Have you guys (running Desktop Dyno) noticed a HUGE increase in both Torque and HP when selecting the "no mufflers" option on any cam? I don't think I'm a hundert percent in belief of that - maybe I'll try doing both the next time I'm at the track.
I am not sure if its huge, but my "Arse dyno" says there is a big difference. Course I have cheap "purple hornies" but it definitely is a strangle hold on the exhaust.
Without going into details, but using an engine setup that I've been "studying," HP gains and torque gains are minimal at lower rpms (without mufflers). For instance: 4500 RPM - 10 HP gain (2.5%); 12 TQ gain (2.9%) 5500 RPM - 14 HP gain (3.0%); 14 TQ gain (3.2%) 6500 RPM - 30 HP gain (5.9%); 25 TQ gain (6.1%) 7500 RPM - 38 HP gain (7.6%); 27 TQ gain (7.7%)
Hey Brad, If you are going to use those heads, get hardened seats installed, that would be a good time to add GT-40 valves, then get the ports gasket matched, heads and intake. There is some easy hps. If you want excellent lowend torque and throttle response, get a 480cfm 4bbl. Ken
For the record ...concerning Mufflers . We all know that each engine combo will respond differenty to changes, and different mufflers /headers/exhaust systems flow (restrict )differently. My car has an oversized 3 inch system with Flowmasters and Dumps hooked to a set of Hooker 6901 headers. At the track ( the full length one Shadow ) I removed my pipes and mufflers between runs ...and it made NO difference in my times at all. Maybe thats because the motor "thinks" its uncapped any way due to the size of my exhaust system.
Ken, we plan on picking up some E7 heads and get some good springs and screw in studs installed and maybe a lil' mild porting and run those. brad
If that were the case, everybody would be running un-capped at the track. I just don't see it. There's nothing more I hate than to hear a loud azz small block going down the track with open headers. Ugh. (let me qualifiy that, I mean a "slow" small block.) Mike's testimony is only one of many, but may not qualify as a true test as he is cheating with a 3" system (okay, so am I). Anyway, I think it's .
Rick, I can think of one thing I hate worse. A SLOW Harley (meaning all of them) making lots of noise and going no where fast!
I took my caps off and actually lost time...The carb is tuned for a certain exhaust, and when I opened the dumps, I lost a couple tenths, and it ran ****ty. Sounded good though. Sounded kinda like Rick Books car...
Ha! You'll have to be more pacific - oh, you mean when it actually runs! Good info too (that you lost et after bypassing the mufflers - which further debunks the Desktop Dyno numbers - assuming your caps didn't cause a restriction in flow themselves).
i have thought about running turn dows right after the header.. open it at the track.. closed for the street.. my car is loud now as it is, and it has mufflers.. i would have to wear ear plugs if i opened the exhaust
