Quote:
Originally Posted by Jay S
The 417NP cast pistons are modeled from the 73 and later pistons. The 72 455’s that I have seen did not have the bevel on the top. I just worked on a original 72 a few days ago. The 417NP pistons have a fairly low compression height (1.481”) , and the piston top is likely .020”-.030” below the deck. That range is depending on if your engine has ever been decked, but it likely falls somewhere in that range unless it was zero decked.
From what I recall the total cc’s is suppose to be between 10 and 11 cc’s on those pistons. The compression will be about 9:1, maybe upper 8s.
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9:1 I could definitely live with for now, I don’t know if it was zero decked, but I doubt it. I’ll have to confirm that, as well as a few other things it seems.
Quote:
Originally Posted by 77 TRASHCAN
I'm not reading. ALL of your ideas/intentions, possibly???
Do you plan to re-use the 66 heads (some of the largest chambered Pontiac heads made?)
The double chamfered pistons are not desirable, BUT in you case, wanting a ONE year temporary engine, they would be ok (my opinion). Use those pistons (even with a low compression, large chambered head).
The 068 or the Summit cams 802 would be sufficient for this "temp" engine. Melling sells their SPV- 7 cam, it's the 068 copy. A great thing about using it IS, it utilizes stock springs.
Your engine would run well enough, in my opinion. Allowing you to step up to something more powerful in the future.
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Oh no, those 66 heads are not going back on!
My plan is to use the 6X-4 heads with the 93ishcc chambers. My issue then became I was planning on a 041 style cam but now I don’t think I’ll have the compression ratio for it to really make sense.
I think I need to do a little more digging on these pistons and my setup so I can get the CR more accurately figured, then I can make a solid cam choice and enjoy it for awhile until I build the new engine. Leaning towards a 400 based stroker I think.
Quote:
Originally Posted by 25stevem
If I was the OP I would be making a call to sealed power to get the CC info on that piston.
All the on line photos I have seen of that piston show no chamfer and far smaller in width valve notches.
If what he has there is only a total of 11 CCs he is lucky!
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They definitely look nothing like the photos I see online of the current NP417 pistons, that’s what makes me think the CCs on these may be even more drastic than I thought on top of the fact they are likely .020-.030 in the hole from what I’ve read as well.
If these are even worse than I thought, I’m wondering if I would actually be better served going to one of the older 72cc heads if I can determine the CR properly…