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Hi All, I recently saw an article in a magazine (don't know which one) about putting 3 two barrel carburetors on our inlines by cutting the center carb mount section from 3 stock intake manifolds, blocking the openings left by the saw cuts and bolting the modified manifolds to the 3 intake ports on the head.
Has anyone else seen this article and in what magazine? Additionally, anyone have thoughts on how well this would work? Thanks to all for any help in finding the article and any insight you might have about this modification.

Gary,

Insight: the three carburetors should match the engine.

What size engine, and what carburetors?

Will you have a progressive linkage, or straight/simultaneous linkage?

Pros/Cons discussion by Tom Langdon.

A discussion in this forum.

It would no doubt look cool. The downside is 3 different carbs. triples the difficulty and they would need to be pretty small cfm carb's.

As a point of reference: About everybody who had the old tri-power set-ups back in the day ended up taking the intake and carb's off, setting them on a shelf in their shops, and installed a single 4 barrel.

There's an advantage to keeping it simple.

I'd really like to see the set-up though. Here's an interesting link: http://www.crankshaftcoalition.com/wiki/Building_an_inline_6_Chevy_250_engine

Thanks you guys for taking the time to answer my questions. I'm still interested in finding that article to see if there's some trick they came up with to make it all work for them. I'm not sure if I saw it while looking at the news stand recently or ??? I've looked at all the magazines I've received in the last month or so to no avail. Hopefully someone on here has seen it and can give me the name and issue it was in.
In reply to your questions: I have a 292 that I plan on building up for cruising with the ability to teenage it up once in awhile. I found a set of stainless steel headers on ebay that were made by Borla for UPS to use on their delivery trucks in the snow belt. I'm assuming they were custom ordered by UPS to combat the corrosion problem caused by the salt and repeated on & off cycle during deliveries.
I also like the QuadraJet idea on the Pontiac engine mentioned by Mr. Langdon and would be interested in any further info anyone could provide. I understand the idea that an engine is simply an air pump and that the faster the air/fuel can be moved through it, the higher the power output should be, all things considered. I also understand that fuel economy suffers greatly anytime these kind of changes are made, but that isn't really a concern. Drivability is a concern for cruising, with the ability to pass a Prious blocking the fast lane.
I hope what I'm trying to do makes sense and if not, I trust you guys that know how it's done can give me some advise on where not to tread.
Thanks again for taking the time to help a fellow enthusiast.

You've got one of the most powerful 6 cylinders already- - - -no real need to mess it up with some sort of off-the-wall home brewed intake setup. I've seen a drag race prepared 292 in a home-built square tubing frame with a fiberglass T-bucket body eat a V8's lunch repeatedly. The things have massive torque, and the usable RPM range is also impressive. Get an Offenhauser 4-barrel intake, put a low-CFM Edelbrock carb on it, and install a camshaft with about a 300-degree duration. Add a free-flowing dual exhaust setup, and you'll be in business without having to go to the sort of extremes you're hearing about. I have 50-something years of experience doing stupid stuff on high performance engines, and almost that much time welding cast iron, and I wouldn't begin to attempt splicing manifold sections that way!
Jerry

Hey Jerry, Thanks for your insight and advise. I can't argue with that kind of experience and knowledge.
I don't believe the article showed any manifold splicing, it actually showed the carb mounting box being cut close to the sides with a plate welded/brazed in to cover the holes on each side. They did this three times to get separate intakes for each of the three intake ports. I wasn't planning on going through all that work just to see if it worked or not, just curious about the results they achieved.
Your further advise on cam, carb and exhaust selection are well taken and appreciated. I've printed the info to put in my project planning folder. Any thoughts about using a QuadraJet on that Offy manifold? I know a lot of people dislike the "Quadra-junk" because of the design flaws and steps needed to tune/adjust them, but I've had great luck with them on my 72 C20 pick up. Another question comes to mind about the intake issue. What are your thoughts about removing the round obstructions and installing the lump port inserts in addition to the changes you mentioned?
The Borla SS header I mentioned above has a single tube collector at the end, but all the segments on this header can be slipped apart with a bit of persuasion so splitting it for duals isn't a problem. Thanks again for helping. You guys are all ACES!!

Good call on the Q-jet, and one calibrated for a 305 like my 85 C-10 runs would be just about ideal for a 292, with little or no rejetting required. You'd need an adapter plate to make it work on the Offy intake, but a little judicious blending of the adapter to the manifold would minimize the power loss from the adapter. I attended one of the first technician training classes GM had on the Quadrajet in 1966, and I've been impressed with its engineering and flexibility ever since. I had a Q-Jet on a 460 cubic inch MOPAR wedge truck pull engine (bored-out 440) that produced 714 HP at 6500 RPM on one carb and gasoline, and those are temperature and humidity-corrected dyno figures, not weed-induced fantasies!

In my decidedly biased opinion, the lump port conversion is only effective on a race-only high RPM application, and that setup would probably benefit from 3 side-draft Weber carbs. It would suck like a Hoover vacuum cleaner at low and midrange speeds. I'd build the engine for low end and midrange torque, and be satisfied with 250 HP or so and a 5-6K RPM top end. That's very doable without breaking the piggy bank too badly. Have fun!
Jerry

EDIT: Here's a though on that Borla header- - - -extend the pipes into two collectors where each tube is equal length to get the same scavenge effect for both manifold sections. The truck pull engine I mentioned above had individual header pipes 8 feet long each going into 6" diameter collector pipes, and the low end torque was awesome.
Jerry

Reference the lump port conversion: Are you saying the removal of the intake port restrictions alone are a waste of time for a street driven engine that will only see 5-6K occasionally? How about reducing the size of those things a bit. They sure look like they choke the crap out of these engines. No offense, I'm just trying to get the best I can out of this engine without re-inventing the wheel. I know a lot of you guys have been down this road many more times than I'll ever be, and 250 HP would totally do the trick for me.

Yes, streamlining the flow around the port restriction can't hurt- - - -just don't get too energetic and grind through somewhere. Enlarging the sides of the port and matching the manifold shape to the wider port in the head might be just as effective at low RPM. Pocket-porting the area under the valves and possibly going to a larger exhaust valve might be an effective approach. On the small block V8 round track engines we went up to a 1.6" exhaust and got as much or more power gain as when we installed bigger intakes. Getting the exhaust gas out is at least as important as getting the intake charge in there.

Getting close to 1 HP per cubic inch isn't terribly difficult as long as a total-system approach is taken. Everything from the air cleaner to the tailpipe must match up, so don't get fixated on only one link in the chain. The biggest mistake a lot of would-be engine builders make is to concentrate on only a couple of modifications without looking at the big picture. Too much cam and/or carburetion has disappointed a lot of people who should have known better if they had stopped to think a little before bolting a bunch of mismatched parts together. Good luck!
Jerry