6327 - Signature Series Dirt Oval Mod Zenoah 4 Bolt 30.5cc Top End

After quite a few years of prototyping our oval racing engines we've come up with the signature series dirt oval mod engine. The 30.5cc version is intended for the advanced oval racer and can be overpowered if you're new to racing. This engine is designed and tuned exclusively for oval racing and is not suited for bashing. It offers a great balance of torque and rpm's and is the fastest engine currently in the DLMRA series.

The following modifications have been done. Just like the rest of our engines this is cnc ported and comes standard with a billet crankcase.

1. Deck cylinder to raise compression without using a thinner cylinder gasket

2. Reshape piston

3. Lighten piston

4. Relieve piston to prevent seizes

5. Modify intake port for better flow

6. Adjust intake duration to our specs

7. Resurface all ports

8. Modify transfer ports for better flow

9. Enlarge and reshape exhaust port

10. Adjust exhaust duration to our specs

11. Remove stock crank and install stuffed crank

12. Install all new gaskets and c-clips when engine is assembled

13. Re-bevel all porting and stock bevels to prevent damage to the piston and/or cylinder

This engine now comes with a TR/OBR billet crankcase at no extra cost. Every long block or engine is now CNC ported and hand finished. CNC porting and hand finishing is all done in-house by the OBR staff. We do not contract out any of our porting so every engine is modified to our exact specifications. We are able to offer higher accuracy this way as well as more power. Our CNC machine has allowed us to take our porting to the next level due to us being able to do cylinder work that is not possible to do by hand.

Replacement full mod or signature series twin top end set. These top ends have been machined for twin use and our billet heat sink. Full mod is our production CNC porting and will have good power from torque through top rpm's. The signature series are ported more aggressively and will have quite a bit more power than the full mod version. We also offer custom tuning on any signature series top ends/engines upon request at no additional charge. If ordering signature series porting please email us if you would like custom tuning. 

Replacement top end for our fat boy reed engines. The 47cc version requires a +1mm stroker crank.

Replacement Zenoah 4 bolt cylinder gaskets. Fits all Zenoah 4 bolt engines.