well how much horsepower can a 347 naturally aspirated make compared to a 331?

 

A real easy way to look at it is this:

How much horsepower can you make with a 331?? 350hp? 450hp? 550hp?? Lets say you can make 550hp (hypothetically now...keep that in mind). 550/331=1.66. That's 1.66hp per cubic inch. 1.66x347=576. That's 576hp out of a comparably built 347...a difference of 26hp.

So here's the thing. Take ANY given rpm and the horsepower made at that rpm by the 331, and apply the above calculation. You'll find that the 347 makes a crapload more power across the board, and it's AVERAGE horsepower that gets things done.

So there you have a rough way to look at things to put it into perspective. Is it 100% accurate?? No, it's not. It's difficult enough to predict what a given motor is going to do, without second guessing what another would do in its place. But, that calculation helps give you a general idea.

Cris

 

yes you can get more horsepower out of a 347 but you get more reliability and longevity from a 331. the shorting stroke saves on the cylinder walls. so it all depends if you want the most possible horsepower or longevity. a well built 331 can make as much as an average 347. but a well built 347 can make more then a well built 331.

personaly i like the 331 and thats what im building. because as i said you get a longer life span from the engine. and it can make just as much as the 347 if you build it right. also its a less popular engine then the 347 so i kinda like that because i dont want to do what everyone else is doing.

 

when you have 550 horsepower, can you really tell that you get 26 more horsepower, its all guna feel the same.

 

The rumors about less reliability and longevity from a 347 are just that, as we've already discussed in this thread. The 347 is not a crazy stroke, look at 383+ cubic inch chevy strokers. Their stroke is more radical, but still have no problems similar to what your inferring.

 

You feel it when your front bumper is on my rear bumper accross the finish line! LOL

 

IMO, the limitation of power of either a 331 or a 347 is block strength...

From what I have HEARD, 425 HP is about all you want to do with a stock 289/302 block.

Might increase this about 50 HP using a main girdle...

I have to go by rumor because I have not split a SBF in half yet....

IMO, reliabliy differences between a 331 and 347 probably ain't much, not enough to worry about....

How many people do you know who actually WEAR OUT their REPLACEMENT Classic Mustang engines?

Ywa,,, that is what I thought...

 

Thank you very much!!

knuckless, it's a very hard thing for any person to accurately say 'one motor will last longer than another', or even 'one motor will last as long as another' until scientific testing on the order of OEM durability testing is done to verify. What I can accurately say, is that each builder, the quality of machine work and assembly...as well as the quality of parts selection is going to impact the longevity/durability of a 331/347 FAR more than any imaginary side loading or rod angularity issues. About the only good reason you have for choosing a 331 over a 347 is the final one you stated, personal preference...which is ok! The unfortunate thing is that the other, incorrect reasons keep being thrown about as gospel, and people with a lesser level of knowledge or experience believe them. Better for you to just say 'I like them cause they are different, and can make good power as well'. Because, no matter what...they're not going to make the same power as a similarly built 347. Anything you do to the 331 to improve it...would improve a given 347 in the same manner.

You bet your *** it can...20-26 more horsepower across a 1500-2000rpm range is HUGE. You may not 'feel' it on the street (depends on how sensitive your rear is lol), with street tires, but you'll certainly SEE and feel it on the track.


Cris

 

im talking about the piston ring wear and oil burning ive read about when researching which engine to build. the piston pin is to close to the oil rings on the 347 pistons which causes excess oil burning. people seem to be split 50/50 on oh its ok to nah id rather have a 347 only for racing not street. you just have to get custom fit pistons to avoid this problem. but you get a shorter rod 5.315" instead of 5.4" which causes the piston crown to become thin and prone to breaking.

i never said the 331 can make more, i said a well built 331 can make more then an average 347. and a well built 347 can make more then a well built 331.

your right you can shave a few tenths of a second off with 26 more horses. my 331 is for the street thats why it doesnt matter to me

 

Due to deck height differences comparing a SBC block to a 289/302 block really ain't apples to apples,,,

But, 331,,, 347.... pretty much is apples to apples... IMO...