Mopar 440 Valve Cover Gaskets Buying Guide

TL;DR: A leaking 440 valve cover is almost never a bad gasket. It is a warped stamped-steel flange, an over-torqued bolt that crushed the cork, or a crankcase that cannot breathe because the PCV side of the system was never sorted out. Buy the gasket that matches how the engine is used: cork or cork-composite for a stock cover you install once, steel-core silicone or molded rubber for anything with aluminum covers, headers, or a set you expect to pull again. Whatever you buy, flatten the cover flange first and torque to the service manual value in sequence — that decides the outcome far more than the gasket material does.

What you are sealing on an RB big block

The 440 is the largest of Chrysler's RB — raised block — wedge V8s, the tall-deck half of the B/RB big block family. It is a two-valve, pushrod, overhead-valve engine with cast iron heads and rocker shaft assemblies under each cover. That geometry defines the sealing problem:

• A long, narrow, flat sealing rail. The gasket has to hold a straight line over the full length of the head, with fastener load concentrated at each bolt and nothing in between. Flange distortion between bolts is the number one cause of a leak on this engine.
• Thin stamped steel on factory covers. Original covers are pressed steel. They deform easily around the bolt holes — usually because someone has already over-tightened them once — and a dimpled flange will not seal against any gasket at any price.
• Rocker shafts, not individual pedestals. The cover clears a rocker shaft assembly, so cover height and internal clearance matter as soon as you change rocker geometry. Confirm clearance before you buy tall aftermarket covers or a valvetrain upgrade.
• A hot, oily neighbourhood. The heads sit directly above the exhaust manifolds or headers. Oil weeping from the lower edge of a cover lands on hot iron and turns into the burning-oil smell that sends people looking for a head gasket. Most of the time it is the valve cover.

If you are working through a broader oil leak on the engine, the seal, gasket and hardware side of it lives in gaskets and seals and in the engine-specific Mopar 440 RB parts collection.

Gasket materials, and which one belongs on your engine

The honest summary: steel-core silicone is the best-behaved option on a driven car, because the integrated metal carrier controls how far the gasket can be compressed. You cannot squeeze it flat by leaning on the wrench, it does not shrink over a winter of sitting, and it survives the removals that a build-in-progress demands. Cork remains the right answer for an original-appearance restoration or a budget refresh where the covers are known good and are not coming back off.

For a full engine refresh, check whether valve cover gaskets are already included in the kit you are buying before you order them separately — many complete kits in full gasket sets cover them.

Before you buy: five things to confirm

1. The cover pattern and fastener positions. B and RB covers were produced across a long model run and in more than one configuration, and aftermarket covers add more. Count the fastener positions on your actual covers and match them, rather than assuming a listing that says "big block Mopar" fits what is bolted to your engine.

2. Whether the covers are still flat. Lay each cover flange-down on a piece of plate glass or against a straightedge. If you can see daylight, or the bolt holes are pulled up into dimples, the cover is the leak. Straighten the flange on a flat surface with a body hammer and a dolly, working the dimples back down, until it sits flat before you buy anything.

3. What the covers are made of. Aluminum covers are stiffer and hold a flange better, but they also have far less give — they want a rubber or steel-core silicone gasket, not cork.

4. Whether grommets and hardware come with it. Breather and PCV grommets harden and shrink with age, and a leaking grommet reads exactly like a leaking gasket. Some gasket packages include them; some do not. Load distribution washers, spreader bars and cover bolts are in accessories and hardware.

5. Your rocker and pushrod clearance. If the engine has been upgraded with roller rockers or a higher-lift setup, confirm cover clearance against the parts actually installed. Valvetrain components are in valves and valvetrain, and the broader family fitment is in Mopar B / RB big block parts.

Installing them so they seal once

The install matters more than the purchase. Most repeat leaks are assembly errors, not product failures.

