Description: BOSS 429 Exhaust Heat Riser Flapper Valve
Year: 1969-70
Model: Mustang
Engine: BOSS 429
Quantity: 1

Accuracy Rating: 9
Best Repro Available: YES

Jack's Comments:

This is an excellent reproduction of the 1969-70 BOSS 429 heat riser flapper valve. It even has the FOMOCO casting just like the original.

Why was this used anyway?
The BOSS 429 was a challenge for the Ford engineers in many ways, especially emissions requirements. For the BOSS 429 to pass the cold start emissions performance standards of the time Ford engineers used this temperature sensitive valve to divert hot exhaust to the intake manifold through the heat riser tubes. Once the engine was up to operating temperature the valve would stay open.