I should have triple checked everything one more time before having machine work done. After going through my parts for a 400 engine build up for our next club meeting, I found that the pistons I have are way higher in compression than what I initially thought they would be.

In short, the compression ratio listed was with a 9.025" block deck height. I forgot to take that in account and had my block decked at 9.000". The block and balanced rotating assembly have been done for sometime now (over a year).

Current setup:
Pro lightning 64cc iron heads with angle plugs
Comp 284XE cam
406 block bored and honed for hyper pistons and decked to 9.000".
10.8:1 flattop H616P pistons (6cc relief) (based on 9.025 deck height). Actual compression will be around 11.5 with 9.000 deck height and .040 gasket. :(

So now I need to make some choices; change pistons or heads. :confused:

If I change pistons, I was thinking of changing to a 18cc dish Keith Black Piston Hypereutectic KB147, that would give around 10.2 (I could not find any info on referenced deck height but used the handy program by Pat Kelly to determine compression ratio), with a comp XE284 cam, the DCR will be around 7.96:1. I am not sure how the balance job and piston bore size clearance would be effected going from the hyper H616 to the hyper KB147. The min clearance for the H616 is listed at .0015" while the min clearance for the KB147 is .002". I guess I would have to measure the bore.

OR

Leave the current flattop pistons alone and get different heads. The heads right now are Iron Pro-Lightning 64cc angle plug heads and are unassembled. I have all the valve train parts, just put it together in a day. But header selection for angle plug heads for a 64 is very limited but did find that the hooker super comp 2116 would work. I was thinking of bare Dart Iron Eagle heads with straight plugs for better header selection.

I think changing pistons would be my best choice, any suggestions. Thanks. - John

Looks like the easiest deal would be to change to a 72cc head.
Should put you about 10.5
Changing the pistons should not be a problem as far as the clearance, it is built into the piston not the bore but you will probably need to rebalance the crank.
If the new pistons are a little lighter (10 gms or so) it's not a big deal but if they are heavier you should rebalance.
I have "overbalanced" cranks for the purpose of tying different pistons before where I balance the crank for the heaviest piston planned. This is not a problem within reason.

Thanks Mike,

Sounds like I need to change the heads to 72cc for the best solution. Swapping out pistons and rebalacing would probaly cost more than buying new 72cc heads and unloading the 64cc heads.

With 72cc heads, the scr would be 10.6:1 and dcr would be at 8.3:1, close to the border for pump gas with iron heads. If I adjust the cam 4 degress, I can get the dcr to 8.0:1. Replacing the .038 thick gasket with a .045 gasket drops it down a tenth also but increases the quench distance hmmm...give and take.

Since I am going to need to replace the 64cc heads, would spending some more and getting Aluminum heads be a better upgrade for tolerating the higher compression?

I have seen some good deals on bare canfield or lightning heads. I already have the springs and hardware. Ideally, the afr 195 would be sweet since they have a 74cc version, but I think they are out of my price range.

Thanks - John

By all means go to the aluminium if it is in your budget. You should have no problem at 10.5 with the alum. with that cam.
The AFR is by far the best out of the box head out there but as you said it isn't the cheapest but I feel it is the best "bang for the buck" ;)
We do sell them but they are about $1200 for the 195's