VCCA Home Forums TECHNICAL - 1945 AND EARLIER 1937-1945 Cast Iron or Aluminum Pistons?

I have had some old-timer machinists comment negatively on me using some NORS cast iron pistons on my 216 rebuild. They have said the tolerance and machining processes were really crude back then (the set I have is "Nylen" brand from late 40's).

They have said that by far a modern aluminum set from Egge would be the way to go.

Of course I've also heard from others that the cast are just fine since these NORS are likely better than the original Chevies and the car won't be a daily driver anyway.

My block has been machined for cast but it wouldn't cost that much to get sized for aluminum so now I'm debating my original decision to use cast.

What are the opinions out there?

Thanks

It's a matter of opinion and you will hear pro's and con's on both. Personally, I wouldn't use Egge pistons on a bet! If you choose to use aluminum pistons I would suggest getting NORS aluminum pistons instead. I prefer cast iron, and if the engine is balanced you should have no problems if you go with cast iron pistons.

Its common for after-market parts to be inferior to the originals. They often skipped improvements, etc. that GM made. As an example the pistons from GM were black in color. This was due to the tin coating to aid in break-in. As far as weight is concerned the GM were not perfect and any set of pistons could be correctly rebalanced.
I prefer a good set of aluminum but in my opinion I would prefer the set of Nylen brand to pistons from Egge. Nulen was a "brand name".
The engine bore size should not be changed to the piston material. If all is done correctly the pistons should be made to fit a bore size. The cast iron called for a .002" clearence, most aluminum called for the same.
I am runnig a set NORS Elgin pistons in my '39. I installed a new bare block 20 some years ago and used the standard pistons with no special fitting and no problems. I prefer the lighter aluminum becaust I do a lot of high speed driving. For normal service the iron will be just fine.....thats driving an engine with a 3.73 rear end at 60 MPH.
What size is the over bore?

I have rebuilt engines with both aluminum and cast iron. I now use cast iron and sell the aluminum. I have run the engines at at higher rpm range that others have told me would cause problems without them. I understand the theory of less weight but at the engine speeds that these old engines run it is not much of a problem.

Sold two sets of Aluminum to one guy because the first set seezed. Apparently the "expert" (had reportedly rebuilt many A & T engines with Al pistons) machinist did not know to finish the skirt cut. The second set gave problems until they wore in and now are fine.

Thanks!

My oversize is 0.030 Gene. It was stock bore before this rebuild.

I'm going to stick with the Nylen Cast pistons. They have some slightly textured coating on them that is suppose to "reduce wear and aid break-in" according to the rickety old box. The coating almost looks like a black powdercoat and a couple oldtimers commented that these were a better quality than they were used to seeing.

I'm getting everything balanced so I suspect that will help a lot over the original assembly as the original weights of rods and pistons was all over the map - this would have certainly caused some "higher" RPM issues.

Thanks!

Actually the pistons were weighed and then identified with a letter. Don't know the ranges for each but all original pistons I have removed (a bunch) have had the same letter stamped into the top. Same for the good replacements. Those in a set have all weighed within a couple of grams or less so never felt I needed to adjust them. Have also weighed rods both end to end and overall. Select rods within a few grams or carefully grind a bit off to get them nearly the same. Engines seem to run well and go fast enough for me. Anything over 55 - 60 for a '31 is enough. The '32 and up with counterweighted cranks will go 60-65 without a problem. Yes they vibrate a bit and make some noise but will run reliably.