BY REFERENCE COMETIC - Reinforced cylinder head gaskets

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BY REFERENCE COMETIC - Reinforced cylinder head gaskets

Reduced price! Reinforced cylinder head gasket Porsche 928 V8 5.0 5.4 32v

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Reinforced cylinder head gasket Porsche 928 V8 5.0 5.4 32v

Reference:

Brand Gaskets Cylinder Head reinforced

Condition: New product

Reinforced Cometic multi-layer MLS head gasket for the 5.0 and 5.4 litre Porsche 928 V8 engines, one part number per cylinder bank.

Engines: Porsche 928 V8 M28.41 to M28.50
Bores: 100 and 104 mm
Thicknesses: 0.69 to 3.56 mm
Replaces: 928 104 367 05 and 928 104 368 05

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The Porsche engines covered

The M28.41, M28.42, M28.43, M28.44, M28.45, M28.46, M28.47, M28.49 and M28.50 are the 5.0 and 5.4 litre, 32-valve petrol V8 engines of the Porsche 928 S, S4, GT and GTS listed in the compatibility table below. Each bank of four cylinders has its own head and gasket: one is needed on the right and one on the left.

Porsche gives two part numbers for the original gasket, 928 104 367 05 for the right bank (cylinders 1 to 4) and 928 104 368 05 for the left bank (cylinders 5 to 8), but publishes neither the bore, nor the thickness, nor the construction. Sized for standard combustion pressure, each reaches its limit as soon as that pressure rises: clamping load drops, the head lifts and coolant finds its way into a cylinder.

Reinforced cylinder head gaskets

The gasket's hold also depends on the fasteners that clamp the head onto the block. A composite gasket is permanently crushed beyond 100 N/mm²; the 301 stainless steel of an MLS gasket withstands 517 N/mm², 5 times more, and returns to shape at every combustion. Replace any head bolt that is stretched or damaged. On this V8, tighten the head bolts of each bank in the manufacturer's sequence and to its torque.

This page presents the part numbers from Cometic, the American maker of racing gaskets, in a single construction: the multi-layer steel MLS. Two bores are offered, 100 and 104 mm, and thicknesses run from 0.69 to 3.56 mm, each value existing for the right bank and for the left bank. 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 and for one cylinder bank only: one is needed on the right and one on the left.

