selecting laminated timing gear

[FrankWest]

Here we go again...
If I decide to use the Laminated gear replacement.. What is the meaning of oversize and undersize selection...
Does this mean that I have to buy 3 gears
One over sized one undersized and one just right?
No wonder people are using aluminum.
There you only have to buy one gear.

[Ron/IA]

Frank - There has been much discussion about timing gears here lately; both metal and fiber.

Standard, under-size, and over-size are used to get the correct gear lash between the camshaft gear and the crankshaft gear. Most engines will use the standard size gear. However, there can be wear which an over-size gear may be needed to achieve proper gear lash. I think it is rare to have to use an over-size, but might be the case if the block has been lined-bored not quite on center.

There is a lot of information on this forum about this subject, and there are much more knowledgeable people than I on this subject. Maybe they will respond to this thread.

[Kurt in NJ]

The alum gears can come in different sizes too, at Hershey I bought a .004 oversized one

try the std one, if it has too much backlash you need the oversized one, if it is too tight you need the undersized one---make sure it is checked in several places of crankshaft rotation ----does the old gear have any oversized or undersized markings?

[FrankWest]

Originally Posted by Kurt in NJ

The alum gears can come in different sizes too, at Hershey I bought a .004 oversized one

try the std one, if it has too much backlash you need the oversized one, if it is too tight you need the undersized one---make sure it is checked in several places of crankshaft rotation ----does the old gear have any oversized or undersized markings?

I did not jnow that. That aluminum gears come in size variations too.
All the places I have check selling them only have One Size?

[FrankWest]

When the cam gear is oversized will it actually bind up when hand cranking?

[MikeK]

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Overlooked is the fact that the steel crank gears can vary on their tooth pitch diameters. Despite the crank-cam centerline being distance being within spec., having a crank gear that is a few thou undersize will require an oversize cam gear pitch diameter for a tolerable mesh.

Wear on the thrust side of the crank gear teeth will also present backlash with a standard size cam gear. Some people attempt to reduce this with an oversize gear. The result is imperfect geometric tooth mesh but much quieter backlash resonance. For the 'just fix it' crowd an oversize cam gear is much easier and cheaper than a tear down to replace the crank gear.

Frank West- your question- If the gear fit is beyond zero backlash and actually has several thou interference you will immediately notice great difficulty getting the new cam gear over the threaded stub pilot and dowel pins on the camshaft. Even forcefully assembled you likely would not notice excessive resistance while hand cranking. The engine would, however, have constant thrust on bearing surfaces in a direction not normal to the engine. The ability of the camshaft (the lighter, more flexible of the two shafts involved) to maintain a complete film of oil to float on within the block holes that serve as bearing surfaces would be compromised. An egg shaped hole would form at the front cam bearing.

[Kurt in NJ]

It's possible, --the crankshaft could be ground off center, this could make the fit too loose at one point of rotation, to tight in another---but other engine drag could mask it depending on how far off it is from original dimensions

The 1$ gear I bought once I cleaned it up showed the .004. and upon close inspection I could see some damage at the edges of the teeth that the crank gear was hammered on, that teeth edge burrs dug into the gear in 2 places, probably had some binding till the steel gear chewed it's clearance, the rest of the teeth show little signs of wear---and the noise was probably blamed on the alum gear, i can clean up the dasmage, it will work fine in my Smiths compresser

[George Miller]

Originally Posted by FrankWest

Here we go again...
If I decide to use the Laminated gear replacement.. What is the meaning of oversize and undersize selection...
Does this mean that I have to buy 3 gears
One over sized one undersized and one just right?
No wonder people are using aluminum.
There you only have to buy one gear.

If you want to get it right you would have to have a accurate measurement between the crankshaft and camshaft. Not that easy if you do not have the tools or knowledge.

Other than that try standard gears. Then use a feeler gauge and see how much clearance you have, Then go from there.