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Old 10-16-2019, 12:11 PM   #21
40 Deluxe
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Default Re: Cam Degreeing/Checking Important

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Originally Posted by frnkeore View Post
The general way of finding TDC, is to rotate the crank, only clockwise, while picking up locations.

Set the dial indicator on the piston and find the approx top of the stroke. Rotate again, set the degree wheel at 0, when the indicator gets to .100 BTDC, then rotate until it's at .100 ATDC. Divide the number of degrees by 2 and that is TDC. Next rev, stop the crank at that number and reset the degree wheel to 0.

You can use any number on the dial indicator but, .100 is covenant.

If you use a bump stop, you'll be close but, you won't be at TDC, because of the back lash, between the crank gear and the cam gear and that's why you only turn the crank CW.

You don't have to turn only CW but, if you don't, you have to go well past your locations and start turning CW again, to be sure you've taken the back lash out.
Backlash? The only backlash involved in finding actual TDC with the positive stop method would be the oil clearance in the rod bearing! The timing gears are not involved in finding TDC. Since you're no doubt using very light checking springs, just hold the cam gear clockwise (against rotation) to take the backlash out when checking the cam timing.

Last edited by 40 Deluxe; 10-16-2019 at 12:20 PM.
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Old 10-16-2019, 01:01 PM   #22
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Default Re: Cam Degreeing/Checking Important

As I was mauling this over last night, I remembered my first roller cam, that I installed in a Low Riser, 427, in 1969. It was a Chet Herbert cam (Father of the roller cam). At that time, I lived about 3 miles from his Anaheim shop so, I picked it up, in person and he told me how to set the cam timing. It didn't require anything but a indicator and a straight edge. At that time, he only made his cams to be installed "straight up" or "spit overlap", meaning that the cam lobe CL is at TDC.

He told me to find TDC, turn the cam, until the straight edge was level, across the lifters, on #1 and install the timing sprockets and chain.

Expanding on this way of setting cam timing, if you first find TDC as described, you can put a dial indicators on both in & ex valves (if the lift is the same) and turn the crank, until the valves are at the same reading and check the degree wheel to see if the cam is installed as it should be. Most FH cams are 0 advanced but, if not, the degree wheel will show you the amount of advance, to check against the cam card or factory spec.

If the lift is different between in & ex, you'll have to use lobe centers as described before.
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Old 10-16-2019, 01:06 PM   #23
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Default Re: Cam Degreeing/Checking Important

Frank
That is as simple as you could make it, and easy to remember.


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Old 10-16-2019, 01:22 PM   #24
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Default Re: Cam Degreeing/Checking Important

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Backlash? The only backlash involved in finding actual TDC with the positive stop method would be the oil clearance in the rod bearing! The timing gears are not involved in finding TDC. Since you're no doubt using very light checking springs, just hold the cam gear clockwise (against rotation) to take the backlash out when checking the cam timing.
I did misstate that a little, regarding TDC but, my point was back lash and unless your working with a roller bearing crank, you do have back lash.

Since your going to have to use a dial indicator anyway, to get accurate readings, why not use it to set TDC?
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Old 10-16-2019, 01:31 PM   #25
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Default Re: Cam Degreeing/Checking Important

Even a cave man can do it.
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Old 10-16-2019, 01:35 PM   #26
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Even a cave man can do it.
Yes, I can
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Old 10-16-2019, 04:36 PM   #27
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Default Re: Cam Degreeing/Checking Important

Bottom line of this discussion... I can no longer build engines. (After 65 years of not attending to these details.)
Great read, by the way.
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Old 10-16-2019, 06:28 PM   #28
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Default Re: Cam Degreeing/Checking Important

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Bottom line of this discussion... I can no longer build engines. (After 65 years of not attending to these details.)
Great read, by the way.
Haha. It is pretty crazy all the details that go into doing a engine dead nuts correct.
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Old 10-16-2019, 09:53 PM   #29
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Default Re: Cam Degreeing/Checking Important

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Bottom line of this discussion... I can no longer build engines. (After 65 years of not attending to these details.)
Great read, by the way.
It's not that they can't be built without checking things, it's just that it might not (and that is more like most probably) run as well as it would with everything dialed in.
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Old 10-17-2019, 12:12 PM   #30
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Default Re: Cam Degreeing/Checking Important

I love it, someone that understands the simple way to check a cam. "Split overlap". Learned that in a shop cals in school. Some old engines didn't have any marks. However, I do like to advance the 400jr on a short track. Comes off the corners like a rocket. A good friend taught me that. That might be a good thing to do with the L-100. Never thought of that 8* would be enough
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Old 10-21-2019, 10:48 AM   #31
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Default Re: Cam Degreeing/Checking Important

RE: Since your going to have to use a dial indicator anyway, to get accurate readings, why not use it to set TDC?

