Wrist pin dilemma

old ford fan

old ford fan

Member
I have been tracking a high pitched knock that I thought was a rod bearing. I dropped the pan and adjusted rods but they were all 2-3 thousandths. I adjusted them all to 1.5 - 2 thousandths and replaced pan. Still had knock plus massive oil leak so I pulled engine. Surprised to see counterbalanced crankshaft, hardened valve seats, adjustable lifters, etc. anyhow the knocking showed up at cruising speed with no load on engine and at high idle. Found wrist pin on #3 is very loose. Can I buy some bushings from one of the vendors and simply remove and pressing new bushing than ream bushing? The wrist pin seems like it has slight wear as well. The other thought I had was that I could use an older wrist pin that I have which measures about .003-.004 larger and ream the piston and existing bushing to fit. I don't have the money to have a bunch of machine work done right now. Is there a secret to pressing out old bushing and pressing in new?
 
old ford fan said:
I have been tracking a high pitched knock that I thought was a rod bearing. I dropped the pan and adjusted rods but they were all 2-3 thousandths. I adjusted them all to 1.5 - 2 thousandths and replaced pan. Still had knock plus massive oil leak so I pulled engine. Surprised to see counterbalanced crankshaft, hardened valve seats, adjustable lifters, etc. anyhow the knocking showed up at cruising speed with no load on engine and at high idle. Found wrist pin on #3 is very loose. Can I buy some bushings from one of the vendors and simply remove and pressing new bushing than ream bushing? The wrist pin seems like it has slight wear as well. The other thought I had was that I could use an older wrist pin that I have which measures about .003-.004 larger and ream the piston and existing bushing to fit. I don't have the money to have a bunch of machine work done right now. Is there a secret to pressing out old bushing and pressing in new?
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The answer is yes. But if you have never done it I would say no. The work has to be right on. You need to ream the bushing a perfect 90 degrees from the rod bearing and in the same plane. Plus the size needs to be a slip fit.
Why not spend a little bit of money and take it to a good engine shop, to have the bushing installed and honed. ( .003-.004 probably will not clean up the bushing that is in the rod.)
 
Yes! But!...... Watch very carefully! If your wrist pin is worn and you decide to replace it, wrist pins vary in mass and weight due to different size hole in the center. You may have to replace all four. George is absolutely correct in what he says about 90 deg.and the honing.
Terry
 
The wrist pin needs to be honed for a .0005" fit and is done on a special machine. That shouldn't cost much to have a machine shop do it, but be careful to find a good machine shop. When I overhauled a Wisconsin engine for a guy I had the machine shop hone the wrist pin, but it came back as loose as the one I replaced. The young kid didn't know what he was doing. It used to be a good machine shop until 15 years ago when a lot of new help replaced the guys that retired.
 
Ok, I guess I'll see if Stipe can do it...they are 5 minutes away. I knownBill has moved to KY but I believe they are still doing model A work here in Plymouth. Anybody know for sure? Otherwise I'll try calling Monday.
 
Buy a set and do them all at the same time. If that one is gone the rest may be on the way it also. That way they will be the same weight.
 
I also would buy a set of new pins. They come in several oversizes. Doing this will ensure all are tight and fit the pistons as well as the rods. e-mail me at jimb4e4@gmail if you can't find oversize pins locally.
 
Tom Wesenberg said:
It used to be a good machine shop until 15 years ago when a lot of new help replaced the guys that retired.
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This is why Ford Barn is an invaluable aid, we can learn from a LOTS of retired guys. It's fun to share things we've learned. Even 1 small tip may save MANY hours of work & frustration!
Bill W.
 
One (1) possible phone call to Mr. Stipe ..... plus mentioning all above helpful advice to him ..... plus a possible five (5) minute ride to Mr. Stipe's shop ....... (if deemed necessary) ...... all sounds like a large "IRS Refund" received in today's mail.
 
Seriously, UNUSUAL piston pin problems should be referred to a competent auto machinest! They're EXPERTS & know what they're doing.
Bill W.
 
I think our Mr. Bill W. is hinting on several outstanding mechanical adjectives ...... UNUSUAL ........ compentant .............EXPERTS ...... coupled with a machinist who knows what he is doing.

Can anyone imagine just a very slim possibility as to "why" #3 piston pin got worn and loose ............. and not #1, #2, & #4 .......... with exact same oil in oil pan and connected to a balanced crankshaft?

"Maybe" a very slim possibility of a very slightly bent connecting rod rotating at 1,800 rpm = 108,000 revolutions per hour ............ and a little (2) hour trip one way in a Model A = 472,000 connecting revolutions.

Competent machinist are used to evaluating wear coupled with rpms.

May sound inexpensive even to replace all (4) pistons and replace all (4) pins ..... but, possibly then develop the same #3 ever increasing high-pitched knock over time.

Maybe something to consider ...... maybe not.
 
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