[Amc-list] Concord header and perf

[Jesse <j2sax@xxxxxxxxx>]

I agree that the header with a stock engine is probably overkill.  

In reality, I would expect more than 5-10 from the 4.0 head change, however, not as much as the claimed 40HP on some websites.   If the head is rebuilt and placed on a low compression, worn out 258, the HP gain will not be as much.   In fact, it may do little more than increase the blow-by at the rings and increase the Crankcase pressure.  

If you really want to increase the power, a good cam and upgraded distributor/ignition are a must, in addition to the aforementioned mods.  Everything has to balance together.  

I had a hopped up 258 with a Crower cam, Clifford intake, Hly 390, and dual outlet header... 2.5 ex out to the rear and 2.25 over the rear end.  It was not a killer off the line, but actually pulled strong to almost 5000 and a little beyond.  Had 2:73 gears, with a 5 speed so a little more gear would've helped off the line, but I could get to 130 before the angel jumped off my hood and I started floating!  Ohhh if the 4.0 head exited back then , I would have had a time!

ANyway, the header is not the best place to start... save your money until you can get at least the intake and ignition to go along with it.  Cam would be that much better.  Good muffler is best, cheapest way to get a good sound, though not a huge jump in power.  

Have a great Christmas, 

Jesse
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