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FORD - Reinforced Engine Parts
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FORD - Reinforced Engine Parts
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Set of 8 reinforced inlet valves for FORD Sierra and Escort RS Cosworth N5B.
The N5B is the 2.0 litre Cosworth four-cylinder with 16 valves and twin overhead camshafts, built on a Ford block and turbocharged. It delivers 204 hp in the Sierra RS Cosworth from 1985 to 1990 and also powers the Escort RS Cosworth.
The engine has 8 inlet valves with a 6.95 mm stem. More boost, sharper camshafts or a higher rev limit load them far beyond the original tune.
On every cycle the inlet valve opens to let the compressed air in, strikes its seat again and slides in its guide, dozens of times per second at high rpm. It runs between 400 and 550 °C; an original chrome-silicon steel drops from 500 MPa of strength at 500 °C to 250 MPa at 600 °C, a 50 % loss.
The FERREA 6000 series valves are EV8 stainless steel: 650 MPa at 500 °C and 550 MPa at 600 °C, that is 30 % then 120 % better than the original steel at the same temperatures.
They come in the standard size (35.12 mm head) and the +1 mm size (36.12 mm). A wider head opens the flow area at the seat: the cylinder fills better and the engine gains power, as long as the 8 inlet seats are cut to 36.12 mm.
| Part number | Brand | Size | Head Ø | Stem Ø | Length | Grooves | Material |
|---|---|---|---|---|---|---|---|
| F6747*8 | FERREA | Standard | 35.12 mm | 6.95 mm | 105.44 mm | EV8 stainless steel | |
| F6749*8 | FERREA | +1 mm | 36.12 mm | 6.95 mm | 105.44 mm | EV8 stainless steel |
Stem tip: 1.6 mm.
| Part | FORD original | Reinforced |
|---|---|---|
| Collets | ||
| Valve stem seals | ||
| Valve guide |
With the +1 mm size, the 8 inlet seats are cut to 36.12 mm; at standard size they keep their diameter.
Both part numbers have a 6.95 mm stem and a length of 105.44 mm.
 | Set up in 1978 in Fort Lauderdale (Florida) by two Argentine engine builders, FERREA Racing Components forges its valves in one piece from bar stock and fully CNC machines them; they run in NASCAR as well as in drag racing. |
The groove is the notch at the end of the stem where the collets hold the retainer; here only the size changes.
| Criterion | Option 1 | Option 2 |
|---|---|---|
| Size | Standard size 35.12 mm head (F6747*8), for seats still at factory size. | +1 mm size 36.12 mm head (F6749*8): about 10 to 12 cfm more per mm of head. Seats to be cut; also makes up for seats already reground. |
| Model | Engine code | Power | Years |
|---|---|---|---|
| Sierra I (GBC) 2.0 4x4 (RS Cosworth) | N5B | 204 hp | 1985-1987 |
| Sierra II (GBC, GBG, GB4) 2.0 RS Cosworth | N5B | 204 hp | 1987-1990 |
| Escort RS Cosworth | N5B |
To rebuild the whole N5B cylinder head, the reinforced exhaust valves are on this page:
| FORD Cosworth N5B exhaust valves → |
