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Changes don't seem to affect performance

11/04/2018 21:23
I have made modification to try to dial in my car at the dragstrip. Over the course of 16, quarter mile runs I have made no significant improvement to mph and I'm wondering what might be holding things back. My mph has varied only a small amount from 94 to 96.5 with very little of that I can tie to the changes I made. I'm wondering now if there are one or two variables that might be holding me back, and the other changes I've made are being throttled by that one variable. I wondered about fuel supply, but it’s not sputtering or otherwise feel like It’s running out of fuel at the top end. I’ve wondered about my exhaust (see attached pics of non-mandrel bends) but the bends don’t seem to be too bad. What could be throttling performance? My changes have included timing (34-40 total), carb spacer, complete tune-up, changing shift points (4800-5300). These aren’t major changes but I would have expected some noticeable change to performance. My setup is 400-bored 40 over, 068 clone cam, long-branch manifold, original 4-speed Muncie, 2 3/4” exhaust (non-mandrel bends), 670 heads, Carter 4-barrel rebuilt by Cliff Ruggles. Thoughts?
11/05/2018 08:40
What's happening at the rear end? When you say "long branch manifold" are you talking exhaust?
11/05/2018 16:03
Yes the RA3 exhaust manifold
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