Lifter and pushrod question / thought
10-11-2002, 02:31 PM
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Lifter and pushrod question / thought Working out some thoughts with milling heads and pushrod length. Lets assume stock cam and pushrods are used:
There are numerous posts about the lifters having "some" degree of preload. It was said you could mill the heads .010+ and be fine w/ stock pushrods. Wouldn't that effectively increase cam lift by .006" assuming 1.7 rockers were used?
Now lets say you mill .030", everything else being equal. You should go to a shorter pushrod - the comp 7.35". Now you have effectively decreased your cam lift by about .012" since you had to shorten the pushrod by .05" instead of the needed .03", correct?
If all that is correct, then everyone running a high lift cam w/ stock heads and pushrods (assuming the cams base circle is smaller), you aren't getting the full benefit of the cams lift. For instance - the 02 LS6 cam has a base circle of 19.0mm from the stock 19.7mm. That .35mm smaller radius comes out to be .014" smaller times the rocker 1.7 is .024" valve lift. So with a cam w/ .550" lift, you only get ~.525" lift out of it.
Any thoughts or comments?
There are numerous posts about the lifters having "some" degree of preload. It was said you could mill the heads .010+ and be fine w/ stock pushrods. Wouldn't that effectively increase cam lift by .006" assuming 1.7 rockers were used?
Now lets say you mill .030", everything else being equal. You should go to a shorter pushrod - the comp 7.35". Now you have effectively decreased your cam lift by about .012" since you had to shorten the pushrod by .05" instead of the needed .03", correct?
If all that is correct, then everyone running a high lift cam w/ stock heads and pushrods (assuming the cams base circle is smaller), you aren't getting the full benefit of the cams lift. For instance - the 02 LS6 cam has a base circle of 19.0mm from the stock 19.7mm. That .35mm smaller radius comes out to be .014" smaller times the rocker 1.7 is .024" valve lift. So with a cam w/ .550" lift, you only get ~.525" lift out of it.
Any thoughts or comments?
