General Category > Quadrajet Carb Talk and Tips
Suggestions For Next Drag Strip Testing Day
Brian B.:
Hi. I was wondering if the more experienced strip tuners could kindly help me with some suggestions to improve. Just had my best 60 foot, ET, and MPH to date with this setup and conditions.
ET - 12.91, MPH - 104.98, 60FT - 1.82, 330FT - 5.333, 1/8 ET - 8.251, 1/8 MPH - 84.31, 1000 FT - 10.768
Air Temp = 50 degrees, Pressure = 30In Hg, Humidity = 57 percent, Water Grains = 38g/lb, DA = 600 Feet.
Mild Hyd Roller Cam @ .050 224 Intake, 230 Exhaust, Lift .552/.528 Lobe Sep 112.0 degrees
Car = 4000lbs, 455 auto 2800 stall, with 3:08 rear.
Stock intake, round port cast iron exhaust manifolds, x-pipe, and Flowmaster transverse muffler.
Launch at 2000rpm with dead hook.
Carb is #7044270 and is stock for my car. Only deviations from stock are jets, rods, accel pump, and choke pull-off.
Primariy Jets are #78 with 45B primary rods. Secondary Rods are DG with G Hanger.
Choke Pull-Off is 1.5 seconds with 3/4 turns on windup spring.
Total timing is 36 degrees all in by 2600 rpms.
Tried 76 jets and car ran slower ET and MPH. Tried CC and AX rods and car ran slower ET and MPH.
If I encounter similar good weather conditions next time, would any of you with more experience recommend any carburetor changes. Thank you for your help.
Cliff Ruggles:
Super Duty 455?
Tiny cam for a Super Duty engine so focus should be on short-shifting and improving 60' times to get the best ET's.
Did you raise the compression during the engine build?
What are the rest of the cam specs, duration @.006" and where is the ICL at?
Running huge jets in a SD carb will require pulling some fuel out on the secondary side. If you have access to them try a CV rod on the next outing.
I've drag strip tested SD carbs with 73-74 main jets in them and found best ET and MPH with rods n the .048-.055" range, but they were custom machined from the same cores and on a "L" hanger.
I used to do a LOT of testing/tuning at private track rentals figuring all this out. Super quick timing curves don't really help either, unless you have a pathetically "low" compression engine in place with too much cam in it.
Not too long ago I helped a customer with a pretty "basic" 455 build using a 276/284, 224/230 @ .050" cam and 9.3 to 1 compression. He was on the dyno and only making 428hp/516tq DONE at 4800rpm's. The heads were professionally ported to 250cfm (96 castings).
I suggested a cam change to a 289/308, 236/245@ .050" cam on a 114LSA with the ICL set at 110degrees. With no other changes made the engine made 514hp/559tq done at 5800rpm's. He also noted it actually idled smoother with the larger cam and improved street manners as well as there were able to put more initial timing in the engine without pinging and "bucking" the starter on a hot restart.
I've built at least half a dozen 455 HO's and SD's here, and the smallest cam I'd even look at using in one would be 230 @ .050 and nothing tighter than 112LSA and ICL not further ahead than 109 degrees. They are "sleeping giants" with those huge round port heads just sitting their waiting for someone to put some cam in them so they can come to life and really show their colors.....FWIW.......Cliff
Brian B.:
Hello Cliff. It is an SD-455. I know I went conservative on cam selection back during the cam swap. I was looking more for mid-range torque at the time. Goal was to comfortably drive back and forth 300 miles to a car show and have some fun track time. Compression is now 9 to 1. Vacuum at idle is 13 inches. .006 is 275 Intake and 285 Exhaust. ICL is 107 Degrees.
I really appreciate your insight. Next time I get weather conditions like these I'll short shift and use my CV rods and K or M hangers. Thank you!
Cliff Ruggles:
Here is a dyno chart from one I did here, 8.8 to 1 compression and 281/287, 230/236, 112LSA cam.
Makes 16" vacuum at 700rpm's....
Brian B.:
That's a sweet wide torque band! It must pull like a freight train. I imagine it would be fun with a 3:42 gear on the street.
Navigation
[0] Message Index
[#] Next page
Go to full version