• Clean both sealing surfaces down to bare metal. Old cork, hardened RTV and varnish all have to come off. Use a plastic scraper and solvent, not a wire wheel that throws debris into an open engine. Stuff clean rags into the head before you start.
• Straighten the flange before the gasket goes near it. This is not optional on a used stamped cover.
• Decide about sealant deliberately. A steel-core silicone gasket wants no sealant at all. Cork benefits from a thin bead on the cover side only, so the gasket stays with the cover when you pull it and the head side comes apart clean. Never lay a heavy bead on both sides, and never use RTV as a substitute for a gasket that fits.
• Retain the gasket to the cover. Adhesive gasket retention on the cover face keeps the gasket from shifting as you set the cover down. Set the cover straight down rather than sliding it into place.
• Torque in sequence, from the centre out, to the service manual value. Valve cover fasteners are a low-torque item and the specification is easy to overshoot by feel with a ratchet — use a torque wrench with a usable low range and follow the factory sequence and figure for your engine. Do not chase a leak by tightening further; past the correct value you are deforming the cover and making it worse.
• Re-check after a heat cycle if you have used cork or cork-composite, which relax as they take a set. Steel-core silicone generally does not need a re-torque, but confirm against the gasket manufacturer's instructions.
• Fix the breathing. A crankcase under pressure pushes oil past any gasket. Verify the PCV valve, the hose and the grommets, and make sure the breather side is actually flowing. Oil and additives suited to a flat-tappet big block are in oil, coolant and additives, and a low-range torque wrench is in engine stands and tools.

Budget this as a short job in shop hours — typically well under a couple of hours per side on a car with reasonable access, more if headers are in the way or the covers need straightening. It only becomes expensive when it has to be done twice.

Frequently Asked Questions

Are cork or rubber valve cover gaskets better for a Mopar 440? For a driven car, a steel-core silicone or molded rubber gasket is the better long-term choice because the carrier controls compression and the gasket survives being removed and reused. Cork is the right call for an original-appearance build with known-good, flat stamped covers that are not coming off again.

Why does my 440 keep leaking oil at the valve covers after a new gasket? Almost always a distorted cover flange, an over-torqued fastener that crushed the gasket, or crankcase pressure from a PCV system that is not working. Check flange flatness against a straightedge, re-torque to the service manual figure in sequence, and confirm the PCV valve and grommets before buying another gasket.

Do I need RTV with a valve cover gasket? No, and with a steel-core silicone gasket you should not use any. On cork, a thin bead on the cover side only helps the gasket stay put during install. Heavy sealant on both faces is a common cause of leaks, not a cure for them.

Will B-block valve cover gaskets fit an RB 440? The B and RB engines share the wedge valve cover family, but fastener patterns and cover styles vary across the production run and across aftermarket covers. Count and measure the fastener positions on the covers you actually have, and confirm the current part number against the manufacturer catalogue before ordering.

Can I reuse a valve cover gasket? Steel-core silicone and most molded rubber gaskets are designed to be reused if they are undamaged and not distorted. Cork, rubberized cork and coated fiber gaskets take a compression set and should be replaced every time the cover comes off.

What torque do the valve cover bolts take? Use the value in the factory service manual for your engine and follow the specified sequence. It is a low-torque fastener where guessing by feel with a ratchet routinely overshoots the intended figure, dimples the cover, and causes the leak you are trying to fix.

Sources

• Core Powertrain Parts internal store handle map (STORE-BUILD-HANDLE-MAP.md) for the collection targets used in this article and the Mopar B / RB product taxonomy.
• Chrysler B/RB big block configuration facts from our Mopar family reference: raised-deck RB wedge V8, overhead valve with pushrods, two valves per cylinder, cast iron heads, rocker shaft assemblies under the covers.
• General gasket engineering principles: compression-set behaviour of cork and cork-composite versus elastomer, and the function of a rigid carrier in a steel-core silicone gasket in limiting crush.
• Field failure patterns on stamped-steel valve covers: bolt-hole dimpling from over-torque, flange distortion between fasteners, hardened breather and PCV grommets, and crankcase pressure driving oil past an otherwise good seal.

All torque values, fastener counts and part numbers must be confirmed against the factory service manual and the current manufacturer catalogue for your specific engine and year. This article deliberately states none of them.