Hi everyone, I am in the process of building a forged 355, lt4 hot cam, Superram Speed density setup. I'm running a t56 6spd with a 3.42 10 bolt. I have the whole setup, less heads. I have been looking at the Pro Topline heads, they are in my price range and flow great out of the box. Since the motor is a 355, I was leaning towards the 180cc heads. Should I get the 180cc iron heads or the 200cc iron heads? I was also going to buy the bare heads. I have a set of lt4 springs, retainers and locks. Would those springs fit on the heads without any machine work? The only other parts I'd need would be the valves. Any advice on 2.02/1.60 valves that will work with the lt4 springs? I assume I'd need lighter valves. Thanks for any help.

180's

A tough choice. Both would work well on this motor.
The LT4 springs are designed to work with the light weight
lt4 valves. (2.00"x 1.56" hollow and sodium filled.)
A normal 2.02 will weight more. May want to go with a bit more spring pressure. The Protopline heads come machined for a 1.46" spring. The smaller diameter Lt4 spring will not sit in the
larger spring pocket with out moving around.
The lt4 spring will need a standard lenght valve stem to get the recommended installed height.

Just got info of a set on the flow bench and they do flow very close to the advertised specs. They have a specific "blueprint" for the valve job. (special back-cuts).

HardCore HotRods