Attention engine builders need help!! I just realized while putting together my second motor that when I measured my rings on the first motor I read the ring specifications wrong. My engines are 502's that have been bored to a 4.5 bore. My ring gap for the top ring is .006ths the bottom ring is .007ths. The spec sheet says top 18 and bottom 20 thousandths. The kicker is I already put the first engine together without realizing this and ran it on an engine run stand fo 10 hours. Runs great and has 175 PSI compression on each cyclinder. If I put this engine in my boat and run it with a tight ring gap what problems could occur if any? P.S. I know it's funny I just want to make sure it will be ok. If I have to I will tear it back down and redo it. Thanks Much! Please give me your opinions.

That gap is way too tight. I am surprised it lived for 10 hours on an engine stand. That tight of a gap, will most likely cause the ends of the rings to butt together, wiping out the cylinder walls and pistons. Unfortunately, you need to tear it down. Follow the recommended ring gap that came in the ring box. If the engine is naturally aspirated, it may be .005 per inch of bore for the top ring and .0055 per inch of bore for the second ring.

Like Vinney said the ring gap is WAY to tight. In my opinion even the .018-.020 is on the tight side. I like to be @ .023 top and .026 on the second ring. You must be very lucky not to have butted the rings after 10 hours. Maybe time to buy a lottery ticket. Hope all works out.

Tear it down. It only lived because there was no load on the engine and it did not build enough exhaust temp. If you would have run it under a load in the boat or on the dyno, it would have come apart.
Sorry......good luck.
Eddie

The ring gap on a marine engine is supposed to be even larger than an automotive engine because of the load and heat generated. The rings expand when they get hot and they will butt together ruining the cylinder bore and maybe even pulling the top of the piston off. RHM is correct about thr ring gap.

Yep, you've got to tear it down and file the rings to spec. If it were .005" off of spec. I may not worry about it, but you WILL have problems once it's in you're boat if you don't resolve this issue.