[SD455DJ]

Originally Posted by KSZR

Very cool, thanks for finding that!

Sounds like the summit 2800 or something similar would be a nice upgrade as far as aftermarket.

A pypes exhaust system should give a nice power bump, which I need anyway because everything behind the converter is pretty rotten.

Here is the dyno session on a '78 W72 400 with the Summit 2800 cam...

Dan had a good dyno session today with the W72 400. He rebuilt the original numbers matching engine with .040" over Icon forged pistons w/4.5 cc valve reliefs that were .006" out of the hole and with .045" x 4.328" Felpro head gaskets to provide .039" quench depth. The 6X-4 heads were minimally cut for trueness and measured 92.45 cc's average for a final static compression ratio of 8.75 to 1. Dan replaced the cast rods with forged Eagle H-beam rods. New 1-pc valves (2.11/1.66) with CC dual springs were installed. A Summit 2800 cam (204/214/112 @ .422”/.444”) with new 'old' Crane hydraulic lifters along with a new Melling 60 psi oil pump. The one modification was the use of old factory D-port ram air exhaust manifolds with the 2.1" outlets with Pypes 2.5" mandrel headpipes. The original 17058263 Q-jet on the factory cast iron intake with the EGR system and plumbing were reinstalled.

The base runs were made with 42 degrees total timing in by 3000 rpm, 45 primary rods/74 jets/CH secondary rods on an I hanger. The 3rd (and best) base pull made a corrected 360.3 hp @ 5000 rpm/456.1 lb-ft torque @ 3600 rpm (351.2 hp/444.5 lb-ft uncorrected). The correction factor was a low 1.026 as the weather conditions were very good...low humidity, high barometer, and very cool temperatures (65 in dyno cell). After rejetting the carb to 40 primary metering rods/72 jets/DA secondary rods on an 'I' hanger (same total timing at 42 degrees), employing the 'big' dyno room dumps for the headpipes, and installing the air cleaner base, the max hp jumped to 371.4 hp @ 5000 rpm/459.2 lb-ft @ 3600 rpm (362.0 hp/447.6 lb-ft uncorrected) on the final pull (#14). The highest torque reading was on pull #13 at 460.3 lbft.

Dennis