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Technical Wich carbs to use on a flathead?

Discussion in 'Traditional Hot Rods' started by Kedde, Nov 2, 2017.

  1. Kedde
    Joined: Feb 1, 2007
    Posts: 61

    from Denmark

    Hi. I havent posted here for years, but I have been lurking alot, and your knowledge have been a huge help through my project.
    But now I need some guidence on wich carbs would suit my project best.

    I have two very nice rebuildable stromberg 81s and I allso have a pair of equally nice 97s.

    The engine in question is a 59-AB with stock 3 3/4 crank and .030 over. The cam is an old Harmon Collins 3/4 race with 258 duration and .355 lift. The intake and exhaust runners have been cleaned up and the ports matched, and the block is relived
    It has Edelbrock heads and about 8-1 compression ratio.
    The intake is an old Edelbrock regular tall dual manifold.

    And it all goes into a fenderless 1929 model A coupe. The transmission is a stock 39 ford unit with a 28 tooth cluster. The rearend has 3.54 ratio and the rear tires are 700x16.

    Would you use the 97s or are the 81s enough?

    Im hoping you all have some thoughts on this.


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    Last edited: Nov 2, 2017
  2. Hombre
    Joined: Aug 22, 2008
    Posts: 801


    I believe you would be happier with the 97's over the 81's simply because the 97 is a easier carb. The 97 is very popular thus there is everything under the sun available for them. the 97 also is a 155 cfm carb while the 81 is a 125 cfm carb. The 81 was only available for the V860 and only produced for a year or two I believe this makes them what some people call rare. Rare does not mean better it means rare.
  3. cs39ford
    Joined: May 1, 2012
    Posts: 748


    dana barlow likes this.
  4. Kedde
    Joined: Feb 1, 2007
    Posts: 61

    from Denmark

    Hombre thank you for your reply. The 81 is exactly the same carb as a 97, it's just smaller, and everything is available for the 81 too. So the rarity or the complexity of the carb is of no concern to me. The only thing im concerned with, is to not end up with an overcarbed dog of an engine... Or an undercarbed engine for that matter.
    If the engine was othervise bone stock, I would no doubt go with the 81s. But im very much in doubt with the setup I have.


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  5. Petejoe
    Joined: Nov 27, 2002
    Posts: 9,985

    from Zoar, Ohio

    Many Flathead’s ran multiple 97’s with no
    Problems. Just adjust the jet size to its liking. Two carbs no problem Three carbs are a struggle but possible. Don’t overthink this. You will be fine.
    razoo lew likes this.
  6. porknbeaner
    Joined: Sep 12, 2003
    Posts: 40,987


    I prefer the 97s but I cannot give you a legitimate reason to not use the 81s. Just that I prefer the 97s.
  7. Bandit Billy
    Joined: Sep 16, 2014
    Posts: 5,230

    Bandit Billy

    I went with a trio of 97s on my flatty. If you like driving your car, I'd go with whatever is easier to service and find parts for.... wherever it is you break down. :cool:
  8. If you doubt the use of the two carbs together, then set up the linkage do you can run them progressive if needed.
    310 cfm is not an overkill for a 239 cid engine.
  9. AngleDrive
    Joined: Mar 9, 2006
    Posts: 666

    from Florida

    97's, 3 is a nice round number
  10. Koz
    Joined: May 5, 2008
    Posts: 2,165


    I know you have the 97's which are the traditional favorite however, I personally like Holley 94's. They are for several reasons a vastly superior carb. Much easier to tune and much less prone to leaks. Like the Strombergs, everything is available for them as well and good cores are generally available and cheap. My choice for a driver.
    drylakespeedshop and chiro like this.
  11. flathead4d
    Joined: Oct 24, 2005
    Posts: 875


    97's. I run three on my 286 CI flathead and straight linkage. As was said above, it's all about proper jetting.
  12. carbking
    Joined: Dec 20, 2008
    Posts: 2,500


    CFM in a multiple carb environment is NOT an additive property!!! Two 125 CFM carbs do not add up to 250. Depending on the efficiency of the manifold design maybe 175~185.

    Two 81's, with perfect spacing on the engine, and running solid linkage MIGHT run as well on your engine as a single 97. Maybe a tad better, due to the spacing, but not because you have more CFM.

    Two 97's, with solid linkage will not overcarb your engine.

