[Amc-list] AMC 304 Stroker build (some thoughts)

[Nick ALFANO <71amx@xxxxxxxxxxxxx>]

Greg,
 
A couple of things to think about here.  Your internally balanced engine is going to need to be rebalanced now with the KB pistons.  They are not the same material or weight as the Venolia pistons you had when the rotating assembly was balanced.  I am sure you know this but by what you wrote below, I wasn't sure as it sounds like the fact that everything was already balanced was part of your decision making.  Now look at the real cost of the KB pistons.  Roughly $250 for the KB pistons, somewhere in the $260 range to bush your rods and outside the pin, cut valve pockets could cost $125-160 and anywhere from $250-400 (depending on if more heavy metal is needed to the crank) to re-balance your engine.  KB pistons for this engine would be fine.  I wouldn't go too high on compression with them as they are not as strong as the Venolia (or other) forged pistons.  
 
Another point on hp numbers.  You can't compare the hp & tq ratings on AMC engines from 68-71 with numbers after 71.  They were calculated differently.  Example, a 70-71 360 4bbl had 290 hp & 390 ft lbs of torque Vs 220 hp & 315 ft. lbs tq in 72 after the gov made auto mfg change where and how the numbers were calculated.  In comparison, the 304 in 70-71 was 210 and 300 and in 72 it was 150 & 245.  So your number comparisons below are not scientifically correct as the base lines are not gathered the same.  It will take a number of improvements on a 304 (even with a stroker) to outperform a 360 built with today's technology.  That is not to say it can't be done, just that it takes a lot more work to get there.  

To say a super stock class 290 is stock is a huge understatement.  I can tell you the guys running in the super stock class have anything but a stock engine.  They have to use parts that are within a certain +- of what was available from the factory but that is where stock ends.  These guys spend tons of time and money doing every trick in the book to get more power and typically have way more in an engine than buying and building a 401.  Like we discussed before, some of them have spent more time and money on filing rings or the valve job than you might spend on the whole engine assembly. 
 
None of this is to say that your stroker build isn't a good idea for you.  Just that the comparisons need to take in the whole picture.  I think it is great when people think outside the box and come up with creative ways to make our smaller engines perform like their big brothers.  There is a lot of potential in all of the AMC engines.  Look at what some have done with the 258.  I have seen them out run big V8s.
 
 
Nick
 
Alfano Performance
4849-76 st.
Kenosha, WI. 53142
262-308-1302
262-942-8271 after 6pm central and weekends 
 
  Were I to start with the current 360 in my Jeep (60K on it), the cost would be A LOT higher in rebuilding, especially to the specs that the 304 is built to.  I looked into putting the 390 crank/rods into the 360, to make a 383" stroker, but I would have more $$ to put into the 360 block to prep it.  The 304 block is nearly done and the build up is internally balanced, weight-matched on components and should make more power than most would expect.  Garrett Ghezzi's SS/C '69 AMX with a 290 v8 (0.060" over) can attest to that.  He's pushing close to 480 HP and just under 400 lb/ft torque with a super stock engine & square port '69 heads.  He routinely beats out 401-powered AMC's with that car.
  
  While I don't expect my stroker 304 to make that kind of power, I am estimating that it will be in the 275-300 HP range and torque should be quite nice for the Jeep.
  
  Please note that my current 360 makes about 200 HP roughly, with 4-bbl carb/intake, headers & single exhaust and a stock 8.25:1 producing a whopping 160-hp (stock).  The stock 9.0:1 304's made 210 hp and 10.0:1 290's w/4-bbl made 225 hp.
  
  Sincerely,
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