LIfter/Tappet Bore Clearances

[Matt Wilson]

Hi guys,

I'm rebuilding a 265 to go into my '49 Power Wagon, and I checked the clearances between the tappets and their bores. One manual says to use a dial indicator, and says the indicator reading is the actual clearance, so I did that, exactly as shown in the figure provided in the manual. Most of the readings are 0.0025 - 0.003", with a couple of them being 0.0035", a couple being 0.0015 or 0.002" and one being 0.004". Two manuals say the clearance should be 0.000 - 0.001" and another says it should be 0.000 - 0.0007". Obviously, my readings are far beyond that, but I also have a hard time believing the clearance should be as small as the manuals say. That just seems like asking for trouble to have such a tight fit. Looking online to find clearance specs for lifters in other engines, it seems that most of them call for a minimum of 0.001" and as much as 0.0025" or some even say 0.003" is ok. Of course, these are for engines like Chevy and Ford V8's, but at least they are for lifters with flat bottoms (not roller lifters). Even so, most of my readings are at or beyond those upper limits.

I also measured the tappet diameters and found them all to be less than minimum for new parts (not too surprising, I suppose), and several are approaching the wear limit. The new part dimensions are 0.6235 - 0.6240" and the wear limit is 0.6225". Several of mine were in the 0.6227 - 0.6232" range.

I have a set of NOS 0.008" oversize tappets that I could take to a machine shop and have them bore out the holes, although they have sat out in the garage for some years, and have some rust on them. I may be able to clean them up adequately, though. I'm a little leery of leaving the engine with this much clearance, because I had a 230 flathead with similar clearances and 3 or 4 of the tappets/bores eventually produced oily trails full of metal shavings. I don't know if that's because of the looseness of the tappets in their bores or something else. I seem to remember that some tappets didn't rotate like they should. I suppose they could have been the same ones producing metal shavings, but I don't know for sure.

I'd like to hear your input. If I do use the oversize lifters, what clearance do you recommend?


Thanks,


Matt

[Frank Irons]

Matt

Since you already have oversize tappets, install them with a new camshaft. I would check with the machine shop to see if they have tooling to open up the tappet bores and hold the factory tolerance. I would try for .0003 to .0005. You could also try a new unworn standard tappet and see if it improves your clearance enough to be acceptable.

Frank

[Matt Wilson]

Thanks, Frank. I spoke to a machine shop who said they would do it (the shop I used for the rest of my work could not do it). The clearances you mention seem awfully right, even though they are within the factory tolerances. I'm just cautious about having them too tight. I've read a couple of posts on other websites from guys who said they had tried 0.001" and ended up seizing their lifters in place, but they were talking about Chevy and Ford V8's, and I'm sure they were hydraulic lifters, so maybe that's the difference.

I do have some standard sized lifters that appear to be unused, and I had considered using those. I'll measure their diameters today, and maybe do the dial indicator clearance check with them installed in the engine.

Thanks!

[Matthew Welcher PWA]

Matt, I am not sure if you have this information for the clearances of the stock tappets.
i would think the tolerance would be the same for oversized as stock.
Take a look at this here if I am understanding your question correctly.

[Matt Wilson]

Hi Matt, I appreciate your asking. Yes, I do have that book and two others. One of those other books says new part clearance should be no more than 0.001", so it agrees with what you posted. The third book specifies no more than 0.0007" for new parts, so somewhat smaller. My only concern is that these stated clearances seem to be a bit too small, considering folks on various other forums (non-flathead) say they have experienced seized lifters when the clearance was 0.001".

By the way, does VPW still have oversize tappets in stock? A few of mine are corroded beyond what can be repaired.

[Matthew Welcher PWA]

Matt I believe they do have. I will check first thing in the morning for you.

[Frank Irons]

Matt,

One thing you haven't considered is that most modern days lifters are bigger in diameter than the .625 diameter of the Dodge lifter. Tolerances are greater on a larger diameter. .001 is very loose on a .625 diameter.

Frank

[Matt Wilson]

Actually, I did think about that, but I still got a little concerned. The lifter diameters they were talking about are somewhere in the range of 0.85 to 0.95. The tappets in our flatheads are 0.6235 - 0.6240, so they are significantly smaller. I suppose aiming for 0.001 clearance would work. Thanks for the reply.