i have a 66 327 2bbl (pwr-pak heads no acc holes) motor was in the car when i got it. Has a serpentine (one) belt system and I am in need of acc holes to mount alternator better. I have a deal on a set new in the box 12558060 vortec heads with rocker arms for 500.00 If put a set of 12558060 vortec heads and aluminum dual plane intake with edelbrock 600 cfm , will I need to do a cam change to match the new stuff, What will performance be if I dont change cams. The deck numbers are gone and I am 99% sure by casting numbers/date codes the motor is 185 base hp truck version.
By looking at the '66 327 specs on the GM Heritage Center archives, the cam is a single pattern grind and has .3987 lift on both intake and exhaust, and it's definitely a very mild cam (the 350 300HP cam didn't come out til '67, when the 350 became available). It would not have to be changed to work with the Vortec heads, but I believe a cam change to a more modern grind would be beneficial.
According to the specs I've found for the '66 truck 327 the CR (compression ratio) is only 8 or 8.5:1 with flat top pistons, purposely kept low to deter detonation in a truck engine pulling hard. With flat top pistons Vortec heads will usually give a CR about 9:1 or a little more, so I believe you'll pick up a little compression. The Vortec heads have much better flow
than your present heads, but they do seem to like cams with a little more exhaust duration (like the 350 300HP cam) because the intakes flow comparatively better than the exhausts. Stock Vortec heads are limited to .475" lift without modifications to allow higher lift. Many recommend a .450" lift limit. With the increase in compression and better breathing, combined with the upgrade to an aluminum dual plane manifold and 600 cfm carb, I believe you'll pick up 40-50 plus HP
over what you have now, it will make a big
difference. But I believe you would maximize your HP gain by going to a "split pattern" cam with a little more exhaust duration (even tho I love single pattern cams). Something like the Summit K1102 would work well. It's Summit's version of cam that many consider an "RV" cam, with a mild increase in lift and duration over the "stock" cams for an increase in HP and torque with strong lowend and will tow well. Specs are .420/.442 lift (intake/exhaust), 262*/272* advertised duration, 204*/214* at .050" duration, 112 LSA. Cam/lifter kit is $99.95 at www.summitracing.com
. This cam will idle as smooth as stock and keep you under .450" lift on both intake/exhaust.
Summit's K1103 is a step up, it's Summit's version of the cam GM Performance Parts uses in the 350HO 330 HP crate engine and the "602" 350 350HP sealed circle track engines that come with Vortec heads. Specs are .442"/.465" lift, 272*/282* advertised duration, 214*/224* duration at .050", 112* LSA. It's also $99.95 at Summit Racing. This cam will give a mild, but noticeable idle, and still have great street manners (good idle, good vacuum for power brakes, and will work with a stock torque converter).
If you would want to upgrade to a little more "modern" grind but stay with "stock" specs, the Summit K1101 is Summit's version of the 350 300HP cam (again $99.95 for cam/lifter kit), with a few thousandths more lift, and (I believe) a couple degrees smaller LSA, so it might be a little "torque-ier" than the stock 350 300HP cam, but little difference.
Something to think about
: Even if you didn't plan on a cam upgrade, with the engine far enough apart to change to the Vortec heads and intake, it will be little more $$$ and work to change the cam/lifters.