1972mc Posted November 7, 2009 Share Posted November 7, 2009 I will be back at the track for one more visit before winter and have a few questions/observations about my car and the setup. Any pointers before my Sunday drag race excursion would be greatly appreciated. Info: -Previous best time in 1/8th with 3.08 gears was 8.89. RT of 2.037, and speed of 79.62. (Not all on same run) -383 stroker (engine dynod at 405 hp 5500 rpm, and 440 torque at 4200 rpm) -Hypereutics, and cast crank -Hedmann headers, 2 1/2 inch pipe, x pipe Dynomax super turbo mufflers -3.42 gearset 12 bolt -T350 with tight shift kit and 2400 stall -GM HP HEI distributor -Holley 750 vac sec carb -air bags in coils, solid lowers, adj uppers -BFG 275 G Force drag radials -High vol Holley mechanical fuel pump and 3/8 lines all the way to the tank -fuel pressure from 4-8 psi -total timing 40 (mfg recomm 34, never had any ping or knock) -primarys 76, secondary metering plate drilled out to .093 -Cant remember whic secondary spring, but it is on the soft side -pump nozzle 40, cam orange in pos 2 -pv 6.5 -park idle 1000, drive idle 750 -park vac 14, idle vac 10 (has a .487Int / .508 Exh & 234 Int / 244 Exh duration @ .050 - 110 degree lobe sep.) -plugs look good- a little dark but I run it rich to keep from torching my cheap pistons at 40 deg timing Issues: -If I don't bring rpm's up 200-300 from idle,at launch, she will stumble badly. -Seems very inconsistent when I am race testing. Helps to clear out the carb right before launch, but not always. I can feel that finally it is starting to spin the drag radials a little off the launch,(only if I load it up) but the most troubling is that when manually shifting, sometimes it pulls hard through 1st gear to 5500, but other times it just seems to flatten out from 3800 to 5500, feels like what happens if I hold it too long at the top of the gear and it levels out (lifter float?) -Timing seems to be best at 40 (seat of the pants feel) -To me the car just seems to feel like a dog. I thought 405 HP would excite me more than it has. It just does not throw me back in the seat from launch or dropping it down into 2nd and nailing it. I will be checking float level and rechecking the idle mix screws today. Seems like my carb needs upgrading to a chokeless with mech secondaries? I see some of you are running Pro Systems carbs. Carl Quote Link to comment Share on other sites More sharing options...
dbreese Posted November 7, 2009 Share Posted November 7, 2009 Hi Carl, What is your initial timing set at? With that cam I bet the engine would like a minimum of 18 deg. This might thelp with the off idle bog. Have all your timing in by 2800-3000. Give that try. You have much more potential with that combo. Easy 12's for sure. Give Patrick a call at Prosystems and let him know about your combo if ya want to go the mechanical secondary route. Good luck and have fun. David Quote Link to comment Share on other sites More sharing options...
Heckeng Posted November 7, 2009 Share Posted November 7, 2009 I agree with David, and also think your converter is a little too tight. I would think you would need around a 3000 stall. If it is too tight, it might be creating a bog because the cam wants to get to higher rpms quicker than it is being allowed. Raising your launch rpm may be helping to get the cam in its happy spot faster. Also, a 40 squirter may be letting the fuel out of the initial shot too quickly leaving you with a lean bog right after you floor it. On the top end, it sounds like you are having fuel problems--weak pump, bad filter etc. Also you should test to see if your secondaries are actually opening up at the track. If they aren't, that will cause a "laying down" feeling. There is a small cork gasket that is known for going bad where the vac pod attaches to the carb body. That often falls out or gets ripped when changing springs or when installing a quick change kit. To test the secondaries, you have to have the engine loaded (revving in idle won't do it). what you can do is get some light wire and bend it around the secondary throttle shaft outside the carb somewhere and bend it such that if the secondaries open up, it will bend the wire in a noticible way. I think they are not opening for you. Quote Link to comment Share on other sites More sharing options...
Guest 72yellowmc Posted November 8, 2009 Share Posted November 8, 2009 Carl what heads are you running .. that makes a difference in what decisions to make in getting your car to make peak performance. Quote Link to comment Share on other sites More sharing options...
1972mc Posted November 8, 2009 Author Share Posted November 8, 2009 Carl what heads are you running .. that makes a difference in what decisions to make in getting your car to make peak performance. Robyn they are iron vortec 2.02/1.60 making 9.5-1 com pression Carl Quote Link to comment Share on other sites More sharing options...
Guest 72yellowmc Posted November 8, 2009 Share Posted November 8, 2009 Carl, I know my engine with the vortec heads did not like the total timing above 35 degress .... initial timing was 12 degrees.... I peresonally do not like vacum sec carbs for drag racing ... there ok on the street.. it seems to me like there are several things in your package that may be mis matched so to speak.... just remember to try one thing at a time ... and DO NOT go by the seat of your pants for hp gains or slower loss in et feel ... take it to the track is the only way to go for true results... don't know how many times over the years I made a change and thought wow that feels a lot better then get to the track and run it and dang that's disapointing!!!! .... but then again .... note temp and wind and humidty as you make changes ... on any given day your car can run 2 tenths slower or faster .... just keep good notes as you make changes and it will all come together. Quote Link to comment Share on other sites More sharing options...
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