2.25 inch exhaust on 400ci engine...

I have a 1967 Chevelle and I'm going to be swapping out my tired 283 for a 408 ci small block. It will have a midrange cam (2000-6000RPM) and have around 9.7 to 1 compression. I was going to keep the exhaust system I currently have in the car until I got the funds to swap it out for something else. But the tips are 2.25", and I'm guessing the rest of it may be as well (would make sense for a 283).. So I'm wondering if that size would cause the engine to run poorly enough to warrant a more immediate upgrade... If so, I may have to get the powerglide trans that's in it rebuilt to save some $ instead of swapping it for a new TH350 and do the trans swap at a later date (along with a new driveshaft and new 12bolt rear end)...

The existing exhaust does utilize full length headers...I don't know what the sizing of the headers are though...

For probably the next few years (until I get the $ for a rear end swap), the car will be running 3.08 gears and probably won't rev that high.... It goes 60mph at 2500rpm with the 283 and rarely revs above 3000....

So would you get the bigger exhaust and rebuild the Powerglide, or keep the 2.25" exhaust and swap to a TH350???


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The current exhaust will not really be a restriction at your existing rpm and power levels. 2.5" will make a little more power, but it isn't a sticking point for you right now. Do your other mods first, do the exhaust when it burns out or you are ready to upgrade it.