306, 331, and 347 have the same bore, 4.030." The bigger cubes mostly come from a longer stroke crank. 3.00" (stock) 3.25" and 3.40" respectively. A 5.0 HO block can 99% of the time be bored +.030" anything past that may be possible, just have a shop check it and make sure it is safe. I think my shop charges $170 to bore a V8
You can bore it out to a 306, the rest has to come from stroke. Boring usually cost about $25-30 around where i live. And you can still use the same heads, intake. You'll just need new pistons/rings if you bore it out. If you stroke it you need a whole new rotating assembly.
1984 Mustang LX - SOLD ($1000) Edelbrock 600 carb, Edelbrock RPM AirGap Intake
1984 Mustang GT350 - TRADED FOR 1989 F-350 Speed Demon 650, Edelbrock Performer RPM Intake, Ford Racing A311 Cam, E7TE Heads, MAC Prochambers
1984 Mustang GT T-Top - SOLD Completely naked
Yeah trust me have an idea or final lan when you do this as it all adds up really quickly. You need to hot tank the block, bore it over, freeze plugs, the main caps ect... that is just machine work. You will be into it over $400 for machine work on a stroker. Then comes the the rest and trust me there is plenty.
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you can bore a 302 to a 331 or a 347 i have done both. A 347 requires notching the cylinders so the connecting rod bolt will clear the cylinders, a 331 is a bolt in and go. As for machining it costed me 700 and depending on what rings you are using is how they are going to hone your cylinders. A 331 or 347 stroker kit worst possible case will be about 2200 for a complete kit and a forged crank which i would recommend. As for the machine work costing 700 i have the heads rebuilt while i was there just for piece of mind, that included valve job, new guide and seals, pressure checking the heads, and decking them. If your going to pay a shop to do the work figure in about 1500-2000 dollars on top of what you already payed for everything so far. Anyway hope this info helped a little bit and good luck on your build
1993 COBRA, 115k miles on car 2k miles on everything else. Stroked and supercharged.
Snakes are still around some with more bite than others!
A LOT OF OVERHEATING!!!!! if you go .060 over, it will be hard as all hell to try and keep the temp. down. To much compression with Forced induction/Nitrious can split the block or crack a cylinder wall unless you sleeve the motor and that case, you will still have an overheating problem and the work to sleeve a motor will be very high in price.
Yeah machine work is just as costly sometime. I went .040 as I got a good deal on a cast crank eagle kit and was a little concerned about it being .040 but have been told it's all good and the block checked out.
There are fully assembled 347s in the classifieds, Ebay, and craigslist for really good prices, look around. Of course you might wind up like me and say, "hmm, if I'm going to stroke something, why not go for the 351 and build a mac daddy 408/427?" Have fun, good luck.