First up, the Lunati sticks with the 114 LCA, fed by the PI fuel-injection intake. As expected from cams with 6 degrees more intake duration and 12 degrees more exhaust, the low-end torque dropped by 8 to 10 lb-ft at 2,800. By 3,800, the bigger cams started to show their worth, and by the time 4,800 rpm came around, they were as much as 10 lb-ft up. All this was fine, but as the rpm climbed, the gains dropped off. At peak power, the new experimental cams were only giving about 4 or 5 hp more. From the stronger midrange and the top-end drop, we suspected that the fuel-injected intake might be at its limit, and possibly curtailing the cams' true ability. Now seemed like a good time to install the Edelbrock Victor Jr. intake and Holley 650 HP carb.
During the ignition programming and carb-jetting session, it was immediately apparent that this Edelbrock conversion was going to be nothing less than outstanding. The dyno chart details the results, but here's the deal: peak power climbed by 43 hp. At 6,400 rpm, the carbureted Victor was up over the injected intake by no less than 94 hp. On the carb, the engine could turn a useful 800 rpm more.
As impressive as that seems, Andy claimed we were not done wringing out the Edelbrock/Holley carb combo yet. There was a trick or two still up his sleeve, but round two would need to wait until the next dyno session. Right now, we had another set of cams to test. Tightening the LCA from 114 to 111 degrees delivered an extra 7 lb-ft of torque and almost 10 hp. Our test numbers do support Andy's claim that you should go for a cam on the right LCA, and if piston-to-valve clearance is a problem, shorten up the duration.
Trick Carb Boosters
We are now at our last power move, and it's a doozy. The Edelbrock intake is a great manifold, but because the intake ports, bank-to-bank, are so far apart, the volume of the intake is truly cavernous, and that's not good on a small-displacement engine. This leads to a damping of the booster signal, and results in less-than-optimal fuel atomization. When a carbureted situation like this crops up, Andy has a carb specialist build a special version of the 650 HP Holley with a high-gain, high-atomization booster. As the results show, this is an outstanding move to make as part of a Mod motor carb conversion. The booster modification restored low-speed torque and added as much as 27 hp at the peak.
|DRAGSTRIP RESULTS |
|Mod: ||1/8-mile e.t.: ||¼-mile e.t.*: ||Rear-wheel hp: |
|1. ||9.72/74.50 ||15.97/84.71 ||182 |
|2. ||9.56/76.21 ||15.68/85.12 ||179 |
|3. ||9.17/78.10 ||14.98/88.30 ||198 |
|4. ||8.86/80.20 ||14.42/91.80 ||215 |
|5. ||8.54/81.70 ||13.85/95.01 ||228 |
|6. ||8.05/84.50 ||12.97/105.02 ||266 |
|7. ||7.23/92.23 ||11.49/117.22 ||313 |
|8. ||6.99/94.88 ||11.06/122.09 ||340 |
|*quarter-mile runs 1 through 6 estimated from eighth-mile results |
1.all stock baseline
2.changed 2.73 gears for 4.10
3.added stock PI cams, shorty headers, and MAC H-pipe and mufflers
4.installed SHM 2730 cams
5.Swapped stock intake for PI intake manifold
6.Ported heads (Non-PI), added 1 point of compression, and Edelbrock long-tube headers
7.Installed Edelbrock intake and Holley 650 HP carbInstalled high-gain boosters in carb, removed 200 pounds from car
These ceramic-coated, stepped,...
These ceramic-coated, stepped, merge-collector headers from Edelbrock are the ticket for 4.6 mod motors having the potential to make 300-450 hp naturally aspirated. They were a significant part of our mod-motor power recipe here.
This is Edelbrock's Mod Motor...
This is Edelbrock's Mod Motor Victor Jr. intake with a Holley 650 HP carb. It proved to be a real powerhouse on our '97 test mule motor. Changing to this setup also involves an MSD programmable ignition module.
The MSD ignition that is paired...
The MSD ignition that is paired with the Victor Jr. intake uses the stock coil-over-plug setup. We mounted the MSD ignition module in the engine bay and programmed it as per the original OE computer.