Topic: what carb should i put on my 351c 4v

[bfsniff]

i just bought a 351c 4v engine complete rebuild , i have a 650cfm carb, but i was wondering if i should put a Holley 750-cfm carburetor, what would the difference be?   ???what do you think i should do? 

Brock


1972 silver mustang fastback mach1

[Soaring]

The size (CFM) of the carburetor depends on the mods the engine has.  If it is a stock engine, then the Motorcraft 480 cfm carb is the right way to go for efficient engine performance. Tell us what mods you have. 

[bfsniff]

PROF, RBLT. BLOCK- .030, NEW PISTONS, PLASMA MOLLY RINGS,FEL-PRO GASKETS, MELLING OIL PUMP, REGROUND .010-.010 CRANK, RODS ARE RECONDITIONED AND SHOTPEENED, BALANCED, CLEVITE 77 BEARINGS, FOUR BARRELL HEADS HAVE 3 ANGLE VALVE JOB, RESURFACED, NEW GUIDES, NEW HARD SEATS, NEW VALVES. RV CAM AND LIFTERS. CLOYS DOUBLE CHAIN AND GEAR SET

[Soaring]

Yeah, that engine is still pretty close to stock.  I would certainly not go over a 650 CFM carburetor.  That 750 is going to be way too much for that engine.  If it was mine, I would put the Motorcraft 4100 on it for peak performance. 

[bfsniff]

how much horsepower do you think it will make? i bought hooker headers for it to.  the guy said 300-350.

[Soaring]

With the hooker headers you are probably looking at around 280-300.  My suggestion is that you take it to a dyno shop to get the real numbers you are asking for. 

[bfsniff]

why would you think that? it says the 1970 4v has 300 horsepower stock. and mine is bored .30 with headers.       

70 ENGINES/ENGINE CODES
T - 200 ci 1Valve 6-cyl. with 120hp
L - 250 ci 1Valve V-6 with 155hp
F - 302 ci 2Valve V-8 with 220hp
H - 351 ci 2Valve V-8 with 250hp
G - 302 ci 4Valve V-8 with 290hp (Boss 302)
M - 351 ci 4Valve V-8 with 300hp-------------------
Q - 428 ci 4Valve V-8 with 335hp (Cobra Jet)
R - 428 ci 4Valve V-8 with 335hp (Cobra Jet-R
Z - 429 ci 4Valve V-8 with 375hp (Boss 429)


and the place i bought the engine from has a dyno but wanted 500$ to dyno it,  dont have that kind of money.   And 300 horses is plenty of power right?   i would think so because i have a 351c 2v thats worn out and it is suppose to only have 240 horses but has power.

[Soaring]

My 03 Mach 1 with a 32 valve 4.6 engine puts out right at 300 ponies and is more than enough engine to get this old man in trouble.  It sits me back in my seat just fine and gives me all the thrills I need for power from an engine.  So, saying your 351C makes around 300 ponies is quite a compliment to a vintage engine of about the same cubes.  The difference is that my Mach has all the modern upgrades such a brakes and bags.  You can build up your engine all you want, but unless you also build up and modernize the rest of the car, all you are going to wind up with is an old car that has a powerful engine that can't be used to its' fullest potential because the rest of the car is old and worn out and dangerous to drive.  An example is that on my 65, I replaced the single brake master cylinder with a dual bowl.  No bags, but that is an impossibility. 

[Thierry]

                  why would you think that? it says the 1970 4v has 300 horsepower stock.

The stock 351 4v has 300 SAE gross horse power while engines from after 1972 are given in SAE net power and it can make a big difference and you will certainly not get 300hp at a dyno for a stock engine. There is no conversion rule but I would say the engine would be around 250/260 hp.
Here is more info about the history of horse power measurements: Wikipedia

[bfsniff]

what gears should go with that engine,  i think it just has the stock gears right now,  i was thinking 4:11 or one or two sizes under that.   i want the car to be quick,  and i really dont need to go 100 miles an hour  just 65 lol.
so what do you guys think?

i really appreciate all your guys help

[Soaring]

Your choice of gears will depend on the  style of driving you will be doing.  If you only want a light to light car, then the 4:11 will be your choice.  If you want a cruiser and an occasional Interstate driver then drop down to say 3:73's or 3:55's.  My Mach 1 has 3:55's in it, but I have a 5 speed for the Interstate, and it is really quick. 

