Should I go with a 331 or a 347?

kissrocksforever · Oct 4, 2010

This winter im looking to do one of these. Just not sure which one. The top end of my 302 is all GT40, heads, intake, etc and makes about 300 hp at the crank. The bottom end is original and have about 155k miles on it. im looking for opinions, what are some benefits of both, draw backs, etc.

modo · Oct 4, 2010

unless your changing the heads at the same time dont even bother

.02

95Grandtouring5.0 · Oct 4, 2010

kissrocksforever said:
This winter im looking to do one of these. Just not sure which one. The top end of my 302 is all GT40, heads, intake, etc and makes about 300 hp at the crank. The bottom end is original and have about 155k miles on it. im looking for opinions, what are some benefits of both, draw backs, etc.

Well depends on what your looking for really. I've heard that for some reason or another that the 347's wont last as long as the 331's. However your obviously going to make more power with the 347. Gt40 heads are decently better then e7's, but they do not flow nearly as well as a top of the line trickflow or afr head. ( I would recommend afr, they are better out of the box and make the same power with smaller valves then the trickflows.) So if you would like to maximize gains, then I'd invest a good $1400 in a set of heads, I know it's a lot but save it up and buy it all at once and put it together. I'd also recommend a trickflow intake, or a holley systemax. Good luck with whatever you choose. But even if you keep your gt40 heads you'll still see quite an improvement.

Last5.0108 · Oct 4, 2010

the reason people say the 347 doesnt last as long is that the 331 has a much better rod to stroke ratio. The 347 has the problem of having too much angle on the rod which caused the piston to gget pushed into the cylinder wall, so over time it wears and could crack or something of that nature. Its true that you'll make more power with the 347 but imo i think the 331 is the better choice for reliability purposes. My buddy just built a DSS 347 with AFR 185 competion series heads with 24 pound injectors and hes running an edelbrock intake, he consulted DSS and they said he should be making about 450 at the motor, we dont know for sure yet since the motors not in yet thats just what we've been told. hope that helps you a little

wannaboost94gt · Oct 4, 2010

You could always port your GT40's and throw some bigger valves in em if you dont have the $$$ for aluminum heads, and you would make some good power/torque. Thats what I did... :angel4:

LAFENATU · Oct 4, 2010

Last5.0108 said:
the reason people say the 347 doesnt last as long is that the 331 has a much better rod to stroke ratio. The 347 has the problem of having too much angle on the rod which caused the piston to gget pushed into the cylinder wall, so over time it wears and could crack or something of that nature.