High Altitude and Air Cleaner

[dirtynails]

For carburated Blazers at high altitude say 5700 feet is it true that the stock air cleaner and housing is not enough oxygen. I have bee told this and have been using a large open air cleaner. It seems to do better most of the time, but with the hotter weather this time of the year, I have to wonder if I should consider something else. It does idle rougher in this hotweather. I've been reading the dual snorkel threads. Cold air ducting in from radiator support sounds good. Is that the direction I should go next? If I go that way what type aircleaner should I go with? Plain old stock paper good enough? Is there a decent way to get thermac working on both snorkels?

 

[dyeager535]

If you notice a difference with hot underhood air, then go back to stock cold air induction. If it helps, you've already improved the situation, even if it is more "restrictive".

Really need to know how efficient the inlet is on flow. My opinion is that on a small block, the stock cold air setup flows plenty for most. (most claim that a 600CFM carb is enough, how much does 3" tube flow?) I doubt your altitude is going to affect that equation much.

THERMAC can be made to work on both snorkles by using a t on the vacuum lines, but the ducting is more difficult for the drivers side. Even without ducting, you are pulling warmer air from the engine compartment.

 

[Blue85]

At 5700 feet the problem is the air density. I don't see how sucking hot air will help that problem.

The factory snorkel is like 3.5" tube (although it necks down some going into the cleaner) which is plenty by itself. I would choose a single factory snorkel over an open element. A dual factory snorkel is probably about the best setup you can get.

 

[roadnotca]

Cool air and keeping out mud and water should be your priorities over 100 mph supercharging.

 

[dremu]

The thermac, btw, takes all of about 5-6 in of vacuum to close, so yeah, teeing it is easy. Plumbing the second snorkel's thermac is harder, but as Dorian says, picking up hot air from the engine compartment is prolly better than nothing.

Still seems like lots of work. I think in your case, a single snorkel and cold air intake might be the ticket... leastaways that's what I'm doing on my 350.

-- A

 

[dirtynails]

Mostly I think I agree with getting away from the open cleaner. I still have my original air cleaner housing with thermac system intact and maybe I need to back in that direction in some fashion. If I find some cleaver and easy way to build a stove on the driver's I'll let everyone know. Don't hold your breath. I do however think that you may be underestimating the effects of the altitude. I believe I have noticed performance gain with the open 14' filter in weather that is not hot. Also the intensity of the sun on a clear day is really, well amazing here. So, I will be looking at fabricating a dual snorkel deal. Are we all agreed that a fancy K&N filter (part number E-1500) with the stock air cleaner housing will not increase the flow as much as two snorkels? Also there is the consideration of driveing on dusty roads. Right now it looks like a used air cleaner housing goes for something like 40 bucks at the junk yard. And that's not the deep dish. I hope I find one more reasonable. Then I suppose I need to get a dremel tool too? The actual work though seems pretty staight forward and easy.

I wish some of us K5 folks living in Colorado could confirm some of this stuff.

While were are talking about heat, air and atltitude, one of the things I did to get relief from the heat soak and hard starting after say stopping at the grocery for twenty minutes and then trying to start again, was a phenolic carb spacer. That helped some for sure. Also when I switched from a Carter afb to an Edelbrock Q-jet I think that maybe I had a little less trouble with the fuel evaporation and hard starting. It seemed that way anyhow.

 

[mrk5]

I don't notice my truck running any different with the temperature change. I run a stock air cleaner housing with the factory snorkel. I have a 670 Truck
Avenger carb. The only extra thing I did was drill three 1.5" holes in air cleaner lid. I keep them facing towards the back. Like I say I've never noticed a difference. And I was running an open air cleaner before.

I also run a 185° thermostat.

 

[Cricket]

Mostly I think I agree with getting away from the open cleaner. I still have my original air cleaner housing with thermac system intact and maybe I need to back in that direction in some fashion. If I find some cleaver and easy way to build a stove on the driver's I'll let everyone know. Don't hold your breath. I do however think that you may be underestimating the effects of the altitude. I believe I have noticed performance gain with the open 14' filter in weather that is not hot. Also the intensity of the sun on a clear day is really, well amazing here. So, I will be looking at fabricating a dual snorkel deal. Are we all agreed that a fancy K&N filter (part number E-1500) with the stock air cleaner housing will not increase the flow as much as two snorkels? Also there is the consideration of driveing on dusty roads. Right now it looks like a used air cleaner housing goes for something like 40 bucks at the junk yard. And that's not the deep dish. I hope I find one more reasonable. Then I suppose I need to get a dremel tool too? The actual work though seems pretty staight forward and easy.

I wish some of us K5 folks living in Colorado could confirm some of this stuff.

While were are talking about heat, air and atltitude, one of the things I did to get relief from the heat soak and hard starting after say stopping at the grocery for twenty minutes and then trying to start again, was a phenolic carb spacer. That helped some for sure. Also when I switched from a Carter afb to an Edelbrock Q-jet I think that maybe I had a little less trouble with the fuel evaporation and hard starting. It seemed that way anyhow.

I ran an open K&N when I had a carb on the 77, it made a little difference in performance. They filter well enough for basic use, as long as you keep it clean and don't live on dusty roads. You can plumb a dual snorkel cleaner for your carb and run a regular paper element or a K&N, whatever you prefer. It will make some difference but probably not a huge one.

To be honest if you want better performance up here you may want to consider fuel injection.

 

[dirtynails]

Ok, so what I have done is to put the factory aircleaner housing back on with stock aircleaner and I have drilled three 1 1/8" holes in the back of the housing. I did some fancy calculations and dead reckoning on how big to make the holes. I believe most of the air still comes from the snorkel and only 35-45% from the three holes. I should still get some benefit from the thermac when needed and the three holes should give enough extra air when needed. Yesterday was a real good hot day and I ran the livin dog "S" out of it and I got a good smooth idle at the traffic lights and had good power climbing the hills. It didn't seem like it was restricted. Drilling the three holes seems to have done the trick. I don't think I will have to fab a second snorkel. Thanks everybody.

 

[dremu]

I did some fancy calculations and dead reckoning on how big to make the holes.

If it's like my fancy calculations, it was the first drill bit you came across, or the only one you had handy?

-- A

 

[Blue85]

Please don't get hung up on the holes. Just remember that it ran bad with the hot air intake and it ran better with the snorkel back on. :-)

 

[mrk5]

Ok, so what I have done is to put the factory aircleaner housing back on with stock aircleaner and I have drilled three 1 1/8" holes in the back of the housing. I did some fancy calculations and dead reckoning on how big to make the holes. I believe most of the air still comes from the snorkel and only 35-45% from the three holes. I should still get some benefit from the thermac when needed and the three holes should give enough extra air when needed. Yesterday was a real good hot day and I ran the livin dog "S" out of it and I got a good smooth idle at the traffic lights and had good power climbing the hills. It didn't seem like it was restricted. Drilling the three holes seems to have done the trick. I don't think I will have to fab a second snorkel. Thanks everybody.

Now you need to come test it out on Moody Hill/Crystal Mtn on July 14th!

http://coloradok5.com/forums/showthread.php?t=210814