How many of you are still using cast iron pistons ?
I heard that some winners of the montana 500 were using them. Maybe they were not so bad. Is there any benefit or they should be avoided at all costs ?
Thanks in advance
I ran original equipment heavy cast iron pistons that came with a 1910 I owned a while back and the car had a ton of torque. Probably due more to the 10 cam, though, than anything else. Also ran NOS cast iron pistons in an original 16 I restored mechanically. Same for an original 17. My take is that idle and low rpm performance is smoother but you get slower acceleration and the performance flattens out above 30 mph.
I don't think you need to avoid them at all costs. There are thousands of T's out there that are still using them, one of mine included.
However, if you were to rebuild, I would use the aluminum pistons. They are very good quality, and come in many styles. Stock, overbore, and high compression to name a few.
Also, the aluminum piston is a little lighter weight. That relieves the crankshaft of a little stress, which is a good thing since their not the stoutest things out there.
HUM! Maybe the use of aluminum pistons is part of the reason that cranks are joining the two peice club. Could it be that the cast iron pistons keep the engine speed down and slower causing less stress? I'll stick with my aluminum pistons, but it is just something to think about!
I think it was a few years ago winners in the Montana 500 used cast iron pistons. Reason was a restriction plate you had to have between the carb and manifold if you used alu pistons, but not if you used cast iron pistons. Later that rule was changed, so there's no gain in using the cast iron pistons in the 500 any more.
My view is that heavier than necessary reciprocating mass acting on the flimsy std crankshaft is a bad thing, shortening the time until the crank will crack from metal fatigue. Yes, it's not if - it's when. With alu pistons & post 1920 lighter rods we might delay that dreaded 2-piece crankshaft club membership some..
Yes, they used cast iron pistons on all 15 million, and yes, they did drive 20-25 mph on bad roads most of the time. Today we give the old iron a hard time with higher speeds. Strain on a moving engine part doesn't double with doubled rpm, it raises by the square.
My recent rebuild of my 1914 Touring engine included cast iron pistons. This is a slow speed car (30 and under) and I've found a lot smoother low end with the cast iron. However,my 1919 speedster engine rebuild started with aluminum pistons and the rest, well............
Cast iron piston benefit:
Quieter than aluminum when cold. Because they expand the same as the iron block they fit in, they are fit tighter so they are quieter when cold. This is their only benefit, IMO.
All four pistons decelerate to a stop and accelerate in the opposite direction at the same time twice per crankshaft revolution. The heavier they are, the more they tug on the bearings. They do not add flywheel effect. Why would you ever want them to be heavy?
There is some four pounds of difference between a set of the early iron pistons with rings as compared to the import replacement set that I used in my car.
Four pounds of reciprocating mass is considerable and eliminating it is a great thing for the crank and the seven poured bearings between the flywheel and the front pulley.
The 1926-27 cast iron pistons aren't much heavier than the aluminium replacements, as I discovered when I was forced to replace mine (cracked one). I haven't noticed any difference in performance between the two types. The engine runs and sounds exactly the same.
However, the pre 26 cast iron piston is another story and feels somewhat heavier. Another reason 26 crankshafts are meant to last longer??
Can someone post the weight of a original style .020 over aluminum piston with rings installed?
I am refreshing a 24 engine that was rebuilt sometime in the seventy's and has very little wear. The re-builder used cast iron pistons and I am trying to determine if it would be worth while to replace with aluminum.
Charlie, you want to re-bore the engine before putting aluminum pistons in due to different bore requirements. Re-bore for cast iron too because these engines cyls don't wear perfectly round. If your seeing "very little wear" with your eyes and fingers, you may be surprised when you find out the actual measurements taken with the proper tools. If your trying to save a buck by skipping a step in the process, you may want to re-think the plan. That way you can enjoy driving your car instead of taking it apart again.
Several years ago, I weighed both the cast iron and aluminum piston and found the weights were almost the same. I don't remember the numbers, but can do it again, as I have both types available. Perhaps the weigh should be done without the piston pin installed. The cast iron piston is reported to weigh two pound in other places, such as for a magnet test weight.
I weighed an NOS .033" OS cast iron piston (later, light weight style) against a new .030" OS aluminum piston both with the wrist pin removed. The cast iron piston weighs 2 lbs 3.7 oz. and the alum 1 lb 3.8 oz. That's more of a difference than I would have figured.
A problem with cast iron pistons is they typically don't weigh the same. I remember a couple times I was going to install a set but the weights were quite a bit different so I opted to use alum. I have never seen an alum set with more than 0.2 oz. variance.
I have just weighed an (apparently) original 1926 piston and bits compared to the new alum +30 and parts...
bare 810 gram
Total... 1052 gram
Total... 770 gram
A 2 Lb magnet tester = one piston, both oil rings and a 1/4' nut
OOPS! Correction to my previous post...
Rings for Aluminum pistons weigh 69 grams
All other individual figures and totals are correct