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Author
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Topic: 331 vs. 347 or...
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gercolla1
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Member # 3068
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posted
 
 
Aside from a possible price differences,isn't bigger better on a na set-up?Why would someone prefer a numerically smaller engine displacement?Is one better suited for daily driving?What is there to consider when deciding between one or the other? ![[burnout]](graemlins/burnout.gif)
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Sf Bay Area
Posts: 2171 | From: Sampan San Francisco | Registered: Jul 2003
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silverLX
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Member # 3207
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posted
The thing I hear is 347's used to be known as oil burners, and some still are. If you are doing the work your self, I also think you dont have to grind on the block to get the rods to clear with a 331, but do on a 347.
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88LX hatch 410w
88LX vert gears, exhaust
95GT H/C/I
Posts: 1613 | From: Sonoma County | Registered: Aug 2003
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JohnB
Tech Moderator
Member # 969
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posted
It all comes down to $$$$. How deep are your pockets? With a 302-based setup, you can run nearly all the stock components (50oz items). Unless you re-balance everything or buy a pricey kit that's setup for 50oz, you will spend money on a good flywheel and balancer.
The days of the oil-burning 347's are about over. Most, if not all *good* kits have redesigned pistons and ring lands. 347's need grinding on the blocks; some 331's do, depending on the rod length used. The block to be used is a whole different story. ![[Smile]](smile.gif)
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1965 Shelby Cobra
1993 Cobra
2012 F150 Raptor
2020 GT500
Posts: 6523 | From: Orlando FL/Redding CA | Registered: Mar 2002
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92stangLX
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Member # 3252
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posted
Bigger is better ![[Big Grin]](biggrin.gif) I would go with the 347. I have also heard that the oil consumption issues have been resolved.
A 347 will give you a bunch more torque. It may consume a bit more gas but a 331 isn't going to be fuel efficient either.
I don't think there is much price difference between the 331 and 347 kits.
Your only other concern will be smog. The cam you choose will have more of an effect on that then the size of the motor.
Posts: 5302 | From: San Francisco | Registered: Sep 2003
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Jeff S
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Member # 371
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posted
Bigger IS better!
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'90 Mustang LX: 8.53 @ 157.92 w/ 1.33 60' on DR's
'10 ZR1: FOR SALE
'14 E63 S: RENNtech ECU
'04 Gallardo: UGR TTG
Posts: 2121 | From: San Jose, CA | Registered: Aug 2001
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2stangs69-91
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Member # 1951
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posted
I had to grind my block with the 331. If I would have went NA I would have gone 347 or if I had a Dart block. I don't think the extra wear issue is a thing of the past just yet. Just do a little research and you won't find to many high mile 347's(I am sure they are out there).
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69 Mustang on hold
1991 LX hatch getting a make over
1994 F150 4X4 351
2006 Yamaha V-max 1200 Modded
Posts: 3711 | From: Redding | Registered: Oct 2002
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93PONY
Mr. Valve Events
Member # 60
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posted
quote:
Originally posted by Jeff S:
Bigger IS better!
Agreed, as long as you can FEED the motor given the intended RPM band.
Don't go slapping on some Edelbrock performers, GT40's, or AFR165's on a 347 & expect it to make power above 5500RPM.
The difference is piston speed. Example:
3.0 stroke @6000rpm = 3000ft/min (the piston is moving 3000 feet per minute at 6000rpm)
3.25 stroke@6000rpm = 3250ft/min
3.4 stroke @6000rpm = 3400ft/min
The same heads/intake/exhaust/cam combo on a 302 making peak power @6000rpm will make that power at 5538RPM on a 331, & 5294RPM on a 347.
Basically, the more piston speed you have, the faster you'll max out the heads/intake/exhaust combo as the longer stroke physically pumps more air through the motor. You need larger parts to make longer stroke motors rev as high as smaller stroke.
No need to worry about oil burning issues. They've even made 5.315inch rod 347 combo's for those that are still not convinced the problems are a thing of the past.
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www.advancedenginedevelopment.com
SCT dealer
Dynotuning
(916)715-7569
Posts: 4265 | From: Fair Oaks, CA | Registered: Nov 2000
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2stangs69-91
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Member # 1951
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posted
Keith Craft isn't convinced on the 347 wear issue for street engines either and he is the Best Ford guy in the country. We just orderd a Dart Block 347 for a friend and they tried to talk us into a 331 for that reason.
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69 Mustang on hold
1991 LX hatch getting a make over
1994 F150 4X4 351
2006 Yamaha V-max 1200 Modded
Posts: 3711 | From: Redding | Registered: Oct 2002
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