Building a new engine 331 or 347 - Ford Mustang Forums : Corral.net Mustang Forum
 
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post #1 of 17 Old 03-01-2007, 12:34 AM Thread Starter
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Building a new engine 331 or 347

Looking to get my turbo kit soon, but im looking to build a new engine and was wondering what you guys think would be better!!! Im leaning more towards the 331 but would mind the extra cube!!!


Thanks all in advace!!!
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post #2 of 17 Old 03-01-2007, 01:03 AM
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I prefer 331's due to the rod-stroke ratio and better oil control. I know someone is going to come in here ranting about the 347s dont have that problem anymore and yadda yadda yadda! Save it, I know the pro's and cons of them both and I would never run a 347 in an 8.2" block.
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post #3 of 17 Old 03-01-2007, 01:13 AM
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I would run a 331 to be honest
Just make sure its in an aftermarket block if you plan on running a turbo setup
stock blocks are really too weak to take advantage of all the power you can make with a turbocharger
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post #4 of 17 Old 03-01-2007, 01:27 AM
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347 all the way for me.. my combo is a scat 347 mex block and a v2 s trim blower. why leave hp on the table because of some old ass stories about oil burning and rod ratio that has been fixed over the years and put to rest .
post #5 of 17 Old 03-01-2007, 01:13 PM
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331 if it was me and my money, even if the rod-ratio has been "fixed" per say, it's far from optimal and I wouldn't want to be putting a lot of pressure on it...

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post #6 of 17 Old 03-01-2007, 01:33 PM
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i have never seen a 347 fail because of the rod ratio ...... i have seen one or two fail because of a engine builder that did not know what the hell he was doing. i would stay away from any engine builder that tried to steer you away from a 347 they probably have had problems with them because of poor builds ( not knowing wtf they are doing)
post #7 of 17 Old 03-01-2007, 05:24 PM
 
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I was told that the 331 will make more power across the RPM range than the 347. And also have heard stories about side load on the piston skirtsand oil cosumption with the 347. If it were me I would go with a 331 just use good parts and a good builder
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post #8 of 17 Old 03-01-2007, 06:05 PM Thread Starter
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Well it looks like the majority is with me on the 331 so ill probably go that route unless i can step it up to a 393!!! Im not worried about a builder, ive got a very good one, so well see how it goes. Thanks everyone for your input!!!!

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post #9 of 17 Old 03-01-2007, 09:45 PM
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Originally Posted by night stalker50 View Post
i have never seen a 347 fail because of the rod ratio ...... i have seen one or two fail because of a engine builder that did not know what the hell he was doing. i would stay away from any engine builder that tried to steer you away from a 347 they probably have had problems with them because of poor builds ( not knowing wtf they are doing)
Ummmmm, Paul Silva has been building engines for Stangs for years..... one of the best in North America and probably the best in Canada. He advises against 347s, not because doesn't know what he's doing. Chances are, if someone reputable is steering you away from something its because they know something you don't. The guy has built hundreds of motors, you can't possibly tell me you think you know better than he does.
Personally, I dont like the idea of shortening the rod length to get the oil control ring above the pin.... it's a band aid. And for the record, all the 347 failures I've seen are usually a broken piston or a break at the 2nd main. It causes too much stress on the reciprocating parts, the guys that insist that bigger is better will always break stuff. In my opinion, a 3.25" stroke is the largest I would run in a factory 8.2" block. In an aftermarket 8.2" block, I'd run a 3.3" stroke max but you can run a big bore.... up to 4.125 which yields some big ass cubes...... (353" I think?)
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post #10 of 17 Old 03-08-2007, 11:22 PM
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All I hear is wah wah wah. NO OTHER ENGINE BUILDER BESIDES SILVA OR DSS WILL RECOMMEND A 331 OVER A 347! I don't even know if Silva still would recommend a 331, so I'm going off of what you say. Honda builds motors very similar to a 347 in terms of deck height, rod length, and stroke from the factory. Guess what? They sell these motors with an 8800 RPM fuel cutoff and a 60K mile powertrain warranty in the form of Integra Type-R's. Go look on Hardcore50.com, and see how completely debunked the myth is about 347's being hard on parts and breaking stuff.


