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BTFH Cam Profile

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dalaymond

Posts: 304

Joined: Mon Oct 25, 2004 12:01 am

Location: Jonesville, Louisiana, USA

Post Thu Jun 19, 2008 9:13 am

BTFH Cam Profile

What is the profile of the cams on a Big Twin Flathead (U, UL, UH, ULH) ?
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Johnny5

Posts: 39

Joined: Sat Feb 09, 2002 1:01 am

Location: Miramar, FL, USA

Post Tue Jul 01, 2008 9:01 am

Re: BTFH Cam Profile

Do you want to know what it is (low-lift, low-rpm, not even modern farm implement profile) or what you'd like it to be?
John, 1934 VL, 1970 Mustang convertible - 351C auto
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panic

Post Wed Jul 02, 2008 3:46 pm

Re: BTFH Cam Profile

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dalaymond

Posts: 304

Joined: Mon Oct 25, 2004 12:01 am

Location: Jonesville, Louisiana, USA

Post Tue Jul 08, 2008 9:43 am

Re: BTFH Cam Profile

Thank you, Panic.
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Johnny5

Posts: 39

Joined: Sat Feb 09, 2002 1:01 am

Location: Miramar, FL, USA

Post Tue Jul 08, 2008 10:04 am

Re: BTFH Cam Profile

Here are some places that will regrind them:

http://www.leinewebercams.com/
http://www.blackwidowcams.com/

Black Widow bought out Sifton, and Leinweber has been in business forever.
John, 1934 VL, 1970 Mustang convertible - 351C auto
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Kurt

User avatar

Posts: 422

Joined: Wed Feb 16, 2005 1:01 am

Location: Tucson Arizona

Post Tue Jul 08, 2008 10:13 am

Re: BTFH Cam Profile

Black Widow bought out Sifton


They may have bought out Sifton, but V-Twin has the Sifton name now. He adds it to all of our BTSV and 45 WL, WLDR & WR cams.........as well as other items......

Kurt
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fhsmith1

Posts: 200

Joined: Wed Jul 26, 2006 6:10 pm

Location: Georgia

Post Tue Jul 08, 2008 4:31 pm

Re: BTFH Cam Profile

All
This may be a little off the subject but it is close. I have a set of the Vtwin Sifton's in my 42 U. Siftons run fine but the engine is very noisey in the gear case. The issue is gear backlash. The bushings are nice and tight but there is a considerrable amount of clearence from gear to gear. The pinion gear is also Vtwin. I know that on the later model big twins the gears came color coded for diffrent sizes but there is only 1 listed for the side valve. There is also a special tool on the later models which consists of 2 pins to measure the gears. Any suggestions?
Forrest
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Kurt

User avatar

Posts: 422

Joined: Wed Feb 16, 2005 1:01 am

Location: Tucson Arizona

Post Tue Jul 08, 2008 4:53 pm

Re: BTFH Cam Profile

fhsmith1

This is a common problem and one that I can only say an experienced machinist can take care of..........there's only one that I know of who does it correctly and if I remember, he's in Germany. There was a thread about his shop and showed his machine for aligning cam bushings here a few years back.....Eric from BOS may know.

When H-D assembled their engines (this is going off of second hand info.....I wasn't there to see first hand) they had bins of cams to select from when assembling a SV engine. They would pick the best fitting cams to install in a particular engine they had in front of them. One set may fit fine in one engine, but completely bind up in another and/or be too loose. When you buy one of our sets......you don't have this option.......you get four cams.

The machine I spoke of allows the bushings to be honed in the correct position for the cam set used.

Kurt
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Pa

Site Admin

Posts: 4652

Joined: Sun Mar 12, 2000 1:01 am

Location: Ohio USA

Post Tue Jul 08, 2008 8:14 pm

Re: BTFH Cam Profile

Kurt...I agree. One must remember a few simple things though. Location is the most critical part of a cam chest. This is why I don't prefer a cam bushing ream job, using factory hand tooling. A milling machine will place the bores in their, almost exact, better than you can with a hand reamer, location, than any other tool available. Accurate readouts are a plus. Measuring the locations is a vital part of insuring correct bore locations, between all bushings. Now....asssuming, the cams are machined and ground correctly, which all can be inspected, everything will fall right into place correctly. Gear back lash will be right, if cams are right. But ??? the bores must be right first. Noise in the cam chest will quite, when all dimensions, locations, and specs held. That is a given. Pa
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George Greer

User avatar

Posts: 961

Joined: Wed Aug 28, 2002 12:01 am

Location: Markt Einersheim, Germany

Post Tue Jul 08, 2008 8:19 pm

Re: BTFH Cam Profile

Unka Kurt.....