Technical specifications

Gasket bore	Thickness	Gasket volume	Gasket type OEM not specified	Brand	Part number OEM 928 104 367 05 et 928 104 368 05
100 mm	0.69 mm	5.42	MLS right bank	Cometic	C5780-027
100 mm	0.69 mm	5.42	MLS left bank	Cometic	C5781-027
100 mm	0.76 mm	5.97	MLS right bank	Cometic	C5780-030
100 mm	0.76 mm	5.97	MLS left bank	Cometic	C5781-030
100 mm	0.91 mm	7.15	MLS right bank	Cometic	C5780-036
100 mm	0.91 mm	7.15	MLS left bank	Cometic	C5781-036
100 mm	1.02 mm	8.01	MLS right bank	Cometic	C5780-040
100 mm	1.02 mm	8.01	MLS left bank	Cometic	C5781-040
100 mm	1.14 mm	8.95	MLS right bank	Cometic	C5780-045
100 mm	1.14 mm	8.95	MLS left bank	Cometic	C5781-045
100 mm	1.30 mm	10.21	MLS right bank	Cometic	C5780-051
100 mm	1.30 mm	10.21	MLS left bank	Cometic	C5781-051
100 mm	1.42 mm	11.15	MLS right bank	Cometic	C5780-056
100 mm	1.42 mm	11.15	MLS left bank	Cometic	C5781-056
100 mm	1.52 mm	11.94	MLS right bank	Cometic	C5780-060
100 mm	1.52 mm	11.94	MLS left bank	Cometic	C5781-060
100 mm	1.68 mm	13.19	MLS right bank	Cometic	C5780-066
100 mm	1.68 mm	13.19	MLS left bank	Cometic	C5781-066
100 mm	1.78 mm	13.98	MLS right bank	Cometic	C5780-070
100 mm	1.78 mm	13.98	MLS left bank	Cometic	C5781-070
100 mm	1.91 mm	15.00	MLS right bank	Cometic	C5780-075
100 mm	1.91 mm	15.00	MLS left bank	Cometic	C5781-075
100 mm	2.03 mm	15.94	MLS right bank	Cometic	C5780-080
100 mm	2.03 mm	15.94	MLS left bank	Cometic	C5781-080
100 mm	2.13 mm	16.73	MLS right bank	Cometic	C5780-084
100 mm	2.13 mm	16.73	MLS left bank	Cometic	C5781-084
100 mm	2.18 mm	17.12	MLS right bank	Cometic	C5780-086
100 mm	2.18 mm	17.12	MLS left bank	Cometic	C5781-086
100 mm	2.34 mm	18.38	MLS right bank	Cometic	C5780-092
100 mm	2.34 mm	18.38	MLS left bank	Cometic	C5781-092
100 mm	2.49 mm	19.56	MLS right bank	Cometic	C5780-098
100 mm	2.49 mm	19.56	MLS left bank	Cometic	C5781-098
100 mm	3.05 mm	23.95	MLS right bank	Cometic	C5780-120
100 mm	3.05 mm	23.95	MLS left bank	Cometic	C5781-120
100 mm	3.56 mm	27.96	MLS right bank	Cometic	C5780-140
100 mm	3.56 mm	27.96	MLS left bank	Cometic	C5781-140
104 mm	0.69 mm	5.86	MLS right bank	Cometic	C5782-027
104 mm	0.69 mm	5.86	MLS left bank	Cometic	C5783-027
104 mm	0.76 mm	6.46	MLS right bank	Cometic	C5782-030
104 mm	0.76 mm	6.46	MLS left bank	Cometic	C5783-030
104 mm	0.91 mm	7.73	MLS right bank	Cometic	C5782-036
104 mm	0.91 mm	7.73	MLS left bank	Cometic	C5783-036
104 mm	1.02 mm	8.66	MLS right bank	Cometic	C5782-040
104 mm	1.02 mm	8.66	MLS left bank	Cometic	C5783-040
104 mm	1.14 mm	9.68	MLS right bank	Cometic	C5782-045
104 mm	1.14 mm	9.68	MLS left bank	Cometic	C5783-045
104 mm	1.30 mm	11.04	MLS right bank	Cometic	C5782-051
104 mm	1.30 mm	11.04	MLS left bank	Cometic	C5783-051
104 mm	1.42 mm	12.06	MLS right bank	Cometic	C5782-056
104 mm	1.42 mm	12.06	MLS left bank	Cometic	C5783-056
104 mm	1.52 mm	12.91	MLS right bank	Cometic	C5782-060
104 mm	1.52 mm	12.91	MLS left bank	Cometic	C5783-060
104 mm	1.68 mm	14.27	MLS right bank	Cometic	C5782-066
104 mm	1.68 mm	14.27	MLS left bank	Cometic	C5783-066
104 mm	1.78 mm	15.12	MLS right bank	Cometic	C5782-070
104 mm	1.78 mm	15.12	MLS left bank	Cometic	C5783-070
104 mm	1.91 mm	16.23	MLS right bank	Cometic	C5782-075
104 mm	1.91 mm	16.23	MLS left bank	Cometic	C5783-075
104 mm	2.03 mm	17.24	MLS right bank	Cometic	C5782-080
104 mm	2.03 mm	17.24	MLS left bank	Cometic	C5783-080
104 mm	2.13 mm	18.09	MLS right bank	Cometic	C5782-084
104 mm	2.13 mm	18.09	MLS left bank	Cometic	C5783-084
104 mm	2.18 mm	18.52	MLS right bank	Cometic	C5782-086
104 mm	2.18 mm	18.52	MLS left bank	Cometic	C5783-086
104 mm	2.34 mm	19.88	MLS right bank	Cometic	C5782-092
104 mm	2.34 mm	19.88	MLS left bank	Cometic	C5783-092
104 mm	2.49 mm	21.15	MLS right bank	Cometic	C5782-098
104 mm	2.49 mm	21.15	MLS left bank	Cometic	C5783-098
104 mm	3.05 mm	25.91	MLS right bank	Cometic	C5782-120
104 mm	3.05 mm	25.91	MLS left bank	Cometic	C5783-120
104 mm	3.56 mm	30.24	MLS right bank	Cometic	C5782-140
104 mm	3.56 mm	30.24	MLS left bank	Cometic	C5783-140

A gasket's volume is the free space it leaves above each cylinder. It adds to the combustion chamber and lowers the compression ratio: the thicker the gasket, the larger that volume. Here two bores are offered, 100 and 104 mm: compare volumes only at equal bore.

