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Increasing Power 73 351c Cobra Jet

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What are some recommendations to increase the power in my 73 351c cobra jet block?  Not looking for a complete engine rebuild, maybe just some different tweaks to it.  I love the sound of a nice lumpy style cam.  Any suggestions or recommendations?


Thanks. ::thumb::

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1 Advance cam timing, go to plus 2

2 Bring all of your ignition timing in by 2500 to 3000 rpms

3 Headers and better intake manifold and bigger carb.

4 Throw more rearend gear at it.

5 Roller rockers , roller cam

6 Aftermarket heads

7 Is your checkbook hurting yet

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Unless you also increase your compression ratio you won't get a lot of power improvement with a lumpy cam, just sound like you should.


Your existing camshaft, assuming stock, is retarded 4° for emissions. You can pick up a small power improvement by advancing it 4° to bring it back to normal, and increase the dynamic compression ratio at the same time.


If you still have the 4300D spreadbore carburetor swapping to a squarebore intake manifold and carburetor will improve driveability and power.


Any large power increases will require better heads, higher compression, camshaft, intake manifold and carburetor, and better exhaust. Increasing compression and power on the rest of the engine components will likely result in something failing, so a complete engine rebuild would be recommend/necessary.


Like Canted 393 said, power costs money.



“If you can't explain it simply, you don't understand it well enough.”

--Albert Einstein


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Before you do anything, you need to decide - do you want it to BE fast, or just SOUND fast.


Easy peasy tweaks for more power-


1) GOOD double roller timing set (Cloyes) with adjustable keyway timing. Advance cam 4*.

2) Put the 4300 carb and iron spreadbore intake on a shelf in the garage. A simple Edelbrock Performer 351-4V intake and 750 Holley will do wonders

3) Ignition rebuild and recurve - upgrade to electronic if in the budget

4) AFTER all that's done, a set of Hooker #6915 headers and 2.5" duals will round it out nicely.


Of course, this is assuming that the engine itself is in excellent condition and has good compression and leakdown numbers.



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Not throwing any stones just information.

The term CJ or Cobra Jet ended about mid year of the 72 model. If you get a Marti for one of the early Q codes in 72 he does state it came with CJ or Cobra Jet 351. In later 72 and all of 73 the Marti will just say Q code 351 4-V.

It is difficult to do just a little upgrade, lol. Like some have said you have to look at condition. When you go with racing parts the engine life will be much shorter, a fact of life. When you stress the engine it does not last as long for sure.

For sure you do not want to try to rev lots of RPM. Torque wins the race not rpm. When a valve floats and head breaks the piston will look like this and probably ruin head and block. That piston is out of a 302 that had jumped timing chain. Stupid brother in law kept moving distributor to try to get home. The valves were hitting the pistons so broke head off and blew it through the piston and ruined head and block.

I cannot recommend any combinations been out of it too long.

Just in from spine surgeon and they want to do surgery on my neck. Disc is pinching nerves and want to clear and add a few metal pieces in there to reinforce the linkage. Sort of like sub frame connectors.

Choose wisely Pilgrim and do not abuse it.







When a man is in the woods and talks and no women are there is he still wrong??:P


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