Got to dyno a customer's 465 inch Tunnel Port a couple weeks back and was rewarded with 696 hp @ 6700 and 589 lb-ft of torque.
This engine had been assembled before and the first time we dyno'd, we made somewhere around the 590-600 hp mark. My customer wasn't satisfied with that, and for the sake of data and experimentation, I jerked the heads and intake off and sent them to Lawes Mayfield to have them ported. I can't sing Lawes' praise enough, this guy is a real testament of talent when it comes to manipulating flow. He pulled 40 cfm out of them, while making the CSA SMALLER. We picked up flow and velocity both, always a win-win.
I also pulled the short block down and ordered a set of new pistons from RaceTec, with a little dome on them. We added another 2 points of compression, going from 10 to 12.
The cam also got switched. The old cam was a 260/270 @ .050" Bullet solid roller, with .600"/.650" lift (heads had some funky flow issues when I first got them), and a 106 LSA on a 104. I ordered a new cam from Comp, 260/270 @ .050" again, but .750" lift and a 108 LSA. Lawes said that he saw a lot of evidence of reversion, so I aimed to bypass that a little as well. When I degreed the new cam, it came in on a 107 ICL, so I left it there. Piston to valve clearance was .093" on the intake side, .076" on the exhaust side. This is a little tighter than what I like to see, and seriously thought about pulling the pistons and cutting them, but I checked it with a dial indicator, checking spring, and a degree wheel (instead of clay), and knew that I would gain a good bit because of pushrod deflection with the actual valve springs...so I let it roll. Didn't sleep good last night, but I let it roll. :-) Spring pressures were 265 seat and 636 open with PAC 1300 series endurance springs, PAC titanium retainers, and hollow-stem Ferrea valves. A new set of street T&D's were used as well.
We also bolted up a new CVR electric water pump, using a set of Jay Brown's pump adapters. Worked very slick.
First pull out of the box was 599 hp. That was at 5200 rpm...LOL I knew we were going to hit a good lick this time. A/F ratio was very rich, 11.5:1, so my Quick Fuel guy worked with the air bleeds and pulled some fuel out. I always like when he gets to pull fuel out, shows that the engine is efficient.
Kept tinkering and the power kept creeping up...654, 680, then 696. The 696 number was with 8 inches of vacuum from the pump (a good safe street vacuum) and 36 degrees of timing in it. A nice solid 1.5 hp/ci and 1.27 lb-ft/ci, and a scream up to 7000 rpm. Loved it.