Pushrod length and lifter preload
Pushrod length and lifter preload I have an LQ9 with 243 heads, stock MLS gaskets, LS7 lifters and MS3 camshaft. My question is this: with the stock pushrods I measure .050 lifter preload using the dial indicator method. I read somewhere that stock pushrods were 7.380 so I was banking on using 7.400 to get me to roughly .070 of preload. However, tonight I measured my stock rods and they are 7.400. Will this be enough preload or should I step up to 7.425 to get around .075?
Generally, with the smaller base circle of the cams ground on Comp billet cores, you need more pushrod to get the same preload. 7.425" is accepted as optimal for a stock engine with a Comp billet core cam.
How did you measure the pushrods? There is actual length (end-to-end) which is easy to measure, and gauge length which is what Comp uses. Just something to keep in mind. I don't know if 7.380 is the actual or gauge length.
Theoretical length is the length of the pushrod without the hole drilled through it, I doubt you measured this. Drilling the hole through the pushrod puts a "flat surface" on the ends effectively shortening the pushrod slightly. If you measured end-to-end, then you measured actual length.
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I measured stock on a LS1, they were 7.385" gauge length. The 7.400" will be gauge length of bought from Comp or several other vendors, which all actually are made by Trend. I would contact Trend directly and get the pushrods. They also have very good technical support who I worked with when I did my double taper pushrods. I would also consider a stiffer 11/32" OD pushrod from Manton.
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Just thought I would update this......My stock pushrods measure 7.397 and my new 7.400 rods measure...well...7.400. So, all this gauge length, theoretical, actual stuff didnt mean a thing. Measure them tip to tip.
