'91 K5 Four Wheel Camper

[America.Mike]

Interesting. I’ve never seen one of those

 

[Fastereddie]

Me neither

 

[mrk5]

Might have been different styles considering how the bottom part slides into the top part with the bolt holes.

 

[ZooMad75]

Isn't it pulling air through the 3 holes in the front? It should be connected to the side of the vertical box section.
I believe that my '90 Jimmy is that way, even though it has the quad lights. I can't remember where and how many of the ejector boots I have seen. I don't believe that I have seen it on lots of them. I think that it is a drain for water entering the intake.
This is one of the extra core supports that I have, engine side shot.

View attachment 365577

I'll have to look at my old core support the next time I stop by Larry's place. I'm betting it looks like yours.

I'm going to look at the GM parts catalog and see if I can tell when that particular system came into play.

So driving home today I had Torque running on my phone monitoring engine data. Intake air temps typically ran 20° higher while the truck was moving. When I came to a stop the IAT jumped to 105°. That was at 35° outside temp. Makes me wonder what that could increase to on warmer days and how much power/efficiency I'm losing.

 

[Capt Ron]

This is interesting. I was watching my intake air temps on Torque while I drove home from Denver. Consistently as long as the truck was moving at 20mph or better I was seeing 20-25° higher temp than ambient for the intake air temp. That's with the open cone air filter directly behind the core support with the 4" hole in it. If I came to a stop the IAT climbed to 100-105° with the ambient temp at 35°. I can only imagine what the split is when the ambient temp is 80-100° in the summer. Just doing some googlefu on the subject comes up with for every 10° change in IAT it equals a 1% change in horsepower in either direction. That means I was seeing as much as a 7% drop in power. In your case, you were leaving a little over 9% on the table with the open-element vs 1.5% with the cold air intake. That is provided that the 10°/1% rule of thumb is accurate for a naturally aspirated engine.

It certainly makes looking at an effective cold air intake a worthwhile addition to maximizing power and economy.

I'll have to look at my old core support the next time I stop by Larry's place. I'm betting it looks like yours.

I'm going to look at the GM parts catalog and see if I can tell when that particular system came into play.

So driving home today I had Torque running on my phone monitoring engine data. Intake air temps typically ran 20° higher while the truck was moving. When I came to a stop the IAT jumped to 105°. That was at 35° outside temp. Makes me wonder what that could increase to on warmer days and how much power/efficiency I'm losing.

Good info, it really makes you start to think about things like airflow, air supply and even things like coatings and the actual part itself ie: a plastic vs metal air intake etc...

 

[82355]

Don’t all ‘89-‘91 R/V series trucks have that intake?

Martin

 

[onetonbb74]

Yes, from what I've seen.

 

[mrk5]

I'll have to look at my old core support the next time I stop by Larry's place. I'm betting it looks like yours.

I'm going to look at the GM parts catalog and see if I can tell when that particular system came into play.

So driving home today I had Torque running on my phone monitoring engine data. Intake air temps typically ran 20° higher while the truck was moving. When I came to a stop the IAT jumped to 105°. That was at 35° outside temp. Makes me wonder what that could increase to on warmer days and how much power/efficiency I'm losing.

You don't need much power when you're going that slow. I still don't buy into the power benefits; I'm sure there might be something, but not enough to really matter. I'm most interesting in coolant temperature. I've seen mentioned on a couple car shows now that sucking in the hot air contributes to engine operating temps.

Since we're discussing it here, I will add my recent findings on IAT from recent experimenting with air intakes on the C10. These numbers on based on highway commute on 25°-35° mornings. None of my set ups are getting air directly from the outside because the 73 doesn't have an opening for the intake tube.

• "Cold air" type with carb hat and cone filter mounted on the inner fender behind the driver headlight: 55° moving on the highway
• Factory TBI air cleaner with intake tube ending just behind core support on passenger side of radiator: 90° moving on the highway
• Classic 14" round open element air cleaner: 135° pretty much all the time once coolant is at NOT (normal operating temperature)

I suspect the TBI set up is warmer than the "cold air" type because the air probably stagnates in the filter housing above the engine.

