Chevy Astro and GMC Safari Forum banner

Intake modification

9K views 56 replies 14 participants last post by  SlowRider 
#1 ·
!cid__0501141748.jpg
I don't like the fact that the stock intake even LOOKS restrictive.
Granted, it's got a better housing than other "cold air intakes" since you can't really have one on these.
Going to change a couple things.

First I'll be making a 3-3.5'' circular cut in one of these 4 locations outlined in red.
!cid__0501141748a.jpg


I don't know if you can see it, but that black rounded rectangle is the stock intake port. I will be cutting a hole in this also.
!cid__0501141749.jpg


And for the first cut, I'll be removing this. Air intake resonator. Useless junk and I'm going to make a second intake hole and pipe lead to take it's place.
!cid__0501141749b.jpg


And then chevymaher gave me a link to another write up here: viewtopic.php?f=43&t=16725&hilit=cowboydan#p177792

I like the idea of the smoother pass, so I may be using it as well.
All short ram pipes.
 
See less See more
4
#28 ·
35 hp?

Lol. I hope that's sarcasm. Though it is lump.

Go but a "NOS" sticker. That's good for at least 50hp.
 
#37 ·
WoodButcher said:
Here you go,
The fans are run through a relay and run at 2 speeds depending on temp, the sensor for the fan thermostat is in the upper rad hose.
That's not a bad idea, just leaving it open. Actually, I like that a whole lot more than using any enclosed piping now that I think about it.
But out of personal preference I think I'll cut or drill some spaces right in front of it through the metal. This way it's still colder coming in and I wouldn't have to worry about water in the intake.
 
#38 ·
There is nothing there to cut but the hood itself. 2 people have done custom intakes here that are worth mention, one swears he has a HP monster and the other has done a pipe that draws from underneath and while both I'm sure are equal or better that what I have done I can't see that either are worth the effort. The at at my intake is so close to ambient temps that ducting would improve very little. What I did was simple and in my case almost free, (I had to buy the fan control) and It gave me room to work on the engine. HP? PFFT, I didn't notice anything...

I'm with Lump on this one, magnets on the fuel line,
but you gotta add the $69 chip!
 
#39 ·
WoodButcher said:
I'm with Lump on this one, magnets on the fuel line,
but you gotta add the $69 chip!
This is an efficiency thing in my case. I'm not going for power in this little endeavor.
This thread has really turned itself into a giant learning experience for me with no actual modding so far :rofl:
 
#40 ·
Okay so I finally got back to this project and found what I was looking for. First was a silicone elbow adaptor that goes from 3.5 inches to 3 inches. From that I went straight to the front of the engine to a cone type air filter. That really did nothing for performance or mileage. That was a bust.
So I dug in a little deeper and found a company that bores & ports the TBIs for the Vortec engines. They take a stock GM TBI bore it out to 74 mm, put in a new butterfly without the scupper, put in a smaller diameter pivot shaft and use round head screws to attach it. I was able to install all the parts in about 1 1/2 hours from the front. No doghouse removal.
That finally gave me the kick I was looking for. At the same time I took the slack out of my accelerator cable. Now the ole van has some new kick. I notice that generally it has more seat of the pants performance. NOTICEABLY ! I took it on a short trip this weekend and was able to p**s the hell out of the CA drivers that thought they were going to cut off the old dude in the beat up old van. HA! I had great fun in closing up the gaps without even dropping gears on the trans. San Francisco drivers are notorious for sliding into the smallest of gaps. A few almost lost bumpers.
Anyway here are pics of the difference. Best $250 I've spent on Vanna yet.
I've already started on the next mod. A console with a B&M shifter. More pics on that probably tomorrow.
 

Attachments

#41 ·
Astro Pop said:
Okay so I finally got back to this project and found what I was looking for. First was a silicone elbow adaptor that goes from 3.5 inches to 3 inches. From that I went straight to the front of the engine to a cone type air filter. That really did nothing for performance or mileage. That was a bust.
So I dug in a little deeper and found a company that bores & ports the TBIs for the Vortec engines. They take a stock GM TBI bore it out to 74 mm, put in a new butterfly without the scupper, put in a smaller diameter pivot shaft and use round head screws to attach it. I was able to install all the parts in about 1 1/2 hours from the front. No doghouse removal.
Interesting; @74mm? What is it at stock?
I'd be interested in seeing the CFM numbers on 74, 75*, and stock.

(*CFM-Tech does a TB port as well at 75mm)
 
#43 ·
Did you try removing the "scupper" yourself and look for throttle response before shipping it off for boring? Do you have any data from the MAF sensor showing there is a significant increase in airflow?

I have heard that a good polishing can put some extra perk in your twerk as well:

polished.jpg


What does it look like installed with your air filter etc?
 
#44 ·
How does it look? Like the normal fleabay "cold air" intake. With our doghouse covering the engine it's hard to see much. The TBI is cleaner though. OH and I'll go for the polishing! Does she do the polishing?
I didn't consider the 75mm from CFM-Tech, where I got this one, 'cause the intake manifold bore is 74mm. No advantage. Possible disruption by airflow hitting lip and setting up turbulence and I didn't try removing the scupper. I was researching that when I came across the bored TBI and from experience with my other car knew it would work. Plus I just didn't want to take the TBI off twice to try the scupper and then the bored TBI. Maybe removing the scupper would give about the same increase, but I'll never know. Ignorance is bliss. I tried getting a reading on the stock TBI bore but my vernier calipers are the short ones I couldn't get down to the bore. I think they're about 70mm.
I also didn't take a MAF reading before, good idea CC, but i'll try to get one now. Anyone know the normal stock reading?
At 221,000 mi on the original engine, it's time to stop the engine mods. I'm afraid much more and she'll blow. So onto interior mods.....camperization and such.
 
#45 ·
97cargocrawler said:
Did you try removing the "scupper" yourself and look for throttle response before shipping it off for boring? Do you have any data from the MAF sensor showing there is a significant increase in airflow?

I have heard that a good polishing can put some extra perk in your twerk as well:



What does it look like installed with your air filter etc?
Wow that is some throtle body! If she is the wife no wonder your so happy;)
 
#46 ·
97cargocrawler said:
Did you try removing the "scupper" yourself and look for throttle response before shipping it off for boring? Do you have any data from the MAF sensor showing there is a significant increase in airflow?

I have heard that a good polishing can put some extra perk in your twerk as well:

What does it look like installed with your air filter etc?
There's a point o.o
How does one "take a MAF reading"?

Yay! More learning things :D
 
#49 ·
I finally got back to getting a MAF reading. I used my little ELM 327 so of course the readings don't correspond to anything I was hoping for. Instead of CFM it reads in lbs/min. What I got was:

Idle 600rpm = .7 to .8 lbs/min
WOT under load = 22.2 to 23.0 lbs/min
Does anyone have readings on a stock TBI for comparison ?
 
#51 ·
I didn't see a load reading on my little monitor. Just to be sure we're talking apples to apples, WOT is Wide Open Throttle. The TPS was maxed out. I was going uphill with my foot all the way to the floor on one test. The other two were on a back road flat & straight again pedal to the floor for about 1/8 mi. I'll try again tomorrow if I can find a load monitor on my little monitor. I'm using OBD Auto Doctor, maybe I'll try some other apps to find it.
 
Top