Last week, my freshly rebuilt engine seized up, at idle. I had been running it since April without a glitch, and had logged a few thousand miles. The oil was exactly what the rebuilder had specified and changed every 500 miles.
The engine banged 4 times and locked up as my wife and l were about to load the car into our trailer to go to the Mystic Seaport Tour. Bags were packed, the truck was ready to go, and our hearts were broke!
We hauled it directly to the engine guy that day, pulled the engine, knocked it down and found that #4 piston was frozen to the wrist pin. A 20 ton press wouldn't budge it. We had to cut the piston apart to free the pin so that the rod could be salvaged. #3 was also rather snug.
Has any one heard of this happening before with the aluminum pistons sold by the vendors. It was as if the aluminum had become "work-hardened".
We had something similar happen to one of the cars in our group except I think it was No. 2 piston.
Yup, the new pistons need to be honed in the wrist pin bores.
Dave, I had one seize up on no4 once, in concert with the piston seizing in the bore. My own stupid fault though. I was relying on an oil sight gauge to keep an eye on oil levels and the air hole in the top was blocked so the glass tube seemed full. Lack of oil caused my seizure, not any fault with pistons/pins.
Allan from down under.
Look down the bore of the pin; is it thicker in the area where the rod clamps it? Full floating pins like Model A can be thin, but not pins clamped by the rod. That will distort the pin and cause the piston to seize.
This piston is from a set that threw a rod. Dunno if bent pin was the cause, as I didn't get that piston.
Pins made to be clamped are much thicker, if not all the way through, at least in the center section. Modren Fords use clamped pins, and the pins are thicker through the center.
Yeh, I learned this the hard way back in '00 with a set of Egges.
Looks like that piston was fit to tight in the cylinder!
I think Herm is right on being to tight. The piston over heated and caused the pin to stick. The clamp bolt is to small to over tighten on the pin. The pins are tapered or bored out to reduce weight. We do this all the time on race motors. Scott
Mike, when you hone the pin bores can you tell us what you are aiming for?? Clearance spec?
Could you use timesaver to accomplish same?
The aly piston expands at what, 2 1/2 times the rate of steel? How does a piston sticking in the bore cause the pin to seize?
My experience was the thin pin bending from clamping, then sticking in the piston and causing it to overheat and drag in the cylinder.
Dave, would you please check that pin for out of round and straightness?
rdr
I have guy after guy tell me that they never need to hone the wrist pin holes. I don't know how they get by. EVERY set of pistons that I get needs at least one wrist pin hole honed and sometimes two or three
Rick the rod clamps evenly around the pin. You would need a ten foot pry bar to get the pin to distort. You had a problem and somebody sold you a fairy tale.
You are right Dave H., we also have found what you stated.
They all need checked, why would you not, and when the pistons stick, can always be traced to a bent rod, or a to tight of piston fit, as in the picture above.
Robert S., I also agree!
Maybe you can explain, then Scott, why pins for OEM clamped pistons are much thicker through the center where the rod clamps to the pin?
Thin pins are for full floating setups like the Model A.
I had a thin pin in a clamped rod, as sold by the manufacturer, and after the pin seized and the piston scuffed on the cylinder, the pin had .001 bow in it. If the pin were true in Dave Young's engine, why did the piston seize tighter on the pin than in the bore?
Waiting for Dave Young's report..
I've bought two sets of .030 oversize alu pistons from Snyder's, one this year and the other maybe one and a half years ago. In the first set all piston pins were tight, in the set I recieved this year all were perfect fit. I test them as I've read here - the rod should fall by it's own weight when fastened to the pin in the piston and held horisontal if the pin fits right.
Making a too tight piston pin fit with timesaver takes some time for sure, but I haven't got any Sunnen hone machine..
Ricks, As the piston got hot and seized it over stressed the pin and bent it. You can use cheap material if you make it thicker. On motors making 3,200 horsepower we use thin pins and shorten them. They may bend if we detonate the motor but its lots more power than you make. Rick what tool are you using that can tighten the rod so tight that it warps the pin? Are you using ARP bolts? The bolt will break or the threads will strip way before you can warp the pin. Think about for a while and then fill me in. Scott
As was said before in this post, every piston needs to be checked to be sure the pin will easily, very easily, slide through the piston. I have bought over a hundred sets of the new aluminium pistons and nearly all have had to have the pin bores honed. Every engine builder should know to check the pin fit.
Never assume that the guy who put the pins in the new pistons was having a good day!
I have found a couple engines with the pins blued and both engines had nothing on the flywheels to throw the oil.
Doc just gave me a shot of steroids into the carpel tunnel and i was good to go!... oh wait... cars.. duh
Here are some pics of the piston. This is a .060 over and has a few thousand miles on it. The pin oil holes were clear when we pulled it apart.
Note the color of the pin and the galling inside of the piston hole. One of the other pins was also quite blue. Judging by the look of the piston, lubrication was good. l see it as a matter of the pins being too tight from the manufacture.
Does anyone see any relationship here to the use of kevlar bands and those fibers floating around with the oil?
The rod of the seized piston was measured for straightness on a CNC mill using an inside dial indicator as l watched. lt was straight. l have no input as to the thickness of the pin, but certainly, checking/honing all wrist pins seems to be mandatory given the fact that imported crap is the norm.
What are you using for oil, Dave Y.?
Also, can you take pictures of both sides of the top of that piston, where the top ring is?
Herm,
l'm running Rotella T 15w-40 as per my rebuilder's request.
l can shoot some other pics tomorrow, if these don't show what you want to see.
I am confused about one thing after reviewing this failure information. If the root cause was insufficient clearance between pin and piston at the rebuild, why did it take "a few thousand miles" to seize the pin/piston? I would say the seizure was caused by poor lubrication at time of failure. The engine was idling at failure and the failure was #4 piston.....seems like oil was not getting to #4 at idle that day and it was perhaps caused by plugged oil line and long idling time ....don't know what oil level was or whether flywheel has the necessary magnets or other appendages to pump sufficient oil at low speed. What do you think?
I agree William, as the only thing that would make the Aluminum look like that in the wrist pin hole, is lack of oil, either from getting there, or if it got there, it did not have the protection.
In my Opinion, and oil below 30 Wt., you are taking a chance in a Model T engine, unless you have larger clearances.
No. 4 cylinder on a Model T runs hotter any way.
This is a car that gets driven just about every day and runs at least a hundred miles on most weekends. The morning that she locked up, it had only run for the few minutes that it took to back it out of the garage and hop out to lower the top (it's a touring). While l was securing the top she made that terrible sound and quit.
The fact that it ran great since May 2012 is so puzzling. The oiling appears to have been normal, as everything was well coated upon teardown. The babbit looked great, the cylinder bores looked excellent and the wrist pin holes were clear.
l totally agree that the seizure was caused by poor lubrication at the time of failure... it couldn't get in there. You would think that it would have failed within an hour of initial start up. Herm, what's your opinion?
Where was the car setting when it quite, was it level, or up in the front, or down in the front, and how did you have the spark lever set?
Herm.
The car was sitting level, idle rpm and a little over half way on the advance lever. Idle time was maybe 3 minutes and it was 55 degrees outside.
That stuff sounds all right, the only thing that comes to mind, is some time when you first started running it, it was to tight of fit, like others have pointed out, and it smeared it, but got past it, and then a smear particle finely broke off, and Balled UP, in the hole, and it was down hill from there.
Herm.
I agree with Herm, The fir was to tight to start with and galling started and the clearances got tighter as time went on till it was near dry and locked up.
the problem was there from the start and got worse as time went on. Scott