 

[ZooMad75]

Don’t all ‘89-‘91 R/V series trucks have that intake?

Martin

Looking at the GM catalog, yes. But there were two versions for '89-'90, one for '91.

'89-'90 had an option K46 for heavy duty precleaner air cleaner. By what I'm seeing the hd option was dropped for '91.

Here's the '89-'90 without K46 and '91 setup (small block):


'89-'90 small block with K46:


'91 big block:


'89-'90 big block with K46:


For a comparison, here's the '88 small block setup. Showing both with K46 and without:


All parts are discontinued.

 

[ktmoutfront]

The last one with just the tube (13) was in my dads 73 with a 454. But he did so much work to it, I will bet money he added it. The truck was also a test bed for GM and Impco Propane, so who knows.

 

[mrk5]

I really want to know what this bit is for?



Seems like an overly complicated do nothing.

 

[ZooMad75]

I really want to know what this bit is for?

View attachment 365688

Seems like an overly complicated do nothing.

I saw that on mine. Looks to be open to the main interior cavity so I'm betting it is a resonator or silencer of some type.

 

[ktmoutfront]

Sound reducer. Dad put a screen over his after removing that. He also thought it might have been to keep rain out.

 

[ZooMad75]

The last one with just the tube (13) was in my dads 73 with a 454. But he did so much work to it, I will bet money he added it. The truck was also a test bed for GM and Impco Propane, so who knows.

Knowing your Dad's connections back then I wouldn't be surprised if he ended up with a proof of concept type part to test out.

Diving deeper into the catalog the first year they list any duct to the core support off of the air cleaner is in 1979. Difference to the prior years is the change in the inlet on the air cleaner housing has a larger round opening vs the tapered small hole on the end of the inlet on prior years.

 

[ktmoutfront]

Now that you posted that, the one my dad had was round. Went to the propane hat which had a large round opening.

I wish we took pictures back then like we do now. Probably would have not gotten as much done.

 

[70jimmy]

Some of mine had a heat operated damper that would be closed until a certain temp was reached then the damper would open. I removed mine from the air intake to the air filter housing.

 

[ZooMad75]

Some of mine had a heat operated damper that would be closed until a certain temp was reached then the damper would open. I removed mine from the air intake to the air filter housing.

That was for the hot air off of the manifold. As in the solid or flexible pipe 99% of us as kids threw away because it was a pain to deal with. It allowed the carb to get heated air off the exhaust manifold to warm up quicker and get the choke open sooner.

My '75 had the stock air filter but had headers so the pipe from the air cleaner was long gone before I got the truck. On a snow run I thought it would be cool to stack up a bunch of tamales wrapped in aluminum foil on the passenger side of the intake and valve cover. Cruising down HWY 50 at 65 mph the engine stumbled and stalled. I coasted to the side and attempted to restart. Nada. Hopped out and opened the hood to realize my need for warm tamales overtook the the engine's need for warm air. It was cold enough the thermal valve in the air cleaner closed and with a dozen tamales wedged in underneath the opening the foil sealed up to it nice and tight. Choked the engine out for air and stalled it. Duh..

Moved the tamales away from the hole and it didn't act up again.

Sad ending though. The tamales never got hot and had the distinct aftertaste of exhaust. I never tried cooking on the engine after that.

 

[ktmoutfront]

Not to derail, but I cook on mine whenever I wheel when it is cold out. Only issue I ever had was sliding down a hill on ice and center punching a tree with the winch luckily. Went to get my burrito out, all that was left was tin foil in the fan clutch. No lunch for me that day.

 

[mrk5]

Snow runs will f things up

 

[ZooMad75]

Digging around on the web might have found a possible solution that would integrate with my existing intake and the cold air box on the core support.

It holds a cone filter inside, 4" inlet and outlet and 10" overall length. I might have to trim up the last 90° to make it fit, but it looks doable.