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-   -   Exhaust manifold flange size (https://forums.maxperformanceinc.com/forums/showthread.php?t=830052)

jamaca85 05-29-2019 10:15 AM

Exhaust manifold flange size
 
What the biggest size pipe that can be mounted on a stock d ports exhaust manifold flange. Looking at the ram air type manifolds. Thanks

form74 05-29-2019 12:40 PM

I have the RamAir 2.5 manifolds with these down pipes in the attachment, which allows 3 inch exhaust all the way to the tail pipes.

https://www.ramairrestoration.com/po...y-headers.html

jamaca85 05-30-2019 06:25 AM

thanks

Sirrotica 05-30-2019 09:07 AM

With log manifolds and 2 bolt flanges 2 1/4" is usually about as big as you can go.

The RA manifolds have larger flange areas enabling 2 1/2" if you enlarge the center hole in the flange.

There is a way to adapt up to 3" pipes using header collector flanges adapted to the 2 or 3 hole flanges, requires welding and fab skills. Basically the old flange pattern is used to build a plate that is first bolted to the manifold and then has the 3 hole header collector flange pattern on the 3 inch pipe that is then bolted to the adapter plate.

Way back years ago, on the 67 GTO in my middle signature picture I built adapters to adapt the 3 hole Pontiac RA head pipes to driveshaft tubing (3 1/2 inch OD) that dumped at the rear axle. The seat of the pants dyno was feeling the improvement...LOL

bill ryder 06-01-2019 02:54 PM

I also have a complete 3" system from RamAir with X pipe and electric cut outs. Fits like a glove. Sounds GREAT..

"Bill"!


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