Rear main bearing cap - simple question???

Topics Last Day Last Week Tree View    Getting Started Formatting Troubleshooting Program Credits    New Messages Keyword Search Contact Moderators Edit Profile Administration
Model T Ford Forum: Forum 2005: Rear main bearing cap - simple question???
Top of pagePrevious messageNext messageBottom of page Link to this message  By Vince M on Sunday, May 06, 2007 - 05:59 pm:

I need an expert opinion:

I have too much play in the third main - so much so i am pretty sure the magnets may have contacted the magnito. Car still ran, and i shut it off quick.

Question - i have a tour in about a week - is it ok to just replace the main cap (s) without a total rebuild? Also - can the mag be replaced without removing the transmission? I have a three dip pan.

Thanks

Vince


Top of pagePrevious messageNext messageBottom of page Link to this message  By jack daron on Sunday, May 06, 2007 - 06:03 pm:

You could fit another rear cap,but the whole shebang has to come out to change mag.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Vince M on Sunday, May 06, 2007 - 06:11 pm:

Jack,

Hopefully the mag isnt damaged. I figure i could pull the engine and know what i have in a couple of hours.

What does it take to fit a new cap? any special machining?

thanks

Vince


Top of pagePrevious messageNext messageBottom of page Link to this message  By Les Schubert on Sunday, May 06, 2007 - 10:35 pm:

Vince
The rear main cap is also the rear main bearing. It should be fit to the crankshaft with a clearance of about .001-.0015". You would have to find a rear amin cap that is bored the right size.
This may not be easy to find!!
People have built up the rear thrust face on the main cap with solder and then refit it using a body file. It is nice to fit it for around .003" end clearance. If you are carefull you can do it.

Take a good hard look at the mag coil and the magnets to be sure you haven't cracked/broken anything. If the magnets come loose you WILL do a lot more damage!!!


Top of pagePrevious messageNext messageBottom of page Link to this message  By VRay on Monday, May 07, 2007 - 12:27 am:

If you know how to scrape a bearing, you should be able to fit one correctly within a day. The problem is getting one the right size. Most suppliers sell them stock or 0.010" undesized to fit worn or ground cranks. Unfortunately cranks are not ground standard and there will be a lot of scraping work to do for one to fit.
If your crank is more than 0.010" undersized you will need a person to pour a bearing for you then machine it to fit.

The next major problem is the thrust faces will need truing. Scraping the thrust face could be difficult.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Noel Keefer on Monday, May 07, 2007 - 02:19 am:

Vince,
If the main is OK on the crank, The solder technique does work. My old friend has done it.
Noel
Quick once the main is off.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Vince M on Monday, May 07, 2007 - 08:04 am:

Noel and Vray - cand i use regular solder or do i need babbitt?

Vince


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ron Patterson on Monday, May 07, 2007 - 09:28 am:

Vince
Read the excellent article that appeared on page 19 of the Volume 42 Number 2 (most recent) Vintage Ford magazine. Ken Foster walks you through the entire process to repair the rear main end thrust surface problem you are encountering.
Ron the Coilman


Top of pagePrevious messageNext messageBottom of page Link to this message  By Seth Harbuck on Monday, May 07, 2007 - 09:31 am:

A well-written article, for sure!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Vince M on Monday, May 07, 2007 - 09:41 am:

Thanks!

Vince


Top of pagePrevious messageNext messageBottom of page Link to this message  By VRay on Monday, May 07, 2007 - 10:04 am:

Bearing metal (babbit) and solder are entirely different material compositions. They should not be interchanged. However, they are both classified as white metals. Ordinary solder would have lead in it. Bearing metal would have essentially no lead for a T engine. That is not to say that bearings for some applications do not use lead. Bearing metal compositions for the correct application is a study all onto itself.

I just grabbed the Vintage Ford Mag and quickly looked at it. It looks like an excellent article. Remember that the bearing has to be fit into the space to eliminate the axial movement. You will have to measure and machine that clearance into the thrust face. Now the guy who did this with a 4 dip rod pan and not pulling the engine is talented. There is darn little room there too, but a lot more than a 3 dip pan.

High quaity babbit is not cheap and the price is getting higher everyday. Now, if you live somewhere near oil field work or shipbuilding there will be a shop that pours bearings and will have the ability to pour and machine the bearing cap for you.

One last thought. Impacting a magnet is usually a great way of fracturing it. I would pull every magnet, recharge it, test its lift ability after the recharge, then wait 24 hours and see if it will lift nearly the same weight. If not, that is almost proof positive that it is cracked. It will create a N-S relationship at the crack and the full strength of the magnet will dimenish. A cracked magnet will come loose with all the dreaded consequences.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Noel Denis Chicoine, MD on Monday, May 07, 2007 - 01:32 pm:

How much end play does Vince have? It should be easy to measure with a dial indicator on the front of the crankshaft and moving the crank back and forth. It should also be possible to pull the hogshead and measure the gap between magnets and magneto at both fore and aft positions of the crankshaft. Maybe he doesn't need to go through the work of replacing the rear main. Vince, what made you think the magnets contacted the magneto? I thought the normal wear was to WIDEN the gap, not close it up.
Noel


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ron Patterson on Monday, May 07, 2007 - 04:53 pm:

Noel
The crankshaft thrust surface wears on both sides, but you're correct, it does wear more on the front side because of the transmission clutch spring pressure being applied.
In extreme cases the wear on the rear side of the thrust surface will entirely close the magneto gap and the results can be disasterious if not address quickly.
Ron the Coilman


Top of pagePrevious messageNext messageBottom of page Link to this message  By Willie in Houston on Monday, May 07, 2007 - 05:08 pm:

Vince
Most of the wear usually lets the crankshaft move away which is toward the rear of the car.
Also when you set the hand brake it pushes the crankshaft toward the rear.
Acessory crankshaft pulley's with a race and ball bearings that fit between the block and the pulley were often installed to hold the shaft forward to get a better mag signal.(in the old days)
If you heard a noise out of the transmission, it was possibly the keeper piece of metal that holds the outside end of the magnets to the flywheel. These are held on by brass screws and they often crystallize and break off.
You might want to look for this 1"x1/2" piece of metal with a hole in the center.
If you have one of those transmission filters, it may have ended up in it. If you find it, I would not run the car until you replace all the brass screws and check for broken magnets.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John H on Monday, May 07, 2007 - 07:33 pm:

brass shim soldered to the back of my 3rd bearing has lasted 2.5yrs so far


Posting is currently disabled in this topic. Contact your discussion moderator for more information.
Topics Last Day Last Week Tree View    Getting Started Formatting Troubleshooting Program Credits    New Messages Keyword Search Contact Moderators Edit Profile Administration