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Old 08-24-2008, 10:33 AM
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406 Cam Choice

Looking for some help in choosing a cam to match my parts that are ready for my 406 rebuild.

Specs for the parts I am using are:
Stock GM22N 400 crank, 2 bolt mains
Stock 5.565 rods with ARP rod bolts
TRW Hypereutectic H601P, +030, 12.5 cc dished pistons, sitting .020" below deck
Bottom end was previously built, blueprinted and balanced, (low mileage 406) so I will just be adding new rings and bearings

1.6 ratio roller rockers
Patriot Performance 195cc ported heads, 65cc chamber
- setup for hydraulic lifters with 550 max lift
- Flow numbers are:
- Intake - 400L = 223, 500L = 252, 600L = 263
- Exhaust - 400L = 170, 500L = 183, 600L = 184
Edelbrock Performer RPM intake
Quick Fuel Q Series 750 carb
Hooker 2210 long tube headers, with dual 2 1/2" exhaust
Transmission is a manual WC T5

The cam I am thinking of going with is
Xtreme Energy XE274H Hydraulic Flat Tappet
Lift: .487''/.490''
Duration: 274/286
RPM Range: 1800-6000

In using this cam, I have run into issues with DCR, thus I am wondering which route is the lesser of the evils. With using the 1.6 rocker ratios the DCR should improve slightly from the below numbers.

1) Deck @ 0.020" and .039" head gasket, gives me 10.28 static compression and 8.32 DCR. The .059" quench concerns me.

2) Deck @ 0.0" and .041" head gasket, gives me 10.72 static compression and 8.67 DCR. The DCR number is too high.

I have calculated bigger cams to help out, but this is for street / strip use so want high mid torque numbers and don't want to spin past 5600.


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Old 08-25-2008, 08:47 AM
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Yeah, with all the new calculators I have been discovering / using, I think I may have lost focus on reality a bit. This is my first complete SBC buildup so I am just trying to ensure I do everything right and have considered all angles. Thanks for clearing up my incorrect rocker ratio DCR as well....makes complete sense..now that I think about it and not follow internet gossip.

I have been looking at that bigger cam too but was worried about driveability, possible brake issues and the higher redline it would create. It would definately get the DCR number inline though. For octane, I am planning to run 91 octane minimum, as this is not going to be a daily driver. I do want some lope to the idle so as you say installing a 284 slightly advanced is sounding to be my best starting point. I am installing a 2 piece timing cover as well so if need be.... With advancing the cam I would suspect this to also lower the maximum RPM of that cam as well would it not? With the stock bottom end components, I am concerned about having to spin it to 5800 - 6000.

The 10 bolt rear currently has 3.42 gears, but I am planning to go to 3.73 for a better 1/4 mile RPM. I will also be fully welding the axle tubes, adding a brace kit and an aluminum support cover to beef it up.

Do you have any suggestions where to start with the timing? I have the HEI distributor that was running in the engine previously (dynoed at 385 HP using ported camel hump heads) so was going to use its existing centrifugal and vacuum advance settings as my starting point and tune from there. The ignition system will be upgraded with an MSD Digital 6 and MSD Blaster HVC Coil.
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