2X2 versus 3X2 manifold

[sanborn]

I have two Edelbrock intakes, a 2X2 and a 3X2. I would like to use the 3X2 intake running the outside two barrel 97s as primary and bringing in the middle 97 as secondary. In other words, treat it as a two carb intake except under full trottle.

Will this give me as good fuel distribution as a traditional 2X2 intake?

[Pete]

It will work but you are going to have to try it on your engine to see if you are happy with it.

This falls in the same category as restrictor plate racing, it is Mickey Mouse.

[Mart]

Normally people run them the other way round - center one as the primary and outers kicking in at WOT. 2 barrel economy for tootling around but all guns blazing when required.
Just a gut feeling, but if it were me, If I were running the two outers as primary, I'd run them and leave the center one as a dummy. Two carbs are plenty for street use in a modest engine, and it would save the complexity of the progressive linkage.
Or just run the 2x2 and be done with it.

Mart.

[sanborn]

I appreciate the comments-----I've just never seen anyone trying to use the outer 97s as primary and the center 97 as secondary. This is what I would prefer----because I have three of the neatest air filters------

[Jack E/NJ]

Well, Sanborn, I think I'd be very tempted to experiment with straight linking the 3x2. Easy enough to rearrange things for running on 1, 2 or all 3 to see which arrangement I liked best. 8^)

Jack E/NJ

[36tbird]

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Yo Jack and all, be careful. I had a buddy running non-prog. 3X2 on an 8ba. He just thought it ran a little rough until it ate a valve. Turns out that it carboned up around this valve so badly that it broke the top of the valve off. Following that, the whole valve seat area around was misshapen and ruined. An engine shop like H&H could probably save that block, but here in S. TX, we wrote it off and he built a new engine. Me, I would put a 48 in the center and run the outers if you are confident on your engine or dummy up the outers given economic current events.

[Ol' Ron]

This is a good place to push JWL's book. He has about 50 pages of his book covering intake manifolds and carburetors. Yhis along with Dyno testing of all thes combination

[sanborn]

Who is JWL?

[Mike51Merc]

I see no advantage (and plenty of disadvantages) to running duals as Primaries, with a 3rd as a "kicker" at WOT.

A center primary will have more even fuel distribution, one set of idle circuits, you only need to tune one carb (no synchronization needed), it will have more low-end torque, and probably better fuel economy. The secondaries should have special butterflies that seal tightly and no idle circuits.

By the way, most flatties can't breathe enough to successfully use 3 97s anyway. A lot of guys put three 81s instead (if you can find them).

[Tim Ayers]

I second Ol' Ron's advice regarding JWL's book.

I also think you need to be carfefull and really look at your intake. They are designed with a specifc "feed" in mind. If you cut off the center, you may be running lean in the two center clylinders it may not be able to completely pull the charge to these cylinders.

Not all 3X2 intake are created the same.

[rotorwrench]

Sanborn: JWL is a regular contributor on this board. You can do a members search off of the tool bar. He should have info on his public page to where you can get the book or send him a PM (personal message).

Look up "Flathead Facts" on Google.

Kerby

[Tim]

A couple questions- What size is your engine and what cam are you running. This is the biggest determining factor. What you are doing is putting a 4 barrel on it with the outsides hooked up first. Then when you dump in the middle It's probably going to stumble like crazy unless you are running some good RPM's. The reason guys run the center is for economy, smoother off idle, and better transition into the secondaries. You will have to feather the throttle alot more until higher RPM's more than likely until the engine can handle all that fuel. To make an engine run at peak performance you need to match the CFM's to the ability of each cylinder. It'll work and your foot controls how much you are giving it, so mess around and see what happens. Start with smaller jets and work into the bigger sets. But dont ever run just the back or just the front as you'll be extremely lean on the other end.

Good luck and keep us posted.

[gerrald meacham]

good to see olron on the barn

[Mike51Merc]

Originally Posted by Tim

A couple questions- What size is your engine and what cam are you running. This is the biggest determining factor. What you are doing is putting a 4 barrel on it with the outsides hooked up first. Then when you dump in the middle It's probably going to stumble like crazy unless you are running some good RPM's. The reason guys run the center is for economy, smoother off idle, and better transition into the secondaries. You will have to feather the throttle alot more until higher RPM's more than likely until the engine can handle all that fuel. To make an engine run at peak performance you need to match the CFM's to the ability of each cylinder. It'll work and your foot controls how much you are giving it, so mess around and see what happens. Start with smaller jets and work into the bigger sets. But dont ever run just the back or just the front as you'll be extremely lean on the other end.

Good luck and keep us posted.

All respect to Tim, but I wouldn't start lean. Lean conditions are silent killers; engine runs great until the hot spots do their damage. I would start at standard size jets.

I'm not a specialist, just a hobbyist, but many people (not necessarily Tim) believe that you can make a big carburetor act smaller by putting in smaller jets. Not true. Jets determine fuel to air ratio and that's about it. A big honkin' carburetor, or a collection of little ones with little jets is just going to be overly-lean no matter what engine it's bolted to.

[Tim]

Originally Posted by Mike51Merc

All respect to Tim, but I wouldn't start lean. Lean conditions are silent killers; engine runs great until the hot spots do their damage. I would start at standard size jets.

I'm not a specialist, just a hobbyist, but many people (not necessarily Tim) believe that you can make a big carburetor act smaller by putting in smaller jets. Not true. Jets determine fuel to air ratio and that's about it. A big honkin' carburetor, or a collection of little ones with little jets is just going to be overly-lean no matter what engine it's bolted to.

My comments were not made to mis-lead. I understand the limits on re-jetting and venturi size relations in regards to making a carb smaller. I was assuming which was probably bad that there was some knowledge of this already. You are correct in your comments about the lean condition. Reading the plugs will let you know what your engine is doing. With the small range for 97's and 94's and the venturi size between both it's very simple to richen or lean out an engine to run better and cleaner. My experience has been a flathead will run very well on one carb, better with two and three can easily be too much unless you are matching components. Bore/stroke and lift all play a big part in this. That was my original question, I'm still curious about those.

Tim

[sanborn]

Thanks for the comments. I found the info for JWL's book, I will order one tomorrow.

My specific question was if anyone had experience with the exact combination I want to try.

I recently purchased this engine, that had been on a display stand since 1965. It is a 1950 Merc, 275 cubic inches, moderate port work, nice bowl work, backcut valves, profiled valve reliefs, GranCor heads, No Name 2X2 intake, Red's Headers, Jahns Pistons, balanced, 30 lb. Merc flywheel. The cam has .365" lift on intake, 240 degrees duration @ .050". The exhaust has .342" lift, 238 degrees @ .050". Of course, Johnson lifters are used. The engine is very clean inside, bearings look new----even the crosshatch remains on the cylinder walls.

[Tim]

That sounds like a wholke lotta fun. Great combination of parts. 2x2's would be just right. It should handle three though. Post a picture we'd all love to see that.


Tim

[sanborn]

Tim, I know that 2X2 would probably be fine------but I have THREE really unique air filters and------. Besides, 3X2s impresses the masses so much more----

[Jack E/NJ]

Then gofer 3x2 straight link pronto. See how it runs. Then report back.

Jack E/NJ

[sanborn]

I haven't built the truck yet!!!!!!!