piston volume question

[Ponydrvr72]

Does anybody know the piston volume increase for the 351C Sealed Power/425P piston? it's a very shallow dish, the Silvolite 1159 is the equivalent piston. Thanks in advance,Scott

 

[c9zx]

Does anybody know the piston volume increase for the 351C Sealed Power/425P piston? it's a very shallow dish, the Silvolite 1159 is the equivalent piston. Thanks in advance,Scott

If it is the w425np030 it has a .080 deep x 2.770 diameter circular dish. That would give an additional 7.90024 CCs over the flat top with two small valve reliefs (about 3 CCs). This is not any kind of performance piston as the stated compression is 7.9:1 with an open chamber head. Chuck

 

[Ponydrvr72]

Thanks Chuck, I've been researching the differences in the 70-71 2V,351C (D) blocks, 250,240 HP and the 72-74 177HP square blocks. This would explain the large drop in compression of these blocks. perhaps the 70 had only one valve relief,71,two reliefs. 72-74 dished. If my fathers brain wasn't riddled with heavy metals I could ask him, he made pistons and rings at Sealed Power for 30 years. This would also explain why i was able to get these 302C heads w/4V valves to run in my mustang, although it was a pain to start and there was hardly any bottom end from the scavenging. I cant wait too take these heads back to the supposed Pro's and say what the ? happened here, people see a closed chamber and automatically think 4v, I hope they can fix it or they bought it!