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thirstybob · 04-04-2020, 08:59 AM

I was surprised to see these on my truck. Can anyone tell me whether or not there is any benefit to having these heads on my '74 C20/454? The engine runs really well, nothing fancy.
The casting numbers are 3917215. I understand they are from a 68-69 396/427.
Closed chamber (I don't know what the means)
Are they beneficial for performance or no?

04-04-2020, 08:59 AM	#1
thirstybob Registered User Join Date: Mar 2019 Location: Denver, CO Posts: 42	Head ID 3917215 I was surprised to see these on my truck. Can anyone tell me whether or not there is any benefit to having these heads on my '74 C20/454? The engine runs really well, nothing fancy. The casting numbers are 3917215. I understand they are from a 68-69 396/427. Closed chamber (I don't know what the means) Are they beneficial for performance or no?