Quote:
Originally Posted by ModelA29
New grade 8 studs have a much higher yield rate than the originals which were probably grade 5. They all rely on some stretch for their holding power. The grade 8 stretches less so it doesn't fatigue as fast. Most newer cars torque the heads 90-100 ftlbs and at 55 lbs the grade 8s should last many rebuilds. Has anyone tried 55+ lbs with the new bolts? My 289 HiPo would blow the gaskets at the stock torque but 5 pounds extra and the problem was cured.
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I presume when you said “bolts” you meant “studs”. I have a 5.5 head and replaced the studs with the high strength when I replaced the head gasket a few months ago. I’ve torqued the head to 65 ft-lb four times now, and each time fewer and fewer of the nuts move. This is a combination of the gasket finally losing its resilience plus stud stretch. (I use the Best graphite gasket #509 plus copper spray). This is the third engine I’ve used the high strength studs and the Best 509 on, quite pleased with that combo (the other two had 4.2 heads so only torqued to 55). I will likely use these same studs and gasket on my Burtz build with the 6.5 head.