Lifter bore clearance, too loose?
12-01-2016, 05:29 PM
#1
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Lifter bore clearance, too loose? Hey guys. So to make a long story short, my lifter destroyed itself last weekend. I took the heads off and took that lifter out(with needle nose pliers). It was kind of sticky coming out, but honestly not too bad, it wasn't mushroomed or anything.
I inspected that lifter bore and there was two scratches that were making a good lifter sort of stick, then slip, then stick, then slip. I used a hone on that bore and it slides in perfectly now but...maybe a little too easy... I got a feeler gauge out and measured that my clearance on that bore specifically is .0019. From everything I read it's supposed to be .0015 MAXIMUM.
My question is: Does anyone here have any idea what kind of troubles that's going to cause? I'm guessing low oil pressure, but wasn't sure how much that one bore being .0004 too big would cause, but I also thought since it's pressurized it could do...something.
I inspected that lifter bore and there was two scratches that were making a good lifter sort of stick, then slip, then stick, then slip. I used a hone on that bore and it slides in perfectly now but...maybe a little too easy... I got a feeler gauge out and measured that my clearance on that bore specifically is .0019. From everything I read it's supposed to be .0015 MAXIMUM.
My question is: Does anyone here have any idea what kind of troubles that's going to cause? I'm guessing low oil pressure, but wasn't sure how much that one bore being .0004 too big would cause, but I also thought since it's pressurized it could do...something.
Last edited by 07V; 12-01-2016 at 06:57 PM.
12-01-2016, 09:05 PM
#2
You really can't get an accurate bore measurement using feeler gauges. If a stack up of .0019 fits, it's actually more than that. The only way to accurately measure is with a bore gauge. Because you did hone it, I would honestly recommend finding somebody that has one or buy one if you can.
That said, if it really was .0019 you'd be alright. I don't like seeing much more than .002 on street cars with .842 lifters. Especially aluminum blocks. I shoot for and recommend .0015, like you said. Any tighter than .001 and you have to be absolutely positive there isn't any taper or roundness issues, even then .0008" is the tightest I'd ever run.
The problem with too much clearance is oil, like all fluid, wants to take the path of least resistance. You can end up starving the lifter of oil. Once you do that they'll make noise and bleed down, causing the valve not to open properly. And of course oil pressure will be down. If only one lifter bore, pressure drop won't be that noticeable unless it's around .003.
That said, if it really was .0019 you'd be alright. I don't like seeing much more than .002 on street cars with .842 lifters. Especially aluminum blocks. I shoot for and recommend .0015, like you said. Any tighter than .001 and you have to be absolutely positive there isn't any taper or roundness issues, even then .0008" is the tightest I'd ever run.
The problem with too much clearance is oil, like all fluid, wants to take the path of least resistance. You can end up starving the lifter of oil. Once you do that they'll make noise and bleed down, causing the valve not to open properly. And of course oil pressure will be down. If only one lifter bore, pressure drop won't be that noticeable unless it's around .003.