Why the RPM Air-Gap and Camshaft Swap?

Upgrading a 350 Chevy with an RPM air-gap intake manifold and a camshaft swap is one of the most cost‑effective ways to unlock substantial horsepower and torque. These two modifications work together to improve volumetric efficiency—the engine’s ability to move air and fuel in and out of the cylinders. The cooler intake charge from the air‑gap design combined with more aggressive cam timing can add 40–70 horsepower to a stock 350, depending on the cam profile and supporting parts. This article provides a detailed cost breakdown and practical advice to complete the build for under $1,000.

Part‑by‑Part Cost Analysis

Below is a realistic breakdown of the parts required, with current market prices. Prices vary by retailer and sales, so we’ve used average figures from major suppliers like Summit Racing and Jegs.

RPM Air‑Gap Intake Manifold

Edelbrock’s Performer RPM Air‑Gap (part #7501) is the go‑to choice for non‑EGR SBC applications. Its dual‑plane design with an open air gap keeps the intake runners cooler than standard manifolds, reducing detonation and allowing more aggressive timing. Expect to pay $250–$280 new. Used units can save $50–$70, but check for warped mating surfaces or stripped threads.

Performance Camshaft

A camshaft is the heart of the power increase. For a street‑driven 350 under $300, consider Comp Cams XE262 or XE268, or Lunati Voodoo 262/268. These offer strong mid‑range torque and a noticeable idle. A budget cam kit (cam, lifters, and springs) runs $280–$350. If you already have compatible springs and lifters, a bare cam may be $100–$150, but new lifters are strongly recommended.

Gaskets and Seals

Quality gaskets prevent leaks and ensure proper sealing. Expect to spend $40–$60 for an intake manifold gasket set (Fel‑Pro 1204), timing cover gasket, valve cover gaskets, and water outlet gaskets. Avoid paper gaskets for the intake—use a thin bead of silicone or printoseal gaskets.

New Pushrods

After swapping the camshaft, you should verify pushrod length. Most aftermarket cams with standard base circles work with stock length pushrods (7.800”), but higher lift cams may need shorter ones. A set of 16 hardened pushrods from Smith Brothers or Comp Cams costs $60–$90. Even if the originals seem okay, new pushrods eliminate wear and weight differences.

Oil and Filter

Fresh engine oil protects the new cam during break‑in. Use a high‑zinc break‑in oil or add a zinc additive. A 5‑quart jug of 15W‑40 diesel oil or dedicated break‑in oil runs $20–$30. A high‑quality oil filter (Wix or Mobil 1) adds $10–$15.

Miscellaneous Hardware

This includes intake bolts, water neck o‑ring, thread sealer, RTV silicone, and a new timing chain set if your stock chain is sloppy. Budget $35–$50. If you reuse the original timing chain, you risk cam timing error—consider replacing it for peace of mind. A Cloyes double‑roller timing set adds about $40.

Total Parts Cost Summary

  • RPM Air‑Gap Intake: $265
  • Camshaft Kit (cam, lifters, springs): $315
  • Gaskets and Seals: $50
  • Pushrods: $75
  • Oil & Filter: $30
  • Miscellaneous Hardware: $45
  • Total Parts: $780

This leaves $220 of the $1,000 budget for unexpected items or upgrades (like a timing chain or harmonic balancer).

DIY Installation vs. Professional Labor

Do‑It‑Yourself

If you have basic mechanical skills, a jack, and a torque wrench, you can complete this swap in a weekend. The main steps: drain coolant, remove distributor, carburetor, intake manifold, valve covers, rocker arms, pushrods, timing cover, and timing chain. Install the new camshaft, re‑install the timing set, button up the front, install the new intake with gaskets, adjust valve lash, and set ignition timing. Total DIY cost (parts only): $780.

Professional Installation

A shop will charge 6–8 labor hours at $75–$120/hour. At $75/hour, labor adds $450–$600. Many shops also mark up parts by 10–20%. A professional install would likely exceed $1,200–$1,400. To stay under $1,000, DIY is essential.

Performance Expectations and Tuning

With an RPM Air‑Gap and a mild cam (like the Comp XE262), expect a peak horsepower increase of 30–50 HP and a similar torque increase. The power curve shifts roughly 500 RPM higher. You will need to re‑jet the carburetor (typically one or two steps richer) and adjust the ignition timing. A Summit Racing or Jegs vacuum gauge and timing light are essential. Also consider upgrading the exhaust to headers and a free‑flowing muffler to fully realize the gains.

Break‑In Procedure for the Camshaft

New flat‑tappet cams require a strict break‑in: run the engine at 2,000–2,500 RPM for 20 minutes with break‑in oil, varying the RPM slightly every few seconds. Avoid idling, as the cam lobes need high oil splash. After break‑in, change the oil and filter. Failure to follow this can wipe a cam lobe in minutes.

Budget‑Friendly Alternatives

If your budget is tight, consider these swaps to save money:

  • Used intake manifold: A used Edelbrock Performer RPM (non‑air gap) can be found for $100–$150. The air‑gap is a slight advantage but not mandatory.
  • Re‑grind camshaft: Send your stock cam to a regrinder like Oregon Cam Grinding for ~$60–$80. You get a custom profile at low cost.
  • Skip new pushrods: If your stock length works and pushrods are not bent, reuse them (less ideal but possible).
  • Bare cam only: Buy just the cam if your existing lifters and springs are good—but inspect carefully for wear.

By choosing used parts, you can reduce the total to around $500–$600, leaving room for a timing chain or better gaskets.

Final Cost Summary

Here’s a consolidated view:

DIY Parts$780
DIY Total$780
Professional Labor (est. 6 hrs @ $75/hr)$450
Pro Total (parts + labor)$1,230

To stay under $1,000, DIY is required. Even with a few higher‑cost items (like a premium cam kit or new timing set), the budget holds. For additional guidance, refer to Edelbrock’s installation instructions and Comp Cams’ cam selection guide.

Conclusion

Installing an RPM air‑gap intake and swapping the camshaft on a 350 Chevy for under $1,000 is not only possible but a popular upgrade for street and mild strip use. By sourcing parts wisely, performing the labor yourself, and following proper break‑in procedures, you can transform an ordinary small block into a responsive, powerful engine. The combination of cooler intake air and optimized valve timing will make every drive more exciting—without breaking the bank.