- Joined
- Oct 9, 2018
- Messages
- 402
- Reaction score
- 238
- Location
- Marysville Ohio
- My Car
- 1971 Mach 1 - "Day 2" restoration; 351C/FMX, trick flow heads, roller cam conversion, CAA AC kit, upgraded springs/shocks & close-ratio steering box
Just about ready to throw in the towel and take the car to a local mechanic who knows classic mustangs. No evidence of an exhaust restriction, poorly seated valves, or head gasket leak, based on both vacuum testing and one of those emissions detector kits you can get at Advance Auto (the ones that you stick in the radiator to detect combustion leaks into the coolant). The head gasket thought was a long shot anyway, my car doesn't overheat or miss - it just falls flat at cruise and 3K RPMs.
As I thought back to when this first appeared, I realized the first time it happened was within a few weeks of installing my new (rebuilt) FMX transmission. I didn't drive much between the installation and about 2 weeks ago, so if it is the trans, that may be why I didn't see this issue sooner. I have not considered this a transmission problem because it does not slip (My RPMs go down, not up). The TC is the same one I used with my previous FMX, so about 90% sure that's not the issue.The rebuild was done through a local rebuilder who has a lot of experience with classic car transmissions, but knowing the FMX isn't a popular choice these days, I wonder if that isn't a greater possibility of a mistake even by a good mechanic.
Any forum thoughts on whether a bad rebuild could result in some sort of drag on the motor at cruise?
The only other thought I have is a possible dropout in electrical power at 3K RPM, shutting off my coil and/or ignition module. battery and alternator look good at idle.
Both of these ideas also feels like a long shot to me, but that's where I'm at... if I don't find this by Wednesday, I'm taking it to a smarter person than me....
As I thought back to when this first appeared, I realized the first time it happened was within a few weeks of installing my new (rebuilt) FMX transmission. I didn't drive much between the installation and about 2 weeks ago, so if it is the trans, that may be why I didn't see this issue sooner. I have not considered this a transmission problem because it does not slip (My RPMs go down, not up). The TC is the same one I used with my previous FMX, so about 90% sure that's not the issue.The rebuild was done through a local rebuilder who has a lot of experience with classic car transmissions, but knowing the FMX isn't a popular choice these days, I wonder if that isn't a greater possibility of a mistake even by a good mechanic.
Any forum thoughts on whether a bad rebuild could result in some sort of drag on the motor at cruise?
The only other thought I have is a possible dropout in electrical power at 3K RPM, shutting off my coil and/or ignition module. battery and alternator look good at idle.
Both of these ideas also feels like a long shot to me, but that's where I'm at... if I don't find this by Wednesday, I'm taking it to a smarter person than me....