James Rogers, Brent, Purdy, etc...question

[tbirdtbird]

I am helping a friend with an engine which has too much clearance between timing gear and cam gear. A used DanM aluminum cam gear was on there, which seemed a bit beat up from being run loose on another motor, so I just now swapped it for a brand new DanM bronze gear.

[J Franklin]

There used to be oversize cam gears to help these conditions. I don't know if you can find any tho.

[tbirdtbird]

yep, looking for input before we order one from Dan...

[James Rogers]

Sounds like the babbitt job is ruined. You can put a .005 over gear on the cam but it will only close the clearance about .003 overall. If the babbitt is wearing like you say it will go south pretty fast and might take some other important parts with it.

[BRENT in 10-uh-C]

I'm gonna think on this a bit but I kinda agree with Mike. My first thought are I would think that a loose gear lash would not run as hot as one without enough lash. Maybe that is not the case?? I'm not sure the noise is totally gear lash. How did they do on setting the crankshaft thrust?

I have a Kwik-Way line Boring machine with the fixtures that align off of one main bolt on each end. Mike Rogers has the same basic machine as I do. I don't know what everyone else uses to locate their boring bars but for me I would see if there was enough shims where I could remove .002"-.004" worth of shims and re-line bore it. I'm thinking it may mostly take the babbit out of the block and just true-up the babbitt in the caps. Again, I would want to think this one thru a little bit more. In the interim, can you give us a mic reading on all three sets of main shims to see what you have?

[tbirdtbird]

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James I appreciate your thoughts

[tbirdtbird]

Brent, the only thing apart right now is the timing cover is off

[George Miller]

What are you going to do if the crank is not on a parallel center line. If the crank is in the right location on the rear bearing. You are going to have some connecting rods moving all over the place. They will be trying to push the wrist pins out,and hitting the piston pin bosses. If the guy was that far off I would not trust the rest of his work.

[Kohnke Rebabbitting]

All align boring bars will bore at an angle

(IF).

The bushings are bad in a Tobin-Arp, to loose, or both arms are not in the same alignment.

If the boring frame type align bore bars have bearings wore out, or excess clearance.

There are alot of shops using wore out tooling.

[tbirdtbird]

OK, I have had a communication from Dan McEachern

[BRENT in 10-uh-C]

I cannot help but think this may go deeper than just excessive lash. Since I have not knowingly experienced this, my guess is if the journals are line bored at an angle, there would/will be all kinds of other vibration and harmonics issues. Theoretically the rods are located differently in relation to the piston bores, and the flywheel would not be parallel with the flywheel housing thus creating a transmission input shaft issue.

I guess the real question is how much will it really affect the operation and longevity? Yes, we all agree it is not correct and none of us would want to be guilty of putting out that craftsmanship, however on the flip side, surely there have been shops in the day that did the same thing. Are some hobbyists unknowingly driving Model-As with engines that are mis-linebored??

[Mitch//pa]

tbird what was the history before you got involved in this motor. from your post that it is basically assembled and in the car was it a whining problem from the gears?

[tbirdtbird]

Though I never heard it, it was described as whining and then some.

[motordr]

Crankshaft gears can look good and still be undersize. They can wear so evenly, that unless you measure the tooth width you will not suspect it as the cause of excess backlash.

[MikeK]

There seems to be an ASSUMPTION in this thread, and we all know what that leads to. The assumption is that all steel crank gears have the same pitch diameter, and they DO NOT. I have a number of used crank gears that have probably seen 100,000 miles grinding against dirt impregnated fiber gears. The pitch diameter has been severely reduced, and they would rattle like crazy against even a 0.005 over cam gear. One of them has so much tooth width worn away you could use it for a chain sprocket.

If this engine was put together with a well-worn crank gear that may be the problem, not the CL-CL distance.

[tbirdtbird]

I believe #15 and #16 are possible.

[pat in Santa Cruz]

I had an engine once with a C to C variance of .007 beyond std. Dan made me two gears that meshed beautifully, one being oversized to correct for the .007, and the engine is now quiet and runs smoother, too. (You should replace gears in sets, if you were not planning on that in the first place.) Dan is da man for this. I can't see the rest of your engine so I have no opinion on it other than if some work was sloppy, I would suspect there is slop in other places.

[Mike V. Florida]

Originally Posted by BRENT in 10-uh-C

I cannot help but think this may go deeper than just excessive lash. Since I have not knowingly experienced this, my guess is if the journals are line bored at an angle, there would/will be all kinds of other vibration and harmonics issues. Theoretically the rods are located differently in relation to the piston bores, and the flywheel would not be parallel with the flywheel housing thus creating a transmission input shaft issue.

I guess the real question is how much will it really affect the operation and longevity? Yes, we all agree it is not correct and none of us would want to be guilty of putting out that craftsmanship, however on the flip side, surely there have been shops in the day that did the same thing. Are some hobbyists unknowingly driving Model-As with engines that are mis-linebored??

Don't a very large amount of A owners think vibration enough to make the rear view mirror inoperative, is normal for a model A?

[Kohnke Rebabbitting]

There is not a one align bore machine that will line up on any one block and get the center distance right.

You can be Plus or minus .010 off.

You have to treat each block by its self to set center distance.

