8 valve relief piston cc
 

Does anyone know the cc of the aftermarket 8 valve relief piston for 400?

Ken from what I recall in total it was 11Ccs, but no less than 10 CCs.

In terms of the compression height I have no recall on that spec for those.

Off the top of my head I don't. But wanted to mention they adjust the compression height with each bore size to keep the compression ratio constant. I also found that Icon copied those pistons for a forged unit they sell and did the same thing with the CH.

A FWIW tid bit......

Their forged pistons with 8 reliefs are listed at 6.6cc.

Post #3
https://forums.maxperformanceinc.com...d.php?t=471719

That said, there is further conversation on the subject.

And here as well.....

https://forums.maxperformanceinc.com.../t-784370.html

Probably not related here but the Speed-Pro Power Forged Pistons for a 400 states a comp. Dist. of 1.714 on their street pistons.



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If it's a cast Silvio-Lite piston then like I posted I recall them having near stock valve size notches for the 14 degree valve inclination angle and the early ones.

The early where about 3.4 to 3.6 and the later angle notches where 6.7 CCs.

I have never had a forged version of these in my hands to check out for notch volume, but if it is only 6 to 7 CCs then it would seem to me that the compression height would be darn short as compared to a factory pistion .

I would love to know the exact details!

UEM FHR Icon’s 8VR forged pistons are much different than the Pontiac’s original 8VR design, it is a different relief design. The UEM Silverlite pistons are rated at 10 cc, and as far as I can tell they are the closest to Pontiac’s 8VR design. Some of the cheap 8VR aftermarket pistons also have a big bevel on the top perimeter, I think they are just over 13cc. Sadly the style with the big bevel is one of the most common OEM cast replacement pistons.

got it figured out.
The smog chamfer is there to make it a universal 67-79 400 piston. same goes for the 8 VR
The dome volume (8 VRs 10cc.+the chamfer = 15cc.
The pin height is 1.70" vs 1.714" for the 4 VR piston. The sealed Power piston has the same pin height for the 5 bore sizes available.

info obtained from summit and Crocie Jr.

Yep. Its like 7.6 to 11.3 to one compression ratio. Somewhere in there Hahaha! We will see if I can get it to ping on 93 oct E15 here in Texas. Its at 18/36 degrees right now