Mac saw engines

[Terry Bentley]

D45

There is another saw worthy of mention during the early years in this standard series of Mac saws. The D45 model. It falls in with the 1-50 series of power output. Introduced in 1960 and only sold in Canada. It is identical in all respects to the 1-51 sold in the US. As much that I can determine it is actually a 1-51 stamped block but badged as the D-45. Also it is a slightly darker yellow than American built saws. It utilizes all six intake and three exhaust ports. With exception to a thicker 0.050 head gasket, it is near a perfect candidate if you find one out there. These saws are way up there on the collectable list. A much higher collector value than all of the other models during this time. If you find one incomplete or poor condition, then go for it. I had a hard time coming to grips with this one. It was in such good condition, I had to leave it as a working saw.

       

D30/D36

OK some more specifics on the first of these standard series saws. These include the D-30 and D36 models.
All of the models covered above and in previous post have the same bearing type on crankshaft. The flywheel side uses a common 203-C3 style ball bearing press fit to a 17mm journal. With exception to the 1-52/1-53 models, all of the others listed here use a a Torrington B-1210 housed needle bearing on 3/4" pto bearing journal. The 1-52/1-53 now use the same 203-C3 ball bearing on 17mm journal on pto.

   

This is what the D-30/36 model look like if you happen to find one. A pinion style starter mounted on top of chainsaw.

These first generation saws actually came with the 3/4" journal on both sides and using a housed needle bearing like on the pto side of crank. They also had a thrust bearing on flywheel side like used on the pto.

   

Here you can see needle bearing and thrust washer on the side cover.

   

The bottom end looks fairly common to newer models. But notice the larger diameter of crank on flywheel side. You can also see the recessed area where that automatic oilier baffle fits on back side of crankcase.

   

You notice the flywheel does not have the provisions for starter pawls to use a recoil starter yet. Also unlike the super series models at the time, there are no reinforcing ribs either.

       

Here is the pinion style starter drive gear used on these first models. The driver engages a ring gear cast on back side of flywheel.  They were soon discontinued and replaced with the standard recoil starter for the remainder of production for this style saw and kart engine.

       

Here are closeups of the Mac flat back and Tillotson carbs. This choke setup is same for the D30/36 and all of the 1-40 series models, that are equipped with a Tillotson HL-87 carburetor. A spring loaded plunger that covers air horn of carb. The spring slides inside of air horn and rests against small tab used for a butterfly stop on choke assembly if so equipped. Not the best idea IMHO. Seems it may be a little restrictive and possibly makes venturi not as functional. On one saw I have with this setup the high and low speed needles are only open about 1/2 turn each to run well.

One more thing to note, on the intake side of crankcase there were no cast in ribs as you have seen in the models starting with 1-40 in standard and 1-70 super series. The intake is similar to the first generation super series D44/55 model with a nearly flat surface that feed the intake ports. Still only two intakes on either side were drilled.

   

This is a D36 block. It has same configuration for the intake tract as the first super series saw motors, including D44/55 and S44/55. Please note the super series has all of the intake ports drilled, unlike the D30/36 model which on has two here as shown.

Even tho McCulloch rarely advertised the rated horsepower on these saws, occasionally it would show up in print. Originally the first of these saws, the super series model D44, followed with the gear reduction version model 55 were rated at 5 HP at 4.4 cubic inches displacement.. That is a reasonable claim since McCulloch usually produced more power than any of its competition.

The standard series starting with the D30 was rated at 3.8 HP, and model D36 at 5.2 HP both with 4.9 cubic inches displacement. The D30 rating seems very reasonable comparing to the D44. Since the D30 has only 66% of the exhaust and intake opening, the HP rating is likely very close to correct. Even with only 66% of the intake ports the D36 may make up the difference with all of the exhaust ports drilled and added displacement.

I will update some of the pics as I get them taken for better clarification of differences between models. Again more to come.