Connecting rod and piston questions

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Model T Ford Forum: Forum 2010: Connecting rod and piston questions
Top of pagePrevious messageNext messageBottom of page Link to this message  By Mack Jeffrey Cole on Monday, December 13, 2010 - 09:06 pm:

Well,being it is colder than the contents of a witches brassiere outside,I have of course stayed in the shop today.
I stopped working on the engine for my speedster a couple years ago when i started clearing for my shop and some other things that came up.
I got it out of the corner today and I was to the point of fitting rods to the pistons and installing rings when I stopped.My dad says i have the crank a bit to tight and it is hard to turn by hand.But I have a couple questions.
All I have are a few sets of used rods and pistons and I dont see any reason the pistons cant be reused maybe with new wrist pin bushings.

But I tried to get a wrist pin out today and couldnt.there is no rust and I did loosen the bolt.the books says just push it out.Hum,what I am doing wrong?

It also mentions supporting the piston when working at removeing and installing the wrist pin.If I take a wooden block to a wood shop and have it cupped out so a piston lays in it,will wood be enough to support the piston?
Are the reamers for the new wrist pin bushings a common size that i can find at a machine shop?

I also am wondering,how do I determine if there is enough babbit on the rod bearings to give some service?I would think there would be a way to measure the thickness of the end cap and get a idea of how thick the babbit is.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kerry van Ekeren on Monday, December 13, 2010 - 09:26 pm:

Mack, the bolt has to be removed in order for the pin to push out.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mack Jeffrey Cole on Monday, December 13, 2010 - 09:37 pm:

Thanks,now I can go down there and give it a shot this evening!
I miss understood the book ,it saying just run out,as being not all the way off.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Hal Davis - Lyons, GA on Monday, December 13, 2010 - 09:38 pm:

I'd think that the number of shims left in there after fitting would be a good indicator of whether you have enough babbit. Use yellow Time Saver to fit them. I think you will be pleased with the results.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Wayne Sheldon, Grass Valley, CA on Monday, December 13, 2010 - 09:39 pm:

The wrist pin bolt must be completely removed to take the wrist pin out as it has a slot in it.
I put an appropriate size drift punch in a big vice and stick the hollow wrist pin on it. Be a little careful, if the wrist pin bolt is really tight and stuck, you could ruin or break the punch. Frank Harris will probably post a picture of a better way to hold the rod and piston.
I used a brake cylinder hone to fit new OS wrist pins in old bushings.
Generally, If the Babbitt is not worn through, it is thick enough. Check for any signs of cracking and "blue and scrape" to fit. It takes a little practice. But it does not take too long to do.
Have fun!
And drive safe, W2


Top of pagePrevious messageNext messageBottom of page Link to this message  By Mack Jeffrey Cole on Monday, December 13, 2010 - 10:14 pm:

Thanks for the ideas,my back went pop so in the chair I went.But as soon as I feel better I will git back down there and see what happens.
I test fit 1 of the rods on the crank and there werent much room if any for shims.I know the book shows fileing the cap and rod.So I know I can do that and get a bit more adjustment.But if these things are wore real thin,may not be worth my time.And it appears rods can be had in 3 undersizes so i may as well check the crank and see if it needs any help.I dont think so IF .003 or less of change is ok on being out of round.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Ted Dumas on Monday, December 13, 2010 - 10:24 pm:

Using a rod or punch to support the wrist pin is a good idea. Don't lock the rod in a vise to break the wrist pin bolt loose or tighten it or you may twist the rod.

You should mike your crank, and blue and plastigage your rod and main journals. The Model T rods are easily twisted such that most crankshaft rod journals are tapered worn high in the center and low on the ends. If the crank is out of round more than 0.002 then it will be hard to maintain the correct rod clearance in your engine. I have driven an engine with tapered journals. You have to scrape and fit each one and be prepared to taken them up twice a year or so.

Why don't you put a feeler out and see if someone has a set of used aluminum pistons the right size that they are willing to part with. Aluminum pistons will cut down on your engine vibration significantly.

If the rods have shims, then you have plenty of babbitt. If they don't, you still likely have sufficient babbitt. Check the babbitt carefully to be sure there are no cracks.

Most iron pistons, I have taken down didn't need new wrist pin bushings. I did have one engine with oversize wrist pins which made it a bear to change the rod.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Richard Gould on Monday, December 13, 2010 - 10:35 pm:

Mack I wouldn't replace the wrist pin bushings. Too many things can go wrong. You can still purchase OS pins. Take the pistons to an automotive machine shop and they can align hone them for the OS pins. Cost is reasonable.
With the OS pins, you'll need to enlarge the clamp end of the rod to accept the larger pins. I've used an expansion reamer to do it.
Nothing wrong with using used pistons if they all weigh the same and the dimensions are OK.
I've done it.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bob Gruber, Spanaway, Wa on Monday, December 13, 2010 - 10:57 pm:

Another thing to think about...you don't know how much has already been filed off the caps in the last hunnerd years or so.
This is probably not recommended by the experts, but I have filed a couple thousandths off a crank to get it pretty round.
Use a good sharp file and chalk it up good to keep the filings from piling up in the teeth and scratching it and be careful not to put a sharp edge in the radius (important!)
Br careful to take the same off both sides and do more measuring than filing. Polish when done.


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