Hello, how much horsepower/torque loss do you think there would be in a 470 street (525 hp) build with a 1 3/4 vs 1 7/8 header? The reason I ask is that the dougs headers for a low deck are $200 cheaper than the tti 1 7/8 inch header. But are also only 1 3/4. I really don't want a 2 inch header for a street car. Thanks

If you're only building for around 525hp I don't think you'll see a huge difference between the two.

The smaller primaries might even give you a little more low end torque.

1&3/4 but I'd suggest 2&1/2 or possibly 3" mandrel bends from the collector flange rearward. You would need an X pipe/proper muffs/resonators in the tailpipes alongside the leafs to keep the noise manageable esp w 3"

Go 1 7/8"

I saw 2 tenths gain going from 1 3/4 to 2 inch headers.

Is a 3 inch system realy needed for a mild street motor. I always thought sdmaller tubes are better for torque and mpg.
Best header would be small diameter long tube set-up with 2 and good flowing muffs. These 3 inch systems are popular with the high horse power set, but I doubt there is any benifit on the street. Well maybe bragging rights. There is a need for bragging rights. Right?

All I can tell you is a run a basic 440 with KB pistons and 906 heads and I use Hedman 1-3/4 headers. Its run a best of 11.49 with them. Ron

My opinion,
1 3/4 will make more low-mid range torque.From the mid range up the 1 7/8 are a clear winner(especially on a car with ported heads and higher rpm capability).
That being said on a heavy car with low-mid 3 series gears the 1 3/4 will likely out perform it on the street.
Any hot 440 will usually see 10-15 hp at the top of the curve.ON a stock head motor I would go 1 3/4.
Any stroker will usually benefit from better exhaust.2.5 mandrel bent pipe will support your motor fine.