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Thread: Help with Heads
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Old 04-03-2013, 09:11 AM
oldbogie oldbogie is offline
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Quote:
Originally Posted by nvyblue03 View Post
i have a sbc 406 with eagle forged crank,eagle forged rod 5.7,kb pistons,xr288-10 cam..236 intake,242 exhaust,110 lobe @.05,edelbrock performer intake,holley 750 mech secondaries......i currently have the jegs aluminium heads 180cc intake,72cc combustion chamber, 2.02 intake,1.6 exhaust.......this motor is just not making anykind of power like i think it should.....should i change the heads and if so what should i get? i just think i need to be making more power. how does this setup look or what should i change to make power. any input will be appriciated.
There can be a lot of tuning problems but let's start on the heads, these are great heads for a 350, they just can't feed a 406. The ports on these heads can't feed the valves, larger valves would be of no help. This engine, as cammed, needs a 210 cc head. 1.6 rockers would be minimally helpful against 1.5s as they will kick the valve open further, faster on the ramp which will let the port feed the valve sooner and stretch out the time the port spends at maxed flow thus will feed the cylinder a little better as it will act like the duration of the cam was extended a bit. Over the top of the lobe the additional lift would not be helpful as the port just can't feed the valve anymore than it is. A longer duration cam would be helpful but then you get into how do you get the compression up to counter the later than you already have closing intake valve. So if you mess with the cam you're going to also mess with the heads and maybe the pistons to get a crown shape that dials the compression in. This can get complicated and expensive pretty quickly.

In the end the only real solution is a large port head while keeping a careful eye on Dynamic Compression Ratio (DCR) while your there.

Bogie
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