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1.6L 16v - D16A1/D16A9
Manufacturers
1.6L 16v - D16A1/D16A9
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Reinforced Cometic MLS head gasket for DOHC D16A. Sold individually.
The Honda D16A9 is the 1.6-litre 16-valve DOHC inline four-cylinder petrol engine of the Civic IV and CRX II, the Concerto and the Rover 200 and 400; the D16A1 is its Acura Integra version. This page covers the D16A1 and D16A9: both engines take the same reinforced cylinder head gaskets.
The original gasket carries part number 12251-PM7-003; some versions of the D16A1 take 12251-PM5-S01. Honda publishes neither its construction, nor its bore, nor its thickness. It is sized for standard combustion pressure: when that pressure rises, clamping load drops, the cylinder head lifts, and coolant passes into a cylinder.
A cylinder head gasket does not create the seal on its own: it holds because the fasteners clamp the head against the block. A composite gasket is crushed for good beyond 100 N/mm² of admissible stress, whereas the 301 stainless steel of the MLS gaskets withstands 517 N/mm², 5 times more, and springs back at every combustion.
This page offers the part numbers from Cometic, a racing manufacturer, in MLS multi-layer steel construction. Gasket bores run from 75.5 to 78 mm, covering the standard block as well as the rebored block, and thicknesses from 0.69 to 3.56 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 individually, one gasket per engine.
| Gasket bore | Thickness | Gasket volume | Gasket type OEM not specified | Brand | Part number OEM 12251-PM7-003 |
| 75.5 mm | 0.69 mm | 3.09 | MLS | Cometic | C4522-027 |
| 75.5 mm | 0.76 mm | 3.40 | MLS | Cometic | C4522-030 |
| 75.5 mm | 0.91 mm | 4.07 | MLS | Cometic | C4522-036 |
| 75.5 mm | 1.02 mm | 4.57 | MLS | Cometic | C4522-040 |
| 75.5 mm | 1.14 mm | 5.10 | MLS | Cometic | C4522-045 |
| 75.5 mm | 1.30 mm | 5.82 | MLS | Cometic | C4522-051 |
| 75.5 mm | 1.42 mm | 6.36 | MLS | Cometic | C4522-056 |
| 75.5 mm | 1.52 mm | 6.80 | MLS | Cometic | C4522-060 |
| 75.5 mm | 1.68 mm | 7.52 | MLS | Cometic | C4522-066 |
| 75.5 mm | 1.78 mm | 7.97 | MLS | Cometic | C4522-070 |
| 75.5 mm | 1.91 mm | 8.55 | MLS | Cometic | C4522-075 |
| 75.5 mm | 2.03 mm | 9.09 | MLS | Cometic | C4522-080 |
| 75.5 mm | 2.13 mm | 9.54 | MLS | Cometic | C4522-084 |
| 75.5 mm | 2.18 mm | 9.76 | MLS | Cometic | C4522-086 |
| 75.5 mm | 2.34 mm | 10.48 | MLS | Cometic | C4522-092 |
| 75.5 mm | 2.49 mm | 11.15 | MLS | Cometic | C4522-098 |
| 75.5 mm | 3.05 mm | 13.65 | MLS | Cometic | C4522-120 |
| 75.5 mm | 3.56 mm | 15.94 | MLS | Cometic | C4522-140 |
| 76 mm | 0.69 mm | 3.13 | MLS | Cometic | C4524-027 |
| 76 mm | 0.76 mm | 3.45 | MLS | Cometic | C4524-030 |
| 76 mm | 0.91 mm | 4.13 | MLS | Cometic | C4524-036 |
| 76 mm | 1.02 mm | 4.63 | MLS | Cometic | C4524-040 |
| 76 mm | 1.14 mm | 5.17 | MLS | Cometic | C4524-045 |
| 76 mm | 1.30 mm | 5.90 | MLS | Cometic | C4524-051 |
| 76 mm | 1.42 mm | 6.44 | MLS | Cometic | C4524-056 |
| 76 mm | 1.52 mm | 6.90 | MLS | Cometic | C4524-060 |
| 76 mm | 1.68 mm | 7.62 | MLS | Cometic | C4524-066 |
| 76 mm | 1.78 mm | 8.07 | MLS | Cometic | C4524-070 |
| 76 mm | 1.91 mm | 8.66 | MLS | Cometic | C4524-075 |
| 76 mm | 2.03 mm | 9.21 | MLS | Cometic | C4524-080 |
| 76 mm | 2.13 mm | 9.66 | MLS | Cometic | C4524-084 |
| 76 mm | 2.18 mm | 9.89 | MLS | Cometic | C4524-086 |
| 76 mm | 2.34 mm | 10.62 | MLS | Cometic | C4524-092 |
| 76 mm | 2.49 mm | 11.30 | MLS | Cometic | C4524-098 |
| 76 mm | 3.05 mm | 13.84 | MLS | Cometic | C4524-120 |
| 76 mm | 3.56 mm | 16.15 | MLS | Cometic | C4524-140 |
| 77 mm | 0.69 mm | 3.21 | MLS | Cometic | C4525-027 |
| 77 mm | 0.76 mm | 3.54 | MLS | Cometic | C4525-030 |
| 77 mm | 0.91 mm | 4.24 | MLS | Cometic | C4525-036 |
| 77 mm | 1.02 mm | 4.75 | MLS | Cometic | C4525-040 |
| 77 mm | 1.30 mm | 6.05 | MLS | Cometic | C4525-051 |
| 77 mm | 1.42 mm | 6.61 | MLS | Cometic | C4525-056 |
| 77 mm | 1.52 mm | 7.08 | MLS | Cometic | C4525-060 |
| 77 mm | 1.68 mm | 7.82 | MLS | Cometic | C4525-066 |
| 77 mm | 1.78 mm | 8.29 | MLS | Cometic | C4525-070 |
| 77 mm | 1.91 mm | 8.89 | MLS | Cometic | C4525-075 |
| 77 mm | 2.03 mm | 9.45 | MLS | Cometic | C4525-080 |
| 77 mm | 2.13 mm | 9.92 | MLS | Cometic | C4525-084 |
| 77 mm | 2.18 mm | 10.15 | MLS | Cometic | C4525-086 |
