3 covette pistons

[Stephen B.]

I have a 63 327 low horse corvette engine apart has approx 50k on it pistons 5 and 7 are broken at the oil ring and #2 land who make a piston identical to gm pistons only want to replace those piston thanks in advance Steve

[John H.]

Re: 3 covette pistons

I have a 63 327 low horse corvette engine apart has approx 50k on it pistons 5 and 7 are broken at the oil ring and #2 land who make a piston identical to gm pistons only want to replace those piston thanks in advance Steve

Standard bore, or ? Any cylinder wall damage?

[Stephen B.]

Re: 3 covette pistons

std bore no wall damage lucky i guess

[Joe L.]

Re: 3 covette pistons

std bore no wall damage lucky i guess

Stephen------


Finding a piston configured like your original pistons is fairly easy. The original pistons were conventional cast aluminum pistons with 4 valve reliefs. For one source, Sealed Power #W310NP will come about as close to the originals as you're going to find in an aftermarket replacement. These pistons are readily available from many suppliers.

The big problem might be whether these pistons match the originals in WEIGHT. If they don't, there could be engine balance problems. However, I still expect that these pistons are going to come about as close as any aftermarket you're going to find.

You might seek out some NOS GM #3799491 pistons. Who knows? You might get lucky. These would be your best bet as far as replacements go.

[Duke W.]

Re: 3 covette pistons

The W310P is not the same as OE. It has lower compression height - 1.654" versus 1.675" for the originals. Also, I don't think it's available in standard bore size. A new OE piston would be okay if it can be found. A used OE piston might work out okay, but this type of repair - a used piston in a used bore - is always riskier than a new piston in a properly refinished bore.

The Sealed Power H660CP has proper compression height. Because it has no pin offset (originals are .060") there are only two valve notches, but they are within 0.5 cc notch volume of the originals. I don't have any weight data, but a significant difference could lead to noticeable engine vibration.

The OP should consider a complete rebuilt. For this I recommend the H660CP or a couple of Keith Black pistons depending on target compression ratio.

Duke

[Larry H.]

Re: 3 covette pistons

Stephen,
I sent you a P.M.
Larry

[Gene M.]

Re: 3 covette pistons

Steve,
Not a good idea. You need to have a weighted set of 8 pistons. The entire assembly will require rebalance. Quick and dirty in this application will not yield good results. Consider cylinder size, ridge, and hone for ring seating. Rebuild the engine correctly.........

[Jimmy G.]

Re: 3 covette pistons

I agree Never replace one piston They all should be martched and balanced

[Stuart F.]

Re: 3 covette pistons

Not to throw some mud on the subject, but I lost one piston in a 58 Fuelie Corvette 283 engine back around 1960. A pivot pin from the secondary air valve of my Rochester 4G (on the engine at the time) dropped out into the no. 8 cylinder, lodging into the piston, breaking every ring land and scratching the cylinder wall. I simply pulled that piston and rod assembly, put on a new standard size/weight OE piston, straightened the rod, honed the cylinder to remove as much of the scratch as possible without affecting the ID, and buttoned it back up. The engine was a factory original with relatively low mileage and parts were readily available so it made the project easy. The engine ran better than ever.

I sold the car with dual quads on it to a Greek Restaurant owner who street raced it every night. A few years later, my buddy put a new L-76 327 in it because the kid had put over 120,000 miles of street racing on it and the 283 was completely worn out. He said he couldn't save a single internal part, yet the engine never failed or blew apart, only burned a little oil.

Just thought I'd throw a little backyard mechanic logic into the mix.

Stu Fox

[Bill C.]

Re: 3 covette pistons

Stephen
Please listen to the advice on engine balance.
I learned this on my L84.
Even if you get a new set of pistons, I reccomend an engine balance.
Best of luck
Bill

[Joe L.]

Re: 3 covette pistons

Stephen
Please listen to the advice on engine balance.
I learned this on my L84.
Even if you get a new set of pistons, I reccomend an engine balance.
Best of luck
Bill

Bill------


I agree. I only made my initial response based upon the OP's stated intention to only replace 3 pistons. Personally, I would NEVER, EVER do that. I would replace only as a set and I'd use modern hypereutectic cast pistons. For one thing, if one has 3 broken original pistons, that's a pretty good sign that the engine has problems. How does one know that after replacing the 3 pistons and getting the engine back together that another of the original pistons won't soon break? Absolutely not worth the chance.

It's time for a complete rebuild and all complete rebuilds should include custom balancing of the reciprocating assembly.

[Domenic T.]

Re: 3 covette pistons

I have a few shelves of small block pistons here and also means to weigh them to the gram. ALL GM pistons for a engine weighed the same. GM was smart as they balanced the cranks all the same. So the truck, vette, pass car pistons all weighed the same, dished, domed, and flat tops all were the same weight. The steel and cast cranks were balanced the same and the rods & pins also. I have never found aftermarket pistons to weigh the same as a GM piston and had to balance every engine they were used in.
Lots of good advice here with offset, weight, balance and bore. If you weigh the old piston against the replacement and check the casting #s on each it will help. Then there are the #s stamped in the pan area on the block. You will see 16, 11, 6, and so on. The 16= .0016, the 11= .0011,
and the 6=.0006 and so forth for each cylinder. If there was no # it was exactly bore size. Some like the Dodge 413 engines did not have that quality control and piston slap could be heard. My gram scale has kept me out of trouble for years. I had to bring 3 GM pistons into the speed shop in So Cal once to show proof of that.

Dom