Please educate me on lifter/pushrod/valve function

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May 18, 2020 | 07:50 AM

#11

Mchad

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Joined: Dec 2014

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From: SWFL

Ok, I’m good. I got what I needed form this thread and this as well:

https://www.hdforums.com/forum/engin...bleeddown.html

The video was particularly valuable.

Thanks everyone.

May 18, 2020 | 08:00 AM

#12

98hotrodfatboy

Seasoned HDF Member

Joined: Mar 2010

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From: Poolville

One thing you'll have to be careful of is RPM and preload... There is definitely a correlation there that can cause a lifter to pump up and create damage, it's happened to me a couple times... A slower bleed rate lifter will pump up after 6300-6500 rpm which could cause a valve to tap a piston. Especially if you've had head work where they shave the heads and lowered everything even closer to the piston... I used to set my preload to .140", I no longer do I'm running .125" max preload because I like to use my motor... Also I have my rev limiter currently set to 6200 RPM.. funny thing is I don't think there's a builder out there that'll tell you this information.. Hopefully I'm wrong

May 18, 2020 | 08:26 AM

#13

Max Headflow

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Joined: Dec 2005

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From: poway

Quote:

Originally Posted by Mchad

Thanks, I understand that part. What I was asking in my second post was what happens if the pushrods were incorrectly adjusted (too long) and needed to be shortened. Do the lifters need to be removed and manually filled, so they can bleed down correctly?

”Specifically, if a pushrod was over extended and pushed the piston to the bottom of its travel (for example) does it have to be removed and filled with oil manually before it can be re-adjusted correctly?’

If you run the lifter past it's intended adjustment and then back it off, the oil in the reservoir above the plunger / piston will fill section below the piston and take up the lash. If you end up playing with it enough, you could eventually empty the reservoir and pump air into the lower part of the lifter. You don't need to remove the lifter and refill but the valve train may rattle until all the air is bled out from underneath the piston and it don't do a good job of holding the plunger. Some like to remove the plugs and crank the motor over until the oil pressure builds but starting the motor and having a little lifter rattle until pressure builds will work also. With Woods low leak lifters it might take a while.

May 18, 2020 | 08:35 AM

#14

Max Headflow

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Joined: Dec 2005

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From: poway

Quote:

Originally Posted by 98hotrodfatboy

It really don't matter where the lifter is set except if the lifter holds the valve off the seat. Then you won't have any compression and the motor won't run. Then you could have contact. The generally only way the lifter can over pump over the set length is by not having enough valve spring for the revs.