Ring gap question

[Those]

I have a clean 340 I bought in 1982 for $100.00 believe it or not. I'm finally getting to it. Nothing but new rings and bearings cam and lifters. I ordered std size rings and when I put one in a cylinder I'm getting a .075 ring gap.  My first thought is wrong rings. The part number on the box is mahle 50787 which is right for 340 std. Size rings. So I take a ring off of one of the pistons that came out of the engine and drop it into the cylinder and get a gap of .080 I know this motor ran because I m put about 200 miles on it back in 1982 then pulled it and sold the car. Would the factory ring gaps have been that wide? I'm working on the theory of .004 per inch of cylinder bore. Thanks to all replies.

[1 Wild R/T]

Measure the bore.... Sounds like it might be .020 over....

[jimynick]

Measure the bore.... Sounds like it might be .020 over....

Yep, if not .030 or even .040 since a decent ring gap these days seems to be in the low to mid 20's. The plot thickens! Any markings on the pistons themselves as to being oversize?

[Those]

Still had the stock 340 pistons. Im sure it was never over bored. If it was the rings that were in it wouldn't also have the .080 gap. I remember it being a low mileage engine. It was pulled from a 72 roadrunner. The guy was going big block.

[Those]

I thought somebody might have the heads of of a stock motor and could check the ring gap. I ordered a set of .040 rings. Figured I can file fit them. I thought maybe 360 rings in a 340 box but that doesn't explain why such a wide gap on the original rings.

[1 Wild R/T]

Reason I suggested .020 over is Pi = 3.14    .020 x 3.14 = .0628.....   Measure the bore...     Plenty of 1970 vintage engines were rebuilt by 82... My first 70 Charger I bought in 77 had been O/H in 75....   Motors weren't expected to live like they do now.... 100K was high mileage... Some engines were worn out by 50K.....   I've seen plenty of rebuilder grade pistons with no O/S markings on the dome..... Only way to know is to measure it...

[Those]

I went to the garage to check the pistons. They have 4 valve reliefs, # on top 3671158 os, inside Chrysler logo, the name bohnalite, and c4930. A rough measurement of the piston was 4.035.  Thanks for thoughts 1 wild r/t.

[1 Wild R/T]

Measure the bore, not the piston....

3671158 os  I wonder what os means.....

BTW where on the piston did you measure?  The proper location is 90 degrees to the pin on the lower skirt...

[jimynick]

In my old fart shop- os means "over sized" 

[1 Wild R/T]

In my old fart shop- os means "over sized" 

Yup, mine too...

[73_Cuda_4_Me]

what year is the 340 engine? On 73's, Mopar made them in STD (4.040), .005 o/s, .020 o/s, and .040 o/s... none of them match that number, though...

[Those]

It's a 1972. I put a telescoping gauge in the bore today and checked it. Came up with 4.052 so I think theres more wear in the bores than I thought. I guess it will need an overbore. I'm just amazed there's almost no trace of a ridge at the top of the cylinders. 1 wild r/t was close on his guess on bore size. That's probably enough wear to put a .080 gap in the original rings.