what are the highest flowing heads? Pontiac has heads for the LS1 now that flow 400CFM! granted they cost more than i make in a lifetime but the point is are people making good stuff for the LT4 anymore? i know that if you get a good job done on LT4 heads they can flow a hair over 300cfm with stage three porting and polishing from a good company. i was just on AFRs website and their highest flowing LT4 heads only flow a maximum of 309cfm! thats pretty crappy. does anyone know of heads that will flow more? at what hp level is 300cfm going to start choking it?

 

There are a couple others offering heads for the LTx engines but I beleive that AFR is the only one doing LT4 heads specifically. Others offer CNC porting services on the factory LT4 heads but I doubt that they are getting that kind of flow numbers with a stock casting. Some may say they come close but realistically there isn't hardly enough casting there to cut away to get the flows that AFR gets. There is also enough metal in an CNC AFR head that allow for even more port work. A friend of mine is using a set of 220's in his blown F body that runs high 9's using a Vortec YS trim blower. It is also his daily driver! He had additional port work done to his heads and his porter says they will do 310+ :eek:

But in the case of heads sometimes bigger isn't always better. Having huge flow numbers often translate to sacrificing low end performance. So it all depends on the intent of the engines usage. The AFR heads that you are refering to were probably their 215cc raised runner heads. With those heads you have to use some sort of custom made sheet metal manfold or an adaptation of a Edelbrock Victor manifold.

Sure these heads would make big numbers but at a much higher RPM where they will peak. I looked into doing an LT4 RR headed engine but the cost was prohibitive, so the plan now is to use either their 220 or 227, I have a blower application so what I may loose in low end flow and velocity will be more than made up for with some boost pressure. Even using the 227 heads requires additional work because of the sheer size of the valves and porting the valve split is a 60/40 split so that means the valves are not in the OE position. And that also means that depending on the pistons that you may use it may require a custom piston to have the valve releifs in the proper location.

 

anyone else?

 

As stated above Bigger is not always better. What is your aplication?
Your heads can be ported to a very hi level of performance. Call me if you want some help.

Greg Parker
Steadfast Performance
Cylinder Head Specialist
Engine Blueprinting
703.609.1200

 

dont underestimate LT4 castings. having it ported to a wrong combination is like a body builder who does the 1500 mile race with a 10 year olds lungs.

 

i got 480RWHP on a NA 409 LT4 with AFR's "crappy" heads... the 220's, by the way.

 

can the AFR 220 and/or 227 be ported even more?

 

sure, AFR offers them in three different stages... as cast, the "normal" or whatever they call it, and then competiton ported.

you can get any geek with a dremel or a drill to hog them out and make them bigger, but that won't necessarily make them flow better/produce more power. you can absolutely DESTROY a set of heads or an intake by disrupting the flow and/or affecting the velocity, etc. it's not stuff that i would trust many people to do... and you know that AFR has major bucks into maximizing their heads. i say don't screw with a good thing. why are you chasing a head that flows more than low 300's anyway? you can make around 600 HP naturally aspirated with 300cfm heads. if you add a power adder you can make much more and the flow is less of a restriction/obstacle. are you planning on driving this car on the street? you want your usable RPM range to be low enough that it's not a turd around town. i doubt you want a motor that has it's power range from 4500-8000.
hope that helps... :cheers:

 

i am not building a motor yet but i am making plans as to what kind of motor i will build when the time comes. i am just doing my homework right now. although i htink i would like to stay NA except with maybe occasional juice so high flow is a must and when i finally do rebuild and stroke it it will be mainly a drag car. its all just thoughts for now. but thanks for being patient with me and helping me learn more about these subjects