This has probably been discussed somewhere but here it goes again. Will early non air injection heads work on efi engine? I know late models had higher hp ratings, are they the same cc's and will the late efi intake and exhaust manifolds bolt up to an earlier head and not sacrifice any stock performance?

Brian

 

Heres my understanding.

Heads and manifolds are interchangeable between efi and carbed. The efi head has about a 0.5 higher compression ratio. The general conclusion if an efi engine is best with enough efi head and a carbed engine is best with a carbed head.

How well will efi run on a carbed head someone else will have to answer.

 

Is it true that the efi heads are more prone to cracking or is this a myth?

 

Hello BWD444,

ALL head on the 240 and 300 I6 are interchangeable and all manifolds (both intake and exhaust) will bolt up to any head like it was made for it.

That said, there are some differences. EFI heads have 16 manifold bolts versus the carb's 13 bolts. Those 3 extra bolt holes are ONLY for ease of installation and alignment of the later style manifolds, so are not necessary in any case. Just handy.

The EFI heads also have fast burn characteristics in the chambers and the computer is designed to take these into account. It'll run without them (like with an earlier head), but I don't think you'll get the best performance out of them.

EFI and 240 heads have smaller chambers so they give a tad of a compression bump.

As for cracking... I've heard this many times, but honestly don't know if it's legitimate or not. My guess is that when they reworked the water jackets inside the head to accommodate for the 3 extra bolt holes mentioned above, they introduced a structural weakness. But, that's ONLY a guess. I've never had an EFI head in my possession.