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Discussion Starter · #1 ·
I am looking to get some quick advice.

I have been planning on building a 347 from the start. I am planning on dropping the block off at the shop tomorrow and am getting cold feet. My main concern is I want the car to be drivable.

Everyone told me my corvette would be very streetable before my work was done. Yes, it drives fine but it is not truly streetable in my opinion. It will idle with the ac on but it shakes you to death. Of course I guess I do not have to worry about ac on this project. I want a large health cam in the cobra, but I do not want it to be so wild my wife will not go for a cruise with me.

Fact is I can build the 347 for only a couple hundred dollars more than a 306. Therefore, I thought I should go ahead and get the extra cubes. I just do not want to sacrifice drivability and reliability for some cubic inches I will likely never really put to use.

Thanks in advance for your input.
 

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Junior Charter Member
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Actually larger cubes usually result in an engine that is more drivable at a given power level because the other aspects of the combo don't have to be as aggressive (cam, tune, etc). For a couple of hundred dollars more I think you'd be crazy not to do the 347.
 

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Living Large
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"no replacement for displacement"

Trent
 

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...is anyone out there complaining that they have too many cubes?

there are a few things in this world of cobras er, um..i mean roadsters, that you will never have enough of....and one of them is power: especially after the first time you get your clock cleaned by some other "car nut".

in this case, more is better.
 

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Kinda seconding what znaut said, it's easy to build a 306 with significant drivability issues, just stir in plenty of cam, intake, and heads. If you're wanting more power/torque than a mild 306 will deliver, a larger-displacment motor can provide that without having to be as high-strung as a 306 motor making the same power numbers. Plus it may deliver those numbers at lower RPM, helping again on drivability and reliability/longevity. Some guys that road-race small block Fords say that under hard use the 331s hold up better than 347s - apparently the "shorter" 347 pistons have a bit more tendency to "rock" at the top and bottom of the bore, plus usually the wrist pins are extremely close to the lower oil ring.

Good luck with your choice - ain't life grand, having the opportunity to make decisions like these
 

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327- basically a 331 with a standard bore. Great performance as well as drivability. I heard the same "rumors" as cobrastang. Besides, I like the variety of responses I get when I say it has a 327 in it.
 

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Former Roadster Owner
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Lets not open the 331 vs 347 debate especially with comments like, "I heard...". Like most rumors, there may be a hint of truth behind it, but many times its just bad information.

If you're letting idle quality and RPM range determine whether or not you should get a 306 or 347 than go with the 347. This would be especially true if you were going to use the same camshaft in either engine. Given the same components the 347's faster piston speed will typically make peak power sooner. Also larger displacement engines typically "tone down" a camshafts idle characteristics--just slightly though. With the same camshaft the peak RPM difference would be 200-500rpm--or close to that.

With all that said, a well built 302 also motivates a light weight Cobra pretty well.

-dan
 

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Hey Mr C5,

How much do you love your wife? Anytime you stroke a motor you'll lose that smooth idle. A 347 stroker will usually produce about 400+ HP, but with a more aggressive cam and a bit more compression so can a 306.

Against popular demand... I'd go with a healthier 306 and spend alot of time driving your wife around. ;)

pauL
 

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Junior Charter Member
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347 I read everything I could for a couple of months before I made my decision( Mustang sites,Hot Rod Magazines, internet info...) You won't be second guessing weather you made the right choice or not. Love mine. Well behaved during normal driving, and crazy power when you get on it. Pick the right cam,and you'll be fine.
I have a 2001 Z06,Cartek hds,cam ported intake pkg,440 RWHP, and the car is totally streetable(I almost went with MTI Z07 set up. Guess I made the right choice). Baron
 

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Either size is fine and will run great. Mostly cam selection (don't put really big heads and intake on it) will make or break your "fun" or drivability factor.

Don't get caught in the sound track of the cam, it has little to do with the fun of driving. Make the combination work for how you will use the car.

You don't need that much power to have a fast FFR.
 

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FFCobra Craftsman
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Sorry if this is a silly question, but EFI or not? I have a carbed T&L 347 and it has a nice loping idle at 1000RPM but a 347 makes a lot more noise and in my opinion is not as streetable as an EFI 302 or (I assume) 306. I havent driven my 347 much but it sounds like a caged animal.....but I love it - my wife is not so keen
Steve
 

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Why would a 347 be any less streetable than a 351 with the same cam, heads, manifold and carb?

Bill G
 

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Discussion Starter · #17 ·
Thanks for the input guys.

It will be a carb, forgot to mention.

Bill- good question. I am not an expert, but I would think the 347 would have a longer stroke and rev higher than the stock 351. Maybe wrong.
 

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Senior Member
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302 and 351 have the same bore, so stroke would be shorter. I would guess that a 347 with a mild cam would be very streetable.

Bill G
 

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347 all the way. I haven't had a chance to drive mine on the street yet but why not for a couple hundred dollars.

My .02 cents

John
 
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