Lifter Bore Measurements

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nm9stheham

nm9stheham

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I never paid attention to this before, but with the oil pressure issues reported on this forum, I begun wondering how much lifter bore wear is a factor, that folks are just not aware of. So I measured a 273 block here; this is an approximate 100k mi engine, original, with cylinder bore wear no more than .003-.004" worst case, and no bad bearings and crank wear under .001", so this engine is a pretty 'limited' wear engine of its day IMHO. Info on the tools used, etc, is at the end of this post.

I set the gauge to the max limit lifter bore on the '65 FSM, which is .9058". All lifter bores were less than this dimension horizontally; but all of them were at or above this dimension vertically. I suppose that is to be expected with the lifter to pushrod angle putting force and wear on the bottom of the lifter bore.

I then set the gauge to larger and large sizes, and finally found the largest lifter bores. They were 4E, 1I, 7I, and 7E,and they were .9061-.9062" max in the vertical direction. The wear seemed to be more at the top than the bottom but I did not really get into that matter in detail.

As a reference to unworn bores: We were blessed with a virgin block with the last build and the lifter bores were all under .9048" or thereabouts. Assuming the bores were consistent over time (1968 to 1970 blocks dates), then this 273 looks to be worn up to .0013-.0014" in the lifter bores.

Per the FSM, the lifters are supposed to be .9040-.9045" diameter. The range of clearance is supposed to be .0005-.0015". So with these mildly worn 273 bores, the clearance with factory spec lifters could vary from about .0012" to as much as .0022", along the vertical direction.

I've measured one set of new Crane lifters (hydraulics) and they ranged from .9040" to as much as .9052". The largest 3 were .9046, .9048, and .9052". So these new lifters can range up past the FSM spec size. Crane was good enough to supply 3 new lifters .9045" and under to replace these large ones, for no charge. (We bought direct from them so they said 'no problemo' to doing this; that is an advantage to going direct to a cam maker.)

Interestingly, according to this '65 FSM, oversize lifters were available in .001", .008" and .030" sizes.. I never knew that! Going to the 2 larger oversizes calls for reaming the bores out. I'll go direct to a cam mfr for this 273 block and ask if they can sort the lifters to be on the large end of production to take up this wear. It'll be interesting to see if they will be willing to do so.

Measurement info: Measurements were made with a telescope gauge set with a .0001" micrometer (vernier scale). I don't have a reference for making sure the micrometer is dead nuts on, but it seems to check right on known parts (like new lifters). (Yes, a 1" reference is on my list!) I have used telescope gauges for 35 years; they are tricky and slow to use, but if you work slowly and carefully and pay attention to their angles and centering in the bores, I've found that you can approach .0001" tolerance. You have to be easy with them and work them back and forth a lot to get good results, and be ready to re-check them, but they will frustrate you, or fool you if you use them casually. And my dimensions could be off .0001" due to temp changes; the tools started at room temp but the garage is at 40F; I tried to keep the tools warm but eventually they cooled a bit.
 
Interesting. And most of us just lube them up and drop them in. Now from what you've said, don't tell me a high volume oil pump wouldn't be a good idea in a 100,000+ mile rebuild.
 
Yes that is good thought IMHO. Well, what we don't know is how much oil is lost through an extra .0005-.001"... or .002" or .003" and on up to how much wear everyone's blocks really have. I suspect some of the sharp machinists here are are checking this parameter... I'd love to hear their measurement experiences and their take on this.

It would be nice to have an easy method of checking this... like Plastigage for lifter bores! Maybe a set of 3-4 precisely ground mock lifters in stepped sizes? Of course then a solution would be need for worn bores. Uh-oh....
 
nm9stheham said:
Yes that is good thought IMHO. Well, what we don't know is how much oil is lost through an extra .0005-.001"... or .002" or .003" and on up to how much wear everyone's blocks really have. I suspect some of the sharp machinists here are are checking this parameter... I'd love to hear their measurement experiences and their take on this.

