Hello Walter,
There are many facets to your question. Lets start with the advantages:
Physical dimensions:
The 289/302 stroked to 331 or 347 ci will fit easier into certain cars, like a '65/66 Mustang, Sunbeam Tiger, early street rods, etc.
Although they are the same length, the 351W has nearly a 3/4 inch taller deck height than a 289/302, making some installations very tight. This is not a problem in a Cobra chassis.
Parts interchange:
If you already have a 289/302, stroking it to 347ci means you could use the same intake and exhaust manifolds/headers, distributor, and
oil pan. All of these things would need to be replaced if building a 351W.
Original look: Nobody can tell that your 289 is 347ci by looking at it! You have a "wolf in sheep's clothing"
Disadvantages:
More power=no more displacement.
If you want more power from your 347, it will have to be done with bigger cylinder heads, more compression and a larger camshaft in order to raise the RPM ceiling because you are just about at the limit of how big you can make a 289/302.
The 351W can be increased to well over 400ci if more power is desired without having to raise the RPM ceiling.
Rod angle: The added stroke of the 347 increases the side loading of the cylinder walls which will accelerate wear.
Oil control: If your motor was built with the 5.4" long connecting rod, which most seem to be, The piston pin intersects with the
oil ring-land. This usually means 347s consume more oil than average. These two issues, Rod angle and oil control, usually mean that a 347 is not a "long life" engine. But in reality, how long is it going to take you to put 50,000 mile on your Cobra?
Longevity is most likely not a concern.
I'm sure I've created more questions than answers, If you need more information, just write.
HTH,
Mike
Hybrid Mode
