331 vs 347

nunly94gt

nunly94gt

Founding Member
Feb 3, 2002
1,595
3
38
Mobile, Al
#1
Im gonna build a stroker moter and hope to push about 400 to 450hp out of it. Im curious if I could get some kind of a bias on the two. Whats the gains of going bigger other than cubic inches. I appreciate this in advance, this way i dont waste money on the 3.400 instead of the 3.25 kit.:flag:
 

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#3
Pokageek said:
347's burn oil and wear out too quickly.
Click to expand...

Stop messing with the guy.

The 347 is going to make a little more power than the 331, and make it at a lower rpm so you won't have to rev it up as high. Not a whole lot of difference, but there really is no advantage to going with the 331. You're better off just skipping to the 347.

Kurt
 
#4
I work on trucks that do nothing but leak and burn oil all day, so it would really ruin my time if it did.

What kind of difference is there in the power band? Cause im really leaning toward a 347.

I figure if my old setup in a 306 was making 340hp a 347 would push me over or close to 400hp. Is that a reasonable number?
 
#5
Some of the the older cheaper 347 kits burned oil. The new ones are fine. I have about 85,000 miles on my 347, and it still makes great power, and doesn't burn a drop. There is really only going to be about 200 rpm difference on where the peak power is made. You're really not going to make much more power over your 306 unless you make the heads flow better, and get a bigger chamshaft. If you put the exact same heads and cam that you have on your 306 onto a 347, it will probably make somewhere around 10 more hp, and peak about 500 rpms lower. You can very reasonably make about 400 hp on a 347 with a very driveable combination.

Kurt
 
#8
WOW! Talk mabout a blast from the past. I haven't seen you on here in years!!! Its good to see that you are getting back into the game! I'd build a 347 if it was me, there are no negatives to extra cubes. I only went with a 331 because I have a turbo kit for it and with the turbo I had at the time I built it, and the fact that my kit is setup for a T4 flange, a 331 made more sense. It wasn't too big for the turbo I had, yet it was big enough to support a T76, which I now own too and have yet to put on. A T4 flange becomes restrictive at cubic inch levels above a 331 too from what precicion turbo and PTK told me.
 
#10
Killercanary........yeah its been a while man. I remember when me and you were the only to n/a 12 second guys around this joint.

Im deffinitly doing the 347 now, you know what they say, no replacement for displacement.

Revhead347- what do you suggest? I was running this setup here, Performer RPM heads, Victor Jr intake, Holley 650 carb, X-303 cam, 1.72 rockers, long tubes with 3" exhaust, and a short belt(p/s and water)
I was running 12.5@110 with 4.10 gears and a tremec 3550
 
#11
Those heads and intake are pretty good actually. If you want to save the money on heads, you can just get some port work done on those, and maybe run a 2.02/1.60 valve setup. Port match the intake and get a custom cam. I think most of the guys here run one from FTI or something like that. If you have the money to spend on some heads, I would go up to a Canfield 192, Canfield High Port, RHS aluminum, or maybe a twisted wedge head. I think you could get 400 hp out of those Edelbrock heads though if that's your goal. I would say 11:1 compression for nitrous or n/a.

By the way, I'm the other 12 second n/a guy who used to post here a lot. I just recently starting checking this website out again.

Kurt
 
#12
Killercanary said:
WOW! Talk mabout a blast from the past. I haven't seen you on here in years!!! Its good to see that you are getting back into the game! I'd build a 347 if it was me, there are no negatives to extra cubes. I only went with a 331 because I have a turbo kit for it and with the turbo I had at the time I built it, and the fact that my kit is setup for a T4 flange, a 331 made more sense. It wasn't too big for the turbo I had, yet it was big enough to support a T76, which I now own too and have yet to put on. A T4 flange becomes restrictive at cubic inch levels above a 331 too from what precicion turbo and PTK told me.
Click to expand...

your 331 numbers in your sig r nuts:eek:
you just dont see them often with efi,& comp that low:nice:
 
#13
revhead347 said:
Stop messing with the guy.

The 347 is going to make a little more power than the 331, and make it at a lower rpm so you won't have to rev it up as high. Not a whole lot of difference, but there really is no advantage to going with the 331. You're better off just skipping to the 347.

Kurt
Click to expand...

Ok so it was my turn for April fools. We all know a well built 347 will not have that old aged problem. :SNSign:

Now I can attest that if you do not have the proper heads, you will not make anywhere near the fancy internet numbers that alot of people claim. :notnice: Everybody likes to say how easy 400rwhp is out of small cubes (347 aint small but..) but you have to pay to play. This means a great set of heads, LT headers and supporting hardware. I have tried to do it cheaper and took the long way around. Also remember the higher u go over the 1:1 ration of c.i. to rwhp, the less low RPM grunt you get. It depends on your preference, for example:

One guy on here is going for 400rwhp with a 331. He is however running 4.30 gears and I blieve a 6 speed trans so that is going to be a fun ride. The gears will make up the loss of the low end and the 6th gear will handle the hwy revs. :nice: Now as to "rock & roll" bucket of bolts effect at a light ,I can only take so much but some peeps like to drive around all day with that noise. I must be getting old lol.:D
 
#15
Pokageek said:
One guy on here is going for 400rwhp with a 331. He is however running 4.30 gears and I blieve a 6 speed trans so that is going to be a fun ride. The gears will make up the loss of the low end and the 6th gear will handle the hwy revs. :nice: Now as to "rock & roll" bucket of bolts effect at a light ,I can only take so much but some peeps like to drive around all day with that noise. I must be getting old lol.:D
Click to expand...

Just came back from Summit in GA today... She will be running tomorrow or Thursday. Then its off to Pro-dyno for the break in tune. :D
 
#18
If you're SBF engine savvy then tossing decent heads on a 351 efi block from a 95-97 truck will put you in a better starting point. get a 351 efi intake and a canton oil pan....if you get the roller motor from a 95-97 efi and it comes with a distributor then its a direct plug in for a 94-95 mustang. either way you'll save the money on the rotating assembly and machining which can touch $2000 alone. Canton pan is $250 and 351 intake is $400- 500 ebay prices. (carb is cheaper) only way i can see doing a 347 is if you're using a dart or svo block because you're starting a build that will make n/a power at the limit of a stock block. Do yourself the favor and go to a 351 block now. only trip to a machine shop might be rebalancing a 351 flywheel and drilling the bolt holes on the 302 heads to fit larger bolts. Go 351 its not a "black art" its pretty easy...btw all your stock accessories brackets will bolt right up. 351 is bigger than 347 stock and the block will take more power. PM me if you have any questions. i have done this a couple of times on a budget with great success.
 
#19
What's going on nunly! Its been a long time since I've been on here too, but I'm back! But I'll probably be hangin out in 5.0 tech. Just bought an 88 coupe.

About your combo, My dad bought a 347 crate motor for his 67 coupe and they dynoed it before they shipped it. It made 409hp and 427tq but thats just at the flywheel. All you'll have to do is a few minor things to bring it over 400hp at the wheels.

Here's the link to the motor: http://www.smedingperformance.com/ford/347+Extreme+405+Horsepower.html
 
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