R16 Timing Components and Cam-SAE vs. Metric

[Curtis]

So I started looking at my 3 main motor from the car I am restoring to evaluate it for rebuild. This SAE engine has some off color blue paint (black is stock) on it which says it has been out of the car and maybe rebuilt.

I have on hand many new timing components I got from what used to be Motor Power Inc. In another thread the subject of a half tooth difference came up.

I pulled the gears from the SAE motor and did a comparison to the metric stuff I have. I got some key stock and lined up the gears from the SAE, a metric engine I bought to make in to a stroker and the new gears.

Based on the photos below I am left to wonder if the SAE motor got metric gears put in it. And how do you tell a SAE cam from a metric. Both cam bolts like to go in both cams.

From left to right the crank gears, SAE, old metric, MP Inc. H20. All the teeth line up.

IMG_2395.JPG

Cam gears, same order, teeth line up.

IMG_2396.JPG

Okay the cams. The top one with the yellowish paint on it came from the SAE motor. The other came out of my metric stroker motor.

IMG_2397.JPG

IMG_2398.JPG

IMG_2399.JPG

End of SAE motor cam

IMG_2400.JPG

End of cam from stroker motor.

IMG_2401.JPG

[JT68]

Looks like you may have all metric sprocket parts.

The cam itself is fairly easy to ID. A 3/8-16 bolt will go in either, but will be a sloppy fit in a metric cam.
A 10m x1.5 bolt will jam in the USS threads cam unless some dingdong tapped it metric. Obviously, It will fit properly in
a metric cam.

Neither cam uses SAE threads, but there were SAE threads on other parts of the early R.

Whatever you do, don't run new style metric sprockets with a USS thread cam vice versa, it will never run correctly.

If you pm some photos of the fronts of the sprockets, we can verify.

J

[Curtis]

Looks like you may have all metric sprocket parts.

The cam itself is fairly easy to ID. A 3/8-16 bolt will go in either, but will be a sloppy fit in a metric cam.
A 10m x1.5 bolt will jam in the USS threads cam unless some dingdong tapped it metric. Obviously, It will fit properly in
a metric cam.

Neither cam uses SAE threads, but there were SAE threads on other parts of the early R.

Whatever you do, don't run new style metric sprockets with a USS thread cam vice versa, it will never run correctly.

If you pm some photos of the fronts of the sprockets, we can verify.

J

What thread was the cam if not SAE? I'll have to get some photos.

[Curtis]

Front of the gears same order.

IMG_2402[1].JPG

IMG_2403[1].JPG

[JT68]

3/8-16. (3/8 NC , 3/8 USS) for the early cam. 10m x 1.5 for metric.

[JT68]

Yes, all metric. Your first photo of the three cam gears lined up lead me to believe they
are all metric.

I'm not sure if there is any significance to the 1 & 2 casting numbers- there may be.
Maybe early 5main vs. late 5main? Maybe a degree or so advance/retard for emissions? (1 degree is hard to see with the
naked eye at the sprocket radius due to parallax etc.

Anyway, those are almost certainly all metric timing, otherwise when lined them up on the keystock, an early
cam sprocket would have been different by about 3 degrees+/- (which is 1/3 tooth).

[Curtis]

Can somebody post a photo of the early one please?

Sigh.....

[JT68]

Yes, but there isn’t much difference visually. The timing marks MAY be a few degrees over so they line up properly with each other. That is about the only visual clue and it’s not reliable since the position of the timing marks is not particularly precise.

That’s why it’s easy to think everything is fine when mixing up the gears. The timing marks line up OK with each other, but the cam is rotated 3 or 6 cam degrees. (6 or 12! crank degree)

Here are a couple measurements. In the photos metric is at zero cam degrees:

PM if you need more help, glad to assist.

[Gregs672000]

Wow, for R16 folks this really could be a big deal this many years later when people are restoring these cars. Information like this would simply not exist anymore were it not for this site and folks like JT68 and others.
Thank you to all on this forum.

[Curtis]

One of the drops guys has the sae components so I will post up a photo comparison. I don't feel like taking apart my other engine.

[JT68]

“As original” early timing gears. Note the timing marks are offset from the teeth in this version, Problem is some metric gears are marked in a similar fashion, so you can really tripped up if you go with visual comparison- the timing marks are just tooth markers and not particularly precise-can be many degrees off.

The method Curtis showed at the top is a decent way to verify- if you have a cam sprocket 1/3 tooth “off” from a late metric sprocket with the key ways aligned, it is an early sprocket.

Another possible way to ID cam sprocket is by keyway, the early sprocket slot is 5/32 which is .001 under 4mm. Thus 4mm keystock is a tight/interference fit. 4mm keystock slips right in the metric sprockets. (This test assumes accurate gears, accurate keystock etc.).

This is also why a metric sprocket will slip right on the early cam which causes big problems.

[Curtis]

How funny, I couldn't get 5/32 so he gave me 4mm and all the sprockets go on no problem.

[JT68]

Yep, that again points to “all metric” sprockets as we already concluded. You really can’t miss the 1/3 tooth error if you line up the keyways with keystock.

If you want to mail them to me, I can confirm 100%. (No charge)

[jake7140]

I think I may have found why, after switching cams during a rebuild, I now have insufficient piston to valve clearance. But once I find out, sounds like I can use a metric cam in a 3 main sae engine as long as I use a metric timing set? This is great never before known time info. Thanks gurus!

[JT68]

Yes, if you use the metric cam AND metric sprockets, that will work just fine. The crank is cut the same, so the 3main engine will never know it has metric timing components. J