Quote:
Originally Posted by 1funride
I was disappointed. I am trying to figure out where all my HP went?? Hahahaha. But seriously I was surprised, maybe even shocked. Good compression, good heads, port matched, ports aligned, the air fuel ratio is a little rich but overall it was good, timing I think is typical pontiac good (I am going to check that again), I degreed the cam, good spark, I expected more from the camshaft (with 1.65 rockers even) as it didn't make power past 5000 and we pushed it to 5700, Is it the exhaust is holding it back......and the cam does have a little more in it? Maybe the flex fan? Is it as simple as just an accumulation of drivetrain loss, flex fan, exhaust, and accessory loads?
Not that I am horsepower chasing, but when you have attention to detail and use parts that should perform a little better you want it to perform to its potential. As stated prior the car has very good throttle response and pulls through entire RPM range, easily breaks the Nitto tires loose when snapping the thrrottle in first gear half throttle driving speeds, spins them pretty good at 2nd gear shifts. The dyno runs shows it running smoothly with no hickups.
The TH400 is power hungry, I have read of real world tests where they take more than 25%, see article below for a real world test and the reality of big auto transmissions stealing your power.
https://www.hotrod.com/articles/ccrp...in-power-loss/ |
Those numbers aren't terrible at all for a 400 Pontiac. When we were at a dyno day there were a handful of mild 400 Pontiacs that were under 300 RWHP. I remember 2 of them were in the same 275hp range you are, one was in the 280's. I was the only 400 that day that hit 301 RWHP and 355 RWTQ. There was even a hopped up 455 with open headers that barely did 320RWHP.
I was running through a 400 turbo with a stock converter, and a 12 bolt rear, all accessories including Alt, PS, Water Pump, Fuel pump, stock clutch engine driven fan, and the factory 70 RA air cleaner in place. All that stuff drags down HP. If you run even the slightest stall converter, it really sucks down the power at the wheels, which I suspect that 455 had, because his RWHP didn't reflect how he was running at the track that day (mid 11's)
If you run steel wheels, steel driveshaft, bigger rearends like 12 bolts, 9 inch, it will all suck the power down. So don't get too worked up over it. They are fantastic tuning tools though.