95_302_StangMan

Hey. I plan on rebulding my engine in a couple of months and cant decide on whether to get a 331 or 347 kit. It will be a daily driver, and also I plan on putting a good cam in it when I rebuild it. What are the pros and cons of 347's and 331's. I dont want it to burn oil and I dont want it to get 10mpg. Do you get much more power out of a 347? Please let me know what you guys know.

cammedlx

Most of the 347 oil problems have already been resolved...since its really the number that you like best since im sure there is only about a 15-20hp differnce between the two with similar setups...And if you're worried about gas mileage stick to a stock rebuild honestly...

stanglx2002

i have a 331 as a DD and i get about 17 mpg

90Mustangfan

I'd go with the 331 it will be more reliable and last longer. And yes you will get worse gas mileage, probally around 10-15mpg or so dependging on how you drive...with a 331 stroker, I doubt you will drive slow. they fixed the problem with the 347 burning oil on the newer kits, some have it fixed some dont. and the lifespan of a 347 is quiet a bit lower also...power will definitly more with the 347, IDK what you can get with a 347 probally around 400-500 with a good H/C/I combo, but if you just do the stroker on stock heads and intake, you will probally see little to no gain

95_302_StangMan

I plan on getting new intake and heads/headers after I build the engine, also I am not doing a stock rebuild that I have ruled out. Gas milage is not that important. What would the average life span of a 347 all forged internals life span be vs all forged internals 331 lifespan? Also did you say that 331 will be worse milage than the 347 or did you mean than stock? Thanks for the info so far.

StangTangGT

Ive heard the difference is even less than 15 horsepower but i guess that could all depend on different setups. I'd say it just means the 331 will be closer to the life of a 302 than the 347 would. Theres gonna be more movement in the cylinders so premature wear of certain parts is expected.

88BlueGT

Im pretty sure that a 347 will need refreshening around 25-30k compared to a 331 where you can take it to 90k (dont quote me, just what Ive heard) and the power difference is not that much. You will make a little but more horsepower with the 347 but there is a notible torque difference between the two (more w/ the 347) but IMO since its a daily driver I would DEF go with a 331. You should look into CHP (coasthigh.com) or some reputable company like that.

HC_CrAzYHoRsE

why not do a 306 with an SC ? it would make more power and be more reliable then both, that's what i plan on doing.

88BlueGT

Yea thats true. But NA is sick. I would go with a 331, even if it made less power.

95_302_StangMan

25-30k??? BS I dont belive you.