springersrolla Posted January 20, 2015 Report Share Posted January 20, 2015 Hey dudes I'm close to getting engine back together and want to know how accurate the "how to build tough k motor" quote is "You accomplish this by lowering the axis upon which the rockers move, which is supported by the rocker posts. Toyota had it pretty well setup from factory, so a good rule is to have the rocker posts accurately machined down by the amount of valvelift you have added to the engine. Stock lift is about 0.340", so say you're running 0.400" lift, you need to have the rocker posts machined down about 0.060"." I'm running approx 500 lift and according to this around 4mm should do the trick??? I am yet to find a decent machinist after my bloke went awol but is this the right starting point for me to ask for?. Tia Quote Link to comment Share on other sites More sharing options...
GJM85 Posted January 20, 2015 Report Share Posted January 20, 2015 If your running hydraulic lifters then yes, that is how you maintain the correct valve lash. For solid lifters there should be enough adjustment in the rocker to take up the difference. Quote Link to comment Share on other sites More sharing options...
snot35 Posted January 20, 2015 Report Share Posted January 20, 2015 Personally, I'd mock it up and check how the rockers wipe the pads on top of the valve. There's no substitute for actually checking. Quote Link to comment Share on other sites More sharing options...
styler Posted January 21, 2015 Report Share Posted January 21, 2015 +1 Quote Link to comment Share on other sites More sharing options...
altezzaclub Posted January 21, 2015 Report Share Posted January 21, 2015 +2 I didn't worry with a lift of 0.4", maybe if I had a wilder cam I'd look at it so you don't get too much downwards angle on the rocker at full open. You do get into areas of low efficiency when the rocker goes further down, but having it touch the cotter or run off the valve stem is far more important. If you're going to race it then cut the posts and retain the original geometry. I don't think you cut the same amount off as the cam is cut, as you are working on a rocker ratio of 1.5:1. You'd remove a ratio of (base circle cut) X (0.67). That would be the same as the extra lift as the lift all comes from cutting the base circle away on a stock cam. You're cutting off 160thou so you'd machine the rocker pillars 107thou. Quote Link to comment Share on other sites More sharing options...
coln72 Posted January 21, 2015 Report Share Posted January 21, 2015 Never bothered, even with the hydraulic lifters. We built one with a re grind that almost left no base circle at all, and again we had no issues. Guess we were lucky Quote Link to comment Share on other sites More sharing options...
springersrolla Posted January 21, 2015 Author Report Share Posted January 21, 2015 Thanks for the tips, when I dummied it up I checked the rocker wipe but didnt bearing blue it. It didnt look too aggressive or look like it would put too much angle. Ill dummy it back up again as I need to make sure I have the right length pushrods. Cheers Quote Link to comment Share on other sites More sharing options...
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