1971 351 Boss / Cobra Jet Engine ?

Discussion in 'Classic Mustang Specific Tech' started by Platonic Solid, Aug 23, 2005.

  1. Can anyone decifer these 1971 351 numbers? Is it a Boss, a Cobra Jet, (can it be both?) and what's the difference anyway?

    Block D2AE-CA date 1-L-29
    Rods DOAZ-A (They are marked DOAE-A on the beam)
    Crank D1ZX-AA
    Balancer D2AE-6316-B24
    Heads D1AE date OM7 and OM15
    Exhaust Manifolds DOAE-9431-G date 9H26 / DOAE-9430-G date OL11

  2. I'll take a shot at this. All the information is from "How to Rebuild Ford V8 Engines" by Tom Monroe - none from my head. :)

    Block D2AE-CA date 1-L-29 Can be a 4 bolt main in a Boss, CJ or it can be a regular 2 bolt main block. The problem is that someone could convert it. I don't know about the date code.

    Rods DOAZ-A (They are marked DOAE-A on the beam) - The rods in all 351C engines are the same. The Boss and HO rods got high-strength bolts and nuts and got magnafluxed by the factory to make sure there were no cracks.

    Crank D1ZX-AA The crank should have a 4M or 4MA casting number on it. All 351C cranks are the same, except Boss and HO cranks were inspected for Brinell hardness - there will be a spherical indentation about 1/8 inch wide in the front or rear face of one crankshaft counterweight. The tested area is also ground smooth.

    Balancer D2AE-6316-B24 - I don't know.

    Heads D1AE date OM7 and OM15 - Listed in the book as 2V heads. The book must be wrong as I'm sure you can tell the difference. My book says the Boss heads have a 66.1 cc chamber and the HO heads have a 75.4 chamber. Of course both are also machined for screw in studs and guideplates.

    Exhaust Manifolds DOAE-9431-G date 9H26 / DOAE-9430-G date OL11 - I can't tell you.

    I hope this is some help to you.

    Edit: oh another difference between the Boss and HO motors besides the head volume is the piston. Both got forged pistons. The Boss got a pop-up piston to give 11.3:1 compression. The HO was a low compression version of the Boss that used a forged flat top 9.2:1 piston that is similar in appearance to the regular cast 351C flat top piston.
  3. Cool thanks! And I actually have that book - I'd forgotten it had all that info. :p On pg. 34 it says the rods D0AZ-A are from a 351C and a Boss would be D0OZ-F. OK, now I'll post the reason for my question:

    1971 Mustang Boss 351 Cobra Jet Motor - ebay auction.

    I have more confidence in Tom Monroe's book's accuracy than some guy on eBay.
  4. Hmm, I thought by rods you meant connecting rods - my answer related to connecting rods. Of course the HO and Boss would have hardened pushrods to go with the guideplates. I didn't realize that pushrods would have a part number on them.

    As far as I can tell that could be a Boss motor. Since it's 0.030" over, it won't be the original forged pistons. Those look like the correct style pop-up pistons though. The chambers are closed chamber as far as I can tell. He doesn't show a photo of the ports, so I can't tell whether they are 2V or 4V.

    Maybe you should ask your question on the network 54 Cleveland forum. Those guys will know a lot of this stuff first hand.
  5. From what part #'s he listed and looking at the auction, it looks to me like a quench headed 4 bbl Cleveland, not a Boss, per se, but built like one. The heads are 4 bbl quench heads, just not original Boss 351 heads. Also the rod #'s he listed were just on the caps, that means squat.As for those numbers, D0OZ and D0AZ are "part" numbers, not what you'll find, forged into the rods themselves. As for that block, thats a 72 block, the Boss blocks were 71's. And if I'm not mistaken, the 2 bolt Cleveland I have, also has that same casting number.
  6. The valve covers look like real "Boss" parts. The heads "might" be real boss heads. The rest looks like a collection of 70, 71, and 72 parts. I didn't see any intake manifold. The boss intake would be aluminum.
  7. A review of the sellers feedback shows he unfortunately sold the aluminum intake sepparately: 1971 Mustang Boss 351 D1ZX-9425-CA Intake
  8. I found boss351registry.com which seems to have a good collection of pics and info. I can't help noting the internal difference between the oil pan pictured on that website and the one shown for auction:


    eBay auction:
    View attachment 505993

    Attached Files:

  9. Last Tuesday I emailed the seller a list of simple questions:

    1. Has the engine been tested?
    2. How would you describe the idle? (smooth, lopey, or rough)
    3. Is it good for street use?
    4. What rear-end gear ratio would you suggest using with it?
    5. What would shipping cost be to my employers loading dock (06442)?
    6. Will it arrive in pieces as pictured or reassembled?
    7. Isn't a Boss 351 different from a 351 Cobra Jet?
    8. Are the heads for a 2V or 4V ?

    He replied: "I stink at typing! It would take me forever to answer all of that. Feel free to give me a call."

    I responded: "For my own protection I require documented answers to my questions. Simple one word responses to each numbered question would be fine."

    He has not replied back. :notnice:
  10. I agree. Not a good sign.
  11. Well, he's got good feedback, but he's a little misleading in his description of what he's selling, but all in all, $1000 starting bid isn't unreasonable for what he's got, if that's what you want. For that kind of money though, I'd have to insist on it being shipped C.O.D. That's what I did with the 3x2 setup I bought for the 331. Cost me a few dollars more, but I didn't have to worry about getting screwed out of $1100.
  12. What peaked my interest (and would be willing to bid on), is what he claims he’s selling: A 1971 351 Boss or 351 CJ. Not a collection of parts that closely resemble a 351 Boss or CJ.

    Though lots of positive feedback is a good sign, serious disputes often end with a settlement and both parties agreeing not to leave any feedback. Not to overlook that the whole feedback thing is a bit skewed towards the positive anyway. It’s the: “I’ll leave positive feedback for you, if you leave positive feedback for me” (even if everything didn’t go quite as smoothly as the feedback might indicate) scenario.
  13. Here are two real Boss 351 engines I own. The one on the stand is the original numbers matching 44K mile motor. The one in the car is also a 71 351 Boss block and heads. The engine has been stroked. I kind of pro-toured the car so I pulled the numbers motor and am storing it. If you need help with part numbers, let me know. Just from a quick glance, the ebay engine is basically a mix of Boss, CJ, and HO stuff.
  14. Here is a pic of the original numbers matching engine for visual reference. Also put shameless pics of the car since I am so proud of her! Afterall, she is the "Boss" :nice:
  15. The seller ended the auction early.

    Nice 4MuscleMachines :nice:
  16. I have that oil pan still with windage tray,It came off my 1972 cobrajet engine, If anybody is interested PM me
  17. something everyone seems to be overlooking is that the 351 boss and 351 CJ were two completely different animals, now the boss and the 351 ho, that's a different story. the cj was basically a hooped up 4bbl cleveland but it still only had a hydraulic cam, while the boss and ho are basically the same except the ho is a detuned version of the boss, lower compression and i think the cam was installed 4 degrees retarded, but otherwise same basic critter.
  18. also i'd say that with a D2 block with four bolt mains it was probably a 351 HO motor originally and the heads with guide plates means the heads were setup for a solid lifter cam originally judging by the C9Z guide plates anyway and being a quench head as well i'd say it's a pretty good chance that was originally a 351 HO motor. of course it could be a cobbled together POS as well, but why bother buying all the good Ford parts like the block, heads, and ford guideplates and stuff. my money is saying that was a 351 HO. i'm also pretty sure the HO's had the same aluminum intake that the boss had and the same aluminum valve covers too.
  19. I think that the HO's had the open chambered heads though. Those pictured were quench heads.
  20. That is exactly what my 351C book says. The HOs had open chambered heads and flat tops and ran about 9.2 to 1 compression. The Boss engines had a pop up piston and smaller chambers for 11.3 to 1 compression.