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Hello all, Question of the day! I have a 69 mach one with the original 351 W 2 barrel Im planning on having the engine rebuilt this coming winter with some performance upgrades and Im curious if I end up needing to go with a 4 barrel carb. Which I already have a factory intake for, will I need to change out the heads to heads from a 4 barrel engine or are heads from a 2 barrel engine compatible? Im looking to bring out a little more horsepower without doing anything drastic like an engine swap or such, as Im the second owner of this numbers matching beauty and just want to give her a little boost. So if any of you Gearheads can give me any input I would be grateful, Thanks Gang!
 

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The 4v/2v heads is a 351 Cleveland issue. Putting a 4v carb and intake on a windsor is a matter of bolting it on.
 

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The 351W 2V used lower compression pistons than the 351W 4V. If you rebuild it be sure to use the higher compression pistons.
 

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You will get a lot of opinions, but you may want to go with something like an Edelbrock top end kit. They advertise 451hp for a 351w, 2v motor with 9.5:1 compression. FYI, the 4V motor (4 barrel) came with 10.7:1 compression. The kit comes with bigger valve aluminum heads, 4 barrel intake, and cam: Performer RPM 451 HP Top End Kit for 1969-95 Small-Block Ford 351W Engines
They also make a 400hp version for considerably less. It takes all the guesswork out choosing performance parts, and of course the combination is dyno tested. Yes you can mix and match parts, but what will you end up with? I believe you can rely on the numbers, and most people will tell you that Edelbrock makes good stuff.
 

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The 351W offered in 1969 came in 2 versions, the 2V with 9.5:1 advertised compression ratio and the 4V with 10.7:1 advertised CR. Note that Ford, typically, was off by .7-.8:1 between their advertised and actual CR numbers so conservatively figure 8.7:1 and 10.0:1 as CR's. The 4V engine also had a "hotter" camshaft than the 2V. Cylinder heads were the same with a combustion chamber of around 60.4cc.

I would expect that adding a 4V intake and modest carburetor (like a Summit M2008VS600 or a 1.12" Autolite 4100) to a 2V engine in good condition might add some additional horsepower, most likely all at higher (4,500+) rpms over the 2V carb while low end torque would probably remain about the same. I'd expect the 2V Autolite 2100 would be a 1.21" unit anyway.... going to a 4V with smaller primaries than the 2V would probably give you a bit better throttle response and, if you kept your foot out of it, a tad better cruising fuel mileage.

It's hard for me to say whether such a change would be "worth it", especially if the car runs well currently... and the money spent might be better spent on a distributor re-curve rather than an intake and carburetor change.

If you were doing an engine rebuild and had the opportunity to replace pistons and do a bit of cylinder head "work", along with a cam change, then I'd be all in for a 2V to 4V swap or a 4V TBI conversion.
 

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Marshall, what trans and axle does your car have ? And what is your useage going to be ? How original do you want to remain ? whatever you choose, I would keep any original parts you might remove safely tucked away in the garage. LSG
 

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Hello all, Question of the day! I have a 69 mach one with the original 351 W 2 barrel Im planning on having the engine rebuilt this coming winter with some performance upgrades and Im curious if I end up needing to go with a 4 barrel carb. Which I already have a factory intake for, will I need to change out the heads to heads from a 4 barrel engine or are heads from a 2 barrel engine compatible? Im looking to bring out a little more horsepower without doing anything drastic like an engine swap or such, as Im the second owner of this numbers matching beauty and just want to give her a little boost. So if any of you Gearheads can give me any input I would be grateful, Thanks Gang!
A simple recipe of a 4 barrel carb and intake, dual exhaust, cam swap and flat top pistons will really wake that 351W up and won't cost significantly more than a standard rebuild.
 

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No intention of saying Woodchuck is wrong, but please let me share my experience. I rebuilt the factory 351W 2V in my '69 Cougar many years ago. It came with dished pistons. I bored the block .030 over and installed SealedPower flattop pistons. The resulting static compression was so high, I had to back off the timing a LOT to keep it from pinging. I was later working on that car at an Air Force base hobby shop. (I was active duty Navy then.) A '69 Ford pickup pulled in next to me. He had rebuilt his 351W 2V the same exact and way and said, "Man, the compression is so high I had to back off the timing and richen the carb to keep it from pinging!".

Thus, I suspect the advertised compression numbers were pretty accurate in this case. So, be very careful of static compression when you rebuild that '69 351W. The combustion chambers in those heads are extremely small.
 
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