Preparation and fitting

Fasteners	Engines	Tightening torque
Original cylinder head bolts	M28.41, M28.42, M28.43, M28.44, M28.45, M28.46, M28.47, M28.49, M28.50	not published by the manufacturer

Before refitting, check the flatness of head and block with a straight edge and have the faces ground if necessary. The Cometic gasket comes pre-coated: do not apply any sealant. Carry out this check on both cylinder heads of the Porsche 928 and on both faces of the block.

Technical guide

The construction offered

Cometic MLS
A stack of stamped and riveted stainless steel sheets. The outer sheets carry active beads that surround every cylinder and every fluid passage. Moderate clamping is enough to seal and the bore stays stable: a versatile construction, from the tuned naturally aspirated engine to moderate boost. The part numbers C5780, C5781, C5782 and C5783 on this page are offered in this construction.

Choosing bore and thickness

Gasket bore. The Cometic MLS comes in 100 mm (C5780 on the right, C5781 on the left) and in 104 mm (C5782 on the right, C5783 on the left).

Thickness. No thickness is published for the original gaskets 928 104 367 05 and 928 104 368 05. 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 not published: measure that of the removed gasket, then choose the closest value offered
Skimmed cylinder head, make up the lost height	The nearest offered value to the removed gasket's thickness, increased by whatever was machined off the head or block faces
Forced induction build, lower the ratio	A thickness above the one read on the removed gasket
Naturally aspirated build, raise the ratio	A thickness below that of the removed gasket, down to 0.69 mm, the minimum of the range

As the original thickness is not published, use a dial gauge to measure how far each of the eight pistons stands above the block's gasket face, especially if the removed gasket is thicker than the value you plan to fit: this reading gives the clearance left between piston and head.

The brand

Cometic Gasket, Inc. is an American company created in 1989 and based in Concord, Ohio, specialised in engine gaskets and sealing solutions. It made its name with the custom gasket, made to the bore and thickness required and manufactured in the United States. Its MLS range also covers the V8 engines of the Porsche 928.

Advantages over the original gasket

Criterion	Original gaskets 928 104 367 05 and 928 104 368 05	Reinforced gaskets
Construction	Construction not stated by the manufacturer	Multilayer stainless steel (MLS)
Gasket bore	not published	100 and 104 mm
Thicknesses available	thickness not provided by the manufacturer	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

When a reinforced gasket becomes necessary

Adding forced induction, or raising boost on an already turbocharged engine
Cylinder rebored beyond what the bore of the original gaskets, which Porsche does not publish 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

Brand	Model	Engine code	Power	Years
Porsche	928 5.0 S, S4	M28.41	320 hp	1986-1991
Porsche	928 5.0 S4 Cat	M28.41	320 hp	1986-1991
Porsche	928 5.0 S4	M28.41	300 hp	1986-1991
Porsche	928 5.0 S, S4	M28.42	320 hp	1986-1991
Porsche	928 5.0 S4 Cat	M28.42	320 hp	1986-1991
Porsche	928 5.0 S4	M28.42	300 hp	1986-1991
Porsche	928 5.0 S	M28.43	272 hp	1984-1985
Porsche	928 5.0 S	M28.44	272 hp	1984-1985
Porsche	928 5.0 S	M28.44	292 hp	1985-1986
Porsche	928 5.0 S	M28.45	288 hp	1985-1986
Porsche	928 5.0 S	M28.46	288 hp	1985-1986
Porsche	928 5.0 GT	M28.47	330 hp	1989-1991
Porsche	928 5.4 GTS	M28.49	350 hp	1991-1995
Porsche	928 5.4 GTS	M28.50	350 hp	1991-1995

OEM part number: 928 104 367 05 (right bank) and 928 104 368 05 (left bank).

Important: the part numbers on this page only suit the M28.41, M28.42, M28.43, M28.44, M28.45, M28.46, M28.47, M28.49 and M28.50 engines of the Porsche 928: check your vehicle's engine code before ordering.

Why switch to a reinforced gasket?

When the original gasket reaches its limit, the reinforced one takes over: under stronger combustion pressure it keeps its shape instead of crushing. On a heavily loaded V8, each cylinder bank stresses its own gasket.

Fitting a bigger turbo, raising boost pressure or increasing the compression ratio puts the head gasket under strain first, as the weak link of the top end. A reinforced gasket prevents the leak, and with it a head removal far more expensive than the part itself. On a 5.0 or 5.4 litre V8 such as the Porsche 928's, the extra pressure is felt at the gasket first.

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