I put aluminum pistons in my 27 Roadster back in 1989. The car has not been driven much and I have noticed the engine had gotten harder to turn over. After pulling the pistons I found the pins are almost stuck in place. A little cleaning with 600 weight sandpaper in the bore where the pin goes has freed everything up, but I now notice that there are no lubrication holes like the original iron pistons have.
Has anyone else experienced this seizing up with alu pistons? I'm not sure if it's due to the very little driving for so many years or if it's the lack of sufficient lubrication. I have been using a 10W-30 mineral oil but want to switch to 5W-30 synthetic when I get it all back together.
Thanks for your input.
I had that Question and was told to drill a hole on where the pin goes all the way past the upper part that holds pin just to the right of the blue dot not to close to the edge and center in the middle
Thanks Lorenzo. Just to clarify, the hole should centered on the right side of the blue dot, not in the middle of it?
Switching to 5-30 is a good idea but not to synthetic in T.
You need to change the oil more often. It would not be done often enough if you used the much more expensive synthetic oil.
You need to change the oil every year or every 500 miles, whichever comes first.
Engine seizing is usually caused by the piston pins but I have had one seize at the pistons due to brown crud on the piston walls.
I think I would drill a 1/8" hole right through both top and bottom of each side.
I took a 235 Chev 6 apart last weak that had stuck rings. Some of the piston pins were very tight. after cleaning them they are just fine. Some rings were rusted in their grooves. The owner was not been changing oil often enough. Although he used 10-30 high detergent oil it had a 3/8" pancake of sludge in the bottom of the pan.
Each piston has two oil holes on the outside of the piston at each end of the piston pin.
Thanks for the timely heads up on pistons without oil holes. I just looked at a set I have, no oil holes.
I looked at my new pistons and they have holes drilled. I do not know if the machine shop drilled them or not.
I've bought a couple of sets of alu pistons from Snyder's in the last couple of years - both sets have oil holes drilled for the piston pins but 6 out of eight piston pins were too tight in their holes - should have been easily fixed by the manufacturer, but instead I had to free them up with yellow timesaver and lots of elbow grease ( )
Here is my new pistons for you to view.... You can see the holes.
Eric, just like travis did,the colored dot i was told is a mark to math weght in sets
I took off the oil pan inspection pan to check it. The engine was under a tarp outside for a few years. Before I installed it in a speedster, The engine runs fine and does not use oil. But the way it was stored I wanted to check the lower end. I found the engine had been over hauled and had new alu pistons installed that does not have lube holes shown or that can be seen. I have driven the car about 400 miles with out any problems, Now my question? Pull and drill pistons or not?
FYI My original cast irons do NOT have any holes...
I am not an expert on model T engines, but being a mechanical engineer (retired) and having read on the forum about many seizure problems on piston pins in aluminum pistons, my opinion now is that a loose pin fit is more important than an oil hole to ensure lube oil is drawn into the piston/pin bearing surface while the engine is running. The pumping action of the pin should transfer the oil splashed into the bottom of the piston as long as the pin is not too tight and the oil viscosity is not too high.......I would be interested to hear what others more experienced with these engines think about my theory stated here.
Larry: Neither am I any expert, but the general rule is if it's not broken, you don't have to fix it
Beware of signs like Eric experienced like the engine getting harder to turn over - or some new kind of noise from the engine.
I have used the brand of pistons in the picture (when they used to be supplied with the proper length pins - they started to come thru with pins that were much too short a couple years ago and I stopped using them - If the pins are much shorter than a stock FORD pin, that may also be your problem with these pistons sticking). Other than that, I can tell you that they work fine if they are properly prepared... With that being said, the pin bores have to be line-honed on a piston pin honing machine prior to use. The pistons appear to be CNC machined and not finish honed at the factory. The bores sometimes have some light machining marks and sometimes are not in exact alignment. Generally if I hone the bore to .001 over the pin, I can look thru the bore and see about 80% fine cross hatching from the hone and 20% of the original un-touched bore. This has always been all that had to be done to get satisfactory service out of these pistons.
I am going to leave them with out the oil holes for now. The engine starts and runs fine and there is no noise. I am putting the inspection cover back and taking the old girl out for a ride. Thanks for the advice.
I tell you what my pins fit like perfect... It is just a smooth perfect fit like it was just made in nature to be together. How can you tell if the pins are too tight?
Travis, here's a citation from Dave Huson in this thread: http://www.mtfca.com/discus/messages/257047/322924.html?1353327910
"Years ago The best T mechanic in the country told me to slap a piston in your cupped hand and if the pin does not drop out its TOO TIGHT. The old method of installing a rod and holding the piston horizontally and see if the rod falls down can still be too tight."
I used yellow timesaver to get that result - lots of work, but still cheaper/faster than taking the pistons to a machine shop for honing..
Thanks for all your input. I'll put some holes in my pistons like Travis'.