Offy Intakes?

[Pirate]

I could see a design where a dual-port setup might work....IF you had a true dual-port arrangement, where you had runners the same size as stock, but with different runner lengths, long for low-end grunt, long side closing off with the short side opening up for good midrange, and only the short side open for top-end power. There are some OEM applications that do the same thing to get a fairly flat torque curve....but to do this with a carbed setup? That would take some work...

[Southern_Pride]

Not that much work. The oem setups work off vaccuum.

[Archangel]

Failed design attempt.......Those are Junk! Run far far away from that intake. An Offenhauser 360 intake (#6150) however is competitive with the Weiand Stealth and the Edelbrock Performer RPM intakes for the 351. I ran one on a Torino a few years ago with excellent results.

Well, the Offy intake I have in my Chevy is indeed a "360" model, dunno how it differs from the one shown in internal structure, but it still has that split port design.

[1987cp]

I don't know a lot, but there seem to be at least two "360-degree" designs, and the ones I know of are quite different internally. One is the divided single-plane "Equa-Flow" shown above, which is a big open single-plane design with a vertical, longitudinal partition down the very middle (visible in the photograph; hence the description "divided single plane") and is still available new from Summit Racing: OFY-5691 ($232.99) for 302s and OFY-5883 ($274.69; appears to be identical to the 6150) for 351Ws. Nominal RPM range is huge: 1800 to 8800 RPM depending on carb selection.

The other 360-Degree design I am aware of is the "Dual Port" dual-plane design like Ivan seems to have; that design has the entire plenum area divided in half top to bottom by a horizontal partition, with the primary carb barrels feeding one half of the plenum (and approximately one-half the normal area of the ports for higher velocity), and the secondaries feeding the other half of the plenum to in theory take advantage of the full plenum volume at full throttle. This is the one that's said to be not quite so useful on a serious modern motor that sees higher RPMs - someone somewhere on GMN claimed it's not even a performance intake at all. The Dual Port doesn't seem to be currently available new, though I could be quite mistaken.

Mercracer, I don't suppose you could elaborate a little on your setup on the Torino? Cam, gears, RPM range, that sort of thing? Like I mentioned above, I've been wondering whether my single-plane Offy is giving me a softer low end than I had expected with my 3.27 gears, GT40 heads, and Crane 444211 cam. Thanks!

[Mercracer]

I do have a Performer 289 on my other engine, and it seems to do pretty well. Seems there was a Ford Racing intake that was said to be really strong on the bottom end but give up by about 4500rpm; if I could find one of those, I might want to put one on the weaker engine and swap the Performer 289 over to the 306 with the good cam and heads where it could really do some good.

The FRPP intake you are talking about IS the Performer. The 306 with good heads and cam will do well with a Performer RPM, Stealth, or 360 High Rise intake. The other intake out there is the "Cobra" intake. High rise dual plane. They were a Ford Off Highway part and they are currently made by someone else. I will take a look.
I would recommend that you stick with what you have for now.

[Mercracer]

The other 360-Degree design I am aware of is the "Dual Port" dual-plane design like Ivan seems to have; ......... someone somewhere on GMN claimed it's not even a performance intake at all. ........Mercracer, I don't suppose you could elaborate a little on your setup on the Torino? Cam, gears, RPM range, that sort of thing? Like I mentioned above, I've been wondering whether my single-plane Offy is giving me a softer low end than I had expected with my 3.27 gears, GT40 heads, and Crane 444211 cam. Thanks!

The Dual Port is definitely NOT a performance intake. It was never marketed as such.
The Torino had a mild cam and 3.25 gears with a 4-speed. A pile of torque down low and would pull to over 5000RPM's.

[Mercracer]

I've got the divided single-plane Equa-Flow on my 306 right now, and while it works pretty well, it seems a tad soft on the low end for the high-lift/short-duration cam I'm running, so I'm thinking on switching to the more modern Edelbrock at some point in the future.

What cam are you running?

[1987cp]

The Crane 444211 is a factory-style hydraulic roller with 208/216 degrees duration at .050 and .530/.530 valve lift. 1000-5000 nominal RPM range with valve float at 5600 with the recommended Crane springs, though a guy at Allfordmustangs.com says he's spun his to 6500 with dual springs.

