Quote:
Originally Posted by PAUL K
The only reason is for a couple of reasons  lol just teasing.
I have two words for you! ..... I like them all. Personally I don't have any issues with headers but I know some can be a real challenge. JMO I feel the build or car may dictate what I perfer. It'd be hard to put headers on a car that came with RA manifolds but if you're building a "day 2" recreation I'm doubting many guys replaced the logs with RA manifolds back in the day.... So I'd perfer headers on something like that. |
Since I lived the time where I saw many day 2 cars, on day 2, the cars with RA manifolds were few and far between. I would say if I was to recollect how many left the manifolds on their cars, it would be about 50/50. Remember we didn't have any dyno tests to refer to, so if you wanted to win the stop light Grand Prix at the local cruise spot, you went with headers. As soon as Pontiac made the RA manifolds available, 5 header manufacturers were making headers to replace them. Case in point, I had a customer that bought a 73 SD T/A, he wasted no time in removing the Q jet, adding a holley spread bore replacement, and ditching the RA manifolds, and replacing them with Hooker headers.
No one knew what power each component was good for. or how much the aftermarket component gained, or lost over OEM. The belief was that OEM/bad, Aftermarket/good. Few people were testing if that latest whiz bang component actually made the car faster. If you asked the owner,how much difference it made you'd hear it gained him 50 HP, but this was total BS, street guys always said it made their car quicker, but nothing as far as timeslips etc. to back it up.
As far as log manifolds, over RA manifolds, over headers. Back before R.A.R.E. was ever conceived, RA manifolds were tough to come across, because in the great scheme of things very few cars came from the factory with them, and if you priced a set from Pontiac, you could buy 3 sets of headers for what they went for over the parts counter.
The first year I raced my 67 GTO dirt car (1975) I ran a 400 with log manifolds as class rules said no intake, and exhaust mnaifolds, except factory cast iron. I knew a ton of people that had Pontiac parts, and raced Pontiacs in my home town. Plus I was good friends with the parts manager, as well as the service manager, at the local Pontiac dealership where I had done my Co-op stint when I was still in high school/Vo-tech. I beat the bushes trying to come up with D port RA manifolds, and came up empty.
Over the winter I bought a 1970 RA III Judge, it came with manifolds on it. The engine had been run for a long time without an air cleaner on it, and it used oil from the rings being bad. It had a P4B and of course a square bore holley. I managed to run it low for oil, and spun a rod bearing in it, but the car also came with a spare 65 389 engine because the former owner planned to swap the ailing RA III. When I swapped the engine i now had RA manifolds for my stock car, that wouldn't fit, until I hacked up the frame crossmember.
After I changed the manifolds, without any other engine mods, the car was much faster, than with the logs. The main thing was it was faster at every RPM, not just at peak RPM. My take is the engine gained the ability to accelerate faster through the entire RPM range, not at just peak HP/torque speeds. The engne spends much more time accelerating from 2500-5500 RPMs than it does for tha split second you reach peak HP/torque just before you let off, and brake for the corner. The dyno figures posted in magazine articles are only looking at peak HP/torque numbers, and leave ot the gains as the engine is accelerating through the entire range. Those dyno tests all the manifold proponents always cite, only show a tiny bit of the picture. As the famous saying says, "We don't race dynos".
The same thing goes for the proponents that say you can make almost the same power with RA manifolds, over headers, they're only looking at a tiny portion of the engine operation over the entire spectrum. Race cars aren't run at the maximum RPM range the entire race, so failing to look at what happens in the time the engine is accelerating is very short sighted in the overall picture.
In my own cars I want the absolute best exhaust system over the entire range, not just at peak HP/torque. Breathing at lower RPM is where the engine spends most of it's time during a race, same goes for dirt track cars, road race, as well as autocross cars..........
