We do things sometimes not from logic, but from passion. I love tinkering. I listen to the heavy hitters, 286Merc, Bruce Lancaster and many others and take great joy listening to their expertise. I suspect these two and others would say 2X2 pro is possible, but fussy and unnecessary. Many would say forget it...I have read the forums. I am asking as I look at the performance of my stock (dual Fenton header exhaust) 37,000 original mile lowered '51 Ford Custom V8. After exercising and tuning this remarkable barn find left to me by my father on his deathbed last year, the old girl runs like a champ. However a little tight on carburetion, with the 94 and the stock vac loadamatic distributor. I know. Ok. Amazing fuel efficiency and driveability. Why change anything? As I said, she's a little tight and would open up with more cfm. The stock heads and cam work fine. We all want more, AND the old look. I have a beautiful mechanical advance Mallory, I have a Offy 2X2 59AB style regular (early model on late for a reason), drilled for under-the-manifold PCV system to cut blowby...and a growing stash of 94's and a 6V electric fuel pump. SO...if you really worked at it...I can almost hear the arguments, I want to hear them, what if I dumped the Loadamatic for the Mallory, tweaked a 1 and 1/16th's Y-block 2110 rigged like a 94 (which it's not but close with more cfm) with a near stock PV jetted .51-.53, eliminating Spark Control Valve and progressively brought in an AA-1 secondary spec 94 at approximately 60-70% throttle with let's say a 2.5 Hg PV? If I did it right, it would work like a mechanical secondary 4 bbl.? I would use one but I love the 2X2 look!
You are looking at a factor...linkage...that is not terribly expensive. Why not go all empirical and just assemble what you are discussing for good road testing? The linkages are generally fully adjustable, and can also be adjusted to non-progressive. So just do it and see how it feels. After a subjective test, if both seem viable, try it out with a stop watch or an acceleration meter and report actual numbers, and driveability issues or benefits, etc. Your setup would be entirely driveable without progressive, so testing it with progressive leaves you with a perfectly good fall-back position if you don't like it. Difference from 4-barrel would be that both carbs are off center. Is this a real problem? Runnit and tell us! An alternative exploration route for a mild car...Mercury four bolt manifold to try with Rochester carb or 318 Plymouth type carbs.
So glad you responded...I read everything you write! It just seems to me that (and you should see the piece of home-engineered linkage that I have put together, put a lot of thought and effort into) adjustable, smooth transitioning linkage with stock sea level jetting (Boston area) and lower Hg PV in secondary with perfect seal 12 degree throttle plates on the relatively close spaced Offy 1090 should work. The torque curve is so good with the limited cfm and vacuum signal of the single 2bbl. Do you think a modified big venturi 2110 (which offers a good 45 plus more potential cfm) would be too much as a primary? As you say I can swap back if needed. I'm getting pretty good at rebuilding 94 type carbs. Would just love to have the 2700 rpm plus top end really open up before the cam falls away, while preserving that low end driveability.
Try it as primary, try it as secondary! Experiment! I suspect the smaller carb as primary would be best, to get the car running on main jets fastest, then bring in the other farther up the curve.
Cool. I had at first rejected the 2110 until I read the specs. Virtually everything interchanges with 94 parts, and the thing was in great shape with no slop and tight throttle plates. I know some guys use it as a primary in 3X2's especially Y-blocks. I suspect you could use it solo too if jetted right on a stock/mild flatty. I am not a fan of over-carbing, the math (and driveability) never lie. I have a sweet concealed PVC setup designed and ready for install, Chrysler V6 over the counter valve split into two ports, one injecting into each plenum for even pull. I am running NGK B6L's which phenomenally better than anything I have used, and using Shell Rotella HDMO 15W-40 and Fram C4P (stacked media type)filter also working wonders. Also a 6.5" air filter, flowing much nicer, plugs are a nice light brown all 8. She's running so well, might not change it 'til something breaks or wears out!
I set up 2 progressive 94s on my friend's '51 Ford. We got the parts from Vintage Speed and we used the aluminum secondary base (with fully closing butterflies and no idle circuits) and we plugged the power valve on the secondary. We used the rear carb as primary because the linkage was easier that way. He's been running it about 5 years and has no complaints.
Great! That's good information. I hear a lot about blocking PV's but many suggest to run a small or matched one in the secondary, which Charlie at Vintage Speed carries, to smooth out the transition and compensate for interruption in vacuum signal. Interesting about using the rear carb as primary, what manifold is your friend using?
What ever you do, read the plugs to make sure you aren't creating a lean condition in the cylinders not getting feed when only one of the carbs is open. From what I gather, the design of a regular or super 2X2 can create this lean out when only running one carb. If you study the design of these manifolds, a 3X2 may work better since the center carb is centrally located and you should, in theory, get better fuel pull into all cylinders due to location. You can set up the center carb to be your "primary" carb and the outer two as the secondaries. I'm curious on what you find out and please report back.
