One of the things about owning any sort of vintage device that was intended to move, is the desire to make improvements along the way. Thus is the case now with my 327F-powered 1966 20-foot Sea Skiff, so I did a little research before spending any money and found some interesting things.
This is what my 327F looked like when it arrived in Nashville. I bought the boat without knowing if it would run or not, and guys I really didn't care. As it turns out it did run with a carb transplant, but with very little extra, such as new exhaust logs, new brass freeze plugs (they were steel), distributor job, new carb, and a nice tune-up, this thing has proven to run like a champ. I have no idea how many hours are on the motor, especially due to the fact that this block once ran on the highways too.
Although I never pulled the motor I did have to rotate it in order to fix a cracked fiberglass crossmember, but hey, that's just an inconvenience. The photo is optically distorted at the bottom, those frames are actually straight.
After a little TLC it proved it was strong and ready to run.
Since I have already done the intake swap on a few motors in the past, including a very rapid 17-foot Chris-Craft (1956) V8, I know the difference a high performance intake can make and it can be pretty significant.
On the 327F, however, I am wondering a bit, because the intake that came on this motor is a good one to begin with.
You can see the numbers here, and guys, I don't know for sure if this is a stock 327F intake or not, because my motor block has been replaced in the past unless somewhere along the line CC also painted them organge, lol (found organge paint under the blue).
The number on my intake is 3844459.
(the letter X in the application section stands for Corvette).
Upon searching the numbers I understand the GM 327 of the era came in two stages of tune.
1). 250-hp at 4500-4800 rpm, single exhaust, somewhat restrictive exhaust manifolds, and 4-jet Rochester carb on a Rochester specified intake manifold. (The Rochester intakes were used on the early 283 CC motors, and these will not accept the Carter AFB or #1409 Edelbrock clone without an adapter).
20. 300-hp at 5300 rpm, dual exhaust, better exhaust manifold, and Carter AFB carb on the Carter specified intake manifold.
Other than that I understand the two motors are identical with the same cam, heads, compression, etc. Since there are so many heads used on these motors, I'll await further info to really make the final call on that one, although I'm told the 250 and 300 engines did get the same heads.
Chris-Craft 327F motors apparently got the 3844459 Corvette intake due to the fact that it was set up for the Carter AFB carb.
The difference in carb, intake, and exhaust side was worth fifty (50) horsepower according to GM. One only wonders why (with the use of the same general amount of liquid metal) GM just didn't cast a "good" intake for everyone instead of using that crappy Rochester intake. Of course, adding the dual exhaust would run the cost up a bit, but hey for 50 more horses ALL 327 automotive motors should have been 300 horsepower rated.
While I think the stock iron intake is probably a very good design, it is not the one GM used for the 340 and 360-horsepower 327 motors and those power numbers were probably obtained at much higher compression ratios and engine speeds than we would generally use in our classic boats. Another thing to consider, look at the photos and you will see a DEDICATED oil fill tube. Therefore, if you are thinking about swapping to an Edelbrock intake, for instance, better check and see if they offer the flat plate section that can be drilled for that filler tube, or you'll have to use a valve cover that has a oil filler cap. I drilled the high performance aluminum intake I put onto my 1956 17-foot Chis Craft Sportsman Utility in order to use the old style oil filler tube and also use some nice finned aluminum valve covers without any filler caps. That stock oil filler tub also ventilates the sump allowing the PCV system to work properly. Last time I checked, the Performer RPM came with the boss provided to drill out for the oil filler tube and the Performer RPM Air Gap did not.
Even with the good iron intake, I think the addition of the #1409 and a Performer RPM intake manifold would produce another 10 to 20 horsepower. Is it worth it? (No), but it would be fun (boatitis)!