We built them, had the machine work done at a local shop, and I did the head work/ assembly. My last car, which I raced at Kankakee, love that track btw, was a bone stock bottom end, pistons included with 80k miles on it out of a friends street car. We turned 8300 at the end of the straights. I went to UNOH and built my head there, milled it .150", port work, and combustion chamber reshaping, and a solid cam, low lift but high duration can't remember exactly what it was. And used a flow bench to test it. The ranger header is a horrible piece of equipment, if you needed to limit power, the stock cast manifold is awesome, even for a bit higher power. But if you are trying to keep the rpms down on a big track, without going slow, a rear gear change is necessary. We ran a 3.73 at shady hill speedway, tight turns longer straights. Turned about 7500. We ran a 3.45 (had a whole rear end to swap out) and 8000-8300 at Kankakee.. If we had a 3.27 at the time, we would have run that.
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If you go to a bigger track and restrict the exhaust, you aren't going.to make the power you need to be fast. And if you were still fast, you should buy a second rear end and do the swap before going to a bigger track. We got it down to about a two hour job after a couple swaps.
1991 Mustang LX 2.3L 5 Speed convert
1989 Ranger 4X4 2.5L 5 Speed solid Dana 30 front axle, 4.5" suspension lift, 3" body. ( blown up....)
Entire turbo kit waiting to be used again.