406 SBC feature in CHP

Allright guys i have a very similar setup to the impercinator 406 that chp built with the vortec heads. Here is my setup:

406-stock crank with 5.7 eagle rods with .30cc dish pistons about 9;1 compression

Vortec heads with screw in studs, guideplates, and high 500 lift springs

Edelbrock RPM air gap intake

Rocker arms... to be decided after cam selection 1.5 rollers or 1.6's

Current camshaft is a comp XE268 with .477/480 lift and 268/280 duration

My question is would i benefit from switching my cams while the motor is apart? I see that CHP used the lunati camshaft with:Adv. Duration: 292°/292°
Gross Lift: .480''/.480''
RPM Range: 2000-6000

Should i use this cam or keep the one i have, or maybe go even bigger? I really want to get a high duration one so it will sound real nice but i know you can just throw a big cam at a motor and make it run awesome.... let me know guys

very close to my motor also i also used the 268X cam but i have 11:1 compression and ported iron heads that flow a little ways over vortechs

but from what im seeing from the extreme energy is the faster snapping open of the valve, which actually is what comp says sets that set of cams apart, the higher duration would defitnely push the RPM up farther and would make more torque but would make it higher, i like my cam and id look at each RPM point at CHP's dyno chart before switching to see where its going to spend more of its time. Also what i see in the lunatti cam is single pattern, the vortech heads's E/I ratio i think would like a dual pattern better but your not running a lot of compression so that might be up for grabs

also for the choice of your rockers check out CHP's flow chart of the vortech heads and see if they would like the slight amount of more lift, the extra lift might be pushing your springs a little more than youd like depending on what there like. on the impersonator II the AFR's didnt flow as well down low as my heads so i didnt use a 1.6 rocker because i didnt fiugre i needed it, a ratio increased will give a slight amount more duration but it increases overall valve speed so it might not be good on guides if its a motor thats going to be driven a lot of miles (that also comes into play how long the springs will last with increasing the lift even more)

hope this helps in your decision a little

Hey, great minds think alike. I also have a 406ci. Also im runnin the 30cc dished pistons from Keith Black. I also will be runnin the 5.7 4340 Eagle or Scat rods with a 5140 3.75" crank. The cam I am using is a Comp Cams. Specs are duration 224/230 at .050 with a lobe seperation of 110. The lift is a little bit bigger at .502 on intake and .510 on exhaust side. Cam range is from 1900 to 5600. This cam will give a lopy nice sounding cam but is on the edge of being streetable for an everyday driver. Im unsure of what the Impersonator head intake and exhaust specs are but I am running ported Dart Iron Eagles which flow 300cc on intake and 245cc on exhaust with guideplates. Probablly going to run an Edelbrock Victor Jr. or an Edelborck RPM Air Gap.

hey homie your cam is pretty much right on w/ the lunati. run a 1.6 ratio rocker and you'll increase lift by .30 and add 3degrees of duration. So your cam specs will be 271 with a 507" lift on intake and a 510" lift on exhaust. though your still lacking duration you'll make up in lift. you'll pull near numbers with your motor.  

Hey-

   I had a quick thought. I am currently running iron heads, (Dart Iron Eagles) with 64cc chambers. Im running 30cc dished pistons that give me around 8.8:1 compression. Im thinking about dropping in 22cc dished pistons to raise the compression to 9.4 or 9.5. I was wondering if this compression is to high for a street driven 406 on premium pump gas, will this compression cause premature detonation on iron heads if run on premium gas?

-Mark

You'd be o.k. with 9.5cr with pump gas.  Although, changing slugs to raise cr by 1/2pt is a lot of work and expense.

There's easier and cheaper ways to accomplish this.  Consider milling the heads or installing thinner head gaskets.  Check out this site, it's the best I've ever seen for calculating cr.  You'll be able to determine what impact reducing your chamber size or thinner gaskets will have on static cr.

www.mindspring.com/~steveflyer/compression.htm 

Hey-

   Actually the expense would be minimal if any, I just got a set from Summit and would be able to exchange them for the 22cc's and they both are for use with 5.7" rods. But I will definitely check out that website. Im hoping this 406 will be close to CHP's impersonator II and so far I should be close.Im runnin ported Iron Eagles with a cam with 224/230 duration at .050 with 110 lobe seperation, the lift is .502 intake and .510 exhaust and may put a set of pro-magnum 1.6 or 1.5 roller rockers. Any ideas for the Crank..? I was looking at the Scat9000 series that CHP used and also at a 5140 forged crank. I was planning on using 4340 Scat or Eagle 5.7" rods. Thanks for the help.

-Mark

Ahh, the timeless crankshaft question... cast or forged?

General rule of thumb for a sbc:  Limit cast cranks to 6,000-6,500rpm and/or 400-425hp.  Anything more than that and your standing at the edge of the abyss.

If you can afford a forged crank, then spring for it.  Cheap insurance in the long run.     

Well we returned the 30cc's to Summit and we are going to get the 22cc's instead to bump up the compression. Also for the bottom end we went with the Forged 4340 Eagle 400 (internaly balanced 350) crank for $360 (pretty good steal). We plan to use the longer 5.7" Eagle or Scat 4340's. The car is a '78 Camaro Z28 and ground clearance is minimal. I was wondering if anyone had any insight on any pans or ways to get a good oiling system with the minimal ground clearance.

-Mark