It would be nice to have an easy method of checking this... like Plastigage for lifter bores! Maybe a set of 3-4 precisely ground mock lifters in stepped sizes? Of course then a solution would be need for worn bores. Uh-oh....
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Bushed lifter bores would be a fix. If the wear was more consistent throughout the bores a simple go/no go plug gauge would work. The best thing would be to overbore and hand fit the lifters. I'm sure it's done in high end engines.
 
nm9stheham said:
Yes that is good thought IMHO. Well, what we don't know is how much oil is lost through an extra .0005-.001"... or .002" or .003" and on up to how much wear everyone's blocks really have. I suspect some of the sharp machinists here are are checking this parameter... I'd love to hear their measurement experiences and their take on this.

It would be nice to have an easy method of checking this... like Plastigage for lifter bores! Maybe a set of 3-4 precisely ground mock lifters in stepped sizes? Of course then a solution would be need for worn bores. Uh-oh....
Click to expand...
If the od of your lifters is that different it makes me wonder about the inside pieces.
 
It's not that critical. Certainly not as critical as the machining on the bores and journals and the resulting clearances. I've run engines with a quantity of lifters with .003+ clearance with no issues with standard pumps. I've also run a standard pump on a block with .0015 clearance on the lifter bores, but with .003-.0032 oil clearnaces and the pressure was lower with that same std pump. Admittedly I drill the main feeds on every engine I do, so potentially I could be making the lower end more of an influence.

IMO - you don't need a HV oil pump unless the bearing clearances start getting big and the gaps on the rotating assembly are hemorrhaging a lot too. The lifter bores can hemorrhage a lot before you see an issue with delivery to the mains, unless the mains are letting a lot out with them.
 
Good info, however it is important that tools used for measurement and items being measured be at the same temperature to reduce error..........warm tools and cold parts to measure says nothing measured was right.......close but no cigar
 
Thanks for your info, Moper. I appreciate the perspective greatly. You sometimes mention bushing these bores; can I ask what drives that?
 
JBurch said:
Good info, however it is important that tools used for measurement and items being measured be at the same temperature to reduce error..........warm tools and cold parts to measure says nothing measured was right.......close but no cigar
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Understood.... 30*F temp difference in iron means .00028" difference across this diameter. So you would increase the measurements by that much at most if the block was at room temp. (What seemed most critical IMHO was to keep the micrometer and telescope gauge at the same temp, since you are transferring dimensions from one to the other. And there could easily be that much in my micrometer too!)
 
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You will pretty much only see me mention bushing for the use of solid rollers. For which I consider it mandatory but less for oil control than lifter performance and longevity. I just got tired of arguing about it, so I avoid those posts now...lol.
 
Learn something every day. I knew mopar had some blocks with oversize lifters but I thought they were all .008 oversize. Don't bet on buying special size lifters. Years ago I bought a good looking 340 block at a really good price. Needless to say after building the engine we had a low oil pressure problem. It took me a while to determine it was the oversize lifter bore. When I did find the problem the local dealer wanted $16 ea for oversize lifters. I called every lifter manufacturer I could find but no one would make me special oversize lifters. I finally had to buy from the dealer but talked him down to $9 ea. At the time I ordered those in 1985 there were only 52 lifters in the inventory. After several years use I still have that engine hanging on an engine stand because I can't get the right size lifters and it cost too much to have them bushed. If I ever do anything with it I guess I'll have to use the same cam and lifters.
 
I think unless they're floppin around sideways in the bore, or they are lifting the band out of the top of the bore, they'll work fine. I've measured a few through the years I really put a lot of money in, but only those. The rest got cleaned up and assembled and I never had any trouble. I am sure some were out of spec.
 
I've noticed some lifters fitting tighter than others and rotating a little harder when installing new ones. Last engine I put a FT cam and lifters in I swapped around lifters between bores if they felt a little tight, it was Howards cam and lifters in a 440 IIRC
 
Good topic.
Bushing lifter bores is usually done to correct the lifter's position over the cam-lobe.

