how much will a set of shorty headers add to a 250-275 rwhp 283? its got stock 305 1 7/8" log maifolds and a flowmaster exhaust with no cat. its making most of the power in the 3000-5500 rpm range. i'm expecting a lot since this engine likes to flow for a 283 and has a ton of backpressure.

 

I may be wrong, I think a whole exhaust system is usually good for about %10-15 increase in power.

 

i dunno, i was running open headers when i put my 350 in, i paid 400 for a full exhaust and it feels a hell of alot slower now, thats no cat and a 40 series flowmaster.

 

Of course it will feel a bit slower, open headers makes alot more power than a full exhaust with mufflers will because there is next to no engine restriction.

 

Yup.

 

i knew it wasn't gonna gain anything, i knew it'd cut back, but i had no idea it was gonna blow that much ***...

 

ehhhh cat-backs dont blow that much "***"......compare it to your stock system and you'll think twice