The reason that many advocate for the positive stop method of finding TDC is due to the amount of piston dwell (in crankshaft degrees) at TDC. In other words, there are a few degrees of rotation where the dial indicator doesn't show movement. One could think they are at TDC with the crank actually being in a slightly different position than the dial indicator shows. So, this causes your TDC "pointer" to be off just a bit.

You can always use BOTH methods - so that your cross-validate one against the other . . . to achieve your final pointer setting.

When I use a dial indicator only, I have to visually pay attention to the "before/after" movement of the crank to figure out where TDC is. Hopefully I'm making some sense . . .
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Old 10-21-2019, 11:14 AM   #32
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Default Re: Cam Degreeing/Checking Important

Another Setup Method: One of the best ways to initially install a cam is very simple (assuming you have adjustable timing gears and a dial indicator):

1) Setup your TDC and pointer (this is needed for all timing tag related work)
2) Read the timing tag, at what degrees of crank rotation does it show the .050 profile intake lift to be at? (On the intake it is usually a BTDC degree value)
3) Rotate the crankshaft so it is at exactly the degree value shown for the .050 lift on the timing tag.
4) Install the camshaft/gears and one lifter for the corresponding cylinder - such that you are at .050 lift for the specified intake lobe. (Using the dial indicator to directly read the cam profile off of the lifter).
5) Lock the cam down at .050 lift.


If the timing tag says here is where the crank should be at .050 intake lobe lift, then you do exactly that and given the above approach, the rest of the numbers should match.

Now that you've installed the cam to match the .050 lift and crank degrees . . . check to see that it is at the correct place on both opening/closing events (both lobes).

I've used a lot of adjustable cam drive systems on various engines (flatheads and OHVs) - the above method is the easiest way to consistently setup the cam . . . and it should match the tag for both lobes on both the opening and closing ramps. If it doesn't match the tag - then I know the cam is incorrectly ground and I cannot "fix it".

Also, if you want to 'advance/retard' the timing, then once again you can use the above method - just move the initial crank degrees to do what you need/want.

There yah have it . . . another man's method . . .

B&S
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Old 10-22-2019, 07:33 AM   #33
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Default Re: Cam Degreeing/Checking Important

I've been aware of this but have never done it as it is not in the factory manuals. B&S made it sound easy as you just need to get one number and either it all lines up or the cam is incorrectly ground. Now I have the question, have any of you ever gone through every lobe in the cam checking for specs? Amazing seeing how much some of these are off.
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Old 10-22-2019, 10:58 AM   #34
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Default Re: Cam Degreeing/Checking Important

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Originally Posted by Bored&Stroked View Post
RE: Since your going to have to use a dial indicator anyway, to get accurate readings, why not use it to set TDC?

The reason that many advocate for the positive stop method of finding TDC is due to the amount of piston dwell (in crankshaft degrees) at TDC. In other words, there are a few degrees of rotation where the dial indicator doesn't show movement. One could think they are at TDC with the crank actually being in a slightly different position than the dial indicator shows. So, this causes your TDC "pointer" to be off just a bit.

You can always use BOTH methods - so that your cross-validate one against the other . . . to achieve your final pointer setting.

When I use a dial indicator only, I have to visually pay attention to the "before/after" movement of the crank to figure out where TDC is. Hopefully I'm making some sense . . .
It's true, that when you get very close to TDC, the indicator slows way down but, at .100, it's still moving at a rate that you can see. If your uncomfortable, at .100, you can use any distance, such as .300 or even .500. The number you pick, doesn't make any difference, it only has to be used on both sides of TDC. The slower the indicator moves, the easier it is to stop it at the distance that you want.

Also, you don't have to set up a stop, when using the above method but, you still do, have to set up a indicator to check the timing. One less tool and thing to do, plus a more accurate TDC setting.