I have noticed the 360 I have has a lot of lifter bore camfer at some lifter bores.
Also I found this also quite interesting piece of info at Hughes website:

The photo above shows an unmolested 340 small block. As pointed out by the arrows, some of the lifter bores are chamfered, or counter-bored. We do not know why Mother Mopar chose to do this. As you can see they are randomly bored to differing depths. The problem with this is that when you want to retrofit your block to a hydraulic roller cam the lifters that you need to use may come up high enough that the oil groove around the outer perimeter of lifter becomes exposed into this chamfer. This is not acceptable with most lifters. Our lifters address that problem by lowering the oil band.
Click to expand...
Blockchamfer.jpg
 
Blucuda413 said:
Learn something every day. I knew mopar had some blocks with oversize lifters but I thought they were all .008 oversize. Don't bet on buying special size lifters. Years ago I bought a good looking 340 block at a really good price. Needless to say after building the engine we had a low oil pressure problem. It took me a while to determine it was the oversize lifter bore. When I did find the problem the local dealer wanted $16 ea for oversize lifters. I called every lifter manufacturer I could find but no one would make me special oversize lifters. I finally had to buy from the dealer but talked him down to $9 ea. At the time I ordered those in 1985 there were only 52 lifters in the inventory. After several years use I still have that engine hanging on an engine stand because I can't get the right size lifters and it cost too much to have them bushed. If I ever do anything with it I guess I'll have to use the same cam and lifters.
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Thanks, that is very interesting that someone actually had these oversized lifters. This all tells us something IMHO: Somewhere between .003" and .008" wear allows excessive flow. (I'd also think that the .008" oversize round bores would flow more, not like an 'ovaled' hole from regular wear.)

BTW, have you looked into having those oversized lifters' faces re-ground? I think Oregon Cams does that, and the fellow who posts as Doctor Dodge over on slantsix.org has a machine for lifter re-grinds. (He does /6 lifter regrinds for sure.)
 
MOPEkidD-3 said:
I've noticed some lifters fitting tighter than others and rotating a little harder when installing new ones. Last engine I put a FT cam and lifters in I swapped around lifters between bores if they felt a little tight, it was Howards cam and lifters in a 440 IIRC
Click to expand...
I can believe it; that last set of lifters from Crane varied in diameter by a bit over .001" from smallest to largest.
 
Just to get a concept of how much flow area is around the lifters bores relative to other known critical areas, I ran some numbers for the exit flow area around the lifters and around the main bearings. Actually flow will vary from these numbers, and depends on a lot of factors like the actual pressure at each point; so this is just for a basic appreciation.

There are a lot of lifters versus bearings so their smaller hole sizes add up. These numbers assume even wear around the lifter bore, which I don't think is the case. So real lifter bore wear will presumably be less pronounced for flow area increase.

Numbers are for different clearances up to .004". Factory nominal clearances. were .001" for both main bearing and lifter-to-bore clearances.

.001" Mains: .079 sq in - Lifters: .091 sq in
.002" Mains: .157 sq in - Lifters: .182 sq in
.003" Mains: .236 sq in - Lifters: .273 sq in
.004" Mains: .314 sq in - Lifters: .364 sq in

You can see how huge the flow area around the lifters would have been for Blucuda413's standard lifters in the .008" oversize lifter bores LOL! Or how much the flow areas increase with big main clearances. At some point, the oils pump's flow is gonna be approached at lower RPM's and the back-pressure is gonna drop like a rock.
 
Thanks for the info on resurfacing everyone I ever talked to said they were too hard to do that. Just wasn't talking to the right people I guess. IIRC when I was looking for lifters I calculated that the slop between the .904 and .912 for combined space was equal to a .500" hole in the oil system. Low oil pressure for sure.
 