You can,t just use a centering Jig that came with the Align Bore machine and expect it to come out right, it doesn't work that way.

Herm.

[MikeK]

Originally Posted by tbirdtbird

...Mike K, are you willing to post the smallest diameter in your pile?

Measuring the pitch diameter of a gear is difficult, if not impossible without specialized fixtures. It can be estimated within a few thousanths against a known standard, but I do not own that measuring equipment.

When meshed against a new bronze cam gear I have (unknown actual variance from standard) a new crank gear vs. the most worn one in my box of junk, the cl-cl distance varies ~ 0.012 BUT, and this is a big "but", at that point the new cam gear I have on hand bottoms out at the root of only the worn gear, AND there is still play, because the wear is uneven and only on the thrust face of the teeth. This may be a function of an excessive addendum on the cam gear, or insufficient dedendum on that particular crank gear. Although those figures can be looked up in a machinery handbook and calculated, I have no way to measure it, as their datum point is relative to the pitch diameter. It's a vicious circle. Literally.

Basicly, a worn thrust face on the teeth makes the actual pitch diameter a false indication of running clearance. Even if a special 'fat tooth' (way over-pitch dia.) gear were made to restore backlash to near zero with a badly worn mate, the compromised thrust face geometry on the worn gear would wear out the new gear in short order.

[KR500]

Herm, One of the align bore fixtures I have is an old Ammco. Lempco also produced one of these. The fixture uses a false camshaft which you install in the A block and it has two equally distanced swing arms which rotate on the false camshaft and lock onto your boring bar in the fixture to establish the cam to crank center line distance. What is your opinion of these fixtures?

[Mike V. Florida]

Originally Posted by KR500

Herm, One of the align bore fixtures I have is an old Ammco. Lempco also produced one of these. The fixture uses a false camshaft which you install in the A block and it has two equally distanced swing arms which rotate on the false camshaft and lock onto your boring bar in the fixture to establish the cam to crank center line distance. What is your opinion of these fixtures?

There was a popular re-builder that would re-position the cam closer to the crank as an "improvement" The sleaveing of the cam in a "miracle motors" engine would preclude the use of one of these devices.

[James Rogers]

Originally Posted by tbirdtbird

I believe #15 and #16 are possible.
If it were possible to change that gear while the crank is in the engine I would but the crank must be out and you must use a press. Of course if we had it to do over....
so lesson 4 is to always change the crank gear too

We have completed one set of measurements and we get a measurement that is .024-.026 over the designated/required 4.154-4.156

Using a different method we are gonna measure again, since our measurement is key to Dan being able to make a correct oversize.

More to come

Mike K, are you willing to post the smallest diameter in your pile?

The gear can be removed in the car. Use a 2 jaw puller to remove it. I have done more than one like this.

[CarlG]

Originally Posted by tbirdtbird

...If it were possible to change that gear while the crank is in the engine I would but the crank must be out and you must use a press...

I changed my crank gear with the crank still in the engine and did not have to use a press.

That was a new crank gear from Dan the Man, purchased as a set with his Bronze timing gear.

[Tom Wesenberg]

Originally Posted by CarlG

I changed my crank gear with the crank still in the engine and did not have to use a press.

That was a new crank gear from Dan the Man, purchased as a set with his Bronze timing gear.

Wish mine were that easy. A few years ago I removed 5 gears from some cranks, and a couple wouldn't even come off using my 20 ton press. I had to heat them with an ox/acc torch and use a puller on a bearing seperator.

[CarlG]

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Maybe I made it sound too easy. Getting the old gear off was done with a gear puller, not sure if I used a 2 or 3 prong puller, just one of my Dad's old pullers. Then getting the new one back on, I dressed the crankshaft smooth with crocus cloth, then heated the new gear (450 degrees for 30 minutes), pressed it on using a socket and the crank nut (which is really a bolt). Engine was out of the car, but the crank was still in the engine.

[tbirdtbird]

Tom W had earlier told me his tale of woe which is why I have not tried it.

[Kohnke Rebabbitting]

Originally Posted by KR500

Herm, One of the align bore fixtures I have is an old Ammco. Lempco also produced one of these. The fixture uses a false camshaft which you install in the A block and it has two equally distanced swing arms which rotate on the false camshaft and lock onto your boring bar in the fixture to establish the cam to crank center line distance. What is your opinion of these fixtures?

If not worn, there is nothing wrong with the Bars or the fixtures, if after you set the fixtures, you check and zero the center distance, or Gear lash.

The things that make a (fixed) center distance not work are, Difference in blocks, wear in cam holes, and a large difference in cam gears and main bolt holes, as they are NOT all the same.

You can get exact center distance, and gear mesh using a Dial.

I lock the cam and what ever gears I use, and leave what ever crank gear loose, and check at 4 points.

They will all be different.

In the case of Dan's gears, he wants .005 at the largest, so that is where I set his at.

A cast gear and fiber has a different setting, and so on, with all the other kinds of gears that I try not to use.

This I use to get an exact setting for a cast crank gear and a fiber cam gear.

[Kohnke Rebabbitting]

This is the set up I use for Dan's Gears, and others. They always are set for what you wanted.

[tbirdtbird]

good pix Herm and thanks for the input

[Mike V. Florida]

Thanks for the pictures!