2v and 4v 289 compression

Hey my first post since signing up to this forum.

My buddy and I were talking about our cougars.
Both are 67 mines an xr7 289 2v with c4 trans and 2.79:1 rear diff.
His is a standard 289 4v with c4 trans and 3.00:1 rear diff.

We are trying to find out if there was any difference in compression in the 2v and 4v. Does the 4v have higher compression from the factory?
He has already swapped motors for a 5.0 fuel injected mustang motor but we are still a little curious.

Don’t know the answer to your question, but will say, Welcome aboard!


The 2V was 9.3 and the 4V was 9.8.

Wow! That was quick! Thanks for the info.

I had a few minutes to spare. I was compiling. http://xkcd.com/303/

The website I have bookmarked as my engine info resource has them both listed as 9.3


So does the other engine guide I have bookmarked…


I was going off of the “Illustrated facts and Features Manual”, the 1967 Mercury sales brochure, and the 1967 Ford Shop manual.

Yeah, not really sure why you would trust the manufacturer and their sales and tech data over random websites. :wink:

Yup! You didn’t get 25 more horse just by two more venturi. FWIW, The 9.8 4bbl compression is many times reported as 10:1 in some Ford and other publications.

With a 427 C.I. 351 stroker I’m hoping for 1,565 HP. Pump gas burning, quad turbo’d Cougar messiah, preaching to the masses! YEAH! Wikkit-pissah kewl! :greenchainsaw:
I’ll be strokin’ it myself. My friend has a hand come-along and he stole his grandpas way kewl butane pipe lighter! Using the come-along and the pipe lighter, we think we can lengthen the connecting rods and build our own stroked motor!
Hey, any of you pork-bellied Christmas ham eating old-times have any tools I can borrow?

Better get used to that… :laughing:


The 1967 Ford Car Service specifications manual dated August of 1966 list the 2v at 9.3 and the 4v at 10.0.


Would there be a difference in compression between a 390 2V and a 390 4V? 1968

No, looking in my '68 shop manual it says the compression ratio is 10.5:1 for both. John

From memory Mercury 2v 390’s had the same compression as 4v 390’s while Ford 2v 390’s were lower compression.


You are correct sir. In my original post, I was aware that ClassyCat (Harvey) had a 390-2V (X code Cougar) and that is what I was referring to. I just noticed the other 390-2V (Y code) in my '68 shop manual. It has a compression ratio of 9.5:1. :slight_smile: John

So, to clarify, one is premium fuel 2v and one is not, while the 4v uses the same compression as the premium fuel engine?