As I recall the 300 didn't have the big valve heads or mechanical lifters like the 340,365 or 375 H.P. versions. also had lower compression not the 11 to 1 of the H.P. engines. I believe it also had the same camshaft as the 250 H.P. engines. i hope my memory isn't to far off.
If I remember right the 250hp had the 1.94 heads and the 300hp had the 2.02 heads and a different camshaft. Did the 300 hp have a Carter or was it a Holley carb? Dang my memory aint what it used to be, I used to know this stuff.
The main difference in the early version of the 250 and 300 horse 327 engines was that the 250 had the 520 head with small valves and the Rochester 4GC carb. The 300 had the 461 head with 1.94 intake valves, a better manifold, (iron), and the Carter AFB carb. I'm pretty sure both engines shared the .398 lift hydraulic camshaft.
The 300 hp 327 had a 390/410 lift cam similar to the old 265 pp cam that was used in standard production 283-350 SBCs for the next 20 years. Yhe intake had an AFB bolt pattern with larger bores than WCFB.
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