427 ls3 headed
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Teching In
Joined: Dec 2010
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427 ls3 headed At what rpm would I expect to see a drop in hp with these heads? Heads will be ported and this is a race application. Just trying to see if its worth the extra cost or is a 4 inch build better.I have the heads not the shortblock
I personally run a Darton sleeved LS2 block with 4.125 bore and 4 inch stroke. The extra bore lets the LS3 heads breath much better than the 4 inch bore which I ran in my 403 build previously so you know what my recommendation is.
Long build thread in sig from the 403 to the 427.
Long build thread in sig from the 403 to the 427.
Go to Wallace Racing Calculators and find the' max HP RPM bases on head flow' calculator. It will give you a solid idea if you know what your heads flow at max lift. My build is too mild to take advantage of max power, but did mine just for the fun of it. Based on a stock LS3 head on a 4.06 bore and 330 cfm flow, my 376 ci engine would have to spin to around 8100 rpms for the heads to become a restriction.
With 427 ci it would be much lower, Im sure.
With 427 ci it would be much lower, Im sure.
From what I've seen, the 376/LS3 head builds carry power about 3-400RPM higher than the 403 builds before they run out of intake with the L76 intake - all things being equal. We picked up 35HP after the chopped up FAST and a NW 107mm TB was added to the 427.
From what I see the Wallace calculator is based solely on head flow. I guess its up to the builder to make sure the intake will keep up. Of course, the cam timing , compression, fueling, the exhaust, too. It just tells you at what rpm the cid cant get enough air to turn higher.
