331 vs 306 wit spray

mustang2k

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Jul 31, 2005
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Im looking to hear about the pros and cons of a 331 cause im thinking of making one for my 91gt as daily driver using a dss rotating assembly or possibly making a 306 with spray
 
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304billet

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Sep 16, 2005
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if ur 302 needs refreshed I would just swap out the stock pistons for forged, use the stock rods and crank and do a 306. throw some boost on it and be done. keep the rwhp at 450 and u will be fine on stock block with a good custom tune. if ur s/b has alot of miles on it like 150,000 I would then do a 331 stroker with forged 4340 rotating assembly, then some throw some boost to it. the only con about a 331 is that it costs more money to build then a 306.
 

blackened88lx

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Aug 9, 2006
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'92 and earlier had forged pistons stock anyway. Why are you rebuilding? does it need it? how many miles are on it? If you have to rebuild it, there's a chance you might be able to keep it a 302, if it has to be bored, go 306. I've said this many times, but I wouldn't waste my money on a stroker kit in a stock block. The stock block is very likely to break above about 450rwhp, so if it does, it will wipe out your pricey stroker kit you just bought. The only time I'd run a stroker in a stock block is if it's staying n/a and won't see over 400rwhp. Freshen up the bottom end if it has to be, and spray it. Or, spend the money you saved from not doing the stroker kit and buy a used blower to go on the 306.
 

mustang2k

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Jul 31, 2005
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ive already had a blower not really to special. it def needs a rebuild cause the people that had it before me beat the hell out of it. and its seen better days i only plan on making 300-350hp
 

ras50gt

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Oct 25, 2005
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I have been thinking about a 331 build and the advice I usually get is to go with the 331. If you do your research, a 331 short block is only a few hundred more than a 306 shorty. I have seen 306 sb from $1000-1600(forged pistons/cast cranks), and 331 from $1400-2100(forged pistons/cast crank, 331 with forged cranks from $2100-2500. Now, everyone is going to tell you that where the cost comes in is the supporting mods that come with the more cubes. And all that depends on what you are trying to achieve. In my case with the 331, I would want something good for the street and would hopefully be around 350hp n/a at least.

It is a somewhat hard decision though because I have always wanted a s/c, so I have been pondering the idea of a nicely built 306 and throw a s/c on it. Only because the chances of splitting a stock block with the 331 increase significantly with h/c/i and boost. Of course if you can afford it, get a dart block or something and throw the worries out of the window, then you can run a lot more boost. The other thing is, I'm going to be getting h/c/i when I build the short block, so why waste my time with a 306 when the new mods work better on a 331. Plus if the cost difference is 400-600 bucks, the hp gain is worth it. My .02 cents....
 

blackened88lx

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Aug 9, 2006
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I have been thinking about a 331 build and the advice I usually get is to go with the 331. If you do your research, a 331 short block is only a few hundred more than a 306 shorty. I have seen 306 sb from $1000-1600(forged pistons/cast cranks), and 331 from $1400-2100(forged pistons/cast crank, 331 with forged cranks from $2100-2500.
There might not be much of a price difference if you're buying the whole kit, but if you're building a 306, most of the time you can use the stock crank and rods, unless the motor is completely shot. So you would probably just need pistons if going with a 306.
 

wicked84gt350

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Aug 20, 2006
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West palm bech florida
This is my expereince on the 306 I have, with the money I put into it I should have built a 351w up Because the stock 302 as everyone knows has a weakness of about 450-500 rwhp. A 70-74 351w will do about ~650~ and the same stuff you will buy for the 302 will fit the 351w so get a junk yard 351w bore it if you want or stroke it and you will do it for about the same price as a 306 if you went stroked then the same price as a 331 and you will have better torque and can give it more happy gas. I would only stroke a 302 if it were a aftermarket block. I am just giving you my piont of view from building up a 306. And in reality the horse power gained from the 331 is not worth it but I have to admit the torqure gain is pretty impressive.
 

wicked84gt350

New Member
Aug 20, 2006
113
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West palm bech florida
This is my expereince on the 306 I have, with the money I put into it I should have built a 351w up Because the stock 302 as everyone knows has a weakness of about 450-500 rwhp. A 70-74 351w will do about ~650~ and the same stuff you will buy for the 302 will fit the 351w so get a junk yard 351w bore it if you want or stroke it and you will do it for about the same price as a 306 if you went stroked then the same price as a 331 and you will have better torque and can give it more happy gas. I would only stroke a 302 if it were a aftermarket block. I am just giving you my piont of view from building up a 306. And in reality the horse power gained from the 331 is not worth it but I have to admit the torqure gain is pretty impressive.
 
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