Originally Posted by
Fast355
LT4 heads are195cc with 2.00/1.55 valves. Their smallish chambers have them at 10.8:1 with the flat top piston. The cam is 203/210 @ .050 and they run 1.6 roller rockers from GM.
I have 205cc copies of Dart Pro1 Platinums on the L31 in my Express van. With a 215/224 cam and 1.7 roller rockers. With the MAF disabled I had to add a good bit of VE above 2,500 rpm. With SD disabled the MAF only required slight tweaking in the lower rpm, lighter load areas to get the fueling back to optimal. Once they were both fixed it was noticeably smoother and stronger across the whole RPM range. Converter stalls 2,500 rpm and I have 4.56 gears with the 30.5" tall tires. I turn 2,600 rpm @ 70 mph in OD. With the travel trailer in tow I have found any real grade has me in 3rd @ 3,500 rpm and if the climb is long enough or steep enough I have plenty of RPM left in 2nd gear if needed as well. 2nd puts me at 5,200 rpm @ 70. My shift points in Tow/Haul let it grunt a bit though and I do not downshift to 2nd unless I am under 65 mph in Tow/Haul.
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