[Lee]

I just finished up a stroker 400, going into a '68 Firebird convertible. This was a milder build, but thought it may be of interest to some.

The owner wanted the motor to look stock, so it has the iron intake, q-jet, stock 400 block, iron longbranch exhaust manifolds, along with the "16" heads. He wanted it to be mild enough to drive in traffic, but enough torque to get it moving. We were not too worried about peak hp/tq numbers, but wanted a broad & smooth powerband.

Dave @ SD Performance did the heads for us, setting them up for a hydraulic roller.

Dave Ray did one of his conversions on the stock distributor.

Dan Finn rebuilt & modified the Q-jet.

We used a forged 4.21" stroke crank, PPR's newer I-beam connecting rods (stock length), and a set of custom Race-Tec pistons. The pistons were dished, giving us a final compression ratio just over 9.0:1. The pistons also were made to use modern rings, with a 1.5/1.5/3.0mm ring package.

The cam is my design. I kept the intake duration at 224 @ .050, as my calculations showed that any larger and I would lose low-end at this compression ratio. The exhaust lobe is bigger than what I once would have selected, but again the numbers suggested it would help me extend the power band, which was one of our goals. The LSA ended up at 114.

As described above, but with 2.25" elbows coming off of the longbranch manifolds (the only pipes we had, which would mate to the dyno's exhaust system), this combo made 494.6lb-ft @ 3600rpm and 408.8hp @ 4900rpm. Torque was 485.8 @ 3100 (where the dyno started reading), stayed above 480 until past 4000, and was still 413.8 @ 5100 (where we ended the pull). HP hit 401.8 @ 4600, and was 401.8 @ 5100.

The motor also idled nicely at 690rpm! The owner picked up the motor today, and should have it in his car soon.