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An oddball the 450
#1
Mac model 450

This saw is not much different than a Super 250. Except it is bored out 0.040 oversize". So the bore size is same as Mc7-93 and Mc30-45. The stock thick ring piston fits a 2.165" bore. This is unique and pistons may be next to impossible to find nos. But if they show up, will offer options to bigger oversize than available for all of the 4.9/5.3 blocks. These usually have up to 0.030" oversize. With model 450 pistons you can now have 0.040, 0.050. 0.060. and 0.070" oversize for saw or converted kart blocks.

Bore is 2.165" with stroke of 1.500". That works out as 5.52 ci or about 90.5 cc's.

Another thing about the 450 pistons is they would be the same as a quick timed style piston that was available for modified engines. The deck height is 0.060" shorter than a standard 6.1 engine. You can bore out the Mc5/6/10 to plus 0.040" and have a stock height piston with these.


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Common to most saws with standard three exhaust ports, stock thick ring piston, except is larger than a Super 250. You can see here there is a quick way to identify if crankshaft has ball bearing on pto. There is a larger seal and if you look closely at one of these blocks, has a steel sleeve integral to the casting for the bearing and seal to fit in.

[Image: attachment.php?aid=4345]


Here is a shot at the crank. It looks just like any of the Mc92/93 double ball bearing, tapered pto and counter weights on throws. It is the identical crank but machined with a shorter stroke. These cranks come with keyed right hand 3/8-24 or left hand with out key.  Also the rod is basically what was used in kart engines starting with the Mc8.

[Image: attachment.php?aid=4348]

Here is the intake track. Same as Mc 8/9/49 and late model 250 style blocks.

[Image: attachment.php?aid=4347]

This block is stamped both 400 and 450. But I am not aware of the model 400 in production. It may have been a Canadian or export model.


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