Rocker ratio and PV

General engine tech -- Drag Racing to Circle Track

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englertracing
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Re: Rocker ratio and PV

Post by englertracing »

How thick are your pistons? Maybe you should send them to Erik at rebco machine, he can make them deeper, and his prices are shockingly low.
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MadBill
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Re: Rocker ratio and PV

Post by MadBill »

1972ho wrote: Thu Dec 14, 2017 7:06 pm If I go from a 1.7 rocker ratio to a 1.6 will that increase the PV clearance.Im running pretty tight on my rebuild of the V-6,I’m at .095 exhaust with .022 lash and only .035 with .020 lash on the intake.Something that was happen while checking pv with zero lash the exhaust was .075 and the intake was .050 this was with 4 degrees advance.Now should the intake decrease with lash or should it increase,every time I have added the lash the exh would increase the pv but the intake would decrease.Shold that happen like that.

First, there's no need to check P/V with and without lash; it's simple addition.

Second, as per previous posts it is impossible for P/V to decrease when lash is increased. At any given crank angle [you are checking every 5° from say 10°BTDC (or more, if the second reading is smaller than the first) to ditto after and recording the smallest values?], visualize using a dial indicator to check valve travel to light piston contact with a 0.020" feeler between the roller and the valve tip: indicator is zeroed at the test crank angle, valve depressed to make contact, indicator shows 0.050" travel. Now remove the feeler, re-zero the indicator by moving the dial 0.020" and again depress the valve. It must now show 0.070" travel to contact!

If you're still convinced the PV clearance is going the wrong way, please chart and report clearance vs. lash from zero to one hundred thous lash and let us ponder the results.
Felix, qui potuit rerum cognscere causas.

Happy is he who can discover the cause of things.
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