I am getting ready to buy the stuff to build my headers and I am wanting opinions on tube size. I will either use 2" or 2 1/8" primary tubes. Will the extra 1/8" make that much difference? My current 9.0 to 1 452 will most likely be the mildest motor the car will see and nitrous may play a part in the equation too. this car (65 Mustang) will be primarily a strip car that may get street driven only occasionally.

I don't know enough about the engine to ask the "Gonk" but I'd guess:
if over 600hp use 2-1/8
If 500-600hp use either one
If <500hp use 2" or 1-7/8 <br> If <400hp use 1-7/8 or 1-3/4, 2-1/8 will likely COST you TQ and HP at this level, been there, done that.

you said (future bigger or more powerful engine, NO2 use, etc.) I'd say for the $ and effort, go larger at 2 1/8". The cost of the larger tubes is almost inconsequential but the effort to (later) make a 2nd set for max hp. is huge. Any loss of low-mid range torque/hp due to too large of an exhaust now with the current engine can't be that much.



I agree with Webry's conclusions as well and we don't know that much about the engine or vehicle. That said, an auto (smaller tube) versus stick (larger tube) application and mainly drag only would also make a difference. At the current 452 cid size, one would only need make 1.35 hp/cid and be at the 600 hp level without a power adder. My guess is thinking you intend to soon be at or over 600 hp (power adder or not). If so, I'll stick to my vote for the larger tubes.

correct. He wasn't telling which headers to buy. I've always had a 2 1/8" tube on my car, but it was fairly light, 4 speed and lot's of rear gear. A street car that didn't care if the HP or Torque was up or down a few.

On serious drag cars, a lot of the Stocker guys have gone downsize on the tubes to gain the maximum possible. Mostly depends on application, but if you're only going to buy 1 set, go big I say. Not many street cars need more than a 2" tube though. JMO as usual!

or less than precisely built ones or with short tubes. I have used it on alot of things that you would think 1.75" would be better, but they work.