6238 - 5.5hp PROSTOCK Ported 30.5cc 4 Bolt Top End

<p>(Our porting is not shown in picture)&nbsp;</p> <p>PROSTOCK - An affordable/mild version of a full mod. The PROSTOCK's are rated at 5-5.5hp, full mod's 6-6.5hp, and full mod long rods 7-7.5hp.&nbsp;<span>We guarantee performance of this top end to be as much if not more than similary priced ported top ends from our competitors.&nbsp;</span></p> <p>The PROSTOCK line has replaced the Race Ported line. The PROSTOCK engines produce more power than the race ports and are more economical.</p> <p>To keep costs down, we focused our time tuning this top end to the areas that would yield the most power possible while maintaining reliability and ease of use. At OBR, we do not believe in stacking or using thick cylinder gaskets. We always machine and reshape the combustion chamber on our stroked engines. To help with reliability, we also relieve the piston. Piston reliefs help reduce the chances of the piston seizing on the exhaust side of the cylinder when running lean or hot. We were the first in this industry to do the piston relief several years ago.</p> <p>Being that this line is a budget/starter top end, we tuned it to run well with any exhaust. We kept in mind that you may not have a pipe. We have seen great performance with everything from an HPI can exhaust to a pipe. If upgrading to a pipe, we recommend the Jetpro Boss. For those of you that are new to ported engines, we shot for ease of use. With proper installation a PROSTOCK engine is very easy to start and to tune the carb.&nbsp;</p> <p>We have left the porting open on this top end. At any time, you may send your engine/top end in to us to be upgraded to a full mod or a full mod long rod.</p> <p><span>*Tech notes: We have ported this top end to not need a modified crankcase. We recommend a standard Zenoah 4 bolt crankcase. This top end requires that you use a +2mm stroker crankshaft.&nbsp;</span></p>