I believe the man's name is Harald Bartenbach, which is also the man that was making the three speed foot shifters.

I saw the photo your refering to in the W&W Cycles Catalog, and it has his email address...but the catalog it at work...

If you want the email address, I will bring it home and post it here.

George
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panic

Post Tue Jul 08, 2008 8:38 pm

Re: BTFH Cam Profile

IIRC the pitch diameter is measured across .105" pins, but there's enough slack in the tolerance that some will run quieter than others.
Too loose is annoying and makes diagnosing other noise-generating problems more difficult, but the gears will last very well.
Too tight is really bad - high temperature, rapid wear and early failure.
Unfortunately, changing the tooth contacts with a fixed set of cams is a nightmare. You need to either move the cam bushing holes, or use eccentric bushings to move that individual cam (up is looser for 2 & 3, tighter for 1 & 4). This will generally play havoc with the pattern for its neighbors, which will then have to be moved sideways for looser etc.
Even if you know the machinist is a brain surgeon, I can't see anyone attempting this (complete diagnosis, tear-down, several mock-ups, making and fitting 8 special bushings) for less than $500.
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fhsmith1

Posts: 200

Joined: Wed Jul 26, 2006 6:10 pm

Location: Georgia

Post Wed Jul 09, 2008 10:43 am

Re: BTFH Cam Profile

All
If anyone has the .105" pins and some cams and pinion gears, it would be interesting to know how much diffrence there is in the ones manufactured today and the old ones. If there is a pinion gear that measures more than mine it may make a good bit of diffrence in the noise mine makes. The most of the back lash is between the pinion gear and cam gear. The cam gear to cam gear back lash is still too much but not nearly as much as the cam to pinion.
Forrest
Last edited by fhsmith1 on Thu Jul 10, 2008 9:54 am, edited 1 time in total.
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panic

Post Wed Jul 09, 2008 3:39 pm

Re: BTFH Cam Profile

That's an excellent thought. For the U etc. not so easy, but for the 45, K, Sportster which used the 24011-37 pinion gear for 40 years there must be a range of sizes.
Perhaps we can set up an informal exchange program?
Unfortunately, .105" pins are not that common (falls between #36 & 37 drills).
I'll be happy to maintain a page with pitch diameters available?
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fhsmith1

Posts: 200

Joined: Wed Jul 26, 2006 6:10 pm

Location: Georgia

Post Thu Jul 10, 2008 9:53 am

Re: BTFH Cam Profile

Panic
Pins are a fairly common tool and are not that expensive. They come in 2 sizes. .105" for the early models and .108" for 1990 - 1999. I wonder who all actually manufactures the gear. Mine came from Vtwin but no telling who made it.
Forrest
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panic

Post Thu Jul 10, 2008 10:48 am

Re: BTFH Cam Profile

If you only needed to rank some cams by size (not get the exact measurement) for trial fits, just use the #37 drill. The .001" smaller diameter will at least give you a consistent read for relative size.
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MOLDTHREAD

Posts: 118

Joined: Fri May 04, 2007 5:46 am

Location: BRANFORD, CT

Post Thu Jul 10, 2008 5:38 pm

Re: BTFH Cam Profile

Ø.105 gage pins are available from MSC #89010508 @ less than 3.00 each.

The rest of this is probably more information than anybody needs.

The pinion gear deails are: 16 DP, 20°PA, 18 Tooth, 1.125 PD.

I have measured the layout of the crank and cam locations on 1 set WR cases and 2 WR timming covers. they agree with those made by WR racer who is also another tool maker that I trust and the locations agree within .0005".While I have not checked the PD of the gears, the center to center distance of the gears is .002-.003 larger than the distance if you use standard pitch diameters on the gears. This will give you the backlash which is designed in. Keep in mind that these were measured on WR parts which may have been manufactured to tighter tolerances then the street models.
When measuring the gears the dim. over pins does not take into account wear. Axtell actually lapped the gears together to get absolutly free running, or different tolerances due to cheap repop parts.

It this blacklash actually the cause of the noise? I'm not 100% convinced.
Probobaly these locations were done on a drill press using a reamer and drill jig, which could wear over time, but I'm stil not sure that a .005 or so backlash in the gears would cause a lot of noise.
What do I know, I race an enfield and you can't talk over the valve clatter.

