1969 390s ??
 

I am considering buying a 69 with an original 390 in it and I was looking in my Chilton's book for that year, and it says that the 390 with an automatic transmission was rated at 270hp@ 4400rpm, and 390ftlbs@2600rpm. The 390 with the manual tranny was rated at 320hp@4800rpm and 427ftlbs@3200rpm.

Both motors are 10.5-1 with all the same specs. Why the difference of 50hp? What was different other than the trannys? Was there something done differently to the engines with manual trannys?

Maybe it was at the rear wheels?!? I'm lost.

Not sure, but I think the 270hp rating is a two barrel, and the 320 is four. Had the 270 2 barrel in my ranchero, after playing with it for 3 years and only getting a best of 15.1, I pulled it and put in the big 460. Havent run it yet, but the diference is amazing. Sorry, back to your question... If your chilton has cam specs, see if there different. Pretty sure for 69 the testing was done at the crank with no accs. so called gross rating.

I love big blocks, wish I knew more. But it sounds like the
270 number is off. The 320 sounds like a hi-po motor. I think
those are alot different, headers, carbs, compresson and cams.
The 406, which didn't come in Mustangs is only rated at about 406 horse, and that is the next step up from the hi-po 390.
Well thats my opinion, I 'am sure there are plenty of better ones out there.
If you can get a hi-po do it, those are great motors.

According to the Chilton's for years 69-71, they are both 4bbl, 10.5-1 compression, and the only specs that are different are the spark plugs, idle speed, and the trannys. This book doesn't even mention a 2bbl at all. I dunno, maybe it's a misprint? How much power is expected to be lost to the drivetrain? Is there an average percentage?
There aren't any cam specs in this book. There's only a measurement in degrees of how far the intake valve opens, and they both say "16B" whatever that means.

all 1960 390's in stangs were rated at 320hp. Chiltons sucks

Dug out my trusty decoder book. The book(Catalog of American Car ID Numbers 1960-69) only lists 2 differnt 390's for 69. Engine code Y(2 barrel 270hp) and S(4barrel/high perf 320hp)
This is the fifth number in your VIN. This is also for all 69 fords. The mustang, according to this book, only came with the S code 390 in 1969. It does not make a distintion between auto or man trans. This also agrees with what I've heard in the past as well. I would think that chilton made a type-o. It happens.

well that makes since. I always had more faith in Chilton's than I did in Haynes, but I guess it really doesn't matter. Nobody's perfect. Thanks for the info guys.

Chiltons
 

My ragged, dog eared, grease stained Chiltons 65-73 Mustang manual says for '69, 4-V only, 320@4600 / 427@3200.

Rev