The Stovebolt Site Forums The Shop Area Engine Shop Survey: Keep CI pistons or switch to Aluminum?

My '52 216 block, pistons/rods, head, etc. are at the machine shop to get "freshened up". The engine has very little cylinder wear (no lip) and I expect the piston to cylinder wall clearance might be fine. If I dont need to bore oversize, I am debating whether to switch to aluminum pistons (and re-bore anyway) or keep the cast iron pistons and leave well enough alone.

I talked about this in another thread, but wanted to get everyone's oppinion to help me decide what to do.

You're spending considerable to freshen up the car you like.The factory thought aluminum pistons and Chrome or Moly rings were a worthwhile upgrade in 1954 and NEVER went back.
Small cost to do it now.
Yes, I know Moly coated top rings weren't out there in 1954.
Cast iron pistons were thought to be more quiet--were more fragile as well as adding unwanted reciprocating weight which adds load to the rod/crank/bearing assembly especially as RPM is increased.
While we are at it rebore to the minimum "cleanup" since we are buying pistons anyway.
Just a note of interest F--- went to aluminum pistons in 1928 in the model A while chevy stayed CI, I think thru 53 in the 216 and Pontiac still had them in the straight 8 in 54.

Lets hear other ideas.

Chev also used aluminum pistons in 1928, (and I believe 27), in passenger car engines.

Gald to see I am not the only person asking about different piston material and whick is the best to use?
I have learned that You should probably upgrade to the aluminum pistons. Brian

I use aluminum pistons in every engine I rebuild, there much easier on the bottom end as Bob mentioned.

I dont care how much of a purist you are, I'd go with the alum pistons since no one can see them and then use every modern trick out there to try to stop all the leaks-maybe even a pcv valve if you can get creative and hide it. Like them model A and B guys do. Your babbit bearings will thank you!

Since the inline 6 crankshaft is inherently well-balanced, changing piston weight doesn't induce any nasty vibrations. I'd definitely reccomend an upgrade to aluminum. Less reciprocating weight will make the rod bearings last a lot longer and the acceleration should be better to boot - - - -less inertia.
Jerry

no question, aluminum.

So, finally had a chance to talk to machine shop: Cylinder bores are marginal - good at bottom, .0045" to .005" at top. Would probably work fine staying with CI pistons, but I decided to have the cylinders bored and go with aluminum pistons, new rings. I am going to stay with babbit rods as all rods still had two shims under the caps so I should be able to get a good fit on the crank.

What I am doing: Deck block to clean it up. Mill head to clean it up. Hardened valve seats. New valve seals. New camshaft bearings. New crank bearings. New aluminum pistons/rings. Staying with original camshaft/lifters.

I'd pass on the hardened seats unless yours are really in bad shape and won't clean up. Take the money you save and get a new set of insert rods. You'll be happy with the trade off.

Completely agree. I've read numerous complaints about trouble from hardened seats coming loose, none about problems because they weren't installed. I had the rods machined for inserts on my '38 216. At about 2500 miles a year I probably won't put enough miles on it in my lifetime to know if it was a good choice or not in relation to longevity.

Just out of curiosity, how many miles were on the 216? The wear seemed pretty minimal for a used engine.

Mileage is unknown, but the speedo said about 80k. Someone has been in the engine before, but all bearings, piston, etc are standard size.

I am going to stay babbit as there is plenty material left and it should last a long time. My goal was to not dump a ton of money into the 216 and if it goes bad in the future it will be replaced with a 235. I just dont know how much use the truck will see and thus am not doing the conversion now.

Pay attention to the VIN on your title. Many if not most vehicles pre '56 were titled using the engine number. If yours has the engine number on the title you'll need to re-title following an engine swap.

Yep, I'm good. Had to get bonded title and was sure the body VIN was used.

Update: Machine shop said valve seats looked fine and recommended just surfacing and NOT replacing with hardened seats. I agreed. Thanks for the advice.