I will measure some gears when I get a chance (i'm getting ready for Wauseon and Mid Ohio). I'll also calculate what the dim should be over drills.

http://www.enfieldracing.com
PEEK Seals and Hot Cams for Flatheads
Bruce Argetsinger
AHRMA Dirt Track # 67J
www.enfieldracing.com
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fhsmith1

Posts: 200

Joined: Wed Jul 26, 2006 6:10 pm

Location: Georgia

Post Fri Jul 11, 2008 6:23 am

Re: BTFH Cam Profile

molthread
I can uderstand some of what you are saying but most is way over my head! I have not measured the backlash to get specific amounts. With the cam chest built up the cam end play was between .005" and .010". This was confirmed through the tappet hole. Through the tappet hole is where the backlash was first noted. There was just a little between the cams but seemed to be a lot between the pinion gear and camshaft. The noise the engine makes at idle can be heard also by just turning the engine over. This was not aparent untill the cylinders were installed. The noise happens when the valve springs push back down after the cam lobe has past the centerline. This makes the gears take up slack the other way.
Engine is running fine and seems happy at speeds. The only problem is the noise at idle.
F
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don

Posts: 551

Joined: Fri Oct 01, 1999 12:01 am

Location: Spokane WA USA

Post Sat Aug 09, 2008 7:23 am

Re: BTFH Cam Profile

If gear noise, read test result and conclusion.
http://www.abrasive-tech.com/pdf/gearhone.pdf
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panic

Post Sat Aug 09, 2008 3:59 pm

Re: BTFH Cam Profile

It appears that honing can improve the surface quality of a gear.
However: is that the problem?
The excess backlash will always be there, so some of the noise will remain.
IMHO some small part of the remainder (noise and problem) is that due to the bad match (actual cam-to-cam center distance is larger than the suggested pitch distance) the curved gear tooth segments aren't making contact in the right place, and are sliding (rather than rolling) past each other to a greater degree.
Lapping, using very fine compound in light oil while the gear are turned with an electric motor, has been used on the KR. This polishes out the contact point somewhat, reducing local friction.
It does require a very lengthy set-up, and trashes whatever bearings are used (Jennings' KR report - although this presumes ball or roller for all cams).
Lapping will also (to a lesser extent) somewhat reduce the far more serious problem - insufficient center distance, but only effective in borderline cases (i.e., almost OK). If it's really tight (effort to turn by hand) it must be replaced.
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Pa

Site Admin

Posts: 4652

Joined: Sun Mar 12, 2000 1:01 am

Location: Ohio USA

Post Mon Aug 11, 2008 1:33 pm

Re: BTFH Cam Profile

The altimate would be to have all the gear teeth cut by the very same tooling, holding pitch, holding tooth profile, holding major and minor diameters, and holding cam shaft journal locations, fits, and finishes. Holding all of the mentioned component correct tolerances, is the icing on the cake. Result ?? No noise, minumum wear, not tight, not loose, but free moving action, between the component assemblies. In other words, know your parts. Examine them all. Make sure they will mate. Blueprint the engine with parts drawings, derived from your measurement data. The cam chest is designed around a particuliar layout. Position of each cam has been predetermined. Hold those locations first. You cannot expect to obtain a uniform running fit on multible running components unless those components are equally spaced from each other. Clearances need to be the same between all of the gear teeth which mesh with each other. Fit the cam gears to those predetermined engineered locations. Hint....the gear tooth pitch of the cams is fitted to those locations in the cam chest. Correct clearances have been calculated in. If the cam gears are identical, with respect to the gear teeth, tooth profile, gear diameter with included clearance, And !!! location is dead on, you can't get it any better than that. Noisy gear case is excessive clearance. It may be between only two gears but nine times out of ten, bore location is at fault. If you find a set loose, you will probably find the other two tight, if the gears are correct. If you expect a dead on location between bores, you got to put those locations there. I prefer a horizonal boring mill for that closeness. It pays to have extra bore stock on hand, to enable one to obtaain such perfection. The extra bore stock is for test cutting in the locations. Accurate readouts are super helpful. The readouts allow you to make those test cuts without destroying your new bushings. Pins to fit your test cuts, while inserted into the test cut bores, allow for accurate measurement of those bores. Once you establish correct locations, via the test cut method, you can finish bore the bores. A set of correctly manufactured and machined cams will fit perfectly then. No matter how good the dimensions are on the cam set, out of line bore locations, will upset, the balance of the engineered design of the components. Some tight....some loose.... Pa
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