Thread Rating:
  • 0 Vote(s) - 0 Average
  • 1
  • 2
  • 3
  • 4
  • 5
Mc 49 Specs Discussion
#1
Jack Canaday,
Looking through stuff, I found this block. Since I cannot do pictures, will try to describe it.
Has 2.125 bore, fixed head, smallest combustion chamber I have ever seen, compression release on side above intake manifold, ball bearing on pto side, provision for late style boost ports, bottom accepts large stuffer, and distance from base to squish same as mc49.
Long winded I know but can this thing be used to build a 49?
Thanks jack

Paul Booth
Jack,
Your crankcase is a red and white Mc49M/C. It has 2.125 bore and 1.375 stroke making it 80cc.
It has fixed head.
Combustion chamber is same as 91 and 101 series motors 9:4 to 1.
 49 motors are 6:to1 compression.
The 49M/C has compression release valve, McCulloch called it a D.S.P. valve.[De Stroking Port]
 It comes with a 4 pedal v-reed and sloper manifold with BDC 22 carb. same setup as Mc91M/C and Mc101M/C.
 It came with dual ball bearing crankshaft with 3/4 pto shaft.
The boobs for the boost ports are on outside of block under coil assembly.
 The block has 3 intake ports and 3 transfer ports and 3 exhaust ports standard.
No boost ports machined from factory.
It also has recessed exhaust port.
It will make an awesome 49 Kart engine with boost ports done.
I have a N.O.S. Mc49M/C and 4 Mc91M/C and 1 Mc101M/C complete engines.
 These are very fast and good engines.
Any more questions just ask. Have a good one
Paul

SteveO
I believe the block has 6 transfer ports, three on each side.
No intake ports since there is no passage on the back side of the block to serve them. It is built to be a reed induction engine exclusively rather than a combo reed/ piston valve motor like the 49, 49c and 49E models.

Maybe just a semantics issue... some people use "intake" and "transfer" to describe the same ports.
But when talking about the early 49 models along with all of the pre Mc 45/75 models the engines typically came with 6 transfer ports and three intake ports opposite the exhaust that are located in the block in a position such that they cannot be seen when the piston is at BDC. Those small round ports do not transfer charge from the case to the cylinder, they transfer incoming air/fuel mix from outside to inside the case so they are often called "intake" but more commonly called "piston" ports.

Engines with the combo induction setup are easier to start with a rope starter and also idle better than the reed only versions.
The first generation Mc 49 came with only four transfer ports, two on each side.
SteveO

Jack Canaday
Thanks for the info, but this block has a combustion chamber smaller than a Mc 6 or Mc 10. Only about .9 Diameter. This makes for really wide squish band. Now for next question. How are builders addressing the extreme squish clearance? This thing must have .055
Thanks Jack

SteveO
I should clarify that I was describing the Mc 49 M/C type block. Yours sounds different.... I have never seen the combustion chamber shape of the 49M/C block to say if that is normal for that engine.
Does the block have a part number stamped on it?
SteveO


Jack Canaday 
Thanks Steve for the reply. No number on block. This thing has at least 60 percent squish band. But a large squish clearance.
Jack

SteveO
Jack,

All the 49 series engines have about the same squish clearance as your block. The unusual part is the small dome. If you can, measure the diameter and depth of the dome and I'll do the same for the 49E I'm working on right now. I'll post the dimensions later.
SteveO

Jack Canady
Steve,
Best I can measure, .9 diameter, and .486 deep. And yes it does look to have about .035 of straight before radius starts. Now with a little math, that is 80% squish band. I have never run more than 50%. Will this be tunable.
Jack


SteveO
Jack,

With the large squish dimension the engine will still be pretty forgiving on the mixture settings but it will have much higher compression than most 49 type motors so it should make more power. Does the motor have the spark plug located in the same position and angle as the other 49 blocks? Does it use a 1/2" reach plug?
Seems like the engine would have to have the plug in the center for it to work out right with that tiny dome.
SteveO

Jack Canady
Steve,
Plug is in normal position, offset over coil. A 1/2 reach shows one thread in chamber, 3/8 reach one thread short. Just as all MCs were. I think the heads had cast in something like .47 to .5 reach. Champion length perhaps. The NGK plugs I used needed an extra washer or no washer and the thick thermocouple.
Jack
Reply


Forum Jump:


Users browsing this thread: 1 Guest(s)