Does anyone know if there are modifications needed to put 351 heads on a 302 block. I built up a new 302 and upgraded to 351 heads and then someone told me that the heads should have been drilled out somehow and that would make it a "Boss" 302 does anyone have tech info on that???
351 windsor heads on a 302 block
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In general a 302W head and a 351W head are identical and completely interchangable. Valve and port size depends more on year and application than engine displacement.
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 ports.
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 ports.
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173 Posts
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.
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you'd need headers for the 302. They're designed to be in the right location for a 302, a 351 head would be higher & out a little from where it would be on a 302.
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i would say you would need 302 headers because the difference in deck height is what gives you a different angle on the exhaust side of the head.
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I would suggest a set of 1969 or 1970 Ford 351 Windsor heads, they had bigger valves and runners, but 60cc chambers, i built up a 1988 mercury 302 non HO and the chambers where 63cc, i got best of both worlds, higher compression and more breathing power. if your going to build that 302 you should build it with 351w heads after they have been ported they do way more good than the clev. heads because they have 67cc chambers and you would loose compression and the only real extreme power gains you can get are from HIGH COMPRESSION. also run with Roller cam not hydraulic hydraulic cams will wear out and will tend to run very bad at high rpms. After my rebuild i went from 150 HP and 220 Ft lbs. to 425 HP and 505 Fl lbs. and in my little foxbody im running 9's im whipping big blocks and it blows there minds because im not even using a stroker. (its all in the gearing LOL) :muha:
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Your right, for some reason I was thinking 351 replacing 302.
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