Dyno Testing
In order to see the effects of renewing our our 650 cfm Holley was tested before and after the rebuild on a moderately built-up 351W test engine at the BIGS shop.

Our tired 650 was bolted on with no modifications other than jetting up to account for the larger displacement motor, and setting the idle speed and mixture. The motor pumped out a peak of 458 horsepower and 460lb.ft. of torque. Impressive numbers, but this is a 500 HP engine with the correct size and tune carburetor.

After BIGS performed their rebuild and calibration, the double pumper was bolted back on the test engine for another round of dyno testing, as well as leak checks and fine tuning. This time the engine responded with 475 HP and 483 lb.ft. of torque, a gain of 17 horsepower and 23 lb.ft. at peak output. More impressively, as the chart shows, are the gains all across the powerband. Average horsepower improved from 389 to 405 horsepower, and average torque was up to 426.5 lb.ft. from 409 lb.ft.

Installation and Track Testing Our plans from the onset were to install the rebuilt 650 on Project 11.99 and perform a variety of track testing.

Installation was the easy part -we attached the fuel line, and bolted the fresh carb on to our 302 motor using a fresh basegasket. Other than setting the idle speed and mixture, all we had to do was ensure our fuel pressure was at 6-7 psi, and connect the throttle linkage.

Based on BIGS recommendation, we left the jetting how they set it, 72 primary and 78 secondary. A couple tips: use a permanent marker to note the jet sizes on the bowls, this way you won't forget and have to pull the bowls off to check! Also if you are running a cheapo chrome plated dual-feel fuel line, splice in a piece of rubber fuel hose as shown. This way you have enough flexibility to remove the bowls and change jets without having to disturb the hard-to-seal fuel fittings.

We've had the BIGS 650 installed for a few months now, with the intention to perform a wide range of testing on Project 11.99, including a comparison of the 650 on a Weiand Stealth dual-plane intake against the 750 cfm/Victor Jr. induction package we had been running. Unfortunately we haven't had a lot of seat time at the track due to many reasons, the least of which is the possibility that our budget 400HP 302 is in need of a rebuild. The last trip to the track revealed low and fluctuating oil pressure during each run. Nevertheless, the BIGS 650 sitting on top of the Victor Jr. did manage a 12.19 @ 115 mph.

The car has run a best of 11.96 @ 116 using the 750 cfm double-pumper and Vic. Jr, however that was in the winter with air temperature in the low 60's. On this particular outing the ambient temps were in the 80's, and we only were able to get off three passes, before having to stop due to fluctuating oil pressure.

Nevertheless, the biggest gain seems to be in driveability. A 750cfm carb may make more peak power on a 302 that runs to 7000rpm, however it is at the expense of driveability and throttle response. The BIGS 650 not only idles and drives perfectly, but the modifications by BIGS make it perform comparable to the larger carburetor, trading some top end power for low-mid range grunt.

As soon as the summer crowds thin out at our local track we plan to get Project 11.99 back out there for a more in-depth track session with the BIGS 650. Look for our dual-plane vs. single-plane manifold comparison soon!