Did the vortec heads make a big difference? Is it worth all the $$? Would you do it again? I've already purchased everything but just wondering if regular gen 1 aftermarket heads would do the same without the bypass headache and expense of the new intake manifold.
I bought a whole entire crate engine from GM (HT383) after my 400 started drinking oil after putting new heads on it. I wanted something with a roller camshaft after I found my old 400 had some lobes flattened when I bought it.
I did a TON of research and thought I made the best decision in the world to get that engine. And I was very happy for a month or two.. then fall and winter hit. Engine ran like crap. All my reading was from people who live in warm climates and they praise vortec heads and that GM performance intake. They suck in cold weather.
Vortec heads were meant for a multi port fuel injection system. Thus there is no heat crossover tube below the carb/tbi. With multi port you want the intake as cold as possible. Once winter hits fuel from a carb/tbi cannot stay suspended when it makes a 90 degree turn- and the fuel drops out of the air and puddles in the intake manifold. Intake manifolds usually have a waffle pattern or a bunch of "speed bumps" to help the fuel break away from the intake and become airborn again. The GM performance intake manifold is 100% smooth on the bottom.
So I bought an Edelbrock 7116 manifold. Has the waffle pattern. Has a heat crossover tube. I couldn't figure how to use exhaust, so instead that became my coolant bypass. In my case I want/need coolant to heat up fast. Going from the water pump thru the block and under the intake avoids being cooled off by the radiator and actually heats up the intake pretty fast (just a few minutes). Without it I could run 14 minutes on the highway and when I stopped the engine would sputter as the intake was icy cold. Unfortunately the casting was very porous. I was losing a lot of coolant. After I shut the truck off coolant would seep thru the intake and start puddling under my tbi. Edelbrock refused to believe me. I had pictures. So I bought a SECOND intake manifold maybe 6 months later. SAME THING! At that point I was so pissed I just dumped one or two of those tubes of alumniseal in the radiator and dropped from my 16? lb radiator cap to something like a 10 lb. Problem "solved".
Ultimately I need to get a multi port aftermarket fuel injection system. That would solve my cold weather issue and my Edelbrock TBI doesn't like it when it gets above 80 degrees either. Starts surging. (I have awesome luck, huh?)
So in my case I kinda wish I would have just put in a 6.0L LS engine... but in 45-75 degree temps it runs great! Lots of power. I don't have to work about zinc content in the oil.
Since you are a California guy then I doubt you will get -20 degree weather.
And I truly do not know why there is so much conflicting info out there about the coolant bypass. Some say they have run for years without one and it is fine. Others have issues. For me the temperature fluctuations only really showed up at highway speeds- maybe not many run 3,000-3,300 RPM on the highway? I also have a 4 core radiator from the 400/454 so I have tons of extra cooling capacity. In winter I even tried blocking off the radiator to help heat it up. Doesn't do any good with a mechanical fan and there is so much air coming in from behind the headlights and below the bumper anyway.
I've read the thermostat drilling trick works well- they said 2-3 small holes are best. But that adds time to the warmup of the engine. For me that was a big issue. Warmer climates probably not.
