Can I bore 5.0 block to 347? - Ford Mustang Forum
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post #1 of 14 (permalink) Old 01-16-2010 Thread Starter
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Question Can I bore 5.0 block to 347?

I have my stock 302 block chillin in my shop and was wondering how far safely can I bore it. I don't even know if it'll go to 347 but thats what I was wanting to know. Or even 331.

Now lets say I do either one, how expensive would it be?

I know then I'd have to get pretty much everything new: HCI, rotating assembly, intakes, etc.

Realistically, I'd be looking around $6-8k, that sound right?

How much you think just to bore the block for now?

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post #2 of 14 (permalink) Old 01-16-2010
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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

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post #3 of 14 (permalink) Old 01-16-2010
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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.

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post #4 of 14 (permalink) Old 01-16-2010
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what they said.

and you can go past a .030 over bore. i'm .040 over with no issues. i've seen people go .060, but the cylinder walls in these blocks are thin, and going that far puts you on thin ice.

boring a block .040 over and stroking them puts them at 333ci with a 3.25 stroke and a 349ci with a 3.40 stroke.

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post #5 of 14 (permalink) Old 01-16-2010
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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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post #6 of 14 (permalink) Old 01-17-2010
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Bore it to 306, Bore and Stroke to 347!!
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post #7 of 14 (permalink) Old 01-17-2010
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Originally Posted by Brutal Metal View Post
Bore it to 306, Bore and Stroke to 347!!

Yep thats what i'd do......
post #8 of 14 (permalink) Old 01-17-2010
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Yes, your stock block can go to a 347 but that's the max it's recommended.

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post #9 of 14 (permalink) Old 01-17-2010
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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

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very informative. if i had that money i would turn my fox into a stroker. im curious, whats the risk in boring out to .060?
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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.
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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.
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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.
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yes I can be I wouldnt go over .30 over to be on the safe side.

Check out You can get a short block from woody for just under 2100 or so.

He also sells rotating assemblies at a good price

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