331 vs 347

1991vert · Jul 19, 2005

ok im reconsidering some things. im buying the dart block for sure. this is where i can't decide. a 306 with a blower or something along the lines of a 331-347.

my main question is my cylinder heads. i have AFR 165's and dont know if they will be too small. so here's a list of questions if someone could answer them for me.

1) Are the 165's too small for a 331-347?

2) Do stroker kits increase emissions

3) 331 or 347; reason for choice also please.

thanks,
Chris

p.s. sorry for so many questions

1991vert · Jul 19, 2005

stock 92 gt · Jul 19, 2005

1) yes too small, go with some 185s
2) i dont know
3)347 .....its a dart block, why not go for a 347 eh?

1991vert · Jul 19, 2005

3) i have 165's and really dont want to sell them to buy another set and a 347 i dont think would be too emissions friendly, but i no one has responded to that yet

IntenseBlue · Jul 19, 2005

They're not too small. They wan't make as much power as most 347s you'll see b/c most are built to perform as best they can. AFRs flow more than GT40s and 351 Lightnings do fine with those. They won't make near as much power as 185s, but they're not too small.

1990LXDropTop · Jul 23, 2005

I would just do a 306. Most people seem to favor a good ole 302 or stout 306 over a 347. A built 306 with your combo and maybe a little boost would be heaven. Just my .02

90mustangGT · Jul 23, 2005

If your going to do a Dart block then go ahead and get all forged internals and do the 347. Maby get the wide bore version and I think that adds up to a 368 or something?

boomr · Jul 24, 2005

90mustangGT said:
If your going to do a Dart block then go ahead and get all forged internals and do the 347. Maby get the wide bore version and I think that adds up to a 368 or something?

I thought it worked out to about a 363.

1) Are the 165's too small for a 331-347? A 306 with a blower or something along the lines of a 331-347.

Maybe not for a 331 n/a motor, but if your going to run a blower or something you might want to consider letting the motor breath.

2) Do stroker kits increase emissions?

I wouldn't think so, if it was tuned correctly

3) 331 or 347; reason for choice also please.

Why not get the maximum bang for you buck

9T3SVT · Jul 24, 2005

Blown 331 IMO and the 165's will be fine I make lot's of power with them and they still have room to grow

just4bob50 · Jul 24, 2005

the Aug. 2005 5.0 just did an article on that exact subject. They used a 347 motor totest on and they found that both heads were dead even upto about 3700rpms. after that the 185's took over. but the peak power difference was 17hp. & 16tq. thats on an engine dyno. so that about 10-12 difference at the wheels. Not worth buying new heads over again if you ask me.

Daggar · Jul 24, 2005

1991vert said:
1) Are the 165's too small for a 331-347?

2) Do stroker kits increase emissions

3) 331 or 347; reason for choice also please.

No, they're not too small if you plan your combination around them. Forced induction with those heads would be sweet.

Strokers don't have migher emissions as a rule. Your cam will have a lot to do with how well it does on emissions. It just so happens that a lot of really great blower cams also do well on the sniffer.

None of the above. If it's a brand new DART block then use the stock bore pistons and stroke it! 327 would be (and is) my caliber of choice.

2000xp8 · Jul 24, 2005

Go for the 347, there is no purpose for a 331, the cost will be almost identical to build both.

Sell the afr 165's and buy the 185's, not because you have to, but because afr's have a high resale value, and you'll only lose about $300. Build it once and build it right.

If done right you won't really even need the blower, you can build the 347 to spin up to 7grand, and with the bigger heads you'll have the power of a blower car, without a blower.

I've seen this setup many times, just with different heads, it's a 10sec NA daily driver capable car. No blowing head gaskets here.

strokedandblown · Jul 24, 2005

2000xp8 said:
Go for the 347, there is no purpose for a 331, the cost will be almost identical to build both.

^ I agree. I stayed with my 331 b/c i already had the ballanced crank, but i would have gone 347 if i had to start from scratch. I would recomend a bigger set of heads and at least a T trim or equivalant. That way you can get it to run @ lower boost and then increase as you get the tune down/ or feel comfortable. The tune with be your #1 issue, i ended up going with a stand alone system b/c the A9L was just @ its limits by far. A PMS or Tweeker would be my second choice b/c you can change the tune. and last choice would be a chip b/c your always stuck w/ one tune and need to reflash for any upgrade. Your on the right track!

Modular2v · Jul 24, 2005

im putting afr 185s on my 331...the bigger the displacement the more air the motor is going to want

89CopCoupe · Jul 24, 2005

Food for thought: On an 8.2 deck, a 331 gives you more piston "meat".

Grn92LX · Jul 24, 2005

89CopCoupe said:
Food for thought: On an 8.2 deck, a 331 gives you more piston "meat".

My 347 with the 5.315" rods has the same "extra meat" as the 331 because I use 331 pistons Its the same part # if you look on coasthigh.com.

If you were gonna sell the 165's for different afr's get 205's. Even though the 165's are a bit small, they'll still make good power especially with a charger. To make a small head make big power, you'll need a good custom cam as valve timing will be critical.

I'd do at least a 347 since its a dart block. 3.40 stroke for sure, you pick the bore size.

89CopCoupe · Jul 24, 2005

Grn92LX said:
My 347 with the 5.315" rods has the same "extra meat" as the 331 because I use 331 pistons Its the same part # if you look on coasthigh.com.

Sure, but your 347 with a 5.315 rod will not have as much meat as a 331 with 5.315 rods ... anyhow.

Grn92LX · Jul 24, 2005

89CopCoupe said:
Sure, but your 347 with a 5.315 rod will not have as much meat as a 331 with 5.315 rods ... anyhow.

Yah true, But I care about power, not meat

89CopCoupe · Jul 24, 2005

Why not built a 408 then

Grn92LX · Jul 24, 2005

89CopCoupe said:
Why not built a 408 then

I care about money more than power And I REFUSE to EVER put a cowl hood on my car. I would have needed one to run the right efi intake on a 408. Believe me, I considered it, then I realized a 347 was my only real bet.

Mike

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