Ring end gap- I really don't know how to address this.
Pull them out, remove them carefully fromt he piston using a ring expander, and then mearsure them by placing them in the bore, using the piston to square them up to the deck surface. If they are too tight, buy a ring filer and file fit them. Chances are they were installed too tight because those pistons have unique specs.
My understanding is the 915 heads are 78.5 CC.
What the chambers on the heads are cut to? I was not aware that this was needed, or frankly what it is. Are we talking about cleaning up the chambers of the heads, or shaving the head surface?
I'll bet several cheesburgers they are larger than 78cc. Most factory are closer to 82-83. You mill the heads to verify they are indeed flat, adn to give the gasket a good surface to bite on to. And last, you mill to get the finished chamber volume to what you want for a desired result.
About a year or so ago I bought open chambered heads and I was informed the compression would not be high enough and I should get closed chamber heads. I was going to use the stock 915 heads on the original engine, but I came across these 915s with the bigger exhaust valves supposedly the best you can get.
The factory '67HPs came with 915s with the 1.74 exh valve. A few non HPs also have them, but most came with the smaller valve. least that's what I leanred and has been my experience. But, it's Mopar. You can never say "only" and "never".
So where do I need to be with the compression?
The 383s I build I aim for 9.8-10.2:1, depending on the camshaft. It usually requires decking the block and milling the heads.
I want to get it right, and avoid mistakes, but the reality is there is a cost concern, and no one I trust or know well enough around here.
Should I take this thing apart, or start over?
Someone say no, please.
No. I only say that so you feel better. :) I would take it apart to check things out. Then you "know".
