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Have the original dual inlet air cleaner housing and top for my 71 BB. Was wondering if the original style open cleaner used on 70 BB would offer any performance gain. I need a new top for the 71 and in most vendor catologs it appears I can purchase the complete 70 unit for about the same price as the 71 top. Also does the 70 have the same breather tube location as the 71.
I doubt that the 65-70 style open element air cleaner (also used for 71-72 LT-1s) will provide any significant power gains. Plus, there are 2 good reasons not to do it:
1) obviously, originality will be compromised in a very significant and instantly visible sort of way;
2) your car will be emissions-illegal and may fail the visual portion of emissions inspections if your car is subject to them.
Other than the breather tube to the right side valve cover what emissions would it effect? Plan on keeping the original base and getting a new top regardless for show and sale purposes. Was more curious about the performance aspect, when you look at the BB and the cubic inches of opening available for air flow on the dual inlet cleaners versus with the open air cleaners the difference is huge.
It's emissions-illegal to use an open element air cleaner on any car originally equipped with a closed element air cleaner. Of course, the swap out for emissions inspection is pretty easy.
As I mentioned, though, I don't think that the power difference is going to be significant notwithstanding the size of the "inlet".
Joe is the open element assembly still available from GM? I bought one over 10 years ago from GM? I used it in place of the late year 70 dual inlet air cleaner that came on my car like Andy's 71. Had to dent the fresh air tube for interference with my Holley double pumper I also installed.
Jim - go to noahperformance.com....he has all the GM dies, including the BB valve covers. He is selling them on his website, and, usually on Ebay and they come up less than the website prices. He is noahperformace for his handle on ebay I believe....Craig
I did exactly this swap on my 1971 small block. It is absolutely the best and cheapest horsepower modification I've ever made to my car. Originally I used an open element cleaner from Summit with a K&N filter, but now that Corvette Central has a "foreign sourced" reproduction of the open element 1970 style for a Quadrajet, I've changed to that with a K&N. In my experience, it made a significant SOTP difference and a difference at top end. I wish I could dyno it both ways, but don't have access to that. My nicely restored 1971 dual snorkel unit is in the basement on a chest of drawers.
By the way, the Summit unit fit in my 71, but not my Dad's 72. Same 350 motor, intake, Q-jet carb, etc. That's why I swapped to the new repro unit, as it fits a fair amount lower and there's no chance of hitting the hood with the carb stud.
Go for it. You'll love it. Emissions is just a state of mind, especially on a well tuned 31 year old car.
Patrick
Vice-Chairman (West), Michigan Chapter NCRS
71 "deer modified" coupe
72 5-Star Bowtie / Duntov coupe. https://www.flickr.com/photos/124695...57649252735124
2008 coupe
Available stickers: Engine suffix code, exhaust tips & mufflers, shocks, AIR diverter valve broadcast code.
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