New oil pump chain, no shims needed?

[KFunk]

I just put on a new Febi oil pump chain from AutohausAZ, started out with a 0.1mm shim, and it seemed way too tight. Only a 1 to 1.5mm or so in either direction with thumb pressure. I tried removing the shim entirely and refitting, and it'll deflect about 3mm inward or outward. I tried switching back to the original chain, and its stupidly loose, even with the 0.1mm shim which was on it.

Also to note, the original chain has dogbone looking links, while the new chain has regular ovals (no indentation in the center).

I'm wondering if the new one is designed to fit tighter and might eliminate the need for shims. I don't know that I'd be comfortable with the shim in there, but it also seems contrary to the usual thought that a shim is always necessary.

And yes, I'm referencing CD's drawing:

[TobyB]

A shim's not always necessary.

I usually find that with all new stuff

one thin one is a little on the tight

side at first, but just a little.

I figure that as things bed in right at first,

there'll be more wear, so a little tight's ok.

t

[KFunk]

Sooo... how tight is too tight?

[tlapham]

Also remember that once the engine warms up, the chain elongates slightly, making it looser.

I would assume that if you made it too tight, you wouldn't be able to install the chain...

[Tommy]

I have this feeling based method although as an engineer I'm more used to exact numbers I think if it's tight - meaning that there is tension on the chain - it's too tight. If it's loose - no tension - it's good. So I'm targeting to "as little loose as possible".

Tommy

[KFunk]

A shim's not always necessary.

I usually find that with all new stuff

one thin one is a little on the tight

side at first, but just a little.

I figure that as things bed in right at first,

there'll be more wear, so a little tight's ok.

t

Is there any way I can get you to define 'just a little' tight?

I know things loosen up later, but I have no idea how much. By the sound of things, I should put the shim in and hope it loosens up.

What will result if it is too tight? Will the chain break?

I really don't want to take everything back apart shortly after putting it together....

[c.d.iesel]

leave the shim out - for your 3mm side play

~ don't want to put stress on the pump

[TobyB]

Tommy's exactly right, it's kind of like front bearing play on a track car-

if there's NO free deflection in the chain, technically it's too tight. However,

the difference between no free deflection and a mm or 2 is

probably .001mm of shim.

So if it's a bit loose without one, I add a small one, and then, if there's

NO free play, try to gauge how 'overtight' it is. If it's stiff, the shim comes

back out. If it's 'springy', then it's a feel thing.

However, if in doubt, CD's right- looser is safer. I've taken old motors

apart that had MILES of slop, and they hadn't broken anything or had

oil pump drive problems.

t

[KFunk]

Tommy's exactly right, it's kind of like front bearing play on a track car-

if there's NO free deflection in the chain, technically it's too tight. However,

the difference between no free deflection and a mm or 2 is

probably .001mm of shim.

So if it's a bit loose without one, I add a small one, and then, if there's

NO free play, try to gauge how 'overtight' it is. If it's stiff, the shim comes

back out. If it's 'springy', then it's a feel thing.

However, if in doubt, CD's right- looser is safer. I've taken old motors

apart that had MILES of slop, and they hadn't broken anything or had

oil pump drive problems.

t

Now you've got me leaning towards using the shim. Reading thru the shadetree engine rebuild guide (by Jim Rowe and someone else), it doesn't even give a spec. Just says to check if it's taut or not. I don't think its completely taut with the shim in place, just very very little deflection. I'll have to torque the pump bolts all the way on and see if it loosens it up some. I tested it with them snugged up, but perhaps they need tightened a few more rotations.

If it's OK to leave the chain fairly snug, then I'd like to do it. Last time I checked the oil pump chain was around 2005 or 2006, and it seemed OK but a little loose then. It loosened up a lot since then, and that seems like a fairly short time to me. I'd rather give it a good start now so that it'll last 10 to 15 years of abuse.

By the way Toby, thanks very much for all your help. You've been the voice of reason in several of my threads.

[c.d.iesel]

go with 'loose' (5mm) rather than tight

That is from the BMW Repair Manual Technical Spec.

the oil pump is just sitting with no load -

Your proposing putting some load on it

with a too tight chain. Adjust the chain for the

condition that it is in now - not hoping for a

certain amount of stretch and the chain coming into proper

tension. A too tight chain will wear more than a chain

with proper side play. This chain runs completly in a oil bath.

It's well lubed and cooled. It'a also very short so it takes

enormous amount of wear to slacken. Of course your tension

measurement should be with the pump mounting tight.

[TobyB]

I don't think its completely taut with the shim in place, just very very little deflection

I'm with CD-

I'd loosen it then, especially if it's not new. Really, the slop doesn't matter

all that much- the thing is under constant load, so once you get going, the

backside is GOING to flop around- but it's so short and light that,

unlike a cam chain, it won't hurt itself even if it's pretty darned loose.

t

[KFunk]

I don't think its completely taut with the shim in place, just very very little deflection

I'm with CD-

I'd loosen it then, especially if it's not new.

But it is new. Everything new.

[TobyB]

Hokay. I don't think anything bad will happen either way.

If there's a little deflection (bump-bump) it's factory perfect.

But I agree with you- right at first, it's gonna wear and seat in the most.

So 500 miles later, it's going to be a bit loose, no matter what you do!

New oil pumps are certainly dear, aren't they?

t

[KFunk]

Here's a pic for funsies, with thumb pressure applied. This is with the shim in place, stuff torqued down, etc. It's actually the old oil pump sprocket, as my new one won't be here till Monday. The old one is actually fairly fresh itself, but the new one only cost me $13, so why not have all new sprockets and chains for the entire engine.

I think I'll leave the shim in there. The chain isn't completely 'taut,' as you can push it just a bit inward or outward. I did notice the new shim actually rubs the oil pump chain, not sure how that happened or why. Everything seems to be in the proper place. I just trimmed it a little bit around the chain, since its flimsy metal that doesn't really do anything in that region.