just thought I'd share some learned knowledge in building up the 406 for my (sorry it's not a thirdgen!) 71 RS camaro.

(1) I used a crane mechanical roller, 232 @ 0.050 w/ 0.525 lift on the intake, and 240 @ 0.050 w/ 0.543 lift on the exhaust, 112 degree seperation angle, it's also a small base circle cam (for 400 stroke clearance). Anyways- NICE cam! It idles at 750rpm with a great exhaust note and a steady 13.5" of vacuum (probably woudln't get as much vacuum on a 350?)

(2) crane 1.5" gold race rockers on fastburn heads with Gm's "black crinkle coat" aluminum cast valve covers, do not clear! the side of the rocker opposite the roller tip, rubs the valve cover ever so slightly. It doesn't rub the top of the valve cover, but rather the vertical side that is closest to the intake manifold. A little grinding on the inside of the valve cover (it's 1/8" thick) and on the rockers would fix it, but i'm probably going to switch to comp's steel rockers, as they are just smaller in all dimensions and should clear no problem. The interference was not bad, it's just enough that the rockers "scuff" the valve covers.

(3) the fastburn heads have an lt1-derived exhaust port. header flanges may need modification to get it to seal and match up right.

anyways, the rest of the combo for anyone who's curious.

gm 400 block 0.020 over (yes yes, this makes it a 405 not a 406)
fastburn heads
arp 7/16 rocker studs
crane 1.5 gold race rockers
crane 232/240 0.525/0.543 mechanical roller + crane recommended springs
crane vertical locking bar pro series lifters
1 5/8 headers (maybe 1 3/4 in the future..)
edelbrock performer rpm air gap for vortec intake
holley 3310 750cfm carb
scat crank, stock 400 stroke
KB 22cc dish pistons
total seal gapless rings (2nd ring is gapless, rest are conventional)
summit stage ii 5.7" connecting rods (not sure if they sell these anymore)
fluidampr harmonic damper (not sure if it's a contributing factor or not, but the engine is soo smooth. no shake or vibration at all).
compression ratio is right about 9.6:1. A little low for an aluminum headed motor, I kind of regretted not going with the 18cc dish pistons for a bit more compression. But this is a 100% pump gas motor, and california only has 91 octane....

one of these days i hope to dyno test it.

 

more info if it helps anyone with their buildups...

i had to get rid of the crane guideplates, the rockers just weren't lining up good enough on the valve stems. I got some isky adjustable guideplates, problem solved.

i went ahead and switched to the comp steel 1.52 rockers, this solved my interference between the rocker arm and the valve cover on the pushrod end of the rocker. the comp's are physically smaller in all dimensions (being they are steel not aluminum).

had tons of problems sealing the rocker studs (the rocker stud hole protrudes into the intake runner, like the AFR aluminum heads). tried teflon and non teflon white goop, coudln't get it to seal. went to silicone, problem solved. anaerobic sealant also probably would have worked.

also, the motor has seen about 50 miles now so the rings are starting to seal up, and with the leaky rocker studs fixed, the motor is actually pulling a VERY steady 19.5" of vacuum at 900rpm now. quite insane for a 232/240 cam, i guess being a mechanical roller with the fast ramps, this is just how it is. The cam was checked and degreed, and it was on the specs.

A pic or two for anyone who's interested. these were obviously prior to getting rid of the crane rockers and prior to dropping in the car. I'll try to get some updated ones in the car.. Does anyone care being that it's not a thirdgen? someone let me know if it's of any use to anyone.

 

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I just ruined my underwear.


Very nice, wish my aluminum heads would hurry up.