John Cunningham
I'm Awesome
Maybe a tri y...but no shorty will ever work...you need some 36 long small primarys and a small collector extra long....I have paid thousands for headers over the years from the best guys there are that make them......Davis Step Headers. Jere Stahl.......Headers By EdCompletely disagree but I understand the desire to keep the manifolds for maintenence and reliabilty.
After I put tri-y headers on the Express it made ALOT more grunt even down in the 1,500-2,500 rpm range. Same torque converter would stall 200 rpm higher. I was suddenly able to climb hills in overdrive that had previously caused the trans to drop to 3rd. My vacuum at cruising speed on the highway also increased 2-3 in/hg at 70 mph.
I am sure header selection plays a HUGE role in the results. If a person was to throw some header with a massive primary and collector diameter on a stock engine I could see it not helping or even hurting through the 4,500 rpm range. A good quality tri-y like Doug Thorley makes will wake up the bottem end and midrange ALOT!
Lemons Headers....I was a serious drag racer and have spent hundreds of hours on engine dynos spanning 35 years....cruising at 2500 rpm part throttle will give you nothing and maybe under full power and exceeding 4000 rpm you might see a little. Most of my engines were tuned for over 10,000 rpm. We shifted at around 9700 and they fell back to at the most 7700 rpm...headers are crucial then. I have dynoed some street engines with kids bring me 1 3/4 headers for 350 street engines.........no power gain below 4000 rpm and had Headers By Ed build me some 1.5 inch 38 long equal length headers and we picked up...The problem is ..........hard to purchase and out of the box header that fits and performs...there all made like crap...I dont want to chase header bolts either. No thanks...1000 rpm to 3500 would not be worth it...