Abina_k

Hello guys. I have a GM 4.8L Liter V8 Vortec L20 Engine. Im stuck in position where my engine builder tells me my heads dont work for my engine. I called texasspeed and bought PCR220AC 15-degree CNC cylinder heads, 64cc. when I emailed them that those heads wont work I got this back.
"These heads are for the 4.8/5.3 motor. I do not have any heads that are smaller than the 220as cast heads. The 4.8 and the 5.3 are the same bore size. The requirement of the stock valve angle is a 15degree angle . These 220 heads are a 15 degree valve angle also. These heads are the only ones that will bolt on the smaller 4.8/5.3 motors. These are the correct heads"

And my engine builder said this it is not about the valve angle but about the combustion chamber is too big for the small bore.

What should I do now?
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Es0x

In the case of purely fitting on the engine there's no reason a 64cc head won't fit on a 4.8. However on 4.8's lot's of people don't like to switch to bigger chamber heads due to lowered compression, as since 4.8's have a pretty short stroke maintaining compression is fairly important. What CR is the engine supposed to run at? I know people running a bigger chamber than 64 on a 4.8 or 5.3

Full Power

You already own the heads, right ?
Put 5.3 crank and rods in, keep the 4.8 pistons, which are flat top, you'll have plenty compression.
.
. You'll get more traction in the GEN 3 section