Air Filters.... HD RPO K47 vs. Standard

[Supercharged111]

I believe the 7.4L air boxes are a different part number, but very similar and take the same filters as you found out.

I'm gonna go with no, but they DID use a different elbow going into the box.

 

[Schurkey]

The K47 option does not flow air better than the standard, it just holds more dirt before becoming restricted.

As my photo shows, the bigger element is intended for "severe dust conditions".

It holds more dust because the pleats are deeper. The deeper pleats means more surface area of filter media.

More surface area should translate to "better flow", except that it doesn't take much of an air filter to flow all the air an engine needs--when it's clean. As it plugs with dirt, more area is a good thing.

And I don't trust that air filter indicator thingie on the Vortecs one iota......

Those air filter restriction indicators are used all over creation--cars, trucks, bigass diesel City Buses, semi tractors, construction equipment.

They're pretty-much the "gold standard" for detecting a plugging air filter.

 

[Schurkey]

I'm gonna go with no, but they DID use a different elbow going into the box.

Wild Guess: The air filter housing fits the vehicle, not the engine. The elbow adapts the housing to the engine.

Therefore, I suspect Supercharged111 is correct.

 

[alpinecrick]

In order to get the air filter indicator to show red, the air filter is so plugged it should've been changed 10k or 20k before......I know, I've seen a couple in the red. A guy could make a sandbox out of the dirt that the filter was holding.

 

[df2x4]

I'm gonna go with no, but they DID use a different elbow going into the box.

Wild Guess: The air filter housing fits the vehicle, not the engine. The elbow adapts the housing to the engine.

Therefore, I suspect Supercharged111 is correct.

I knew about the elbow difference, but east302 mentioned the 7.4L air boxes having a different part number in that thread I linked earlier and based on a quick search it seems like he may be right. I'm seeing part number 19201266 referenced on a couple sites for the 7.4L trucks, instead of the 19201265 for the 4.3/5.0/5.7Ls. Then again one of those sites is Nemiga Parts, which is one of the only places I could actually find any part numbers since most of this stuff is discontinued. I'd be curious to see a 7.4L box and a 5.7L box side by side.

 

[L31MaxExpress]

Stock intake setup was very restrictive even on a 305 Vortec with a mild cam. My brother swapped his stock air intake out on his 99 Suburban with a LT1 cam for a Volant. Ran noticeably better. I later put the same Volant on the 99 Tahoe and it ran better. Was not a placebo effect either, it had about 5-6 kpa higher map reading at WOT after the swap. Stock air intake with a K&N filter was pulling down to 93 KPA and it only went down to 99 KPA after. Baro was 101 KPa at the time we tested it. Those values were from the 305 Tahoe with a 218/218 flat tappet cam and 1.6 rockers but otherwise stock. Stock 350 exhaust had over 5 psi of backpressure with the 305 pumping into it as well. Back pressure reading was taken in the front 02 sensor port and probably higher at the exhaust ports with the log manifolds. After LT headers, high flow cats, 2.5" pipes to the muffler and a dual in/single out magnaflow it had less than 2 psi back pressure. Intake/Exhaust and Headers gained 35 hp at the tires and 40 ft/lbs of torque.

 

[alpinecrick]

The mechanic I use when something is above my pay grade used to work at 4wd/race shop 20+ years ago. The shop had a wheel dyno. He said even with the air filter assembly removed, hood open and a fan blowing in front of the trucks the 5.7's didn't see any gain in hp or torque. The brother of the shop owner had a shop and wheel dyno down in the Phoenix area and had the same results. He did say with the air filter assembly removed they saw a wider power band with the 5.7's.

As per what L31 mentioned, it wasn't until they went to bigger cams and other mods they saw a need for more air flow from the intake side.

My mechanic also says when they calculated for drivetrain and altitude loss, when new the 5.7 Vortecs consistently dyno'd at around 260 hp and 330+ ft lbs.

 

[L31MaxExpress]

The mechanic I use when something is above my pay grade used to work at 4wd/race shop 20+ years ago. The shop had a wheel dyno. He said even with the air filter assembly removed, hood open and a fan blowing in front of the trucks the 5.7's didn't see any gain in hp or torque. The brother of the shop owner had a shop and wheel dyno down in the Phoenix area and had the same results. He did say with the air filter assembly removed they saw a wider power band with the 5.7's.

As per what L31 mentioned, it wasn't until they went to bigger cams and other mods they saw a need for more air flow from the intake side.

My mechanic also says when they calculated for drivetrain and altitude loss, when new the 5.7 Vortecs consistently dyno'd at around 260 hp and 330+ ft lbs.

The restriction is not the filter. It is the tubing and the vortec hat. The airaid eliminates the hat with a smooth radiused tube and no accordian boot.

My 97 5.7 put down 185 whp and 250 wtq on a Mustang dyno. The Mustang dyno I ran it on reads 10% lower than any Dynojet in town. 4L60E and 8.5" 10-bolt loses about 18%. 185/0.9/0.82 = ~251 and 250/.09/0.82 = ~339. 97 Express was net rated at 245 hp and 335 tq at the crank. Stock it was dead on the money. Marine intake, Tri-Y headers, high flow cats, walker dynomax bus muffler, 395' marine cam, 1.6 rockers, 25% underdrive pulley and tuned on E85 put me at 272 hp and 330 tq at the wheels on a Dynojet through a 4L85E and 9.5" 14-bolt. I figure the drivetrain loss was around 22% on it. The 8.1 Vans, Suburbans and Avalanches were 25% loss with the 4L80E/4L85E and 10.5" 14-bolt. At 22% loss my 5.7 was making about 348 hp at the crank and about 423 tq at the crank. With the stock van vortec hat and 2001-2002 air intake with a K&N filter it was pulling down to 90 KPA at WOT. Same setup with a Lunati Bare Bones 218/228 hotcam made 290 rwhp and 340 rwtq. About 372 hp and 436 tq at the crank. With the hotcam it was pulling down to 87 KPA at WOT.

 

[alpinecrick]

Interesting, and good info L31!

 

[vr1967]

92-95 6.5 diesels had the flat filter. I don't know about older 6.2s, I would assume though that from 88-95 all GM diesels would have used the flat filters. It would be a complete waste of time to put a flat filter on anything because they don't seal easily around the bottom edge.

the 6.2s all had the round filter that sat on top of the intake like the carb/tbi vehicles.
My old 93 and dad’s old 1995, true 3500HD both had flat filters for the 6.5T