Topic: pre May '71

[desperadoron]

did any of the early '71 mustangs have the 300 hp 351 c motor?

[nham3407]

Not per the AMA Specs.  Not to say something may have slipped into the production run outside of the planned equipment, but I am not aware of any.  I have included the first page of the AMA specs detailing the engine combos. The second page was 429 combinations so I did not include as it was beyond your question.

[desperadoron]

  I though I read a article that said some ordered before May of '71  had the 300 hp. I ordered mine early April . what other ways can you tell it has the bigger exhaust  ports?

[J_Speegle]

Be careful of believing everything you read.

Haven't studied the issue but I would look to casting/engineering numbers on the heads and or the exhaust manifolds. Don't know if the heads your referring to are open or closed chamber heads but those have different markings in the upper corners visible with the valve covers on.

Considering that emissions standards can chance during the production year would have thought (may not relate to this subject at all) the change would take place at the end of the calendar year.

[cobrajet_carl]

did any of the early '71 mustangs have the 300 hp 351 c motor?

Well at least one early 71 had the closed chamber 4V heads; I had one built in September of 70. I think the heads were D1AE with the 4. But technically I guess it was the 10.7CR 285HP instead of the 11.0CR 300HP. So if you were wondering if any 71s had the D0AE heads, almost certainly not. The D1 heads have a slightly larger combustion chamber than the D0 heads which results in lower CR and HP.

There is an August 70 on ebay that has the D1AE heads.
The open chamber 351CJ was available starting in May but only 144 were made. It was a "Q" engine code instead of an "M."

Interesting that the AMA spec docs don't mention the Boss engines for either 70 or 71.