Larry you can bet the heads are cheated to get better flow. There isn't a single stock d port 400 head that will do that kind of job without some kind of help.. NHRA doesn't check the heads against two or three bone stock heads, they just look for casting lines and casting marks that might be in the heads. If those areas look ok then it passes. Those marks are easy to keep if you know about silicone. Silicone, some port work and acid works wonders for so called stock heads. I don't care about what the rules state, it is something everyone does! That stock car wouldn't be able to drive 50 miles without having some kind of problems. The rear might burn out of it.
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