Air Flow Issues?


Number of posts : 20
Location : Calgary AB
Registration date : 2013-01-18

Air Flow Issues?

Post by Stomper on Sun Jun 11, 2017 9:20 am

I'm the new owner of a 69 display van with a 250 six. It runs poorly and I'm thinking it might be fuel mixture.

Someone removed the bottom of the air filter housing, exposing the air filter. I've noticed in many photos of G vans the air filter assembly is replaced by a small exposed filter directly on top of the carb. Not sure if this is just for looks. My van starts a lot easier when the dog house is open.

Are there inherent air flow problems with the G vans? Am I reading too much into this? Should I just focus on tuning the fuel mixture?

Number of posts : 1412
Location : New Jersey
Age : 64
Registration date : 2013-08-18

Re: Air Flow Issues?

Post by Vantasia on Mon Jun 12, 2017 5:42 am

Hi, welcome, there are many differing opines on air .02....using a small hot rod cleaner over the hot exhaust manifold makes for rough idle and poorer performance especially at idle in hot traffic. áThe factory GM air cleaner with the long snorkel was designed to draw in cooler air from the "cold" side of the doghouse and directly from the fan. áMy van came with a little one and I switched to a factory setup and it runs great under all conditions. Yes, there are airflow problems by the overall design of an engine in a box. áThe bottom belly pan with its louvers is necessary for proper cooling. áThe two side shields extensions from the pan also help, mine runs 5-10 degrees hotter without them in place, I was amazed at the difference when I finally found a pair for my 1st Gen. They apparently help pull the air out of the doghouse at speed. I'm sure GM Engineers ran wind tunnel smoke tests on these vehicles back in the day to figure it all out. áIn addition to air flow, good air will do you no good without a fresh clean radiator, either a refurbished stock one, re-cored one or a new replacement, there are several that can be adapted. áIf your van has its original 50 year old radiator, get it checked at a shop for clogs...With a good radiator and the pans in place, you should be fine. áStay away from extra electric fans, they just block the air flow, all just MH(and experienced)O's....

Number of posts : 11676
Location : San Diego, California
Registration date : 2008-05-12

Re: Air Flow Issues?

Post by donivan65 on Mon Jun 12, 2017 8:33 am

Do a fuel test,,,,,,when its running,,,,spray a shot of carburetor cleaner or starting fluid down the carburetor,,,,,,,if the engine runs smoother, you have a lean condition to repair,,,,,,,

Number of posts : 321
Location : Rocket Ranch Lompoc, CA
Registration date : 2008-05-18

Re: Air Flow Issues?

Post by 64chevy on Mon Jun 12, 2017 11:12 am

I run those little hot rod air cleaners on my 1st gen vans and never had any issues with them. Run up and down the freeway and around town all day. With that little 6 in your big 2nd gen doghouse you should be getting plenty of air flow. If it starts easier with the doghouse lid off maybe it's boiling the gas out of the carb after you stop it. No air flow. I'd add one of Donivan's "Hamburger fans" to cool it down after stopping. Helps gets rid of that gas smell also.

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Re: Air Flow Issues?

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