Mac saw engines

[Terry Bentley]

Adding ports to saw blocks

What do you do with those saw blocks that are missing intake and exhaust ports?????

Ask Ron Popeil? Does he have a Ronco Portable Porting Protractor? It calculates, it locates, it drills, it sizes, it recesses, it does it all. But for only three payments of.......

Maybe not, but would be nice. Now the next best thing. After several years of use it still puts those ports exactly where they should be. By locating on the existing ports, lays the exact position for either missing intake port. It also recesses the back side of block for the welch plug to be placed after drilling new port.

Sounds too good to be true. Just like the Ronco Pocket Fisherman.

   

Nice idea, but I was never able to pull in the big ones. Or on a regular fishing pole for that matter.

   

This is the fixture. It will fit all standard and super series blocks with fixed or removable heads. Since all of the ports are measured from bottom of block it is easy to build a fixture to add ports. The side plates are both  drilled for all three intake ports. The two existing ports are used for locating points. Pins are driven in on both sides and then all the bolted together plates are snugged up. This will align the cylinder block for missing ports perfectly. The location of missing ports have drill bushings that are precisely sized for tooling to add missing ports.

   

On the back side you can see the two solid pins that slide in tightly and locate exactly where missing port will be drilled.  

   

From the top you can see the pins where pressed in and also inside you can just see where they almost protrude in to bore.

   

With a few choice pieces of tooling, the ports can easily be drilled and made perfect for the ideal kart engine. Taking most any of the early chainsaw cylinder blocks and precisely add the ports, you have a correct vintage and exact replica of an existing kart engine.

The block installed in this fixture is one that was pictured in the D30/36 details previously covered above. This block has all three exhaust ports, but missing two of the intakes. This will get these intake ports added, and later I will walk thru the process of adding two large booster ports as seen in the Mc 91B/92/93. Since most of these saw blocks do not have the third port induction, these two larger boost ports can be easily added without issue.

More to come.