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Thinking about stroking my 289 to a 347, but I've never done any crank shaft work. How hard of a job is it to stroke the motor? How will it affect my cooling? Is it possible to stroke it with a .060 bore?
 

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I think it's safe to go 30 on the small block but not 60. On cooling it seems to be a hit and miss because some people have problems and most don't. Be ready to upgrade the cooling system with a larger radiator, fans mechanical or electric and shrouds.
 

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I think it's safe to go 30 on the small block but not 60. On cooling it seems to be a hit and miss because some people have problems and most don't. Be ready to upgrade the cooling system with a larger radiator, fans mechanical or electric and shrouds.

well said. while the max overbore for the 289 is .060, if you want to go that far out you best have the block sonic checked for core shifting. personally i would go no further out than .040 on a 289 block.
 

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I wouldn't go over .040. Also, correct me if I'm wrong, but aren't the 302 cylinders a tad deeper than the 289 to accommodate the longer stroke of the 302 crank, let alone another 4/10 of an inch with the 347 crank? Just curious, but I thought that to be the difference between the 289 and 302 all else being the same (deck height, bore, etc.). If that's the case wouldn't another 13/100 on top of the 4/10" be kind of a deal breaker being the total stroke difference is over half an inch (.53 to be exact)? I could be wrong about all of this but my thoughts are that if the 302 has deeper bores to accommodate just a small difference in stroke, then wouldn't the combination of almost 1/2" of stroke along with a shorter piston, put the piston below the bottom of the cylinder, or at least dangerously close?
 

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I have a 289 bored .060 over. I have a stock radiator and no special fans. Never has overheated. Runs great. Lots of power. We put a bigger cam in too, but I don’t remember the size right now. Sorry, I don’t know about stroking a 289.
 

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It's not recommended to bore 0.060". The cylinder is getting REALLY thin at that overbore. What little there is to be gained with cubic inches... is lost with thin, weak cylinders that are not stiff and lose ring seal. Only overbore as much as is necessary for cylinder integrity. No reason to go over 0.030", unless it won't clean up at that, and then I'd set my limit at 0.040" before looking for a different block.

As for cylinder length... I have measured several 289 and 302 blocks, and found no significant difference. Plus, the 'new' Boss 302 block Ford sells as aftermarket has FAR shorter cylinders than either 289 or regular 302 blocks. Most advise against using the 3.4" stroke (347) cranks in them, but some do anyway. Those blocks are so short, a portion of the PISTON PIN is actually below the cylinder at BDC!
 

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There are many .060 over 289 blocks out the running cool. Most people nave no clue. Just freshened a genuine 289 Cobra engine that surprised the owner by being 4.060. He commented "it never ran hot". Sonic checking is the only reliable way to determine cylinder wall thickness. I agree that there is no practical reason to bore a block any more than it needs. Custom pistons can be made at ANY bore size that there are complementary rings for. 4.005 4.006 whatever. It is important for people to remember that HALF of the total size increase is being machined , so 4.060 is only .015 more material per side. That small amount has little affect on a cylinder without core shift. It is FAR better that the STUPID idea of sleeving all 8 cylinders back to stock. If you need to know why just ask.
Randy
 

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Block strength / integrity goes from early 6 bolt blocks being the best and only getting worse as they moved toward the pathetic hyd roller blocks . I don't care how many girdles or braces you use increased HP will crack a roller block. Switching up to a four bolt '69-71 Boss block is good , the A4 and R blocks are better the new Boss is thick but suffers from the short cylinder length n2oMike called out. A Dart or World block would be the strongest of all. The aluminum blocks are light but will not make as much power as an iron block. Not EVERY engine needs a high end block. For 300 or so HP a late roller block will go 200,000 miles. Early blocks can handle 400 or a little more. 450 and up should be looking for four bolt mains . Sure the blocks will all make more power but the blocks will begin cracking with extended use.
Randy
 

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There are many .060 over 289 blocks out the running cool. Most people nave no clue. Just freshened a genuine 289 Cobra engine that surprised the owner by being 4.060. He commented "it never ran hot". Sonic checking is the only reliable way to determine cylinder wall thickness. I agree that there is no practical reason to bore a block any more than it needs. Custom pistons can be made at ANY bore size that there are complementary rings for. 4.005 4.006 whatever. It is important for people to remember that HALF of the total size increase is being machined , so 4.060 is only .015 more material per side. That small amount has little affect on a cylinder without core shift. It is FAR better that the STUPID idea of sleeving all 8 cylinders back to stock. If you need to know why just ask.
Randy
I've seen that done, sleeve all eight cylinders on a restoration just because the customer wants a standard bore. The block hadn't been bored previously and the customer had OEM pistons.
It wasn't even a high performance motor. Lol
 

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Iowan,
Here is why "I" say it is stupid top do that. The walls are already thin. a sleeve is typically .125 wall or thicker. that means you have to bore a 4.250 hole or bigger into all eight places SO much material is removed that water jackets are exposed and the "deck" or top of the block has LITTLE parent material tying it to the main webs. But it's STANDARD is all people care about. The sleeves are only press fit into the block so the bolt areas are weakened and "pull" up under bolt torque MUCH easier. People think "standard" makes a part a virgin.
Randy
 

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Iowan,
Here is why "I" say it is stupid top do that. The walls are already thin. a sleeve is typically .125 wall or thicker. that means you have to bore a 4.250 hole or bigger into all eight places SO much material is removed that water jackets are exposed and the "deck" or top of the block has LITTLE parent material tying it to the main webs. But it's STANDARD is all people care about. The sleeves are only press fit into the block so the bolt areas are weakened and "pull" up under bolt torque MUCH easier. People think "standard" makes a part a virgin.
Randy
A 0.125" is a thick wall sleeve. Thin ones are more like 1/16" wall.
And, yes... boring a block that big simply to sleeve it back to standard is counter-intuitive.

For best cylinder wall integrity, don't bore a cylinder any more than necessary.
 
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