Hydraulic roller lifters tick only under crankcase vacuum

[Geoff2]

I think it is the difference in oil pressure, cap on v cap off. Cap off allows gravity to act on the oil level & help feed oil to the pump, increasing oil pressure slightly, pumping up the lifters. A slightly higher viscosity oil might quiet down the lifters, by virtue of slight increase in idle oil pressure.

[BILL-C]

I think it is the difference in oil pressure, cap on v cap off. Cap off allows gravity to act on the oil level & help feed oil to the pump, increasing oil pressure slightly, pumping up the lifters. A slightly higher viscosity oil might quiet down the lifters, by virtue of slight increase in idle oil pressure.

Oil pump is external dry sump. Oil pressure only changes 1 psi cap on to cap off in the approximately 35 psi range at 950 rpm idle. Same clatter change happens at higher rpm , say 2000 rpm with 50 psi.

[dannobee]

Are you certain that the noise is in fact the lifters?

Crankcase vacuum does strange things to crank seals and distributors, too.

[BillK]

Some interesting theories here. I have a hard time believing the vacuum is keeping the 35-50 lbs of oil pressure from feeding the lifters. But stranger things have happened

Just curious, have you asked Howards to see what they think ?

[Tom Walker]

Please keep us informed what is causing this situation. This is a weird one for sure.

[piston guy]

Bill
This is a real interesting situation. Vacuum in the crank case is "everywhere " DUH. But thinking of that "I" think the vacuum IS pulling oil out of the lifter causing minor lifter collapse because the "restriction" that keeps oil in the lifter has decreased ( essentially) creating a lifter "bleed down" condition so to speak. Since you have an external pressure adjustment , why not try to adjust the oil pressure higher ( instead of increasing rpm to do so , and thereby restoring "pressure" the lifter sees without the cap on. It is common to see a smaller loss of pressure on a dry sump versus a wet sump with a vacuum pump , YET the lifters are still feeling the 10"s of vacuum. That is my point about vacuum being everywhere. Yes only one psi on the gauge but still 10"s pulling oil from "everywhere" inside. As good as you are you may have already tried this , it's just my take on the situation.

[PRH]

My thoughts are similar to Piston Guy.

The oil will flow to the path of least resistance.
There is vacuum on the pushrod side of the lifter, but not on the pressure chamber side of the lifter.
The oil is being drawn right up through the lifter from the oil feed hole to the pushrod seat and not being forced into the pressure chamber.

That’s my theory anyway.

[BILL-C]

I figured it out! My assembly guy made a mistake assuming that just because the first lifter you check for oil band alignment is barely ok that all of them will be ok. We know better. Sometimes we need a kick in the nuts to remember the hard lessons we learned in the past. The combination of small base circle cam core,FMS BOSS block,and oil band location of Howards/Morel lifter resulted in most of the lifter oil bands being exposed by about .005-.010 on base circle. It's an embarrasing rookie mistake by a bunch of veterans. Now to fix it. Comp has a lifter that has perfect oil band location, but body is .0012 smaller in diameter that the Howards/Morels [which are identical in od to comp's flat tappet lifters]. It would be nice if the lifter people would all just duplicate the factory lifter od instead of this BS. If we use the comp lifters we will definately have loose oil clearance. The howards/morels measure .950 from bottom of roller wheel to bottom of oil band. These don't work. The Comp lifters measure 1.100. Now i need to find a link bar lifter with Comp's oil band and Howards/Morel body od.

[Tom Walker]

Glad you diagnosed the situation and thank you for sharing what was actually causing this. On the surface, it appeared to be one of those mystic type of issues that definitely had a lot of us interested in what was the cause.
Thanks again and rest assured, we all have and will again, make similar mistakes, we are only human.
You have probably helped someone else with the education that this situation provided.

[FC-Pilot]

I am going to ask this not to be a pain, but because I don’t know what the current price is these days. With lifters costing so much would it not be cheaper to put bushings in the lifter bores? You could run the clearance a touch tighter if you wanted and have the bushing extend a little bit lower therefore keeping the oil band inside the bushing. Also it would provide a little more support for the lifter, would it not?

Paul

[GARY C]

I figured it out! My assembly guy made a mistake assuming that just because the first lifter you check for oil band alignment is barely ok that all of them will be ok. We know better. Sometimes we need a kick in the nuts to remember the hard lessons we learned in the past. The combination of small base circle cam core,FMS BOSS block,and oil band location of Howards/Morel lifter resulted in most of the lifter oil bands being exposed by about .005-.010 on base circle. It's an embarrasing rookie mistake by a bunch of veterans. Now to fix it. Comp has a lifter that has perfect oil band location, but body is .0012 smaller in diameter that the Howards/Morels [which are identical in od to comp's flat tappet lifters]. It would be nice if the lifter people would all just duplicate the factory lifter od instead of this BS. If we use the comp lifters we will definately have loose oil clearance. The howards/morels measure .950 from bottom of roller wheel to bottom of oil band. These don't work. The Comp lifters measure 1.100. Now i need to find a link bar lifter with Comp's oil band and Howards/Morel body od.

Is it not possible to machine oil band on the lifters you have

[Tom Walker]

Or change cam to one with a different base circle dimension.
Unfortunately, it will take some effort and expense to correct.

[BILL-C]

Or change cam to one with a different base circle dimension.
Unfortunately, it will take some effort and expense to correct.

No larger cam cores are available at this time. That's why we have this problem. Dam Covid.

[BILL-C]

I figured it out! My assembly guy made a mistake assuming that just because the first lifter you check for oil band alignment is barely ok that all of them will be ok. We know better. Sometimes we need a kick in the nuts to remember the hard lessons we learned in the past. The combination of small base circle cam core,FMS BOSS block,and oil band location of Howards/Morel lifter resulted in most of the lifter oil bands being exposed by about .005-.010 on base circle. It's an embarrasing rookie mistake by a bunch of veterans. Now to fix it. Comp has a lifter that has perfect oil band location, but body is .0012 smaller in diameter that the Howards/Morels [which are identical in od to comp's flat tappet lifters]. It would be nice if the lifter people would all just duplicate the factory lifter od instead of this BS. If we use the comp lifters we will definately have loose oil clearance. The howards/morels measure .950 from bottom of roller wheel to bottom of oil band. These don't work. The Comp lifters measure 1.100. Now i need to find a link bar lifter with Comp's oil band and Howards/Morel body od.

Is it not possible to machine oil band on the lifters you have

Oil band is already too low.

[Adger Smith]

Bill,
Will Morel build you a set of the lifter body you have with larger diameter rollers?
That would pick the oil band up...