Ring End Gap

[FirstEliminator]

   Hey guys,

   I am putting together a 445 with about 9.5:1 compression, 234/240 hyd roller. The car is going to be a street driven car with an occasional run down the strip. As I am filing the ring gaps I am of course choosing to go with the minimum as per the manufacturer, which is .016" gap. So far, I have a couple top rings that came out to .017-.018. Would it be best to put these in cylinders 4 and 8? My thought is those cylinders may run a little hotter and help to even out the end gaps. What is your thought?

   thanks in advance,
       Mark

[jayb]

I guess I wouldn't worry about which hole they go in; the difference in gap is so small I doubt it will make a difference to the engine.  JMO - Jay

[FirstEliminator]

     Cool, thanks Jay.  Tonight I put in the cam bearings, assembled the rods and pistons and put on the rings. I was planning on putting in the crank, but realized I don't have a rear main seal. Perhaps Advance Auto will have one tomorrow. There is a chance as long as it isn't unique only to FE's.

   thanks,
     Mark

[FirstEliminator]

   I was talking about the 445 build with a friend today and he felt .016 was a bit tight on the ring gap. I don't have the pistons installed yet, so it wouldn't be a big deal to open the gap a little more. My friend's thought was if the gap is a little bigger, you'll never know the difference. Or, if the gap is too tight and the ring ends butt together breaking the piston then you WILL know the difference.

     Should I open them up a thou or two?

   thanks,
      Mark

[My427stang]

I am a firm believer that bigger is safer with no downside unless it gets ridiculous

I run .0045 x bore top ring and then round up if required, .0055 x bore for the second ring.

With a 4.08 bore the top ring would be .01835 and I wouldn't think twice about .020

The second ring would be .0225 and I wouldn't lose any sleep at all at .024

IMO the keys to good ring seal are bore condition, both in surface and shape and stability of the ring in the land.   Basically if a ring moves a lot, either expanding or contracting to a conical bore or flutter in the land, it's not very happy. The gaps themselves aren't a huge issue unless they are too small

In a dynamic environment, a staggered set of gaps, even when getting larger, do pretty well at holding compression

[jayb]

I am a firm believer that bigger is safer with no downside unless it gets ridiculous

I run .0045 x bore top ring and then round up if required, .0055 x bore for the second ring.

With a 4.08 bore the top ring would be .01835 and I wouldn't think twice about .020

The second ring would be .0225 and I wouldn't lose any sleep at all at .024

IMO the keys to good ring seal are bore condition, both in surface and shape and stability of the ring in the land.   Basically if a ring moves a lot, either expanding or contracting to a conical bore or flutter in the land, it's not very happy. The gaps themselves aren't a huge issue unless they are too small

In a dynamic environment, a staggered set of gaps, even when getting larger, do pretty well at holding compression

+1 on all that information.  I didn't do the math on your original combination, but I also use .0045 for each inch of bore diameter on the top ring, so I would run those gaps to at least .018".  I usually just add 3-4 thousandths to the top ring gap for the second ring.  You will notice that most ring instructions will want you to gap the second right tighter than the first, which is fine, but a bigger second ring gap will keep combustion gasses from getting trapped between the top and second ring; this can lead to ring seal problems.  As a result current thinking on performance engines is to make the second ring gap a few thousandths bigger than the first ring gap.

[FirstEliminator]

    Thanks guys. I guess I will be turning the ring grinder some more.

[FirstEliminator]

  It's fixed. 18-19 for the top and 22-23 for the bottom.


    thanks again for the advice,
     Mark

[Barry_R]

I'm late to this - but we gap our +/-500HP 445s at .017 top and .022 second - - you'll be perfectly fine where you're at.