Still-and this is my 2-cents worth-when you move to a niche engine with a healthy narrow-LSA cam, you must be prepared for at least some manual programming intervention, particularly on cold-start, idle control, and/or off-idle throttle-tip-in response. Comp officially says that with its sister Company FAST's self-tuning EZ-EFI system-which includes a special pre-programmed fuel table in theory matched to the Thumpr's unique characteristics-this cam should still work because the aftermarket system's MAP sensor, ECU (computer), and wideband O2 is designed for compatibility with performance modifications, as opposed to less latitude built into OE-based computer setups. Traditional thinking is that with fuel-injection you want to see at least a 110-degree or wider LSA. That's OK with traditional carburetion-and these specs are what gives the cam that healthy lope-but traditionally it's seen as a little flaky for fuel-injection because of lower than normal idle vacuum (may confuse MAP sensor), as well as greater overlap for a given 0.050-inch duration value (may dilute exhaust gas with unburned fuel at low rpm, confusing the O2 sensor). The recommended Thumpr cam for your 348/409 is ground on 108-degree LSA (lobe separation angle), with the intake centerline 5 degrees advanced. To order the custom (standard firing-order) version, call into the tech line, and, Overfield says, "Tell the Tech you'd like to order the 48-600-10 4/7 swap profile on a standard firing-order core, and the tech will take it from there." The 4/7 swap PN 48-600-10 uses an 8660-steel core and the 48-000-14 custom cam ground for the standard firing order uses an 8620 core." Both cams come with a pressed-on cast-iron distributor gear that's compatible with the standard factory-type distributor driven-gear. Comp's Robert Overfield says the nearly $125 price change "comes from the difference in core material. $582.19 for the 4/7 order (official Comp pricing you may do better from one of the large online outlets). Even though it's a special-order, the Comp Cams direct price is lower: $458.21 for the standard firing order version vs. However, I'm told a "standard" firing-order billet cam is now also available on a custom-order basis (basic generic 348-409 custom hydraulic roller cam PN 48-000-14). Lamar Walden offers its own new and improved Z-11 aluminum heads as well as a 2x4 Z-11 mini-tunnel-ram intake.īut why would a mainstream streetable catalog cam be special-ground for the 4/7 swap in the first place? I'll hazard a guess that a 4/7 swap Thumpr cam grind was specced because of cam core availability at the time the current catalog was printed back in 2016. Back at the turn of the century, a pair of them were already going for $10,000/pair. Original GM iron Z-11 heads are nearly impossible to find today. Even in original stock form they're said to flow about 300 cfm. Pretty revolutionary for 1963, the intake ports are raised considerably and have a nearly contemporary straight-shot valve-bowl approach. 731) were used only on limited production 1963 427 Z-11 engines and are unique unto themselves. Edelbrock aluminum heads conform to the high-perf 409 head intake-runner profile. Instead, the intake bolt-hole is raised for clearance. 583 or 690) have larger rectangular ports, and the taller paired-port roofs are not cut off at their adjacent top corners to clear an "in-between" intake manifold bolt.
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