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346250 Intake

31K views 4 replies 3 participants last post by  PA-Farmer 
#1 ·
Anybody have an opinion on the stock GM 346250 intake manifold that came on 76 four barrel 350's?
Since I've got the top of the engine apart I was wondering if there is any reason to upgrade the manifold to an after market. The 350 with 882 heads and a Holley Street Avenger carb is in a '31 Chevy five window coupe with a Seville rear with 2.73 gears and I am most interested in getting good gas mileage. I drive the car to town frequently and the motor has plenty of power for the light coupe.
Any reason to spend money on an after market manifold?
Thanks
 
#2 ·
A stock intake is fine for a daily driver, and there wouldn`t be any good reason why It wouldn`t work with your combo. The only thing I can see bad about it is you mentioned a Holley carb, which requires a adapter to bolt on a Square bore carb to spread bore intake. Most adapters aren`t what there worth. You can either get a Weiand Action Plus, or a Edelbrock Performer. Both will give it a slight power gain, and both have a multi carb flange, meaning you can bolt on a holley or a Quadrajet without the use of a adapter. These intakes are often on ebay at a good price, but new the price is good also. One thing I`ll advise on, do not use standard fel pro intake gaskets, the standard ones are for use with a heavy cast iron intake, the intakes weight crushes the gasket so it seals, A aluminum intake isn`t heavy enough to crush the gasket resulting in a leak. I usually use the standard off the shelf Mr. Gasket paper intake gaskets, they seal well with any intake.
 
#3 ·
346250 intake

Doublevision,
If you think it's the weight of the manifold that crushes the gasket down to make it seal, think again. :nono: If that was the case you would only need a bolt or two to hold the manifold and keep it from sliding off. The reason those fel-pro gaskets don't seal with aluminum is that their materials can't match the greater expansion and contraction rates of the aluminum intake(the gasket can't "spring back" enough to stay sealed after some heat cycles) Weight is not an issue. :spank:
 
#5 ·
Thanks for the comments.
I never did care for the adapter I needed to bolt the Holly on the stock intake.
Keeping with the theme that my '31 is pretty much a lesson in recycling and I'm more interested in fuel economy than power, I found a 70's Edelbrock S.P. 2-P dual plane aluminum intake built in the seventies for low end torque fuel economy. I read some of the previous posts on this intake and, like lots of things, opinions vary.
Once I get the motor back together, I'll you know how the combo works out.
 
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