OK, so headers make more hp, but since hp is directly related to rpm, what about low rpm, like under 3000? How big a difference is there between manifolds, ported manifolds, and headers while cruising along the highway, especially in terms of efficiency? Of put another way, at what point to headers really start to make a difference?
On my engine according to the dyno sheets the engine made its peek hp and peek torque numbers at about the same rpm...with or with out headers. But with headers the engine made more hp and torque over a larger rpm range. For example it made 35 more ft. lbs of torque @ 3500 rpm. And where with the manifolds hp was starting to drop off at 5200rpm, with headers it was still making power at 5700rpm. The manifolds tested were top of the line (ported). There is no argument that headers are more efficient at making hp. Manifolds on the other hand do their job quietly without much objection...No painting or gaskets to maintain. They both have their place.
I think for the Most part headers are better when in the higher RPMs. The also make the car louder. :3gears: :beer
I would say that if you're going to be under 3000 most of the time (cruising), headers will be more trouble than you'll want. As stated above: louder, eventual rust-out, gasket/collector leaks, ground clearance, steering gear clearance, installation, engine compartment heat, cost. But then again, I like headers.
headers vs manifolds... I have a 1970 GSX Stage 1 455 bored out to a 464 I have used Gregg Tomlinson ported 67 exhast manifolds and have in 2003 installed in their place a set of TA Jet-hot coated headers. I have run the car in the 1/4 mile at PIR in Portland and run 12.90 @ 105.89. The car does not seem any faster with the headers but I haven't run it at the track with the cast iron manifolds. But I have now chaged back to the cast iron ported manifolds.The headers look really cool but they seem to create more heat and are the pits to work around when you want to do anything under the car and you always have to be thinking about what you will hit next under the car due to low ground clearance. Headers are great if you need all the power you can get at the strip on a higher RPM car with a bigger cam but I think they arn't worth all the hassle for a street car as far as I am concerned. My cam is a Crane 218 dur. / 112LC / 448 lift. Turbo 400 BB transmission, stock intake with ported heads, 3.64 gears. ( Iam changing the rear to a 3.08 posi for better cruzin on the highway. :3gears:
An engine is simply an air pump. Any way you can reduce resistance/restrictions in the air flow path will give you an increase in efficiency. As an example - when I swapped out my stock 400" for a stage1 462 with KB118 cam, the car went from 15.8 to 14.6 - this was still using the stock exhaust system from the 400" which was the intake manifolds and the stock size 2 1/8th ?? exhaust pipes. I expected ALOT more for all the money...... o No: Switching to a set of 1 7/8th" headers into a mandrel bent 2.5" exhaust system ALONE dropped another 9/10ths off the time immediately, down to 13.7 and with further tuning and a gear swap I was in the 13.0's While your car might not race, any car will increase its efficiency/performance from a change from stock exhaust to a performance setup. ......Look at all the Cat-Back systems that exist for 'stangs and F-Bodies for sale for years. Must be something to it :Smarty: :Comp:
