mountain4x4
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I am considering Vortec Heads for my '90 Burban. The intake manifold gaskets are leaking, so while I'm at it... BUT, it will be pricey. Used Vortec heads are about $250. If they need any work, you might as well buy them new. Chevy makes a TBI/Vortec intake mani. for $300, or I could get a Vortec style carb mani. and an TBI adapter plate and save $100 or so. The computer should be modified for this. In my research, not my own experience, I found the CR will be 10:1 with Vortec heads and flat-top pistons in a 350. The heads are more effecient, and require less timing than the older heads, and the increse in CR will require less timing as well. The volumetric effeciency will go up, especially with a free flow exhaust system and intake, so the fuel maps will probably make the motor run too lean. Lean burn plus over-advance timing = melted or cracked pistons. I was thinking of gettint the EPROM emulator and laptop software to custom tune the motor, Emulator is $180, software is $100, plus time on the Dyno or a W/B o2 sensor and gauge to make sure it's tuned right.
Regardless of airflow numbers, the Vortec heads develop more low end torque than the tbi heads, and probably most aftermarket heads due to the effecient heart-shaped combustion chamber design, and will probably be equal to or better than many aftermarket heads at higher RPMs. Vortec heads were designed for a truck. This isn't backed up by Dyno testing, so take my OPINIONS for what there worth...
If CR is a concern, you could open up the combustion chambers in the Vortec heads, and give it a nice polish job. If you CC the heads to the same volume, it'll be an improvement in performance as well as an adjustment to the CR... This is what I'm doing with the 113 cc heads I'm using in the 496 I'm building for my '74 GMC camper special, it's a good day's work, but not too dificult. I did the preliminary port/polish work first, then the valve job, then cc the heads and make adjustments to get all the chambers the same size.
It'll be over $1K... Maybe I'll just slap the $20 Gaskets on and wait for a full rebuild with a 383 rotating assembly or (most likely) a 350 Vortec swap. I can get a 350 Vortec/4L60E complete for the swap for $2K. It'll make 300 HP with intake, exhaust, and computer mods. Had one in my fj55 'cruiser and it was pretty swift and got 20 MPG!
Regardless of airflow numbers, the Vortec heads develop more low end torque than the tbi heads, and probably most aftermarket heads due to the effecient heart-shaped combustion chamber design, and will probably be equal to or better than many aftermarket heads at higher RPMs. Vortec heads were designed for a truck. This isn't backed up by Dyno testing, so take my OPINIONS for what there worth...
If CR is a concern, you could open up the combustion chambers in the Vortec heads, and give it a nice polish job. If you CC the heads to the same volume, it'll be an improvement in performance as well as an adjustment to the CR... This is what I'm doing with the 113 cc heads I'm using in the 496 I'm building for my '74 GMC camper special, it's a good day's work, but not too dificult. I did the preliminary port/polish work first, then the valve job, then cc the heads and make adjustments to get all the chambers the same size.
It'll be over $1K... Maybe I'll just slap the $20 Gaskets on and wait for a full rebuild with a 383 rotating assembly or (most likely) a 350 Vortec swap. I can get a 350 Vortec/4L60E complete for the swap for $2K. It'll make 300 HP with intake, exhaust, and computer mods. Had one in my fj55 'cruiser and it was pretty swift and got 20 MPG!