BTW, 'Doctor Dodge' is Doug Dutra..... in CA. If you get on that site's message forum, you can get in contact with him to see if he does non-/6 lifters. He and Oregon are worth a shot.
 
nm9stheham said:
.001" Mains: .079 sq in - Lifters: .091 sq in
.002" Mains: .157 sq in - Lifters: .182 sq in
.003" Mains: .236 sq in - Lifters: .273 sq in
.004" Mains: .314 sq in - Lifters: .364 sq in
Click to expand...

Can you show me the math on that? Math is not my strong suit, but I can't see how the surface area available for leaks on a lifter (the perimeter on top and bottom of a smaller-than-an-inch lifter) is equal to the two sides of the main bearings that are 2.5" in diameter.
 
Ford 351W used a .002 clearance target. .0007-.0027 was the acceptable reading. I had a set of Hemi rollers and they were all .0005 undersized .9035...consistent on all of them when compares to a set of new SB lifters at .904. Dont know if it was wear or if the roller aspect changed the spec. Why they offered .001 oversized lifters when it was within tolerance is past me. The internals of a hydraulic lifter are super tight. When you can spec a leakdown of .0625 in 5-50 seconds with a 200psi load using no lip seals is pretty amazing with motor oil. For a manufacturer to be so loose on OD spec and keep the ultra tight tolerances on the inside is another mystery. Also there is alot of oil flowing in a motor. when you can see 10psi at idle, that means that 10psi is being maintained throughout the system, that is plenty to maintain a hydrodynamic wedge on all rotating parts, even the slow rotation of a flat tappet lifter. Your really bleeding oil at your stamped rocker arm fulcrums as they are not machined.
 
.904 lifter (r x h) is about equal to 5.25 inches of surface area and that includes subtracting the .484 oil band area that's factored in (further reduce area when lifters are being acted upon reducing the surface area). Multiply by 16 and you get 84 square inches of lifter bearing area. Use a .002 lifter to bore acceptable clearance and you get 84 x .001 (.088) "bleed" in your pressurized oil circuit. That is petty considering that you have an oil pump that can produce 10psi through this and everything elde at 800 rpm. Now increase that to .008 and you get .088 X 4 or a .336 bleed. now we are talking an exponential drop in oil pressure.

>> not sure if the Mopar oil band would affect leakage out same .002 clearance. as it is a block design<<
 
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Thanks Pishta.
But we aren't talking about the load carrying surfaces. Only the leakage points, right? We're looking at computing the area of a disc that is .906" OD(estimating .002" clearance) and an ID of .904, X 2 (for the top and bottom). I'm assuming no pressure losses at the internals of the lifters.
I did it this way: Area of the bore minus area of the lifter or crank journal
Area of a circle is PixR^2 so (.904/2)^2 x 3.14 = .6415sq" Area of the bore: (.906/2)^2 x 3.14 = .6443sq" Bore area - lifter area: .6443-.6415 = .003sq", x2 for the top and bottom = .0057sq" for oil to leak.

For a typical main bearing with .002" clearance, assuming no taper and a round bearing shell ID (not technically the case but an assumption here):
Area of main bore: (2.50/2)^2 x 3.14 = 4.9062sq" Area of crank journal: (2.498/2)^2 x 3.14 = 4.8984sq" Bore area minus crank area: 4.9062 - 4.8984 = .0078sq", x2 for front and rear edges = .0156sq" for oil to leak.

Now those are both one in a system. So it looks like if you had 16 lifters with the same clearance, you would have the potential for pressure loss of .0912sq".
So now do we add the rod bearing leakages to the main bearing side of the equation? They are "down stream" so I'm not sure if that's a valid add.

Adding the other four mains we have .0780sq" of leakage with only the mains. So lifter leak more per the math I understand. Unless it's totally wrong - which I'd say is a solid 50/50 at this point...lol
 
yes, your correct that it leaks only at the edge of the lifter. Realized that when I was mowing the lawn.....That is nothing! Especially when you consider in a Magnum that each lifter bleeds at the pushrod seat too. Also Im guessing the stock pump flows about 8GPM at 3500, and a huge amount of this is bled off.


Notice who commented on this 2 years ago! :icon_fU:
 
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