.030 vs .040 lifter to cam lobe clearance

[mcjweller]

So...building a 1776 with a brand new AS41 case. Before buttoning things up for the final time, I realized that there may have been a mix up in the ordering of lifters (reusing from an old motor but the cam/lifters had less than 500 miles).

I decided that I wouldn't take the chance and ordered a new cam (the same as the old, Engel W100) and this time ordered Engel lifters to go with it, instead of the unknown versions that came with the old motor. And besides even if the lifters were not mixed after all, its a different case so therefore they will not be put together in 100% the same relationship to each other. Better safe than sorry.

But now, unlike the old Engel W100 and unknown lifters which gave 0.042" clearance lobe to lifter face, the new Engel lifters are a tight 0.030"

I know VW recommends .040". My question is why??? As engine clearances go this is HUGE and it is free play anyway.,,dead space that can't get taken up unless something breaks (and if it does, then there are bigger issues...)

I'm not keen to have to machine the lifter bores, I know there is a tool but to get it (here in Canada) is more cost (with exchange, our silly taxes etc. it is basically double the cost on everything) and a lot more time. I'm not interested in doing anything that isn't absolutely necessary at this point...and I needed this thing out of my garage two months ago.

P.S. - I did search for other posts on this, I did find some that just say it has to be 0.040", but I didn't see any that say why.

[Rob Combs]

A couple reasons off the top of my head

Differing expansion rates between case material and cam/lifter materials might make that static clearance more “dynamic” at different points in the heat cycles

In a perfect world, the lifter tracks the cam perfectly. But that isn’t always the case. Valves sometimes float.

If those two worlds collide, you may find yourself with zero safety margin and the lifters could hit the case. That could get pretty destructive.


That’s my fear of an overly-tight static clearance. Others may see it differently.

[jsturtlebuggy]

Yes minimum .040" (1mm) clearance like has been said for expansion. Aluminum/magnesium expands more than steel.
Depending on design of lifter, clearancing for some only require using a countersunk tool. Others you need the tool like Gene Berg sells.
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Joseph
Fair Oaks/Orangevale, CA
Elrod Motorsports
Motion Tire Motorsports
Having fun with Dune Buggies since 1970
Into Volkswagens since 1960

[Brian_e]

Engle lifters have the fattest heads of them all.

You can could also chuck them each in a lathe, and trim the underside of each lifter .020", and it would make more than enough clearance. Quick and easy without making a mess in the case.

Brian
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[modok]

I don't think 1mm is enough
Would you run your valve springs .040" from bind?

[mcjweller]

Thanks everyone.

The thermal expansion argument (given the different thermal profiles between steel and magnesium and how they may be prone to "grow" at operating temp is something I wouldn't have thought of. Still, seems like a lot.

I ordered the Gene Berg tool and I guess I'm going to cut some clearance into these things.

I wonder how many times I will have cleaned, rifle-brushed, and power rinsed this case to eliminate shavings/metal particles before I'm finally done?!

[Rob Combs]

The extra cleaning certainly won't hurt!

You're doing the right thing. Best of luck.

[txoval]

Take your time with the tool…it cuts quickly.

You don’t need much

[SBD]

txoval,
Do you have a recommendation for what speed to run the Berg tool at? Mine came with nothing in the way of instructions.
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[txoval]

It has been 6-7 years since I’ve had to do this and it was on an aluminum case.

I believe it was set at 750rpms, but hopefully someone who has done it more will reply. I just remember it cutting much faster than I expected.

I would call Berg as well, they should know

[jsturtlebuggy]

I bought this from Gene berg sometime in the late 1970s with no instruction included. What I did was pinned a 1/2in deep socket on it and use a 3/8in speed handle tool to drive it by hand. it has worked well for me over the years I have needed to use it. Magnesium cases cuts easily with it.

_________________
Joseph
Fair Oaks/Orangevale, CA
Elrod Motorsports
Motion Tire Motorsports
Having fun with Dune Buggies since 1970
Into Volkswagens since 1960

[mcjweller]

Good advice! My cutter should arrive tomorrow. 750 RPM isn't much, and the tip about doing it by hand is interesting too. I've been trying to figure out how to jig the case halves on my drill press, maybe that's not even necessary.

I need to take about .012" off to get where I need to be. Not much indeed, I appreciate the warnings that it cuts quickly!

[txoval]

It fits in a 1/2” drill…hand drill would work just fine.

[modok]

You could go up to 750 rpm, but faster isn't necessarily better.
The best speed is whatever speed between 60 and 750 that gives you the best control and even cutting.

[Dougy Dee]

I suppose you could improvise a stop or limiter by bridging across the case halfs and providing a reference line or clamp around the Berg tool to limit the travel...

[rayjay]

OP, do you have a junk case to practice on?

[mcjweller]

Nope. Nothing to practice on but this brand new AS41 case that's been machined for 90.5 cylinders but, I'm not new to cutting/milling soft materials so I will just remove tiny amounts and sneak up on by checking frequently.

[Dougy Dee]

I have a junk case here in Niagara/Hamilton area.
You could try Joe S, too...

[mcjweller]

Thanks for that. Yeah I've met Joe, great guy. Wealth of knowledge too.

So here's some progress. Measure twice, cut once. I decided to re-measure clearance, because you know, new day, etc. found it was a lot closer but still under (.036") got curious, measured clearance on every other lifter and lobe. I discovered that I was .037 and .036 on lifters for cylinder 1, .041 for both on cylinder 2(within spec) and .042 on cylinders 3 and 4.

So, I milled the lifter bores on cylinder 1. Used a hand drill with a very stable chuck, died the surface so I could just kiss it and stop, and ran it just fast enough to avoid chatter with no pressure at all into the lifter bore. These now clear at .042" each.

But...the Gene Berg tool cuts a different profile than the case came with. (See pics) it is a gradual bevel vs flat surface with an inner chamfer

Does this matter? Do I need to go kiss the other 6 to match the profile? And if I do what is the upper limit above .040"? My book doesn't specify

[txoval]

I’d only cut the ones that need it.

On the ones you cut, drop the lifter in and check clearance. I didn’t add the bevel