Re: 396/375 cam for street 454?
 

Jim,

DO you have the full part numbers for the heads you
mentioned? I want to look into these a little more.

Steve

Re: 396/375 cam for street 454?
 

Good info Jim...I'm not a machinist and I was tryin to say what you mentioned about the valves and the grinding. I have always been kind of in the closed chamber world and should have deferred to the OC users. I'm going to check some of the heads I have in the shop to see if I have any of those numbers. What's your opinion on the hardened seats?? some folks don't use them..they say a good stainless valve is sufficient. I really enjoy the discusson of BB ideas....always good stuff. Thanks for setting me straight. tom

Re: 396/375 cam for street 454?
 

353049 or 356781 both are pretty much interchangable...smog pick-up truck OC Oval port heads. [OC is the only way to go...]

Just put big valves in 'em and go run high 10's.. The heads on my 496 in my GTO came off a 454 that ran high 10's and had never been ported, just unshrouded..

Wilma knows Nelson, my engine guy [he built my 496, my L-88 and my brothers 454] and another place for ultra solid advice is team Chevelle. Those guys won't steer you an inch off course..I'm 'L-78 Guy' over there....

Re: 396/375 cam for street 454?
 

[ QUOTE ]
353049 or 356781 both are pretty much interchangable...smog pick-up truck OC Oval port heads. [OC is the only way to go...]

Just put big valves in 'em and go run high 10's.. The heads on my 496 in my GTO came off a 454 that ran high 10's and had never been ported, just unshrouded..

Wilma knows Nelson, my engine guy [he built my 496, my L-88 and my brothers 454] and another place for ultra solid advice is team Chevelle. Those guys won't steer you an inch off course..I'm 'L-78 Guy' over there....

[/ QUOTE ]

Jim,

Can Nelson perform the larger valve installation and the
unshrouding you mentioned when I find a set of these heads?
I would rather go with someone that is well versed in this.

Lastly, I was planning on doing this to a 402 + 0.040 L/34
that is just waiting for something like this to happen. Do
you see any issues with valve unshrouding aginst that bore?


Steve

Re: 396/375 cam for street 454?
 

With the 396 it is a good idea to add the flow notches in the tops of the bores as well for better air flow. Without using a flow bench, any grinding in the ports can just as easily hurt the air flow numbers as increase them.

Re: 396/375 cam for street 454?
 

Nelson can perforn the work but truly ANY quality engine machine shop that has has ever built some BBC engines will be well versed in this procedure.

Unshrouding the valve in this case really, in my mind, doesn't constitute, 'chamber work'. Certainly notching the bore to match the whatever you do to the head ala 'gasketmatching' could only help as Keith mentions...all neatly done. All could be done at home with a die grinder.

Re: 396/375 cam for street 454?
 

Tom, Jim & others,

Can any of you tell me the flow differences between the
oval port heads mentioned in this thread? I don't need
actual numbers, but I am trying to understand if what makes
one oval port head better than another was the combustion
chamber, and/or the intake runners, and/or the exhaust
ports.

Stated another way, do any of the oval port heads of
interest here have significantly different intake or
exhaust flow numbers? I always wondered about all the
different heads Chevy developed and more importantly - why.

Steve

Re: 396/375 cam for street 454?
 

Open Chamber vs. Closed ...Open was Chevies answer to a Hemi...OPEN allows better spark travel..as far as port design... Ihave no idea as to why GM made so many versions of the same thing except to assume it affects the RPM which peak horsepower is made.

Open Chamber also lowered emmisions dramaticly..