I am getting close to installing my engine and transmission. I am having second thoughts on my engines power and torque. My 1969 Mercury Cougar XR7 M Code came with the original 351 Windsor 4V High Output, FMX Transmission, and 3.00 Nine-Inch Differential. The FMX has been rebuilt. The Differential has been rebuilt with the addition of Limited Slip. The car has AC, PS, and Tilt-away. All the vacuum components are working and I plan on using them.
The original 1969 351W was rebuilt with lower compression dished pistons (Sealed Power 463P) and a mild RV Cam (Engine Pro MC1775). The original cast heads received New Intake Valves (SB International Ford 351 Windsor 1.842" Intake Valves) and (SB International Ford 351 Windsor 1.539" Exhaust Valves).
The engine retains original 4V intake, exhaust manifolds, and a rebuilt Holley 4160 600 CFS. The distributor has been restored and recurved with Pertronix II added.
Essentially, the engine was rebuilt as a 2V with 4V intake. Now I want more horsepower and torque without losing my vacuum. A definet lack of proper planning due to the fog of restoration. The engine has not been run. It appears my options are to either increase compression with domed pistons or increase compression with aluminum head/cam combination or some combination of each.
How much improvement would an aluminum dual plane intake provide after the above has been addressed? The Weiand Stealth Intake seems to be popular. I may have to get a larger CFS carburetor but I can check that after running the engine. I would prefer to keep the stock exhaust manifolds verses headers but that can be addressed after running the engine as well.
What are the best options to get an additional 30 to 50 plus horsepower and corresponding torque without losing the vacuum required to run my accessories? The engine is out of the car so now is the time to make changes to give the car some more sass!
While I can’t answer directly to your questions, you did mention the Weiand intake manifold. The guys on engine masters did an intake comparison, and the Weiand, didn’t come out on top. The Edelbrock performer RPM was best over all. I have the Weiand on my 351, I bought it instead of the RPM for clearance purposes, and I probably saved a few bucks on it.
You might check out that episode, before you spend any money on a new intake manifold.
If you are still contemplating different pistons then i am going for some KB flat top pistons,
I used these on a previous engine build some years back and worked great but i don’t know how good your gas is over there.
I enlarged my DOOE chambers to about 62-64 cc which gave me a approx comp of 10:25:1
You could find some alloy heads with larger chambers ?
I used the OE 4v cast ion manifold which meant every thing was a bolt of for all the bits and bobs on the manifold, this also ensured air filter
clearance etc.
A small RV cam.
I used Try-wy headers for added torque.
Tons of vacuum, very drivable .
This will be very street able, if you want to rev big numbers then thats a whole another game.
Royce and Bluestuff, thank you for the input. I have decided put the Windsor in as it is and take it to the exhaust shop to add the headers and new exhaust after breaking it in for awhile. The stock exhaust manifolds and exhaust are ready to bolt on after the engine and transmission go in. The Performer or Stealth intake manifolds were going to be too tall for the original air cleaner and did not appear to add very much compared to what I already have with the original manifold. I will run the car see how I like it - after 5 years I sure it will feel great!!!