CNC Cylinder Heads-Any Experience?
Pro
Joined: Feb 2001
Posts: 662
Likes: 0
From: Denver CO
Re: CNC Cylinder Heads-Any Experience? (Joe90)
Joe,
Sorry to hear about a shady dealer like him. Anyway, I am glad you got a something in return. I will never call on him for a part, that is for sure.
Cheers,
Robert
Sorry to hear about a shady dealer like him. Anyway, I am glad you got a something in return. I will never call on him for a part, that is for sure.
Cheers,
Robert
Melting Slicks
Joined: Apr 2002
Posts: 3,019
Likes: 0
From: down that one road next to that big tree
Re: CNC Cylinder Heads-Any Experience? (Bob Mosaic)
joe 90 see my sig, engine is very very similar. i'll have dyno results in a month or less. i'm very curious what kind of hp the smaller zz4 cam will make compared to yours.
Safety Car
Joined: Jun 1999
Posts: 3,570
Likes: 3
From: Austin, Singapore, Kuala Lumpur, Houston, Dallas, Hong Kong, Elgin, etc.. Texas
Re: CNC Cylinder Heads-Any Experience? (Joe90)
Just for reference, stock LT4 heads flow about 230 cfm at .500 valve lift. With pocket porting and 3 angle valve job they pick up another 20 cfm. In my case, the heads flowed almost 15-20 cfm better all the way from .100 to .480 valve lift, the limit for the stock LT4 cam.
First, the most critical area is the proper contour to the short side intake port radius and the throat area just before the valve. If the air does not follow the port wall all the way to the camber, then it will tumble and reduced the port flow dramatically. Its a very subtle but important thing that all head machinist know about.
If I was upgrading to the Hot Cam, then it may make sense to do additional port work to get another 10 cfm (or 260 - 270 cfm at .525 lift). However, under .500, it is doubtful that more port work would yield any flow improvement.
One last thing I learned during my research is flow numbers at or near max valve lift are of little importance. Since the valve spends so little time in the higher valve lift ranges, you should really be looking at flow values at lower valve lifts especially in the .100 to .300 lift where the valve spends the vast majority of its time.
First, the most critical area is the proper contour to the short side intake port radius and the throat area just before the valve. If the air does not follow the port wall all the way to the camber, then it will tumble and reduced the port flow dramatically. Its a very subtle but important thing that all head machinist know about.
If I was upgrading to the Hot Cam, then it may make sense to do additional port work to get another 10 cfm (or 260 - 270 cfm at .525 lift). However, under .500, it is doubtful that more port work would yield any flow improvement.
One last thing I learned during my research is flow numbers at or near max valve lift are of little importance. Since the valve spends so little time in the higher valve lift ranges, you should really be looking at flow values at lower valve lifts especially in the .100 to .300 lift where the valve spends the vast majority of its time.
Melting Slicks
Joined: Apr 2002
Posts: 3,019
Likes: 0
From: down that one road next to that big tree
Re: CNC Cylinder Heads-Any Experience? (Mez)
see above exp..this is why a L98 Dport and a 441 casting have the same .500 flow stock but the L98 will be faster. mid flow is MUCH stronger
