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Tech Question
Jim Johnson, Lawton, OK, 1965 Dodge Dart 273
Rick, once more I need your sage wisdom on a problem. I have a '65 two door Dart, 273, 904 column shift automatic that I have been building up to mimic your Green Brick (handling, brakes, rear end etc.). My question is: How much motor can I build with the restriction being the tight exhaust space? I want to build up a 360 to put in the car but TTI says their really cool headers won't fit with a column shift auto. Anyway I don't want to build any more motor then the exhaust can handle. So what are your suggestions?
Jim-
Very good question. On the Green Brick ('69 Valiant, 3.79" stroke, 0.040" O/S 340, W-2 heads) we had a very expensive set of custom Tri-Y headers built. They suck. Looking at the engine's dyno curve, it "noses over" (passes the peak HP RPM) way too early. We estimate that a set of big TTIs, w/3" pipes, would probably net us over a 75 HP increase! The car "works" because it is low mass, but it would work way better with either a milder cam or the aforementioned exhaust upgrades.
From reading between the lines, it sounds like you'll be using iron manifolds. If that's the case, by all means, tune for torque and mid-range. Keep the cam mild, especially re: overlap (wide lobe sep. angle). I did have some reasonable results years ago with a 340 in a narrow A-body, using 273 manifolds that were painstakingly port-matched and hogged out. The other option are the re-issued "Spitfire" headers from Layson's, which are surely way better than even '68-'70 340 manifolds (which will not fit an early A-body, incidentally). At that point, you can be a bit more radical.
Rick
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