[Amc-list] 304 head swap

["Bruce Hevner" <scramblr@xxxxxxxxxxx>]

 I have done the 290 head swap both ways.
I had a Javelin which had the 343 in it. Since it was a daily driver I
didn't want it out of commission while I modified the heads for "stock"
class racing. I bought a set of new castings from the local AMC dealer and
modified them in my spare time so I could just swap heads and keep the car
on the road.
I did a 3 angle valve job, a little "blending" in the bowls, cc'd and milled
them to the minimum and a set of stouter valve springs. It definitely helped
the performance but not by a lot.
  Anyway that left me with the OE stock heads. A friend of mine had a 290
AMX and wanted to see how much a "big valve" head swap would help. While the
heads are a bolt on replacement I still needed to notch the cylinders AND
the piston notches. I did this IN THE CAR by greasing the gap around the
piston at TDC and then using a die grinder to notch the pistons and edge of
the block till I had .060 (using clay) at all points. As you might imagine
this took a LOT of time!! The results were mixed. It absolutely KILLED his
bottom end power and response but did help power after about 3000 RPM. I
couldn't say what the difference was since this was "back in the day" before
gTechPro and dynos were so readily available. I would say it probably was
faster overall, just can't say by how much.
 Then later on I wanted to do some more work on the Javelin heads (which
were on the car) so I decided to temporarily use the 290 heads. While it DID
increase the mileage and low RPM response by a good bit. It KILLED power
above 3000 and I was BARELY able to make it to the shift point of 4500 RPM
(automatic with a shift kit).
 So if I were giving advice to YOU (not knowing the rest of the specs on
your build) I would STRONGLY advise you against the big valve heads UNLESS,,
you have a 4 speed trans and a decent gear (3:70).
I do NOT think you would be happy using that combination in a heavy car with
an automatic and 2:70 rear end!!
REMEMBER,,, it's the RIGHT COMBINATION that wins the race!!!

But HEY,,, that's just ME!!
Bruce Hevner
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