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Ford's Big Bore Boss 302 block

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mlplunkett:
I'm planning the engine build for my 65 GT350R tribute and want to use modern internals (a 302 roller block) while maintaining as much of the original external appearance of the Hipo 289 as practical. I'm thinking about stepping up to the large-bore Boss 302 block from Ford Performance. It would give me the strength of 4-bolt mains and additional interior webbing, roller lifters, extra displacement from the 4.2" bore (in addition to what I would get from 331 stroker components) and with aluminum heads (my only external giveaway) and 10:1 compression I think I'll have upwards of 450 HP. Is anyone aware of anything about these blocks that would prevent me from using all the other Shelby external parts (intake, carb, valve covers, distributor, competition oil pan, etc.) to make this modern block look like a 289?

https://shop.watsonracing.com/BOSS-302-CYLINDER-BLOCK-BIG-BORE-M-6010-A460BB-p/wr-6010-b302bb.htm

gt350hr:
  Maximum safe bore on those blocks is 4.155 not 4.200. They do not accept a "standard" camshaft because of the "common size" cam bearing machining. 1/2" head bolts ( 351W) head bolts are required as well. The block is significantly heavier than an early 289 block. "I" would ( and have) use a '65-69 block and add Cobra Automotive "HiPo" caps. My 520hp 331 has done this for 20 years without issue. However it is your money.
   Randy

98SVT - was 06GT:
Trust Randy - put that $2,100 somewhere else in the motor. The best rotating parts you can find is the secret to long life at high RPMs. If you're stuck on four main bolts find a good used Boss 302 block. Of course the screw in freeze plugs will be a give away.

gt350hr:
   "My way " is NOT  "the only way" for sure but it works. The "big bore" is not a great advantage on an "inline" valve head. It is a big deal on a canted valve ( Boss 302) head. Been there , done that. As my friend pbf777 reminded me there IS a "conversion" cam bearing set from Durabond that allows the "standard" cams to be used. "I" would still spend less and use a stroker crank/rods , just me.
   Randy

pbf777:

--- Quote from: mlplunkett on August 30, 2021, 11:27:26 AM ---Is anyone aware of anything about these blocks that would prevent me from using all the other Shelby external parts (intake, carb, valve covers, distributor, competition oil pan, etc.) to make this modern block look like a 289?

--- End quote ---


      To the best of my memory, the only components not compatible between the O.E.M. production blocks would be the head retention fasteners (the BOSS 302 blocks utilizes fasteners with are about 1/2" longer), a few other fasteners, the cam bearings, and perhaps a little "fitting" of the oil pan.

      Now I'm not sure how much like an O.E.M. 289 block you expect to try and make any of the current production aftermarket blocks to be, but the castings are quite different in external appearances.

      If I were wanting an improved block over the production unit, but that replicated the originals' appearance, the one to find is the older Ford Motorsport M-6010-A4 unit (though these were not intended for the .125+ over-bore); but these are not easily found as they are searched for by many others with the same intent.     ;)

     Scott.
 

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