Small Bore/long Stroke vs Big Bore/Short stroke
Quote:
Originally Posted by
Bob Gibbs
my plans for the 300 engine in my special include the following,
Eagle rods CRS6000S3D 4340 FORGED H-BEAMROD 6.000'' (small journal 327)
buick forged 3.8 turbo pistons
TA heads and the new 215 intake with custom spacers
Rover roller cam
Sanderson shorty headers
the 300 has a very short stroke and with the right heads and intake will rev like a chevrolet 283 or 327, add a turbo or centrifugal supercharger and you have mighty mouse on steroids
When compaired to other domestic push-rod V8's of similar displacement, the Buick 300 has a small bore and a long stroke. Example: Chevy- 283, 3.875x3.00 in. 302, 4.00x3.00 327 4.00x3.25 Ford - 289 4.00x2.87 302 (5.0),4.00x3.00. As I mention before, TA will for sure have to spread the valve centers on their new head inorder to fit bigger valves than what comes stock on the iron 300/340 head. They will likely convert to a Chevy style stud mounted rocker system to accommodate the relocated valve centers and also because the stock Buick valve train has issues even with the stock cam and weak valve springs. By the time you buy the heads and the related valve train it will be expensive.
Even with relocating the valve centers, they will not be able to put in anywhere near as big of valves as the above mention Chevy and Ford engines because of the small bore of the 300/340/350 Buick engines. When Buick intorduced the 350 in '68, the engineers knew that they had a deficient cylinder head and that it was limited in valve size because the valve center demensions of the 300/340 heads are the same as the little 215. So, they designed a new head to accommdate larger valves and bigger ports. Still, the valve size of a Buick 350,1.88x1.55, is small when compaired to Chevy,Ford,Mopar, and AMC V-8's of similar displacement.
With a 3.8 bore there is enough room to put in a bigger than the 350 1.88 intake valve, but because the small bore shrouds the larger valves, the full benifits of larger valves will not be relized.
When it comes to making big horsepower the bigger the bore the greater the horsepower potential, especially with parallel arranged/two valve heads. This is evidenced by the fact the NASCAR Cup motors, limited to 358 c.i., feature large 4.200 bores and NHRA Pro Stock 500 in. motors have nearly a 4.700 in bore!
Making big horsepower, in relation to the displacement, with a normally asperated engine requires good breathing and spinning the motor to very high RPM. Besides needing good parts in the lower-end, you need a very good oiling system, which the Chevy/Ford/and Mopar small blocks have but unfortunately is another weak point of the Buick.