I need some advice on some initial carb tuning changes for my model 8007 390 cfm Holley. Here’s my situation:
The car is a 1965 Chev Nova station wagon. It weighs 3059 pounds without the driver. I don't drive the car much around town other than to get to the drag strip which is only about five miles from my house. The primary use for the car is the drag strip with an occasional weekend car show. The 230 ci inliner was a rebuilt engine when I bought the car three years ago and didn't have many miles on the rebuild. It has been bored .040 over and is a “standard” rebuild without balancing, or any special lower-end work; thus, I limit the rpms to 6000 just to be safe.
The rear end is a 4.11 positraction. I've been running 24 inch tires, which means I'm through the 1/4 mile traps at about 4800 rpms. I have been shifting the Powerglide at around 6000 rpms. The PG has had a rebuild, a shift kit installed, and I'm running a 3000 stall speed converter. I can foot-brake it and the rpms climb to 3000 before the rear tires break loose. I usually launch the car at around 2800 rpms.
The headwork has been done by Tom Lowe. It includes 1.94 intake valves, 1.60 exhaust valves, bolt-in lumps, ported head, 3/8 screw-in studs, and performance valve job. Compression ratio is about 9:1. The cam is a Schneider 295H grind with .510 lift, intake is 224 duration at .050” and exhaust is 230, with lobe separation of 110.
I’m running an Offy intake manifold with a Holley model 8007 390 cfm 4-barrel carb. I use Langdon headers with 2¼” exhaust system with a cut-out near the driver’s door. I use a Pertronix electronic ignition. The distributor has been recurved and is all-in at 3000 rpms. I normally run about 32 to 36 degrees total.
I’ve been to the drag strip once this year since the head work was done, along with the new cam and the 4-barrel intake system. I got in three runs with a best ¼-mile time of 16.8 and 79.3 mph. My best 60’ time of the three runs was 1.989.
This is my first 4-barrel carb on the car and I need some tuning suggestions. My questions are: The carb came with 50 jets on the primary side. I’ve purchased 52 and 54. What should I start with? DO I change the secondary side to the same jets? Do you have any suggestions for a power valve change? It’s a 65 now and I can purchase a 45 or a 35. I’ve purchased a quick-change secondary diaphragm spring kit. Holley provides a chart with the kit that is supposed to help with choosing one of seven different springs. Of course, the chart is not at all designed for my combination. I’ve posted the chart here:
http://s1220.photobucket.com/albums/dd449/jimrj/Chart/?action=view¤t=Chart.jpgWhere do you think I should start? It has the plain color spring now. I don’t mind experimenting; in fact, that will be fun. But my question is: Where do you think I should begin my experimentation?
Of course, I also take general suggestions for changes/improvements. The goal is quicker and faster, right?
Thanks for your help.