| 77 mm | 2.34 mm | 10.90 | MLS | Cometic | C4525-092 |
| 77 mm | 2.49 mm | 11.59 | MLS | Cometic | C4525-098 |
| 77 mm | 3.05 mm | 14.20 | MLS | Cometic | C4525-120 |
| 77 mm | 3.56 mm | 16.58 | MLS | Cometic | C4525-140 |
| 78 mm | 0.69 mm | 3.30 | MLS | Cometic | C4526-027 |
| 78 mm | 0.76 mm | 3.63 | MLS | Cometic | C4526-030 |
| 78 mm | 0.91 mm | 4.35 | MLS | Cometic | C4526-036 |
| 78 mm | 1.02 mm | 4.87 | MLS | Cometic | C4526-040 |
| 78 mm | 1.14 mm | 5.45 | MLS | Cometic | C4526-045 |
| 78 mm | 1.30 mm | 6.21 | MLS | Cometic | C4526-051 |
| 78 mm | 1.42 mm | 6.79 | MLS | Cometic | C4526-056 |
| 78 mm | 1.52 mm | 7.26 | MLS | Cometic | C4526-060 |
| 78 mm | 1.68 mm | 8.03 | MLS | Cometic | C4526-066 |
| 78 mm | 1.78 mm | 8.51 | MLS | Cometic | C4526-070 |
| 78 mm | 1.91 mm | 9.13 | MLS | Cometic | C4526-075 |
| 78 mm | 2.03 mm | 9.70 | MLS | Cometic | C4526-080 |
| 78 mm | 2.18 mm | 10.42 | MLS | Cometic | C4526-086 |
| 78 mm | 2.34 mm | 11.18 | MLS | Cometic | C4526-092 |
| 78 mm | 2.49 mm | 11.90 | MLS | Cometic | C4526-098 |
| 78 mm | 3.05 mm | 14.57 | MLS | Cometic | C4526-120 |
| 78 mm | 3.56 mm | 17.01 | MLS | Cometic | C4526-140 |
Gasket volume: the space the gasket leaves above each cylinder. It enlarges the combustion chamber, and the larger it is, the lower the compression ratio. Values compare with one another at identical gasket bore.
| Fasteners | Engines | Tightening torque |
| Original cylinder head bolts | D16A1, D16A9 | Not published |
Before fitting, check the flatness of the cylinder head and of the block with a straight edge and have them skimmed if necessary. These gaskets require no sealant: Cometic supplies them already coated.
 | Cometic MLS Several stamped and riveted stainless steel layers. The outer layers carry active beads around each cylinder and each fluid passage. Sealing is achieved with a moderate clamping load and limited bore distortion. This is the versatile choice, from a prepared naturally aspirated engine to light forced induction. |
Gasket bore. The Cometic MLS comes in 75.5, 76, 77 and 78 mm.
Thickness. Honda does not publish the thickness of 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 | The value closest to the thickness of the removed gasket |
| Skimmed cylinder head, make up the lost height | The thickness of the removed gasket + what was removed |
| Forced induction build, lower the ratio | A thickness above that of the removed gasket |
| Naturally aspirated build, raise the ratio | A thickness below that of the removed gasket |
With a thickness finer than that of the removed gasket, measure piston protrusion above the block with a dial gauge: it is what determines the remaining clearance between piston and cylinder head.
 | Cometic Gasket, Inc. is an American manufacturer of engine gaskets and sealing solutions, founded in 1989 and based in Concord, Ohio. Its speciality is the made-to-order gasket, in the bore and thickness required. All its products are made in the United States, from American materials. |
| Criterion | Original gasket 12251-PM7-003 | Reinforced gaskets |
| Construction | Not specified by the manufacturer | Multi-layer stainless steel |
| Gasket bore | Not published by Honda | 75.5 to 78 mm |
| Thicknesses available | Not published by Honda | 0.69 to 3.56 mm, 18 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 |
| Acura Integra | D16A1 | 100 and 114 hp | 1985-1990 |
| Honda Civic IV (EC, ED, EE, EF) | D16A9 | 130 and 132 hp | 1987-1992 |
| Honda Civic V (EG, EH) | D16A9 | 131 hp | 1991-1996 |
| Honda Concerto (HW, MA) | D16A9 | 131 hp | 1989-1992 |
| Honda CRX II (ED, EE) | D16A9 | 131 hp | 1987-1989 |
| Rover 200 II (XW) | D16A9 | 130 hp | 1990-1995 |
| Rover 400 II (XW) | D16A9 | 131 hp | 1990-1995 |
OEM part number: 12251-PM7-003, 12251-PM5-S01 (D16A1).
Important: the SOHC D15B, D16A6, D16A7, D15Z1, D16Y and D16Z6 take other cylinder head gaskets: they are not covered by this page.
A reinforced gasket holds where the standard one reaches its limit: at higher combustion pressure it keeps its shape instead of being crushed.
As soon as power goes up, turbo, supercharger or raised compression ratio, the head gasket becomes the weak link of the top end. Switching to a reinforced gasket is then not a comfort but a safeguard: it is what prevents the failure and the head removal that comes with it.
