My '21 has a tired '27 engine in it. I want to rebuild the '21 engine that came with the car. I'm planning Chevy valves, mild cam, balancing etc. My question is why spend $400 for a Z head, when high compression pistons are at around $120? I'm going to instal aluminum pistons anyway, why not spend a little more here, and shave the cost of the Z head of of the rebuild cost.
What pros and cons are there to consider?
The pro to hc pistons is the cost. The con is you won't get as much hp increase as with a Z or Prus head. The accessory heads gives an improved compression chamber shape with a squish area over the pistons, the result is a better efficiency and more hp than with just the compression raise you get with the hc pistons. Another con could be higher weight in the domed pistons, but I haven't had any to measure if there is any significant difference from std style alu pistons?
I have been running dome pistons for more than 10 years. With a modest cam, early type intake and Stromberg OF and a low head. The car runs very nicely. I'm not saying you will be happy though, but I am.
Sure, HC pistons will give more power than std and a lot of T's still runs ok with std pistons and head
I basically asked the same thing a while back, I have decided to use plain alloy pistons and then see if I want more in the future, I have never had a fresh engine so I may just like it fine mostly stock when done.
I've noticed the "Z" head combustion chamber promotes better fuel combustion noted by the cleaner piston tops and head chamber, not to mention cleaner burning spark plugs, especially #1 plug. Seat of the pants will tell you your engine has better "umph"
I have never heard what CR comes with domed pistons. I have some running...for 30 years and I am not sure I sense anything special...of course the engine is in a TT.
I seem to see more of a boost from the Z head than the domed pistons but there were other concurrent changes so not the most fair comparison. Just the same, I'd pick a Z head instead of domed pistons if doing it again.
BTW, from the ad in the Vintage Ford, the Z head is $310 plus $15 S&H if you order directly from Harlon or Steven Zajicek (Texas residents add sales tax). $325 to my door seemed real fair to me.
Doug -- See my post on this thread:
The combination of domed pistons and a low head milled 1/8" or so will give you similar results to the high-dollar aluminum head. The pistons cost more that non-domed ones, and having a head milled 1/8" costs about $100 here and varies with location. It's still less than the cost for the high-comp head.
low heads are not just layin around any more either. the last few on ebay have brought 125-150. at least its an iron head though
The high compression head is a bolt on accessory. It will take you at most an hour to put it on. The results are immediate. In an hour or less, you can put the old head back on, and it is back to original.... It just doesn't get any easier than that.....