Reinforced head gasket Ford Lincoln Mercury 3.5 T35PDED C35PDED

The Ford, Lincoln and Mercury engines covered

The T35PDED and C35PDED petrol engines, V6s of 3.5 litres, power the Ford, Lincoln and Mercury models in the compatibility table below. Each takes two head gaskets, one per cylinder bank.

The original gasket carries the part number 7T4Z-6051-AA. Its bore is 94.5 mm; the manufacturer publishes neither its construction nor its thickness. It is engineered for the standard combustion pressure: when that climbs, the clamping tension drops, the cylinder head lifts slightly and coolant finds its way into a cylinder.

Reinforced cylinder head gaskets

The head gasket does not guarantee the seal on its own: the seal also depends on the fasteners, which clamp the head onto the block. A composite gasket is crushed for good beyond 100 N/mm² of allowable stress, whereas the 301 stainless steel of MLX gaskets holds 517 N/mm², 5 times more, and springs back at each combustion.

This page brings together the part numbers of Cometic, an American maker of racing gaskets, around a single construction: the MLX with its chamber stopper. Their bore is 95 mm, 0.5 mm larger than the original gasket, and the thickness offered is 1.22 mm, enough to adjust the compression ratio without touching the pistons or the cylinder head. As a rule, the gasket bore chosen is at least 0.5 mm larger than the actual cylinder bore. Each part number is sold on its own. As the engine uses one gasket per cylinder bank, place an order for both part numbers, one per side.

Technical specifications

The gasket volume is the room it leaves free above each cylinder. It adds to the combustion chamber and decreases the compression ratio, the more so the larger it is. Only set these values against each other for gaskets of the same bore.

Preparation and fitting

Before assembly, check the flatness of the head and block gasket faces with a straight edge, then have them resurfaced if needed. These gaskets are fitted without any sealing product: Cometic supplies them already coated.

Technical guide

The construction offered

Cometic MLX A multi-layer stainless steel gasket whose folded centre layer forms a stopper around the combustion chamber, with a high-temperature coating. Clamping rises locally without adding to bore distortion. It is the most resistant of the all-steel gaskets, to be kept for severe boost; it is offered here in 95 mm only.

Choosing bore and thickness

Gasket bore. The Cometic MLX only exists here in 95 mm (C15404 and C15405).

Thickness. The manufacturer gives no thickness at all for the original gasket. A thicker gasket enlarges the combustion chamber and lowers the compression ratio; a thinner one reduces it and raises the ratio.

As the original thickness is not published, measure with a dial gauge the height by which the pistons stand above the block's gasket face, even more so if the head has been resurfaced: it governs the clearance that remains between piston and cylinder head.

The brand

Cometic Gasket, Inc. is an American maker of gaskets and sealing solutions for engines, founded in 1989 and based in Concord, Ohio. Its speciality: the gasket produced to order, at the bore and thickness requested. Everything is made in the United States, from American materials.

Advantages over the original gasket

When a reinforced gasket becomes necessary

• Adding forced induction, or raising boost on an already turbocharged engine
• Cylinder rebored beyond what the 94.5 mm bore of the original gasket covers
• Looking for a compression ratio different from standard, higher or lower
• Engine that has already lost its gasket, or is consuming coolant
• Competition use, where the gasket goes through repeated temperature rises

Vehicle compatibility

OEM part number: 7T4Z-6051-AA.

Important: the part numbers on this page only suit the T35PDED and C35PDED engines, which take two gaskets, one per cylinder bank: check your vehicle's engine code before ordering. Supplier designations: C15404-048 for the right side, C15405-048 for the left side.

Why switch to a reinforced gasket?

When the original gasket hits its limit, the reinforced gasket replaces it to good effect: under a higher combustion pressure, it holds its shape instead of being crushed.

When more power is sought, with a turbo, a supercharger or a raised compression ratio, the head gasket is the first link to weaken in the top end. Opting for a reinforced gasket means betting on reliability: it spares you the failure and the cylinder head removal that follows.