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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 CFM-20 head gasket. Sold individually, one gasket per engine.
The Toyota 18R-G of 2.0 litres powers the Celica Coupé (RA63) listed below.
The original gasket of these engines carries the part number 11115-33010. Toyota publishes neither its bore, nor its thickness, nor its construction. It is sized for the original combustion pressure: if it rises, the clamping load eases, the head lifts and coolant passes into a cylinder.
Sealing is not down to the gasket alone: the clamping provided by the head fasteners counts just as much. The CFM-20 combines a galvanized steel core with an asbestos-free compound laid on each face.
This page describes the part numbers from the American maker Cometic, a specialist in racing gaskets, in a single construction: CFM-20. The bore is 92 mm and the thicknesses 1.09 and 1.5 mm. Each part number is sold individually.
| Gasket bore | Thickness | Gasket volume | Gasket type OEM not specified | Brand | Part number OEM 11115-33010 |
| 92 mm | 1.09 mm | 7.25 | CFM-20 | Cometic | C4172-043 |
| 92 mm | 1.50 mm | 9.97 | CFM-20 | Cometic | C4172-059 |
A gasket's volume is the room it leaves above each cylinder. It adds to the combustion chamber: the bigger it is, the lower the compression ratio gets. Compare these figures only between gaskets of the same bore.
| Fasteners | Engines | Tightening torque |
| Original cylinder head bolts | 18R-G | not published by the manufacturer |
Before assembly, lay a straight edge across the head and block gasket faces to check they are flat, then have them resurfaced if needed. Do not coat the gaskets: Cometic gaskets are supplied ready coated.
| CFM-20 Cometic A galvanized steel core covered on both faces with a soft asbestos-free compound made of aramid fibres, mineral fillers and elastomer binders. This laminated construction, part metal and part fibre, combines the strength of steel with the softness of the compound. It is offered here in one bore and two thicknesses. |
Gasket bore. The Cometic CFM-20 comes in 92 mm, in that bore only.
Thickness. No thickness is supplied by Toyota 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.
| Your goal | Thickness to choose |
| Keep the original compression ratio | Original thickness unknown: read it off the gasket you removed, then keep the offered value closest to it |
| Skimmed cylinder head, make up the lost height | The offered value closest to the thickness measured on the original gasket, plus the height taken off when resurfacing |
| Forced induction build, lower the ratio | 1.5 mm, if the removed gasket is thinner |
| Naturally aspirated build, raise the ratio | 1.09 mm, if the removed gasket is thicker |
For a thickness under the original, first use a dial gauge to read how far the pistons stand proud of the block deck: that figure gives the clearance remaining between piston and head.
 | Cometic Gasket, Inc. is an American company set up in 1989 and based in Concord, Ohio, producing engine gaskets and sealing solutions. Its speciality is the made-to-measure gasket, cut to the bore and thickness wanted. All manufacturing stays in the United States, using American materials. |
| Criterion | Original gasket 11115-33010 | Reinforced gaskets |
| Construction | Construction not stated by the manufacturer | Galvanized steel core, asbestos-free compound on both faces |
| Gasket bore | not published by the manufacturer | 92 mm |
| Thicknesses available | thickness not published by the manufacturer | 1.09 to 1.5 mm, 2 values |
| Compression ratio adjustment | None | Through the thickness chosen |
| Resistance to overpressure | Limited to standard output | Designed for forced induction |
| Model | Engine code | Power | Years |
| TOYOTA CELICA Coupé (_A6_) 2.0 (RA63_, RA63R) | 18R-G | 120 hp | 01.1982 - 12.1985 |
OEM part number: 11115-33010.
Important: the gaskets on this page are listed for the Toyota 18R-G engine of 2.0 litres in the table (1982 to 1985). For any other vehicle, note the engine code before ordering.
Once the original gasket has run out of capacity, the CFM-20 steps in: the galvanized steel of its core keeps its shape and the asbestos-free compound seals the contact between head and block.
With a turbo or a supercharger, or after raising the compression ratio, the cylinder head takes greater loads and its gasket turns into the weak point. A reinforced gasket avoids the leak, and the head removal that would follow.
