Baseline engine is a 385 fastburn GMPP crate engine. Changed heads to max ported world Heads. Changed cam to LT4 hotcam and changed stamped rockers to 1.6 rollers. Changed the dual plane to single plane self racing brodix intake. The engine shop said this setup should net close to 500HP. It has gained 0HP. I have not lost any power but have gained none. Can anyone tell me what I have done wrong. THANKS

 

Single plane intake is probably too much for the mild Hotcam in a 350. Also, what size chambers on those World heads? Fastburns are ~62cc, if memory serves- might have dropped compression if your new heads have bigger chambers. Also, what size intake ports?

Other than that, the tune is about all I can think of aside from a cam that's not installed quite right or possibly not-immediately-obvious vavletrain problems.

 

What fuels it?

 

750 holly dp The head are 64cc chambers.

 

Great airflow capability doesn't always mean commensurate increase in engine power ---- because of poor burn speed and the need for large amounts of ignition advance.

You removed fast burn heads and replaced them with something that probably burns much more slowly. That could be the main reason why you gained nothng --- the increased airflow exactly matched the poorer combustion. If the engine makes slightly more power with more ignition advance, then I think you'll have found the problem.

Dropping the compression also reduces burn speed.

 

More ign advance made no more power.

 

64 cc heads put you at about 9.2:1 compression. That's kind of low for high flow heads. The fast burn heads would work out better on that combo. You would get better throttle response from a 650 carb, and a dual plane... That 750 dp is over-kill. All that would net you over 400 hp, but not much over. Either that or bring up the compression to at least 10:1 to help the cam work the way it's intended.

350 cid 426 hp 432 lbs of torque at the flywheel.
self ported vortec heads, 10.24:1 comp., xr282 hyd. roller, 3301 holley 750, and a summit dual plane. $1,800 including machining.

 

I am changing back to the fastburns this week. GM claims the hot cam and roller rockers will take it from 385hp to 430hp. I guess we will see.