EdM
Well-known member
- Joined
- Jun 5, 2014
- Messages
- 589
- Reaction score
- 29
- My Car
- 1973 Mach 1 Q code, a 427 Dart based Windsor, Pro Flo 4, Len Tech AOD, A/C, 12.7:1 steering conversion, SoT coil over and Dakota Digital dash.
As I wrap up my first week of retirement I have had some time to play with my car (73 q code 4 speed Mach 1). The previous owner had the original engine rebuilt in 2005 and the car has 5k on it since the build. It has 9.5:1 CR, an Offenhauser 360* intake, a Comp Cams hydraulic cam with 218* at .050" intake and exhaust, .494" lift at 110* CL, a 750 Holley DP, Hooker long tube headers and a Mallory Unilite. It ran OK but was a pain to start, idled rough and seemed sluggish pulling. I swapped the non-choke Holley out for a Quickfuel HR 680 CFM with vacuum secondaries. Initial timing was set at 8*, the vacuum advance was connected to ported on the carburetor, all by the previous owner. I worked on the timing setting the initial to 13* with 37* total all in at 2500 fps. I swapped the vacuum advance to manifold vacuum and set it to 10* at idle so 23* "total" at idle. The engine idle smoothed up, the vacuum is a steady 13" and the exhaust smell cleaned up. The car now pulls much stronger and cruises at highway speed with a very light throttle and what seems like a quieter exhaust note. Zero detonation in a number of tests. Really nice. That said, I have a flat spot or stumble just off idle or just off lugging (low RPM) if in a higher gear. I have thoroughly checked for vacuum leaks and can find none. Suggestions?