The jury is still out as to the performance increase gained with something like this compared to more conventional dual setups (especially a "Super").
@MattCUK did you read this today? Sound familiar? https://www.jalopyjournal.com/forum...ch-8ba-too-rich-cruise.1319102/#post-15281864
Yes as a matter of fact that's the Offenhauser manifold I'm running and the secondary carb opens at about 2/3 throttle. I ran it with solid linkage for a while but was never happy with it and runs better with the progressive linkage.
Just to confirm; you are running the front carb as the primary, aren't you. With that type of manifold, I don't see how a straight linkage would work at all well.
merc v8's were not 8ba's they were 9cm's 2 97's they ran fine, when we ran 3-97's they tended to over fuel
I've literally just been on the phone to Miles @ Jackhammer in Farnborough this morning about everything Stromberg for my stock 8BA, he recommended a 'normal' 97 for stock or a single BIG97 for a warmed over motor both with the efire dizzy
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