351 with 302 heads

[Bryan Wilson]

Does anyone know of any problems with putting 302 heads on a 351 block any pros and cons are welcom.
Cheers,
Bryan

[Rick Parker]

As long as the compression ratio is acceptable you're OK. Some applications have valves that are smaller than 351 OEM spec but the architecture is the same.

[Igofastr]

Doesn't the 351 use larger head bolts?

[Bill D]

Originally Posted by Igofastr

Doesn't the 351 use larger head bolts?

Yep! OEM 302 heads have 7/16" head bolt holes. 351 heads have 1/2" holes. Most if not all aftermarket heads have 1/2" holes

[diverrick]

Years ago when I used to run fast, I built a 302 up from scratch. I used 351 heads on the 302 block. That gives you bigger valves as well as a bit more volume. Then I added pistons that had to be machined to fit. It all adds up to more power. Not sure why you go the other way and put 302 heads on a 351 though. Maybe for higher compressions?
Trying to remember if the 351 heads didn't have stronger valve springs as well.
One note though. If you are planning on pushing the engine, make sure you swap out the pressed in rocker studs for threaded no matter which head you use, or the pressed in ones will pull out, particularly with a high lift cam. BTDT

That motor tried to kill me more than once. I finally totalled the vehicle and told the insurance folks from my hospital bed to keep the motor. I am guessing some one got themselves one hell of a motor. Bottom end was balanced within 1/4 gram!
That thing spun up like an electric motor.

[Igofastr]

Originally Posted by Bill D

Yep! OEM 302 heads have 7/16" head bolt holes. 351 heads have 1/2" holes. Most if not all aftermarket heads have 1/2" holes

Thanks for the confirmation.

My point is that the holes in the heads will be too small for the 1/2 inch bolts that the 351W block needs. I would assume that the heads will need to be machined to fit the bolts through.

[k98dave]

The Ford Racing GT40X alum heads have the 1/2" bolt holes. I used them on a 302 with the bushings that come with ARP bolt kits.

[Mark O'Neal]

Or, Edelbrock has a bushing you can use instead.

Part number 9680 at about 55.00 a set.