- In stock
Reinforced exhaust valves BMW 325i E30 525i E34 M20B25
Set of 6 reinforced exhaust valves for BMW M20B25.
- Brand: SUPERTECH
- Engine: M20B25 (325i E30, 525i E34)
- Dimensions: 36 mm or 37 mm head, 7 mm stem
- Material: black nitride stainless steel or Inconel, 3 grooves
BMW engines covered
An inline six with two valves per cylinder, the M20B25 displaces 2,494 cc (84 mm bore, 75 mm stroke) and was built from 1985 to 1993. It is found under the bonnet of the E30 325i and the E34 525i.
It has only 6 exhaust valves, with a 7 mm stem. Very popular for tuning (camshafts, supercharger, racing use), it then makes these valves work far from their original operating conditions.
SUPERTECH reinforced exhaust valves
An exhaust valve opens into the gases leaving the chamber: the temperature of its metal reaches 760 to 870 °C on a naturally aspirated engine and exceeds 1,000 °C on a turbocharged or supercharged one. To cool down, it relies on its seat (about 75 % of the heat) and its guide (about 20 %). The benchmark taken for the original steel, an EV8 family steel, drops from 550 MPa at 600 °C to 300 MPa at 800 °C.
The BMEVN-1084 is made of black nitrided EV16 stainless steel, with a micropolished stem. The BMEVI-1085 moves up to Inconel, a nickel superalloy that holds 860 MPa at 732 °C and 554 MPa at 816 °C, about 85 % more than EV8 steel around 800 °C: the version to choose for a supercharged or turbocharged M20.
The BMEVI-1085 also takes the head from 36 to 37 mm. The larger flow area empties the cylinder faster and improves the next filling, with a power gain; the exhaust seats are then cut to 37 mm.
Exhaust valve technical specifications
| Part number | Brand | Size | Head Ø OEM 36 mm | Stem Ø OEM 7 mm | Length OEM 102.5 mm | Grooves | Material |
|---|---|---|---|---|---|---|---|
| BMEVN-1084-6 | SUPERTECH | Standard | 36.0 mm | 7 mm | 102.5 mm | 3 | Black nitride EV16 stainless steel |
| BMEVI-1085-6 | SUPERTECH | +1 mm | 37.0 mm | 7 mm | 102.5 mm | 3 | Inconel |
Valve fitting
| Part | BMW original | Reinforced |
|---|---|---|
| Collets | 11 34 1 307 136 (3 grooves) | KPR-VW7-T (3 grooves) |
| Valve stem seals | Kit 11 34 9 059 172 | |
| Valve guide | Inner Ø 7.0 mm |
Both valves on this page have 3 grooves and take the KPR-VW7-T collets suited to the M20.
With the BMEVN-1084, the head stays at 36 mm and the exhaust seats are kept; the 37 mm BMEVI-1085 requires the seats to be recut to its size.
Technical guide
Our brand
 |
SUPERTECH Performance, in California, has been producing racing valvetrain parts for more than thirty years. For the M20, it offers a nitrided stainless steel exhaust valve at standard size and an Inconel version with an enlarged head. |
How to choose
Two versions, which differ in head size and material:
| Criterion | Option 1 | Option 2 |
|---|---|---|
| Size | Standard, 36 mm Seats kept. Nitrided EV16 stainless steel (BMEVN-1084). |
+1 mm, 37 mm More exhaust flow, seats to be cut. Inconel (BMEVI-1085). |
| Material | Nitrided EV16 stainless steel For a tuned naturally aspirated M20, road and track use. |
Inconel Recommended for forced induction or intensive racing use. |
When reinforced valves become necessary
- Supercharger or turbo conversion (Inconel version recommended)
- More aggressive camshafts or reinforced valve springs
- Track days or historic rally events
- Rebuilding a head with burnt original valves
- Seeking more flow with seat cutting (+1 mm oversize)
Vehicle compatibility
| Model | Engine code | Power | Years |
|---|---|---|---|
| 325i (E30) | M20B25 | 170 hp | 1985-1993 |
| 525i (E34) | M20B25 | 170 hp | 1988-1990 |
OEM part number (exhaust valve): 11 34 1 287 814
Don't forget the inlet valves
For a fully rebuilt M20 cylinder head, add the inlet valves:
| Inlet valves BMW 325i E30 525i E34 M20B25 → |
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Brand
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ReferenceBMEVN-1084-6
