few photos of a similar set-up. First photo has throttle open. Last photo shows dual return springs for safety.
NICE setup you have.
Early on when I bought the ’63, the guy that sold it to me had a factory 4bbl manifold and carb he was planning to put in. At some point dual exhaust was installed, only 2-inch. In ’63 the Plymouth and assume Dodge 318’s weren’t available with a 4bbl or dual exhaust. This was dropped as I understand after ’62. Installed the 4bbl, electronic ignition, and swapped the axle housing to ’65. Added 3:23 sure grip. Just these changes added the pep remarkably and drove it for another 15 years.
Came time wanting to rebuild it finding out that at some point the motor had already been bored .30 and hardened seats installed. It was a CA car so reckon someone knew hardened seats were a good idea running unleaded gas.
So motor was knocked out another .30, mild cam, solid lifters, heads, crank, etc. re-machined, some 340 parts, headers, and larger exhaust/ X-pipe. Actually, too large for this motor – 3”. Was recommended by the shop for some reason that after getting wiser about this, shouldn’t have been done. Initially after the build, had Flow Master 50’s on it that sounded nice; but drove me crazy with the volume. Installed Hemi mufflers reducing the in and out to 2.5”. New stall convertor around 2500 and switched the 3:23’s to 3:55’s. Intake manifold? Heard a bunch, as I’ve read here, that dropping the factory one wasn’t worth it for this build anyway.
Results? Definitely more power top-end. BUT, couldn’t say the giddy-up was all that different low-end. Futzed with the timing getting mis-firing at different RPM’s when vac was connected. So been running all mech advance since as it runs smoothly this way. I posted about this getting nice advice from distributor experts about the distributor curve being wrong likely thwarting low-end performance. Haven’t tackled this yet including a few other car projects that keep getting pushed off due to family matters fixing old houses and mine when time allows…add a couple of surgeries. I’ve saved those posts for when I can get to it.