I am running a small block with 450 hp. I have to buy new exhaust manifolds. Imco´s powerflow series locking good for my engine. Is there any one how has experience for those or can recommend adders ?
Which duration on the cam are coursing water problems?

well said too old

I was happy with Stainless Marine's manifolds and polished stainless risers on my 383 stroker engine. The engine was built by Tyler Crockett and Stainless Marine was his recommendation. If I remember right, the engine was 445 ft/lbs torque, and 400+ horsepower.

I don´t know if I like Stainless Marine´s manifolds. I have today Marrs manifolds hows look like a headers and is maid of aluminum. They has cracked inside and I am worried about my engine. I think Imco´s manifolds looks nice. Isn´t it anyone how has experience off those manifolds? My engine has a stroke at 383, 420 ft/lbs at 5200 rpm and 450hp at 5600rpm.

What is it about Stainless Marine you don't like? At least what I got form that is that you don't care for them. I honestly have to say, I'm not sure what the rest of the post was saying.

The biggest reason to go with Stainless Marine rather than IMCO is that IMCO uses a through the flange water passage just like the stock manifolds. Stainless uses a jump hose from the manifold to the tailpipe.

Blow a gasket with the IMCO's and kiss you just might suck water into your engine.

does Dana make small block manifolds?????

I ran a 406 CI spinning a 15.5 X 27 four blade Hydromotive with solid lifter Ultradyne cam to 80+ (GPS) at 4200 rpm in an 18' Formula using Stainless Marine System. Exhaust never reverted (in two years of operation) idle speed 1000 rpm. Blew a drive, way crazy too much power. Stopped dial in (needed to upgrade fuel delivery system, as leaning out at WOT) as boat was undriveable even with tabs down. Stainless Marine with the warranty is the way to go on a budget.

I believe you can get imco's either way, through or bypass, those stainless marines look way better than the powerflows IMO,and with the way Imco has been doing biz lately, TOO OLD's getting ALL of my biz.