The Offy regular 2x2 (and I believe the Edelbrock also) has equalizer tubes so there's really no such thing as individual carb feeds or starvation from single carb feeds. I managed to get Charlie Price on the phone and he spent about 20 minutes talking to me about this subject and he simply reminded me to take a look at the difference in runner lengths on a straight six and how that carb in the middle feeds the cylinders at the ends with no problems.
Yes, this is true, but its the length of the runner which may, and I say may, cause a leaned out condition. The equalizer tube is smaller than the intake port of the manifold. That said, if the plugs read fine, then you are good to go. I don't know the firing order of a straight six, but having two less cylinders is also part of that equation. As Bruce mentioned, I think you'll find a pant seat dyno result when running non-progressive v. progressive. Of course, your results my vary. If you have some time, here is some light reading for you on the topic: http://www.btc-bci.com/~billben/intake.htm
Great info guys. What I like about the Offy 1090 regular dual (left) is A) the primary (front carb) location is pretty central and clears the stock generator fine. B) Using an early Offy 1090 on a later 8BA cleans up under the hood, eliminating the road draft tube and filler(I am using a concealed PCV system injecting directly into both plenums under manifold drawing from shortened oil tube) also replacing mech. fuel pump with electric. I will most likely use the front carb position as the primary. I intend to have three carbs rebuilt in preparation; two "true" 94 AA-1 types, and a big venturi 2110 modified to "true" 94 specs and several jet sets. I will also have a few PV's of various Hg rating. Will see if I can get the 2X2 working the way I want progressively. See the pics, one is the Offy 1075 (right) for the 8BA (see road tube, and slightly forward and off center front carb) compared to the Offy 1090 59AB style...I am using the latter. Also take a look at these nifty concealed PCV setups...one from Dirty Dan on fordbarn, and one by Fourdy on the HAMB. Mine will be slightly different in that I am splitting the air "leak" caused by the PCV and injecting into both plenums of the Offy manifold. http://www.jalopyjournal.com/forum/threads/motor-flathead-pcv.14648/ http://www.fordbarn.com/forum/showthread.php?t=36295
Will-do. The project may take awhile to actually install, but I can post my linkage design, showing adjustability, transitioning geometry, and the PCV system I have designed inspired by posts that I have listed in the thread. I posted comparative pics of the Offy 1090 (that I am using) and the 1075; the 1090 has a much more centralized primary carb (using front as primary as I intend) position. In the end with a Uni-syn, a few carbs, asst'd jets and PV's I'll drive myself crazy but have fun doing it. The car is running pretty damn well stock, so I may wait...or build another motor LOL!
OK, here's more. Both of the regular dual 1090/1075 intakes allow room for a stock generator. The reason the carbs are not positioned the same on the two intakes is because the early pre-49 engines are "shorter" at the front. Also, the early engines were mounted level (because of torque tubes) so the carb bases are level to the engine. The post '48 cars went to open drivelines and required an angled carb base to level the carbs because of a tilted engine/trans. Running an early intake on a later post '48 car will result in the carb(s) angled to the rear, and imo can look strange, along with messing up the float setting(s). (However, capping off the 8BA front stand pipe, installing a pcv, plumbed to both intake plenums, and allowing fresh air into the stock early fuel pump stand is the best ventilation solution with an early intake on a late engine, if you stay with this plan.) The carb placements on the 1075 are really closer to being properly over the intake ports, although you probably wouldn't notice any difference. But, progressive duals are a total waste of time and extra cost, imo. What is the supposed advantage? I also have a '51 Custom with a stock 239". I initially installed an Edmunds regular dual with two 94s, straight linkage and the stock loadomatic distributor. (I followed 286 Merc's write up many years ago on setting up the carbs and distributor ) I eventually switched to an Edelbrock regular dual because of the weird carb spacing on the Edmunds, and then to a Chevy point conversion distributor mainly because I want to use 97s in the future. I have not been able to measure any mileage difference between the single and straight-linked dual 94s, if that's what your after. I would stay with a late regular dual intake (Offy, Edelbrock, Weiand etc), remove the road draft tube, install a pcv with a hose to manifold vacuum and straight linked 94s. I also get around 20 highway mph on my '32 with a built 286", 3 97s and ...straight linkage!
Bob, love to hear the arguments! I guess I am just an experimenter and love a challenge. Thanks for that angled carb info...I never would have known that until I mounted on the car ha ha. I guess in the spirit of the original hot rodder I wanted to think through the problem, and seek out advice. Keeping a stock cam, stock head 239 in a "big" car I feel that it is important to keep that torque curve with a proper vacuumm signal until extra cfm would be needed, which would be as the torque starts to roll off. The cfm requirement for a stock 239 at a generous 85% efficiency at 3500 rpm (HP starts to roll off over 3200 in most charts that I've seen) is around 200-210 cfm. Most 2X2's and certainly 3X2's exceed that so my thinking was more about mimicking a small mechanical four barrel. I appreciate and listen to experience, and may in the end go your way. Thanks for responding...and being nice about it!
Thanks...I have seen that thread before...a great one that helps clear the cfm ratings up too. Cheers, S
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