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Camshaft Gears

Yes, we offer camshaft gears!

We are committed to helping you get a gear that ACTUALLY FITS!

After 35 or so years of building engines for these wonderful machines, and after having amassed a collection of around 30 lose camshaft gears - many brand new - I was working on an engine where I tried every single camshaft gear on hand and NONE of them fit that engine, not even close!

After pondering this, I realized two vital details:

1) In all these decades of engine building, I've never needed a larger gear, only "smaller ones". So, naturally, what gets left over are the larger gears. I called many other engine builders and we all have had the same basic experience: your best bet is to put the one that came out back in, and failing that, you'll probably need a smaller size! And;

2) The markings on the gears are worthless. I took all the gears on hand and rank-ordered them by size, and sure enough, I had brand new minus fours (-4) that were larger than used plus ones (+1)! This is not supposed to be! And, note that absent markings that actually reflect the real size of a gear, it means that gears have to be selected by trial-fitting each one.

(Note, by the way, that gears aren't measured by the diameter of the outside of the teeth - like threaded fasteners are - but rather by the contact face where two gears mesh. So, it's harder to measure than most people realize.)

What to do about it? You COULD begin manufacturing of new gears, but for one engine, that seems rather silly. Or, you could cut a large gear into a smaller one! AH, but if you do that, exactly what size do you cut your gear to - given, mind you, that you don't yet know what size you need?

Why, you need a whole collection of gears, ranked by size, then trial-fit them until you pick the right one!

And so that's exactly what we've done and now we're offering the benefits to you!

Here's our deal when you buy a gear from us...

  1. Try your original core and tell us the results of your attempted fit as outlined below: if it rocks out when you turn it backwards, it's too tight, and the closer it is to staying put, the closer it is to fitting. If it doesn't rock out, is there any lash? Can you hear a click when you wiggle it in reversing directions? Find complete directions below.
  2. Send us your core along with the results of your attempt to fit it.
  3. We'll send you a gear that's an estimate based on your results from following the procedure outlined below.
  4. You then try the gear we've sent you - how well does it fit?
  5. If the gear we send you doesn't fit to your satisfaction, return it us, in the same condition as we sent it, along with your new results of trial-fitting, and we will send you another one. All the shipping is on you, of course. If our smallest gear is still too big, we'll cut one down for you. And, if our biggest one is too big, you may have to wait a while for a big enough core to come in, or we'll refund your money - but we highly doubt that will ever happen! We will repeat this process until either you get one that fits to your satisfaction or we run out of gears to try and refund your money.

Please note that there were many different manufacturers of these gears. Some have bores for dowel pins and some don't. Some are magnesium and some aluminum. Nearly none are perfect in all regards. Many of our gears are new, but we're not promising new, only helping find a good fit on a gear that's runable. And, the gear on the crankshaft matters, too - YOUR "crank gear" - it may not be round! It may have burrs on it, etc.; its flaws can appear to be flaws with the camshaft gear. With regard to our exchange service, we are only concerned about size ("fit"); you may or may not get a gear with dowel pin holes - if you request it, we can try to find you a gear with dowels, but that's not really a part of our service (you can have a machine shop add dowel pin bores for you - but they need your camshaft to do it). Further, because we have no control over the crank gear or the camshaft to which the gear is fitted, we offer NO GUARANTEES whatsoever of any kind, only that we'll keep swapping out gears for you when you pay all the shipping and keep returning to us the same gear in the same condition that we sent you - as described here.

How To Fit A Cam Gear

Camshaft gear fit depends on many factors, but here's a straightforward procedure to figuring out the fit of any particular gear pair in any particular crankcase.


  1. The crankshaft gear must be inspected for burrs or "dents", and any found must be either removed or a better gear selected - this is best done before the gear is mounted to the crankshaft.
  2. The crankshaft gear must be installed properly onto the crankshaft, with all the details that entails.
  3. The crankshaft itself must be properly fitted to the crankcase with all the details that entails.
  4. The camshaft's gear mounting surface must be clean, flat on the threaded surface, and the outer rim where the gear mounts must be round, and both concentric and perpendicular to the camshaft axis.
  5. The camshaft gear must be mounted to the camshaft with the timing mark on the gear perimeter (usually it's a dot, but sometimes it's a line) directly in line with the oil pump drive slot, and the bolts tightened to 18 foot lbs. The bolts should be "grade 10" (marked 10K), or grade "10.9" (marked 10.9), and just long enough to go all the way through the camshaft's mounting flange and not more. Any other bolts should be rejected. For trial fitting purposes, no thread locking should be used - that can (and should) be added after gear fit is confirmed.
  6. Both gears must be perfectly clean and dry with no shavings, oil, or dirt of any kind in or on either gear - a small nylon-bristle brush can be helpful.

Trial Fitting

In the following discussion, we need to discuss what "size" means. ...In doing our research, no specific reference could be found as to what a "zero" camshaft gear's effective (tooth-contact) diameter is, nor did we find any specific reference as to what the "step" is between sizes. And, we proved via actual observation that today the size markings on gears are useless because they no longer relate - if they ever did - to actual gear size probably, at least in part, because they were made on different tooling at different times. (Unfortunately, saying "a plus two (+2) gear is just barely too tight" is meaningless because the +2 marking is relative only to the tools that made it.)

What IS useful, though, is a relative measure (which is what the original markings were all about - they just aren't useful today). We presumed that the gap between the official sizes was defined as equal to the official tolerance in lash such that if you just barely have too little lash, you need the next smaller gear, for example. We then measured all OUR gears. So, when you send us YOUR gear AND tell us your trial-fit results, based on the following, we have a pretty good idea which gear you might need because we're going to measure YOUR gear on the same tooling as we measured ours!

  1. Engine assembly is traditionally started with the installation of parts into the LEFT case half - so, we presume use of the left half here.
  2. There are two dots on the crankshaft gear - one on either of two adjacent teeth - and one dot on one tooth of the camshaft gear; the gears are meshed with the one dot on the camshaft gear going between the two dots on the crankshaft gear. Rotate the crankshaft so the two dots on the crankshaft gear are just above the horizontal (case seam).
  3. Align the cam gear to mesh with the crankshaft gear and lay the camshaft into its bearing bores, gently - wiggle it as necessary to confirm it's seating in its bores as best it can - DO NOT FORCE IT.
  4. If the camshaft won't lay flat into its bores reasonably well, the gear fit is perhaps five sizes too big or more - that's a guess.
  5. If the camshaft appears to lay flat in its bores, rotate the crankshaft counterclockwise, so the gear mesh is going "up", away from the crankcase half. Here's how to interpret the results:

Please note that these estimates of how far off any given camshaft gear is from a correct fit for any given case, crank, cam, and crankshaft gear, are just that; estimates. The purpose of this is to help you inform us about how good (or bad) your present cam fit is so we can more easily help you find the right gear for your engine.

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