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Are 302 and 351 blocks the same?

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  • Are 302 and 351 blocks the same?

    Are old style 302 and 351 blocks the same? If one wanted to upgrade a 302w to a 351w.

    If i remember correctly,late model 351 heads flow the same as the 302 so if you are upgrading the heads the ones to get are the early style.... But the difference are the bolt size on a 351 windsors are 1/2" and they are 7/16 on 289/302...late model heads have 1.78 intake & 1.46 exhuast valves and early ones have 1.84 & 1.54 & also slightly larger intake and exhaust runners.

    Ford began using the same basic head casting for both the 302 and 351W in 1977.

    These later 351s, originally identified as 351Ks, have the rectangular 302 intake water passages and 6 intake manifold bolt holes. Original 351W heads have L-shaped water passages and 8 intake manifold bolt holes.

    Also, the late model 302/351 heads have a larger water passage at the rear,
    which means the intake gaskets are different between early and late models.

    If you swap "real" '69-'76 351W heads onto a 302 you need to use the
    351W style intake manifold gaskets, as the 302 gaskets will leak water
    at the unique 351W intake manifold water port

    You do sometimes need to drill out the steam pocket relief holes (there the real small holes you see on the head gasket) in either the block or head when swapping between 302 and 351 windsor parts. You use the head gasket as a guide. You just make sure each one in the head has a matching hole in the block.

    Am i right or am i missing something?


  • #2
    Re: Are 302 and 351 blocks the same?

    All 351 block 69 though present has been cast to accept the 3" main crankshaft bearings that all 351's have, you can't stick a 351 crank in a 302 block it wont fit, the bare blocks look similar side by side and anyone who doesnt know couldn't hardly tell them apart, but if you flip them over and look at the mains you'll see the difference, they beefed up the 351 mains to handle the added stress of the longer stroke, hence what Bubba said "oil pans won't swap" thats because of the larger mains, yo Bubba you didn't mention timing chain covers I'm thinking you can't swap them either?
    '90 Chaparral 2000SL
    5.8 Cobra
    '67 MFG Westfield Regal
    80hp V-4
    (No private messages)

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    • #3
      Re: Are 302 and 351 blocks the same?

      351 and 302 dizzy will not swap. the 351 uses a bigger diameter oil pump shaft and the 2 dizzys are different lengths.

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      • #4
        Re: Are 302 and 351 blocks the same?

        I was thinking the front main saddle seal area on the 5.0 cover will be too small, just like the rear oil pan saddle.
        '90 Chaparral 2000SL
        5.8 Cobra
        '67 MFG Westfield Regal
        80hp V-4
        (No private messages)

        Comment



        • #5
          Re: Are 302 and 351 blocks the same?

          yes 351 and 302 oil pans are different at the front and rear main. 351 has bigger mains.

          Comment



          • #6
            Re: Are 302 and 351 blocks the same?

            Originally posted by Bubba1235
            Gawd I wish this boat had come with a Chevy...
            If I had a nickle for every time that sentence had been uttered...

            Could be worse, Ford could be putting their 5.4 liter engines in there, and launching spark plugs out of the heads, left and right...

            At least they realized they have no business building engines 30 years ago, and started putting Chevy engines in 'em.

            Once you get that 351 all sorted out though, you'll probably be glad you went to the trouble.

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