CLASS RACER FORUM - View Single Post

Tom Turner · 05-14-2017, 03:13 PM

I think the original reasoning behind shimming the hyd lifters was to stop the lifter from collapsing and thus breaking the stock rockers or blowing the pushrods through the seat. It also (if properly adjusted only gave the lifter about .0075 to "float".) The HP gains came later when we discovered that stiffer valve springs, very light motor oil and much higher RPM thresholds yielded big gains in performance. One of the few "win-win" deals in drag racing. Solids are legal now so most won't use this method anymore.

05-14-2017, 03:13 PM	#3
Tom Turner Member Join Date: Jan 2005 Location: Lake Tapps, Washington Posts: 137 Likes: 0 Liked 0 Times in 0 Posts	Re: Shimming Hydraulic Flat Tappet Lifters I think the original reasoning behind shimming the hyd lifters was to stop the lifter from collapsing and thus breaking the stock rockers or blowing the pushrods through the seat. It also (if properly adjusted only gave the lifter about .0075 to "float".) The HP gains came later when we discovered that stiffer valve springs, very light motor oil and much higher RPM thresholds yielded big gains in performance. One of the few "win-win" deals in drag racing. Solids are legal now so most won't use this method anymore.