306 vs 331 help me decide

hi guy and gals, i recently had to put the 302 to rest but am being torn in 2 directions with what to put in her i originally wanted to do a 331 with a f cam and my gt 40 x heads with 9.5to 1 compression, but once i told my machinist what was in the rest of my car for a drive line he is trying to point me in the direction of a 306 with the same parts, his reason which makes sense is do to the weight of the car,a 5 speed, 3.55 rear gears, and 17 inch tires he is affraid with the 331 the power curve of the motor would not be a match, supplying the power and lots of torque of idle would just turn the car into a tire spinner were the 306 would have a power curve at a higher rpm causing less stress on the drivetrain, he claims that bigger is not allway better because you should mantain a proper horse power to chassis balance if any one has either combo please help me make this decision i like this car way to much to make a wrong call thanks jeff

 

personal advice is listen to the machinist 90 percent of the time they are right they do it all the time and if its areputal machine shop they dont have just anyone working there.

 

302 parts on a 331 motor make 302 power, you might as well save your money and just build the 306, they have plenty of power with the right combo of heads,cam and intake and,exhaust.

I appeciate the fact that the builder pointed you in the right direction.

 

i got plenty o power from my long rod 306,shaved gt40's and an e-cam

 

There's no replacement for displacement. Plenty of Mustangs out there run similar combos with excellent results.

This really couldn't be further from the truth. The 331 is definitely going to make more torque, and we're talking about GT40X heads with an F cam, not exactly stock H.O. parts.

 

i would say 331. it will give you more low end torque and lower rpm power band. this will make it easyer on your clutch first of all. you wont have to slip it as much. as for added wear on the rest of your driveline, thats just a mater of how you drive the car. if you drive it like you stole it, it will wear and possibly brake parts with either size motor.
the 331 and 302 will make really close to the same horse power. the 302 will just have to spin up to a higher rpm the make the power and that is extra wear on the internals of the motor. the 331 will make more torque than the 302.
with your 3.55 gears, i would go for the 331. you would probly find that the 331 with 3.55s will have similar performance to a 302 with 4.10s. i know that your engine builder said the opsite of what i said and it is your choice on what to do.

 

331s are supposed to be one of the best-revving small block Fords because of the rod/stroke ratio. With your combo of gearing in a light car, I imagine it would be matched pretty well and a blast to drive. You might not use first gear too often, though.

Did you have those heads on your 302? How is the 306 going to be different than what you had in there? It sounds like you are looking for more power out the new motor.

If you are just driving it on the street, the 306 would be good. If you take it to the track you'll want the 331.

Food for thought ... aluminum heads remove about 50 lbs off of the nose of the car.

 

I'd do the 331. But then, I am doing a 331. I also have a 5 speed but am undecided on rear gears. I'm thinking more like 3:25s just because I want more mpg. Ask 10 different people about your set up and you'll get 10 different answers. But there may be some common ground to decide what to do.

 

if he is a machnist and not an engine builder then it's just his opinion..there is a difference in someone that turns cranks, resize rods and bores blocks and an engine builder.
my ...engine builder...sent the block out to a machinist be machined to his specs. and then assembled it with the rest of the parts of his choice. the machinist has no idea what specs. my motor has, just that the block was bored. ...the rotating assy.(347) came from somewhere else already balanced ready to install. my engine builder chose the cam, carb. and in my case what thickness head gaskets to use...

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thanks for all the advice even though every one has a different idea you all have some good points. I,ve got my heart set on the 331 but i figured i would give his 306 idea a fair fight first thanks again jeff

 

331. The emblem will look cooler than 306.

 

If you have your heart set on the 331 go for it or you will always be asking yourself "what if". You will be happy

 

A 306 is nothing more than a 302, 30 over. If your spending money, go 331.

 

the 347 is about the same money as the 331...
My 347 is...9.5:1...87 octane motor...

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My answer is this , IF you will be spending the money to buy ALL of the supporting hardware,meaning Heads,intake Camshaft and carb...then build the stroker.

Jay Allen (camshaft inovations) and Woody (fordstrokers.com) say the ONLY reason to build a 331 is because you don`t want to go as fast as a 347.

Also to quote Jay Allen: "A 347 with 302 heads and induction WILL make 302 power." That being said refer back to my first statement.