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post #11 of 17 Old 03-08-2007, 11:26 PM
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All I hear is wah wah wah. NO OTHER ENGINE BUILDER BESIDES SILVA OR DSS WILL RECOMMEND A 331 OVER A 347! I don't even know if Silva still would recommend a 331, so I'm going off of what you say. Honda builds motors very similar to a 347 in terms of deck height, rod length, and stroke from the factory. Guess what? They sell these motors with an 8800 RPM fuel cutoff and a 60K mile powertrain warranty in the form of Integra Type-R's. Go look on Hardcore50.com, and see how completely debunked the myth is about 347's being hard on parts and breaking stuff.
your wasting your time .......this guy has made his mind up on what motor to use because some guy heard from someone else who heard it from their friend that a 347 is a oil burning rod breaking pos
post #12 of 17 Old 03-09-2007, 12:11 AM
 
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I would build a 306 or 308. Faster spinning motor and the turbo will give you all the torque you will need. I like this setup if going into a 5 speed car. If an auto is to be use then I would probably pick a 331 stroker.
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post #13 of 17 Old 03-09-2007, 05:25 PM
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I was told that the 331 will make more power across the RPM range than the 347.
Whoever told you this, never speak to them again.
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post #14 of 17 Old 03-10-2007, 07:31 PM
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your wasting your time .......this guy has made his mind up on what motor to use because some guy heard from someone else who heard it from their friend that a 347 is a oil burning rod breaking pos
I never said I heard it from anyone, I was there when one blew up..... actually I was behind the wheel when it started ticking in the form of a busted piston. And these were not your run of the mill 347 stroker kit parts. These were Oliver 5.4" rods, custom forged Ross pistons, and a steel crank. The motor had moly rings, yet always had blow by. And yes, it was spec'ed and properly set up. The car made great power, 347 with Vic Jr heads, fully gutted/welded and ported Cobra upper and lower, 1 3/4" long tubes, x cam, and a whole slew of goodies. It lasted less than 5,000km and was very well maintained although beaten on. A 347 is a great motor to make power, but I personally have yet to see one last 30k with lots of abuse. I've seen plenty of 302's, 306's, 327/331's make it to that mark but not one 347. And I'm talking an engine that sees beatings daily and track outings at least once a month. You can argue against that last sentence, but if I'm building an engine you better believe I'm going to kick the crap out of it all the time and it better hold up. And I do not have faith in 347s holding up for very long.
And for the record, I've worked as a machinist and engine builder and have built many engines that have made power and very durable. How many motors you got under your belt? Sorry, but I live in the real world and not on the internet like some of you internet racers.
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post #15 of 17 Old 03-11-2007, 06:07 PM
 
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Whoever told you this, never speak to them again.
Let me correct you....It's been documented a couple times that the 331 will make more power than the 347 with the same parts....But the 347 wins everytime in the torque department....Not sure about which one is the best when it comes to power adders when using the same parts....All the tests I've seen done were N/A......
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post #16 of 17 Old 03-12-2007, 09:14 AM
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Let me correct you....It's been documented a couple times that the 331 will make more power than the 347 with the same parts....But the 347 wins everytime in the torque department....Not sure about which one is the best when it comes to power adders when using the same parts....All the tests I've seen done were N/A......
You weren't the one that told him were you?

I don't buy any of that garbage for a second.
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post #17 of 17 Old 03-12-2007, 12:59 PM
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Go with whichever one is cheaper and if they are the same price then consider the more cubes you have the more the motor breathes and sometimes the bigger the turbo you need just to have an efficient combo. Fact is with a turbo you would slap in a 306 and still be making tons of power.

As far as which is worse, I have ran both and I have put or help put in a lot of 347 motors over the years. I am unaware of any of them failing unless someone was just doing something stupid. Most of these motors have 10s of thousands of miles on them because initially they were used in daily drivers and years later became garage queens. Believe what ever theories you want or whatever engine builder you want, but at the end of the day I am going to believe what I have seen with my own eyes.

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