Linky: http://www.cranecams.com/index.php?s...11&lvl=2&prt=5

[Pirate]

The Crane 444211 is a factory-style hydraulic roller with 208/216 degrees duration at .050 and .530/.530 valve lift. 1000-5000 nominal RPM range with valve float at 5600 with the recommended Crane springs, though a guy at Allfordmustangs.com says he's spun his to 6500 with dual springs.

Linky: http://www.cranecams.com/index.php?s...11&lvl=2&prt=5

....and why would anyone want to rev it to 6500? The cam stops making power at 5000 or so RPM, yet we are concerned about valve float at 5600? You can spin a stock 5.0, with a stock 266/.444 cam, to 6500, provided you have a strong enough valvespring in there. It stopped making power well before 6500, but it will continue to climb in rpm after the power peak, as anyone running an engine dyno can attest to. Not chewing anyone out, just pointing out a couple of things.

Concerning the intake? Yep, it's pretty much a single plane with a divider. The whole purpose of a single plane is power delivery above 3000-3500 rpm. While some engines make a lot of power with single planes all over the rpm map, usually, they are reserved for race engines at the track, not street engines, unless you have a screamer big block you want to take some of the low-end grunt out of (blowing off the tires at launch on the street, for example).
A modern dual plane? What the intended purpose of a modern dual plane, is in essence, to make two V4 engines out of a V8. The longer runner plane (the one that goes deeper into the intake, usually), operates best in the lower rpm range, following the firing order (alternating between low and high plane), and the short plane pulls at higher rpm. You could have a single plane intake that pulls like stink at low RPM, most stock EFI manifolds only have one plane, port, etc, and they pull really well at low RPM for street use. No dual plane tricks, just small, long, high-velocity ports, and a large plenum. Only in the carb world usually do you see a dual-plane setup, or if you have split-port intake designs, like the later 3.8 V6 engines from Ford, which is a true dual-plane, with ports actually being shut off depending on RPM level.
Interesting thing about dual plane intakes: Some experimenting was done with NASCAR short track engines some years ago, where the teams concerned wanted an engine that would pull from 3000 to 8000 rpm, and have a flat torque curve. Using the dual-plane theory of two V4 engines, they actually made a camshaft with two sets of different cam patterns, 8 lobe sets with a smaller cam profile for pulling at low RPM, and a larger set of 8 lobes for pulling at higher rpm. What resulted was an engine that delivered exactly what was promised, an engine that had an almost flat torque curve from 3k-8k. However, the engine was down a bit at peak HP, so it wasn't used for very long, not to mention it didn't really sound that healthy. For street cars? This would be a killer.

Just some food to chew on...just get a Stealth intake for it later on. It works good, and doesn't have the fuel distribution problems of the regular Perf RPM...which might be discussed later.

[1987cp]

Great discussion! I hadn't actually thought about it quite that way. And I like learning kewl factoids!

[OVERKILL]

The two sets of lobes is basically the same design as Honda's V-TEC.

[Pirate]

The two sets of lobes is basically the same design as Honda's V-TEC.

Nah, the circle track engines were fixed lobe designs, not the additional lifter setup the Honda has. The lobes were simply ground with a smaller profile on 4 cylinders, like running 4 on a 272 duration cam, and the other 4 on a 292 duration cam, with an intake to match.

[OVERKILL]

Nah, the circle track engines were fixed lobe designs, not the additional lifter setup the Honda has. The lobes were simply ground with a smaller profile on 4 cylinders, like running 4 on a 272 duration cam, and the other 4 on a 292 duration cam, with an intake to match.

Ahhhh, now I getcha, I thought you meant that it would switch lobe profiles

[Nathan in MI]

Nah, the circle track engines were fixed lobe designs, not the additional lifter setup the Honda has. The lobes were simply ground with a smaller profile on 4 cylinders, like running 4 on a 272 duration cam, and the other 4 on a 292 duration cam, with an intake to match.

So with that setup, one bank of cylinders would make the lion's share of the power at low RPM, and the other would make the majority at high RPM, correct?

[Pirate]

So with that setup, one bank of cylinders would make the lion's share of the power at low RPM, and the other would make the majority at high RPM, correct?

Sort of...they didn't do it side to side, more like following the firing order, easier to balance....but your theory is correct. With modern multiport short/long runner intakes and variable cam timing, this sort of arrangement isn't needed....but might be made to work well on an older carbed engine, provided you use a dual plane, oversized valves on only the top end 4 cylinders, etc...