Regarding checking all cylinders for timing, I haven't heard of anyone doing that. For the layman, by the time that you've done #1, your probably not interested in doing others but, for the ambitious, it would be good to check #4 in the firing order.
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Old 10-22-2019, 12:44 PM   #35
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Default Re: Cam Degreeing/Checking Important

To Find TDC with a dial indicator, I run the piston up until the piston goes past TDC bt .1--". Mark it. now go back until the piston goes back down .100" mark it. TRU TDC is between the two marks. Just liker the tie wrap.
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Old 10-22-2019, 03:55 PM   #36
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Default Re: Cam Degreeing/Checking Important

My positive stop is a big-ass washer and a 7/16 coarse bolt . . . the crown of our domed pistons will hit the hard washer stop and you now have a "dead stop".

Two is Better Than One: I always double check TDC - with both a positive stop and the dial indicator . . . helps me sleep at night. Of course I also mark my front pulley in 5 degree increments - from 0 to 30 degrees BTDC (for future ignition timing settings).

Cam Gear Mesh, Thrust and Backlash: Depending on what year flathead you're building and what type of cam gears 32 - 48 versus 49-53 . . . the cam thrust will vary. On 32 - 48 engines the cam thrusts toward the block - on 49-53 it thrusts toward the timing cover. The reason this is important is that in order to get accurate cam timing events, you need to know that the cam is fully against the block - or fully against the cover. On 49-53 engines it tends to "walk" away from it. This screws all your calculations up if you don't have the cover on!

So, on a 49-53 engine it is really best to have the timing cover in place (with the correct backlash amount) before you do all the cam timing work. As the timing will change as the cam walks forward. You really want the cam to be touching the cover before you start doing all your timing checks. On earlier engines, I use a small rubber mallet to tap the cam gear - making sure it is flush with the block.

Timing Cover Gaskets: On a side note, make sure your timing cover gasket is the correct thickness! I've seen gasket sets from Speedway that have timing cover gaskets that were about .0245 thick - the correct/stock gasket is .0145 thick. By using the Speedway gasket, you've now increased the cam backlash by .010 - that is not good. This also effects your cam timing as the cam can now move forward an additional amount (more than it should) - and since the gear teeth are angled, the cam rotates as it comes forward and the timing changes.

In the end, the little stuff matters . . . . but Hey, I'm a tad bit of a perfectionist! LOL

Good luck,
B&S
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Old 10-22-2019, 05:28 PM   #37
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Default Re: Cam Degreeing/Checking Important

On an 8ba it will also effect the ign timing.
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Old 10-23-2019, 07:06 AM   #38
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Default Re: Cam Degreeing/Checking Important

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On an 8ba it will also effect the ign timing.
Lawrie
Not an 8ba because the distributor is times to the crank with a light. The earlier motors it might be a problem because the distributor is timed on a machine and fitted to the cam. You've raised a good point thought about how changing the cam timing might change the engine timing.
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Old 10-23-2019, 08:19 AM   #39
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Default Re: Cam Degreeing/Checking Important

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Not an 8ba because the distributor is times to the crank with a light. The earlier motors it might be a problem because the distributor is timed on a machine and fitted to the cam. You've raised a good point thought about how changing the cam timing might change the engine timing.
What he is probably talking about is that by having too much backlash, this allows the camshaft to move in/out by more than Ford intended (in the discussion, another .010 or so). The "normal" backlash is around .004 to .007, so by increasing the backlash, your allowing cam timing to change/move and the same with the final ignition timing.

To give you an idea about how this is important, on a recent 383 SBC build (high horsepower street engine), when we had it on the dyno, we noticed that the ignition timing was moving around by about 3 - 5 degrees - when it should have been at a steady state. It so happened to have an adjustable timing cover (nice Cloyes piece) - where you can externally set/control the backlash of the cam.

We tightened down the cam button just a bit and the timing then steadied as it should have. What started our checking was that we were getting inconsistent dyno pulls - HP was fluctuating about 15 - 20 HP . . . we needed to figure out why. The 'why' was the backlash. Now to bring this in context, this engine makes 520 HP . . . more than 5 times a stock 59AB.

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Old 10-23-2019, 08:45 AM   #40
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Default Re: Cam Degreeing/Checking Important

I still find it hard to believe with all the emphasis on precision (especially in engine building) that a cam could be designed, cast, and machined that doesn't conform to spec in the most elementary way. What's worse is that obviously it happens enough that cam degreeing is a routine part of engine building. Is it really so hard to machine it in line with the spec?

Makes me wonder about other faults that are out there.
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