    Besides, somewhere out there is a Model A dude with a 4-banger that would just love your 81's

  13. Hombre
    Joined: Aug 22, 2008
    Posts: 801


    I would have to completely disagree with you on a couple of points. In no way and in no universe is the Holley 94 Superior to the 97. It for sure is not inferior either, but vastly superior? I rate them actually pretty close, the Holley is not as easy to tune as the Stromberg and the 94 is prone to leaks for the same main reason the 97 is and that is fuel pressure, both of these carbs don't like pressure over 1 to maybe 1 1/2 lbs. One problem with the 94 is when it does flood it does so at the float bowl vent tube and the fuel is dumped into the top of the carb. This raw fuel is not a good thing. The Stromberg is no damn better as to much pressure and it leaks out of the top of the fuel bowl and leaks onto the manifold. neither is a very good thing, but both carbs leak unless you do your part.

    I think most folks who have messed around with these old carbs will agree that the 97 is easier to tune as well. The vacuum operated power valve can be a problem on the Holley in tuning that carb. It certainly is tunable but not quite as easy as the Stromberg with its mechanical operated secondary is easier to tune.

    Both the Holley 94 and the Stromberg 97 are pretty good carbs, they both have there Pro's and Con's though. Both are pretty simple when you get into them, both are not the best design carburetor but both will get the job done, but one "Vastly" superior to the other--not in my book.
  14. mwhistle
    Joined: Feb 19, 2007
    Posts: 308

    from sacramento

    I've been using 97s for years and they are simple to work on. The good news is that the Strombergs are now being reproduced with many accessories. Go to for complete information including multicarb use.
  15. 36fordguy
    Joined: Feb 13, 2007
    Posts: 22


    Holly 350 4B -Good everything over the 97 or 94 36fordguy
  16. Koz
    Joined: May 5, 2008
    Posts: 2,165


    Hombre.... send over all those 94's you don't want. I'll take 'Em anytime over a 97. I admit both carbs work well and are a piece of cake to work on. Holley 94's replaced the Strombergs for a reason. Like any other part of the engine, (and the rest of the drivetrain), as long as everything works together your good. I stand by my original opinion, the Holleys are the better carb. This fellow is lucky in that he has the carbs already. Market conditions make the Strombergs several times the money of the Holleys around here. They do look cool I admit, especially large logo Strombergs.

    The best running setup I've ever played with on a flatty is a 390 Holley on the Offy 1079 with a 1 1/2" spacer. Super streetable smooth power in a reliable package but who wants to look at it?
  17. This is kind of like arguing whether you like Sprint, Verizon or AT&T . . . for everybody who loves one, the other guy hates it! LOL

    The 81's are a bit small for your cubic inches - so go with the 97's. ALL these carbs are easy to work on - as long as you know the basics of working on carbs, know how to tune, can synchronize them and have the patience. It is the same set of problems - just in different packages.

    Good luck!
  18. Fred A
    Joined: May 3, 2005
    Posts: 267

    Fred A
    from Encino, CA
    1. Upholstery

    Ran some of these considerations years ago and thought I had it figured too. Reading some of the replies couldn't help but chuckle a few times. Reading along and the advice however convincing, then comes the punch line where I wonder where they get these ideas. Back to the question: Most of my assumptions and preferences started from when we could still real gasoline. Difference seems to be that enrichment with current Peoples Republic fuels is that enrichment comes in too soon. In the case of Chandler Groves design carbs, any shift toward delay of the power valve like choosing a lower number even in the case of a single 94 reduced my wet plug problem I saw even with a single carb. I have also used 81s in pairs and wondered why I didn't just use the Holley 92s (no not 94) and back off a couple of points on the power valves and jet from there. Kedde's engine is really not very large and the third carb would not be worth my money to achieve the cool factor vs the increased work to make it run right. For the 81s or the 92's I found the so called poor performing common Thicksten PM7 manifold (per H&H report) great, forgiving my ignorance of such quoted wisdom. Good Luck sorting this one out. Fred A
  19. Heck, another option . . . rebuild both sets of carbs (making sure you have the right parts for each), try them both on the engine and test on the road, keep the set that performs to your liking. You can easily sell the other set of carbs. That is probably what I'd do. When you're in the rebuilding mode - doesn't take much longer to do four than two.
    Jet96 likes this.
  20. Look good = 97's or 81's, run good = small 4 barrel hidding under a Hellings air cleaner.

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