Mopar Action On-line – Tech Questions
chad kelly, bowmanville, ON, canada, 1968 dodge dart gts 340
My father has owned a numbers matching 1968 Dodge Dart GTSsince he was 18 years old. Finally, with the help of my brothers and me, wecompleted a ground up resto this year. It is two tone green, dark on top andlight on bottom with the longitude stripe. It is a 340 4 bbl with 727TorqueFlite and 3:9:1 gear. My question is: The engine is pretty stockexcept a Crane cam for low to midrange power and a 3 angle valve job. We setthe timing which was recommended by the (engine guys) to 10 degrees abovetop dead center. Now it runs okay but it seems to lack that grunt from offthe line. The carburetor is 625 Carter AVS, 1800 stall converter, and 3/8fuel line and sending unit with high volume fuel pump. Could you possiblyhelp a lifetime Mopar lover like my dad out with some tuning tips? Any helpwould be greatly appreciated.
Obviously it’s not a resto! Anyway, I’ll be happy to make a few educatedguesses. First, it sounds like you have installed a milder-than-stock cam,so there should be plenty of low-end torque to light ’em up, especially withthat axle ratio. So, yeah, something’s wrong. The most obvious is thattorque converter: 1800 RPM! Jeez, stock was 2350! I have no idea why youguys did that.
Next place to look: Spark. 10 degrees initial may or may not be OK, plus, Ihave no idea what you mean by “above top dead center”. If you meant to write”after top….” the spark is way, WAY late. But I’m betting it’s really at10 degrees BEFORE TDC, or the car would run pretty lousy all-around. Since Idoubt the distributor is stock, either, we need to know how much mechanicaladvance, and by what RPM, is built-in. One simple way to get close is tohold the engine at 3,000 RPM (w/vacuum advance temporarily disconected) andset the timing at 35 degrees BTDC. Then see what it is at idle. If it’s tooretarded to idle properly, the advance mechanism needs to be reworked foryour application.
You may also have the secondary air door set too loose, but, typically, itbogs bigtime or backfires if you do that.
The cam could also be installed significantly retarded, but I doubt that.