[jethat]

The 351c isnt like other engines. They like the lower gearing. I think the car would respond well to 4.11 gears and I also think you would do well with a vacuum secondary 750 cfm Holly I have a close match to your engine and I've used a 750 holly on it and it really liked it although the carb I used has a problem so I switched back to the ed 625 cfm carb. I also would be surprised if you didnt dyno over 300 hp at the wheels. Again the 351c is a different animal. Most people just dont grasp what its capable of. There was the change back in 72 from sae to net but Ford was actually under estimating the Hp of the 70-71 engines on there ratings they say. People forget the fastest Mustang of the Muscle car era was the Boss 351. I would Say go for the gears and get that 750 cfm carb. if you want to learn more about your engine you can do that here http://www.network54.com/Forum/119419/

[Soaring]

Welcome Jethat.  It's good to have a different perspective thrown into the mix.  You say that the C is a different engine, and yet you don't give proof of that.  Horsepower is horsepower, and how you make it is by an internal combustion engine.  Now, what is so special about the C that makes it any different from a W in the ability to produce HP?  And, what is it about the C that likes the lower gearing?  Explain.  An engine is an engine, and only supplies power to the rear. The same power that any engine would supply.  The C is no different. 

[jethat]

Welcome Jethat.  It's good to have a different perspective thrown into the mix.  You say that the C is a different engine, and yet you don't give proof of that.  Horsepower is horsepower, and how you make it is by an internal combustion engine.  Now, what is so special about the C that makes it any different from a W in the ability to produce HP?  And, what is it about the C that likes the lower gearing?  Explain.  An engine is an engine, and only supplies power to the rear. The same power that any engine would supply.  The C is no different.

The Cleveland is an engine that is all about air flow. The heads the OP has are the best small displacement heads you could get on an engine of that era. Canted valves 2.19 inch itake 1.90 inch exhaust. They like to move air and do it better then any engine in its class. Clevelands dominated the dragstrip of the 70's and 80's and it wasnt until aluminum heads with modern rollerised valve trains and all that they had competition from others in its class. To this day Cleveland styled heads are the way to go to get the most out of a performance block. The Popular Hotrodding engine masters challenge from it beginning  a few years ago has proved the superiority of the cleveland heads year after year.
I provided a link to the best all cleveland board on the web and if you want to learn more about the Cleveland go there.

[jethat]

BTW Soaring thanks for the invite. Nice board you have here.

[Soaring]

OK, here I am, a 3:55 gear in a Ford 9" rear end.  Now, how do I act differently with power coming to me by a Clevo as opposed to a Windsor?  Again, power is power.  Sure, I know the Clevo was the best engine during its' short life.  The only problem it had was that it had top engine oiling problems.  Now, if you are saying the Clevo had more power from the factory than the Windsor, then yes, you are correct sir!
Thanks Jethat.  We are not real big yet, but we are friendly.  Pull up a chair and hang with us. 

[jethat]

The oiling system really isnt flawed thats kind of a myth. A restrector kit and some minor modifications and the block is good for extreme use. Clevelands like to move air. Thats how they make power. Lower gears get it moving air faster and that means its making power faster.

[Soaring]

OK .  Nice theory.    Moving more air only produces more horsepower.  How is a gear in the rear going to translate the more horsepower is coming from a C or a W?  Again, horsepower is horsepower.  The gear in the rear is not going to give a shit if the power from the engine is coming from a C or a W.  It will take whatever it is given and transfer that power to the wheels. 

[jethat]

I hope we aint getting into the C vs W arsument. The Windsor is a great engine. So is the small block chevy. The Cleveland is different from those designs it was built to produce horsepower. The way Ford did it was through a radically different head design. The lower gearing give you the ability to take advantage of that head design. The engine gets into its power range quicker.  I could provide links to prove the Cleveland to this day is superior but I really think its a pointless argument.

[Soaring]

No, we are in agreement that the Clevo is/was a superior engine over the W primarily because of the heads.   So, what you are saying is that if the clevo runs with higher RPMs with lower gears, (4:11)  it breathes better and produces more horsepower at slower speeds.  Hmm.  Doesn't any engine do the same?   The more RPMs you are running, the more horsepower, right?  I'm not sure where you are coming from with this breathing theory that the clevo breathes better  and uses more air than other engines other than the fact that the heads on the clevo can possibly use more air to combust.