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Yes, but I know in the prior years, the heads were different castings. The 300 hp got the "double humps" and the 250 hp got the "double triangles/diamonds." Don't know about '65s.
There are three different valve sizes at play here on 327 engines. Only two sizes regarding the 250 and 300 engine.
The '62-'64 250 hp used small valve heads, 1.72/1.50. All 300 hp engines used big valve heads. The '65 250 used big valve 1.94/1.50 heads. So, I used the term "big valve".
The "bigger" valve 2.02 heads weren't used on either of these two engines.
Its all in the chart I posted from GM Heritage website.
Strange information on that chart. It shows that the heads on high horse SB engines have 25 degree valve angles. News to me. AFAIK, ALL production SB heads have 23 degree valve angles.
The OP's question is wrong. It should be about "big port" vs. "small port" (283 size) heads.
The '62-'64 327/250s have ...896 heads that have 283 port and valve sizes (1.72/1.50") but larger chambers (about 60-61cc) than 283 heads to keep CR at a reasonable level with the longer stroke. These engines also have a 283 port size manifold and the small (about 400 CFM) Carter WCFB.
The two long blocks are identical - same cam, pistons and everything else.
For '65 the 327/250 got big port 461 heads with the "standard" 1.94/1.5" valve sizes (same as the 327/300), but retained the same manifold and carburetor. Go figure!
SHP/FI engines got the same 461 heads in '64/'65, but were machined for the "big" valves (2.02/1.60") including the inlet side chamber relief cut centered on the inlet valve.
The 327/250 configuration never made sense to me as the cost difference between 250 and 300 HP engines must have been near nil, but the 327/250 has unique head castings and added to inventory by having four available engines instead of three. I would think that this would actually add operating cost.
Apparently GM figured this out too, and for '66 the 327/300 became the base engine.
The reference to "25 degree valve angle" in the '65 AMA specs is clearly a typo that didn't get caught and corrected.
Strange information on that chart. It shows that the heads on high horse SB engines have 25 degree valve angles. News to me. AFAIK, ALL production SB heads have 23 degree valve angles.
There are some typos. You spotted one. Eventually somebody would mention that another line says 396 V8 -- 350, 365, 375 hp. Obviously also a typo.
You may not gain much by going to the 2.02 size if that is a goal you have in mind. From what I understand the bigger size only helps in the upper RPM range and only if the head has the valve unshrouded. Couple of photos showing the unshrouded area in the factory head Duke referred too.
For 65 three engines had the 2.02 size valves L76, L79, L84
You may not gain much by going to the 2.02 size if that is a goal you have in mind. From what I understand the bigger size only helps in the upper RPM range and only if the head has the valve unshrouded. Couple of photos showing the unshrouded area in the factory head Duke referred too.
For 65 three engines had the 2.02 size valves L76, L79, L84
Just wasn't sure what they had. For what I will be doing with the car the originals should be fine. I plan to put a 65 original 350/365 h.p. intake and carb on the original 300 h.p. engine and possibly a hydraulic L79 cam in it but I will see how it performs without the cam first. Thanks for all the responses.
When my double-hump heads were redone for the 2.02/1.60 valves with hardened seats, and pocket ported and port matched by among the best in the business, the heads were unshrouded, as was the block.
Just wasn't sure what they had. For what I will be doing with the car the originals should be fine. I plan to put a 65 original 350/365 h.p. intake and carb on the original 300 h.p. engine and possibly a hydraulic L79 cam in it but I will see how it performs without the cam first. Thanks for all the responses.
I think you will gain very little with the carb/manifold change alone. Put the cam in the engine with the manifold change. The 300 cam doesn't do anything for your intake change.
Think matched components.
Years ago, my cousin had a 300 hp '65 Chevy II (rare car). It wasn't much to write home about as far as performance car. It'd run with a GTO. He put a l 79 cam in it and that really woke it up. Later, I put one of my spare Rochester FI units on it and made another improvement in performance. The cam helped the power, the FI helped the driveability and throttle response.
I think you will gain very little with the carb/manifold change alone. Put the cam in the engine with the manifold change. The 300 cam doesn't do anything for your intake change.
Think matched components.
Years ago, my cousin had a 300 hp '65 Chevy II (rare car). It wasn't much to write home about as far as performance car. It'd run with a GTO. He put a l 79 cam in it and that really woke it up. Later, I put one of my spare Rochester FI units on it and made another improvement in performance. The cam helped the power, the FI helped the driveability and throttle response.
You are likely right but I am going to try it without first.
02-05-2018, 07:37 PM
Doe both the 250 h.p and 300 h.p 1965 engines have the small valves in the heads?
