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Lifter Bushings

December 21 2011 at 11:15 AM
  (Login c9zx)
from IP address

If lifter bore bushing are installed can the oiling hole be drilled large enough to run hydraulic lifters without losing the benefit of improved crank oiling? Thanks, Chuck

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(Login tinman351)

flat tappet hydros

December 22 2011, 3:43 AM 

no doubt

i think 'someone' suggesting to use the same size orifice in the bushing as what the lifters have in them?

gonna be a whOle lot smaller than the galley feed and will still hold presure to the bottom end if it somehow manages to spit out a lifter or 3

probably what i'll do for versatility, even though i'm using flat solids i'll be able to swap in a Hydro... and not worry about starving the springs

there'll be phantoms, there'll be fires on the road... and the white man dancing

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(Login gpence)

Valve Train Lubrication

December 22 2011, 1:06 PM 

so far the hydraulic lifter oil feed holes I've measured have fallen in the range of 0.080" to 0.090". For instance, the Crane hydraulic roller lifter has two oil feed holes, 0.060" each, which are equivalent to one hole 0.084" diameter.

Since the hole in the lifter bore bushing is enlarged in order to feed the lifter adequately, the subject of oil control to the valve gear must be considered. The bushing shall prevent excessive oil lost in the clearance between the lifter and the lifter bore, but an orifice of 0.080" to 0.090" may not restrict oil flowing to the valve train adequately.

My solution is to restrict oil flowing to the valve train downstream of the hydraulic lifter, using the push rods. A set of push rods can be ordered with an 0.040" or 0.060" restriction in the tips. It may be confusing that I've recommended two different orifice sizes so I think a quick explanation is in order. The issue is not oil supply, the smaller orifice supplies plenty of oil to the valve train. The issue is clogging. Some engine builders believe the smaller orifice is so small that it is too easily clogged by debris, therefore they prefer to use a larger orifice to reduce the chances of clogging. I'm not going to tell you what to do, I'll leave the decision up to you.

A similar way to restrict oil flowing to the valve train with hydraulic lifter applications is to order a set of 5/16" push rods with 0.120" wall thickness. The passage in the midle of such push rods is only 0.072" diameter, making the push rods an 0.072" orifice that is over 8" long. They're nice and stiff too, the way a push rod should be.


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(Login c9zx)

Thanks for the replys

December 22 2011, 3:14 PM 

I was just curious about creating a good block that works with either solid or hydraulic lifters. It sounds like a .090 hole in the bushing and .060 restrictor in the push rod should work. I wonder if a slightly higher than stock oil pressure at idle would be needed to hold off hot weather at idle hydraulic lifter "rattle". Thanks, Chuck

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(Login ZZ28)

Re: Thanks for the replys

December 22 2011, 6:54 PM 

You will discover that you will not need any more oil pressure with the lifter bushings installed as they control the oil loss to the top end so well that the stock pump volume and pressure will be more than adequate.

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