Flow CFM on Stock LQ4 Cast Iron Heads
03-22-2005, 02:57 AM
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Flow CFM on Stock LQ4 Cast Iron Heads I have always wanted to hand port a set of heads to see what I could do after doing a lot of study on the subject and practicing on an old small block head. I have a 2000 Yukon XL, K2500 with cast iron heads (which are favored for torque due to their heat retention. I bought a pair cast iron heads from a guy in Iowa for $50 plus shipping and I have worked on them in my basement in the last month. I've also had the head milled .005" for flatness and a good hand lapped 3 angle valve job. Here are some pictures and my flow numbers without a pipe on the exhaust. Note on the nearly finished exhaust, I had drill out and insert a Helicoil. I had to do this on three of the eight exhaust manifold bolts. It seems that the truck manifolds are bad about pulling the bolts in half on the most aft and fortard portions of the exhause manifold.
Does anyone know what the approximate stock numbers are on a stock cast iron head?
Steve Bryant
Does anyone know what the approximate stock numbers are on a stock cast iron head?
Steve Bryant
Last edited by Steve Bryant; 03-23-2005 at 11:10 AM.
03-22-2005, 03:57 AM
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Steve, the LQ4 iron heads flow nearly identical to the 853 LS1 castings from past testing. I have attached some flow #s from a 853 casting.
If you are interested in getting the heads re-flowed, shoot me a PM and I'll do my best to help you out as much as possible.
Jason
If you are interested in getting the heads re-flowed, shoot me a PM and I'll do my best to help you out as much as possible.
Jason
03-22-2005, 06:27 AM
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Jason,
Thanks very much for the flow chart information. I left the Swirl Ramp and Mixture Dam in place and just tried to enhance each of them and blended the bowl and valve throat area and smoothed any hint of ripple on the short side radii while leaving the radius of the short side turn as large and as stock as I could. I used Joe Mondello's guidelines in an article from about 2001. I have several more pictures that I want to post of the before and after chambers that I have resized to jpeg that are less than 100 kB and the LS1Tech.com server won't let me. My heads were flowed with a radiused inlet on a SF-600 Flow Bench. When I swap heads, I plan on taking the stock heads to Cylinder Head Specialities in Winfield, KS and that way I can have a true Before and After on the same bench.
Steve
Thanks very much for the flow chart information. I left the Swirl Ramp and Mixture Dam in place and just tried to enhance each of them and blended the bowl and valve throat area and smoothed any hint of ripple on the short side radii while leaving the radius of the short side turn as large and as stock as I could. I used Joe Mondello's guidelines in an article from about 2001. I have several more pictures that I want to post of the before and after chambers that I have resized to jpeg that are less than 100 kB and the LS1Tech.com server won't let me. My heads were flowed with a radiused inlet on a SF-600 Flow Bench. When I swap heads, I plan on taking the stock heads to Cylinder Head Specialities in Winfield, KS and that way I can have a true Before and After on the same bench.
Steve
Last edited by Steve Bryant; 03-22-2005 at 07:27 AM.
