Line bore not indexed

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Model T Ford Forum: Forum 2005: Line bore not indexed
Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob shirley on Thursday, May 24, 2007 - 03:23 pm:

Ya'll get out your get out your your handkerchiefs this is a sad one. I bought a "rebuilt" T block off of Xbay about a year ago. I am in the process of cleaning it up and checking everthing. The bore job is fine. The crank is turned 10 under on rods and mains and mic's round and the babbett is new. The babbitt looked very nice with a very fine finish. I changed the timeing gears because I had .018 backlash. New gears form Snyders and still had .0155 backlash.Cam bearings good. I called Don at Sniders, we talked about the quality of the gears and he said they have had no problems with them. It came down to the new babbitt. I bolted up Genes boreing unit and checked it. Whoever line bored it did not refrence the cam and the rear was off about .130. It looked so good I sure hated to cut it out,But I had no choice. Repored the block last night and the caps today. I will rebore it with Gene French's unit tonitght. I sure never thought that workmanship that looked so good could be so wrong. My Thanks to Don and the rest of you guyes for all the Great help.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ray Belland on Thursday, May 24, 2007 - 08:14 pm:

BOB a fella here in my city was doing the same thing with model A motors flooding the market thru e-bay with a lot of questionable work it got to the point i quit doing babbit work because i was afraid people would associate me with him the city isn't that large and he was located about a 3 minute drive from me his unscrupulous work ruined a great passtime for me but luckily he hasn't been heard from for at least a year now busy in court no doubt.
Sorry to hear about your problem but i can tell you that GENE FRENCH'S unit is well made and will perform the operation properly just measure twice and cut once. RAY


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dan McEachern on Friday, May 25, 2007 - 01:38 am:

Bob- unfortunately you did have another choice. You would be suprised how many line bore jobs are done with the wrong center distance. I regularly get calls for special gears to fit either too long or too short center distances. As a result I usually have oversize and undersize cam and crank gears on the shelf. If I don't have what you need, I keep uncut blanks in stock for just this purpose. Too bad you did not post your problem before you redid the mains.

Dan McEachern


Top of pagePrevious messageNext messageBottom of page Link to this message  By Les Schubert on Friday, May 25, 2007 - 10:44 am:

The correct centre distance for a T is 100 mm (millimetres). I use a original T lineboring bar that centred off a "dummy" cam shaft. I could never get cosistent gear fits until I realized that Ford's tolerance in the vertical location of the cam shaft was quite loose!. After studying some NOS original straight cut gears I realized that Ford had used metrric gear pitch, and it worked out perfectly to 100 mm centre distance. I made a pair of "links" for between the dummy cam and the line boring bar and now good gear mesh every time! It is easy when you have the right information, frustrating as hell when you don't.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kenneth H. Todd on Friday, May 25, 2007 - 10:45 am:

Quote: the rear was off about .130.
I didn't think there was that much room at the rear main. Did you mean .013"?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Seth Harbuck on Friday, May 25, 2007 - 10:58 am:

Les,

I tend to doubt the metric gear thing. If the pitch diameter of the crank gear is 2 5/8" and the pitch diameter of the cam gear is 5 1/4", then if Ford had intended the gears to run exactly on their pitch diameters - the center distance would be 3.9375" (3 and 15/16 inches).

100 mm is 3.937"

Spec is 3.9367-3.9375" on machining that dimension.

Also, if you multiply those pitch diameters by pi and divide by the number of teeth (24 and 48), you very conveniently get 11/32".

Are you sure that cam drive is metric?

Seth


Top of pagePrevious messageNext messageBottom of page Link to this message  By Les Schubert on Friday, May 25, 2007 - 11:22 am:

Seth
Well I tried every standard imperial gear pitch and nothing worked. As soon as I tried a modular (or metric) pitch it worked perfectly. I did not have access to the "machining dimension" information and had to work this out on my own. This forum did not exist at that time.
But lets face it the Eurpoeans were well ahead in car design when Ford got started and Ford bought as much of the parts of his early cars as he could and only made what he had to (which is the smart way to start up any manufacturing business).
The NRS use the same gears as the T. I don't know about Fords before that. Using metric gears would certainly slow down the copiers and "spurious" parts builders and would not have cost Ford 1 penny more to make. Right from the beginning Ford was concerned about capturing the spare parts business. Considering the NRS gears ran out in the open in the dirt and grundge, their life would not have been great. This is my speculation on a motivation but I certainly would have done the same in his shoes.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Seth Harbuck on Friday, May 25, 2007 - 11:34 am:

Well, it makes no real difference one way or the other, but I did think it was quite a coincidence that the inch equivalents worked out that way.


