TedH

Well,

Gotta hand it to Mark (Mean Green 2000) and Cecil from the C5 forum for arranging another dyno day at Tune Tech up in Tarpon Springs, FL (or is that New Port Richey?). This is my second day of twin-pulls and came away with alot more technical advice and information about my C3.

August 25, 2001:
My first outing, I wanted to see what the results of my 1999 engine rebuild would yield. Much to my disappointment, it was clear that the smog heads (882s), stock exhaust manifolds and single-cat 'dual' exhaust were a bottleneck since I yielded rear wheel peak torque of 212ft/lb at 3550rpm and hp of 160 at 4320rpm. The torque curve looked more like a downward avalance from 3550 (looked like it hit a brick wall at 3550 and crashed from there); finishing with a paltry 145 ft/lb and 140hp at 5000 rpm. For the day, about 160hp and 212ft lbs at the rear wheels :U (corrected DOWN after the engine recovered from the 2-3 shift that yielded a 'phantom' 167hp and 256ft lbs in 2nd gear; The tuner gave me the higher numbers to ease the pain and dissappointment compared to the 280-300rwhp performances from the C4/C5's in attendance).

I still didn't match the performance of a 230hp L82 fresh out of the box with 30% parasitic losses at the rear wheels (I have an L48). So much for Accel performance HEI distrib, edelbrock performer intake, Crane energizer cam, K&N filter, dynomax super turbo mufflers and a number of other internal improvements (bore, pistons). Gotta address the heads soon!

February 9, 2002:
This time out I added true 2.5" aluminized duals from Mid-America, 700R4 from Bow-Tie (1800rpm stall converter) and a new blueprinted replacement differential with 3.54's from Spicer along with the required rebuilt/shortened drive shaft, rebuilt halfshafts, radiator support and trans lines. The tuner said 700r4 and gears won't show on the dyno; just on the track. Although, the converter may have helped. Anyway, peak torque was about 210 but at 2700rpm (more and sooner) with peak hp of 165 at 4500rpm. At 5000rpm I was still making 170ft lbs and 160hp so a much broader, usable torque and hp curve. With resplectable performance (relative to my prior pull!) from 2300rpm right up to 5500rpm. The car did run leaner (about 14.8:1) than my original 13.1-13.6 so it still needs a 'session' with jetting and timing advance adjustments. The car really sounded good with no mis-fires.

Bottom line: I gained usable hp/torque (not as much as I would have liked!) with the broader power curve. The engine also appeared to have a cleaner power curve with fewer variations (peaks and valleys) throughout.

I have a set of Dart Iron Eagle 180 heads (72cc chamber, 2.02/1.60 valves) sitting on the shelf under my workbench that I will install at my first opportunity. Depending on when the house sells, I may swap them in and return to Tune Tech before heading for the frozen tundra of Ohio. I've also bought a fresh set of stock length hardened pushrods (the heads require them as they use guide plates), Summit 1.5 ratio stamped rockers with anti gall pivot ***** and the Fel Pro gasket set to do it all right. May also install the recommended set of headers and play with the duals (can you say chambered side pipes :D ...)

I'm hoping to elevate those hp/torque numbers the next time out while sustaining or even broadening that curve. Sure would like to see the performance potential of the Energizer cam and Edelbrock intake the original engine rebuild should have yielded :D Lots of fun! :chevy


[Modified by TedH, 6:20 PM 2/9/2002]


[Modified by TedH, 6:22 PM 2/9/2002]

Budman68

Yea, those L-48 heads are the reason you are not making the power. Open that motor up and it will product the power numbers you are looking for.