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BY REFERENCE COMETIC - Reinforced cylinder head gaskets
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BY REFERENCE COMETIC - Reinforced cylinder head gaskets
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Reinforced Cometic head gasket in CFM-20 for the 3.5 litre straight-six of the Jaguar Mark V. Sold individually.
The Jaguar 3.5 litre straight-six, labelled here "3.5 Litre", powers the Jaguar Mark V, listed for the year 1950 and detailed below.
We have no confirmed original gasket part number for this engine, so the original bore, construction and thickness are not stated. An original gasket is sized for standard combustion pressure: when that rises, the head loosens, lifts and lets coolant into a cylinder.
The gasket does not seal on its own: the bolts or studs that press the head onto the block matter just as much. The CFM-20 combines a galvanized steel core with a soft asbestos-free compound that fills small flaws in the sealing faces.
This page offers one part number from the American maker Cometic, a specialist in racing gaskets, in a single construction, CFM-20, with an 84 mm bore and a thickness of 1.09 mm. It is sold individually.
| Gasket bore | Thickness | Gasket volume | Gasket type OEM not specified | Brand | Part number |
| 84 mm | 1.09 mm | 6.04 | CFM-20 | Cometic | C14067-043 |
A gasket's volume is the recess it leaves above each cylinder: it adds to the combustion chamber and lowers the compression ratio. Only two gaskets of the same bore can be compared on this point.
| Fasteners | Engines | Tightening torque |
| Original cylinder head bolts | 3.5 Litre | not published by the manufacturer |
Before fitting, run a straightedge over the head and the block to check their flatness, and have whichever needs it resurfaced. Every CFM-20 gasket leaves Cometic after a flatness check.
| CFM-20 Cometic This construction stacks a galvanized steel core with, on each of its faces, a soft asbestos-free compound made of aramid fibres, mineral fillers and elastomer binders. Between metal and fibre, it brings together the strength of steel and the softness of the compound. Only one model is shown here, with an 84 mm bore and a thickness of 1.09 mm. |
Gasket bore. The Cometic CFM-20 is offered in 84 mm (C14067-043), with no other bore.
Thickness. We have no confirmed original thickness for this engine. A thicker gasket enlarges the combustion chamber and lowers the compression ratio; a thinner one reduces it and raises the ratio.
| Your goal | Thickness to choose |
| Keep the original compression ratio | Original thickness unknown: measure the removed gasket and compare it with the only gasket offered, 1.09 mm |
| Skimmed cylinder head, make up the lost height | Only one thickness exists, 1.09 mm: weigh it against that of the removed gasket, plus whatever resurfacing took off |
| Forced induction build, lower the ratio | 1.09 mm, if the thickness measured on the original gasket at removal is smaller |
| Naturally aspirated build, raise the ratio | 1.09 mm, if the thickness measured on the original gasket at removal is greater |
With no confirmed original thickness, use a dial gauge to measure how far the pistons stand above the block's gasket face, particularly if the removed gasket is thinner than 1.09 mm: this gives the clearance that remains between piston and head.
 | Founded in 1989 in Concord, Ohio, Cometic Gasket, Inc. designs gaskets and sealing solutions for engines. Its expertise lies in the made-to-measure gasket, cut to the bore and thickness requested, and all production stays in the United States with American raw materials. |
| Criterion | Original gasket not confirmed | Reinforced gaskets |
| Construction | Construction not confirmed | Galvanized steel core and asbestos-free compound (CFM-20) |
| Gasket bore | not confirmed | 84 mm |
| Thicknesses available | thickness not confirmed | 1.09 mm |
| Compression ratio adjustment | None | Through the thickness chosen |
| Resistance to overpressure | Limited to standard output | Designed for forced induction |
| Model | Engine code | Power | Years |
| Jaguar Mark V | 3.5 Litre | not published | 1950 |
OEM part number: no confirmed original part number.
Important: the part number on this page is listed by Cometic for the 1950 Jaguar Mark V: for another model year or version, check the 84 mm bore before ordering.
Once the original gasket is spent, this CFM-20 takes its place: the steel core does not deform under combustion pressure, while the soft compound on both faces follows the slight flaws of the head and block.
An engine pushed close to its limit often loses its head gasket before any other part. The reinforced gasket removes that risk, and it costs far less than the head removal that would follow a leak. The extra cost stays limited to the part itself.