Top of pagePrevious messageNext messageBottom of page Link to this message  By bobster on Friday, May 25, 2007 - 11:51 am:

I have a block that will soon go out to have the mains babbitted. Pardon the basic question, but does the camshaft need to be set up with the timing gear in the block before this can be done? Or can I just specify to the machinist (babbitter?) what kind of camshaft I intend to use?

Thanks for the info! Bob


Top of pagePrevious messageNext messageBottom of page Link to this message  By Dan McEachern on Friday, May 25, 2007 - 05:48 pm:

Guys- all straight cut Model T timing gears are 8DP. (21T +42T)/(2*8)=3.9375" Center Dist.
The later helical timing gears are all 10 NDP.

I have found that Ford was pretty consistient in
using American Engineering practices in their designs. The only exception to this that I can think of is metric ball bearing sizes used in generators. Possibly front wheel bearing diameters, but I would have to check.
The fact that 3.927=100 mm is interesting, but it
just happens to be a coincidence. If Les has had good luck using Modul pitch gearing that's great, but it is not what Ford designed the engine to use.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ron Patterson on Friday, May 25, 2007 - 06:41 pm:

Bobster
If you commission your engine to a reputable Model T main bearing rebabbiting shop they will know exactly what/how to obtain the correct distance between crankshaft and camshaft centers.
If you have questions about the process/supplier, ask questions here first (especialy they kind of tooling they use) and challenge the workmen. If they cannot explain exactly how it is done in a few minutes, turn and leave the shop quickly holding your wallet in thanks.
As with most things Model T there are folks out there (rebabbitters & crankshaft grinders) who are not familiar with the Model T and the process required to get a quality main bearing job.
Forewarned is forearmed.
Ron the Coilman


Top of pagePrevious messageNext messageBottom of page Link to this message  By bobster on Friday, May 25, 2007 - 07:07 pm:

Ron, thanks for the advice. I wanted to avoid dragging the block to the rebabbiting shop, only to find out it was not ready because it needed the camshaft installed first.

I will most certainly be asking many questions in the weeks to come!!

Thanks, Bob Sacchi


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ron Patterson on Friday, May 25, 2007 - 07:30 pm:

Bobster
The camshaft you ultimately use in your engine is not at issue assuming it a quality product. As I said reputable Model T main bearing rebabbiting shop they will know exactly what/how to obtain the correct distance between crankshaft and camshaft centers. They have special tooling to set these distances when rebabbitting and machining the engine block.
Ask questions and you will learn how this process works.
My point is when you walk into a babbitt shop or crankshaft grinding shop with Model T engine you have to know just as much about the process as the workman.
If not you are at their peril.
Ron the Coilman


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Shirley on Saturday, May 26, 2007 - 05:24 am:

I got it all back together yesterday. I have done 3 A'a but this was my first T block with Genes rig, it workd flawlesly and no I don't get paid by him, but the man builds a good product and is a phone call away if you need help. The rear main was over 1/8" out of line before I started, I saved the rear cap as a reminder,it realy showes up if you look at the flanges and there is room even more out of line than than .130 and you can bevel the sides and hide it. The one question I would ask if I were to send a block out is, How dose your shop find the center lines of the new babbitt? Ron speaks the TRUTH- and in my case,if I oversized the gear I might removed the excess gear lash but the crank would still been pointing towards the right rear tire and the ball cap would have been %^**. It's like that tower in Italy, sooner or later a screw up is going to show. Anyway,I blued the crank and checked the clearence and it looks great put the cam in and now have .002 gear lash with a running clearence of about .053. Now all I have to do is tear is down clean and lube it and I will be right back where I should have been Tuesday when I got the new gear.


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