Tom. I have lifted the heads on the dyno with a pump gas, 8-71 roots deal when I surpassed the timing threshold trying to make power. I actually saw the compression blow out. It had Cometic head gaskets on it and I figured they were done after that. Did leak down, all good. Backed two degrees out of it and finished the dyno tuning with no problems. No water leaking, no compression loss. I was pretty impressed that they stayed sealed up after I abused them so much! Was running 14 psi with BDS trying to make 900hp. Needless to say, I'm not impressed with that blower. That engine would make 750 NA pump gas.
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