I tried doing a search and didn’t manage to find anything, so here’s my question…
There seems to be quite a bit of variation as to what the S-code 390 was rated at. I’ve seen 315, 320, 325 and 335. Does someone have a timeline for when they had those ratings? I had always thought it was 320@4800, but there is obviously more to the story. The '68 XR7-G at the Henry Ford Museum says it was rated at 335hp. I assume by the time the 428CJ came out it was rated lower than 335. I’m guessing there were some tweaks along the way (thermactor, etc) that were possibly running changes, but I wouldn’t mind having better information than my guessing. Also, does anyone know if the Mustang and Cougar ratings were the same at any given time?
1967: 320 hp / 1968: 325 hp Marauder 390 GT V-8 Engine (6.5 litre)
F 302 2V 210 @ 4400 295 @ 2400
J 302 4V 235 @ 4800 318 @ 3200 Premium Fuel
S 390 4V GT 320 @ 4800 427 @ 3200 Premium Fuel
R 428 4V CJ 335 @ 5200 440 @ 3400 Ram Air
X 390 2V 280 @ 4400 403 @ 2500 Premium Fuel
I’ve always assumed that all S code 390 engines in a Cougar are 320 hp. Except for the XR7 G which is always advertised as the 390 Marauder GT engine with 325 hp. The extra 5 hp might just be a marketing thing. The 280 hp comes from the X code with a 2 barrel carb. I’ve never seen the 390 in a Cougar advertised at 335 hp. That was the 428CJ.
A Ford engine engr. once told me its depended on what RPM is picked and what the marketing people wanted to say. I’ve always wondered about the transverse muffler but they continued to be used on CJ Mustangs and all Shelbys 68 on. Or Ford wasn’t concerned about a few HP.
Those are the numbers I’ve always had stuck in my head. To add some confusion to the 335hp rating, I recently got a reproduction “'68 Cougar Illustrated Facts and Features Manual” that is supposed to be genuine Ford material. Here’s a picture of the engine option page:
I couldn’t find a date or revision on it, but assume it’s from very early in the production year cycle, as it doesn’t mention anything about the base interior introduced in January/February '68 or the 428CJ. I’d be interested to see what the early '68 owners manuals said for HP.
The whole topic is probably more a matter of semantics and marketing rather than actual performance of the engine, but it’s still interesting to me. If I ever get a 390 (or 428 for that matter) put together, it’ll definitely have more horsepower than what it was originally rated at.
The '69 390-4V used in 1969 Mustang / Cougar is not a GT. It has a smaller Autolite 470 CFM Model 4300 carburetor, and a milder camshaft, and different cast iron intake manifold than the earlier 390GT engine. All these things were done to be able to eliminate the Thermactor Smog system.
