The Stage I modification takes your cylinder heads and turns them into TRUE performance heads. The Stage
I uses your existing valves and springs, but does a complete, full port to both the intake and exhaust runner. The old cast
guides are replaced with new manganese guides, new seals replace the old ones, and a competition valve job is done as well. Deck surfacing is always offered in every application.
Many others simply leave the old
cast guides in place. While this save A LOT of time and hassle, correctly porting in the guide boss area is not possible.
Also, with manganese bronze, tighter clearances can be used between the valve and guide for better oil control, improved heat
dissipation, longer life and quieter operation.
Check around, the
Atwood Performance Stage I is the best bang for the buck on the market.
I modification includes:
- Full porting of both intake and exhaust runner.
- Polishing of both runners to ideal surface finish. 50 grit intake, full polish exhaust.
- New manganese guides.
- New viton seals.
- SuperFlow SF600
flow test @ 28" depression.