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351w heads on a 302


Logan95

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I’ve been searching for cheap heads for a little while for my 302 as I bought it with no heads.

It’s a 5.0 from an 89 f150

I stopped to visit my uncles yesterday and my cousin gave me the heads off his 2.5 ton bronco with a built 351w as he recently went with a set of AFRs

Now I’ve searched and searched, some say nothing has to be changed some say some things have to be changed. I’ve seen you can run a 302 intake, some say you HAVE to run a 351 intake.

The 302 is bored .030 over with flat top pistons, .498/.498 cam

Any of y’all have any knowledge on this? What head gasket to use? Intake? Compression issues? Headers?
 


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alpine67

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As I recall the head bolt size is different, can't remember which way, but there are head bolts made just for this swap. Otherwise they bolt right on (I think). I was going to do this very thing back in the 80's and still have the good 1970 heads somewhere in the shop and probably the bolts, as well as pushrod guide plates for screw in rocker studs . I'm sure someone will chime in if I'm wrong about needed changes to make them work!
 

Logan95

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As I recall the head bolt size is different, can't remember which way, but there are head bolts made just for this swap. Otherwise they bolt right on (I think). I was going to do this very thing back in the 80's and still have the good 1970 heads somewhere in the shop and probably the bolts, as well as pushrod guide plates for screw in rocker studs . I'm sure someone will chime in if I'm wrong about needed changes to make them work!
Yes the 351 heads take a 1/2” bolt as the 302 takes a 7/16” bolt

And I could be wrong but judging by the casting number on the heads (I could’ve decoded it wrong) they’re from a 75 truck? EB-D5TE? The heads are also complete
 

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You will lose compression as the 351 has a larger combustion chamber, the head bolts for the 351 are larger, 1/2 vs 7/16 for the 302 (as you know) which can cause issues with the heads shifting, making them prone to blowing head gaskets.

The big idea with doing it for "performance" was that the 351 had bigger intake valves and so it could flow better, the problem is that with the mistmatched cylinder and intake port/valve you end up lowering intake velocity, and reducing overall performance.

It will work if you need heads cheap to free to get the engine running, but it is a less than ideal setup, and it may cause you issues.

As for the intake, I would think you'd need the 302 intake. The 302 and 351 intakes are different widths because the blocks are different widths, (taller block at the same angle makes a wider top of the V) and the intake width should be determined by block height and angle.
 

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They'll bolt on with the right bolts but you don't want them. Mid 70's 302's and 351's used rail rockers which put tremendous side loads on the valves and wear out the guides, they have lousy ports and small valves, and big chambers to drop the compression. 69 and maybe 70 351w's had bigger valves but that didn't last. The common E7TE heads used on 5.0 Mustangs should be plentiful and cheap, they were also original equipment on 351 trucks in the 90's, that's what the 95 F150 351 I'm building for my Ranger came with. If you can find heads from a 96 Explorer they are GT40 heads with truck springs and they have the 1.84 intake and 1.54 exhaust valves used in 69 351's.
 

Logan95

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You will lose compression as the 351 has a larger combustion chamber, the head bolts for the 351 are larger, 1/2 vs 7/16 for the 302 (as you know) which can cause issues with the heads shifting, making them prone to blowing head gaskets.

The big idea with doing it for "performance" was that the 351 had bigger intake valves and so it could flow better, the problem is that with the mistmatched cylinder and intake port/valve you end up lowering intake velocity, and reducing overall performance.

It will work if you need heads cheap to free to get the engine running, but it is a less than ideal setup, and it may cause you issues.

As for the intake, I would think you'd need the 302 intake. The 302 and 351 intakes are different widths because the blocks are different widths, (taller block at the same angle makes a wider top of the V) and the intake width should be determined by block height and angle.
It’ll be temporary as I’m on a tight budget until my daughter is born and my wife is back to work, I might just sell the heads and buy 302 heads
 

Logan95

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They'll bolt on with the right bolts but you don't want them. Mid 70's 302's and 351's used rail rockers which put tremendous side loads on the valves and wear out the guides, they have lousy ports and small valves, and big chambers to drop the compression. 69 and maybe 70 351w's had bigger valves but that didn't last. The common E7TE heads used on 5.0 Mustangs should be plentiful and cheap, they were also original equipment on 351 trucks in the 90's, that's what the 95 F150 351 I'm building for my Ranger came with. If you can find heads from a 96 Explorer they are GT40 heads with truck springs and they have the 1.84 intake and 1.54 exhaust valves used in 69 351's.
I ran GT40P heads on my last 302 ranger with explorer manifolds. Is there any headers you can run with those heads? The manifolds seem pretty restrictive
 

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The "P" heads would be later, 97 at the earliest and they sacrifice some HP for low end torque and emissions reduction. 97 Explorers had the world's crappiest tube headers, the awful 98 manifolds were an improvement. It would be worth looking into building your own headers if no one offers them. 96 Explorer GT40 heads work with ordinary Windsor family headers or manifolds. There are a lot of small chamber/higher compression 289 heads out there but some have tiny valves, which would be OK if you're looking to build low RPM torque and not worried about high revs.
 

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the 351 and the 302 engines are the same. Any ford head for a small block ford is going to be complete garbage. Even the gt40 x/y/p/z etc... heads are all junk. It's not worth wasting the time and effort to swap anything other than an aftermarket head on a sbf.
 

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Someone used to make head bolts to do exactly what you're asking. I don't recall who. They were 7/16" thread with a 1/2" shank.
 

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the 351 and the 302 engines are the same. Any ford head for a small block ford is going to be complete garbage. Even the gt40 x/y/p/z etc... heads are all junk. It's not worth wasting the time and effort to swap anything other than an aftermarket head on a sbf.
That was helpful... :rolleyes:
 

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the 351 and the 302 engines are the same. Any ford head for a small block ford is going to be complete garbage. Even the gt40 x/y/p/z etc... heads are all junk. It's not worth wasting the time and effort to swap anything other than an aftermarket head on a sbf.
Depends on what you are doing. For a 4x4 that needs low end torque aftermarket heads are a joke.

But for racing they are far less than ideal, depending on what hp goals are I tend to agree.

I put a wanted ad on craiglist for E7's and like three Mustang guys responded wanting to offload their perfectly good E7's they had replaced with aftermarket heads. $75 later I had a pair of heads.

Aside from the headbolt dia I don't know if there are intake differences or not. The 351W block is wider so a 351W intake will not work.
 

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Depends on what you are doing. For a 4x4 that needs low end torque aftermarket heads are a joke.

But for racing they are far less than ideal, depending on what hp goals are I tend to agree.

I put a wanted ad on craiglist for E7's and like three Mustang guys responded wanting to offload their perfectly good E7's they had replaced with aftermarket heads. $75 later I had a pair of heads.

Aside from the headbolt dia I don't know if there are intake differences or not. The 351W block is wider so a 351W intake will not work.
I know a guy who literally has stacks of E7 heads in his shed. Came in handy last December when we were doing head gaskets on his buddy's truck and found a crack between the valves in cylinder 8.
 

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The Explorer GT40 heads on my Mustang allow it to run a 13 second quarter mile on street tires with a relatively mild cam with a reasonable idle and get about 20 mpg on the highway. I'm using mildly ported E7TE heads on my current 351 because the RPM range I want will be lower and I want to keep the port velocity high. The philosophy if enough is good, more is better, and too much is just right doesn't apply to heads, cams, or carburetors unless all you're after is bragging rights.
 

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Those heads if D5TE have the smaller chambers at 60cc, later years were at 69cc.
 


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