1978 Mercury Cougar XR-7 302 V8 from North America


I really like the body style


Started leaking and burning excessive oil at 120,000 miles. Engine stopped, factory timing chain slipped at 147,000 miles - which bent the valves. Driver's side seat started to tear.

General Comments:

Even though there were some serious engine problems, I know that the car had lots of potential. The body was in almost perfect shape with just a couple door dings. The shiny "lipstick red" paint still looked good. It also had the fancy Mercury chrome spoke hub caps. I kept the stock look which includes white wall tires.

For the above reason, I decided to rebuild the engine. I have a friend that owns a machine shop that helped me with the project. I decided that since I had his help, I would hot rod it up a little. But talking about going mild to wild. At first I just wanted a little more power then stock, but then the ending project turned out to be very aggressive.

Among the MANY modifications I performed, here is a list of the FEW major ones. I installed a 351W cam which changes the firing order, traded in the stock 302 heads (with bent valves) for 351W heads that contain Chevy 2.02"/1.60" valves and 5 angle valve job, bored out block to.040" overbore, installed Keith Black 9.5:1 pistons with Teflon coating on skirts, Headman Headers, added dual exhaust with 2.5" diameter pipe, 2 Thrush California Turbo mufflers, Edelbrock intake and 4-bbl 600 cfm (cubic feet per minute) carburetor with auto choke, high output mechanical fuel pump, replaced Ford 9 inch rear third member 2.75:1 gears with Richmond 3.55:1, rebuild C4 transmission, and added B&M Shift kit.

We estimate the power output to now be around 380-420 HP.

Would you buy another car from this manufacturer? Yes

Review Date: 27th November, 2007

18th Feb 2012, 10:27

I don't think that engine has anywhere near that much horsepower.

2nd Mar 2014, 10:14

I can assure you it is nowhere near that. That build, well sorted, is worth just under 300 HP. Please be realistic!

10th May 2015, 22:06

Help, I have a 1978 Cougar with a 351. I'm looking for headers that will fit.

1978 Mercury Cougar XR-7 351 Windsor from North America


It is the bomb, glad to be restoring it


When I was sixteen, I had to replace the alternator as soon as the car got running.

When I was 18, I had to replace the distributor gear... it just sheared. I still am yet to explain that one.

Shortly before I joined the Marines, I bought a rebuilt block and rebuilt the motor, because the front and rear mail seals were completely gone; oil spills everywhere I went.

General Comments:

My name is Randy Martin, I am currently 21 years old (in 2006) and I started working on my first car when I was 14, and to me it will always be my favorite car. It is a 1978 Mercury Cougar XR-7.

Now granted, when I did some reading up on the XR-7, I found out that these models were to be the luxury edition of the Cougar. Mine however is not. I do have a 351W with the stock C-5 transmission. I am currently trying to find a suitable donor car that has functional fusebox with power applications, and doors with power locks and windows, as well as power seats. Please let me know if you can help me via email microtek_man@hotmail.com

Now that that is out of the way, I must say that the car is quick (not as quick as my 'stang), but it's ate up a few Civics and Hondas in town.

I really do love this car. As a matter of fact, that is why I want to restore it to its former beauty. My parents say the car isn't worth it, but it's my first car and I still drive it.

Would you buy another car from this manufacturer? Yes

Review Date: 14th March, 2006

30th Oct 2006, 12:15

You can't go wrong with the C6, but the 400 was the worse engine in these cougars. The 351/400M have what I call a "bread pan" manifold gasket. Both motors, but especially the 400 tend to suck the gasket out of position resulting high oil consumption.

Also, the 2bbl carb is too small to properly feed this beast. The two cylinders closest to the firewall end up running too lean (and too hot). Expect to replace these spark plugs often.

I'd first check that it really is the 400. If it is the VIN code will contain an "S", if it's an "H", you have the 351M. Both motors are identical in appearance. Only the crank shaft and connecting rods are different.

20th Sep 2007, 19:56

I am in the same situation as the guy before me. My car is a 1978 Mercury Cougar Xr7.351w. My parents both told me it was a POS, but I saw potential in her, and by the way her name is Sheikra. I got her for a g, but think that it happened to be a little overpriced, but the guy just would not budge with the price, so I bought it with my graduation money, and have been pouring money into it ever since.

I do have some questions about this particular car: What are some of the most common engine problems; how much mpg does it get; what kind of carb rebuild would I need for the Edelbrock thunder series carb do I need; and finally, does anyone have any thoughts on my fuel gauge not reading the fuel level, could it be the float or the wiring?

If you have any ideas send an email to Coltonbyrnes@hotmail.com, thank you.