Ring Gap?

[johnnyrod]

I have 348 40 over and I have molly rings. What is the ring gap , do I have to file the rings to fit or are they allready sized? I am useing Hastings rings. The package the rings came in says .004 per inch of cylinder diameter. Any help or other info on my first rebuild at home. I had a pro shop do all the machine work and I am goig to assemble. Her goes thanks guys. John

 

[CHEV601234]

.014"-.016" regardless of bore. The rings have to have the right arc in the first place to match the overbore. DOn;t take a std bore ring and file the crap out of it to get to gap.

 

[johnnyrod]

I have 40 over rings new ones. Thank you for the info. If need be can I use a small file to adjust them? John

 

[Tom Kochtanek]

File fitting

I file fit my rings to the overbored holes, one at a time. Not sure everyone has to do this, but I did. Slip the rings (one at a time!) into the hole they will be going into (you will mark these after filing, so you get 'em back in the right holes when the rings are on the pistons). You want to get the ring exactly square in the bore, and to do this some of us use a quart paint can (empty), which is about 4 inches in diameter, and wrap duct tape or some similar tape around it until it approximates the bore of your sleeves. Use this "device" to push the ring down a bit and "square" it up in the bore, then gap them. If they are .014" - .016" as mentioned (not "in the range", rather pick which size you want to go with a do them all the same - better yet, read your tech manual that came with the pistons and rings for exact specifications.) then you are good to go. If not, then file fit to size (file and check gap, file and check, file and check until you get the right gap) and repeat for the other rings in that set.

Set those aside, well marked, then move to the next set and tackle those. Once done, you then arrange the eight pistons in the order that you will be inserting them (holes one through eight) and put the corresponding ring sets on those pistons/rod sets. Then sharpen your fingenails and slip those piston sets in the correct holes and begin to button up that bottom end .

I may have left something out, but you get the idea. I can't recall if I gapped mine all the same, I just read the instructions that came with the pistons and the rings (Ross tech notes). There may some additional tricks that the wizards know and use, I am sure they'll chime in. Have fun!

BTW, I used a manual (crank and turn) file fitting tool rather than a hand held file. Makes the filing square to the ring and does both ends at the same time. Don't take tooooo much off . There are electric powered tools as well. Borrow one if you can (either manual or powered) as they save a lot of time. This took me hours to do, but then that's me .

Good luck!
TomK

 

[models916]

I use speed pro specs

RING END GAP RECOMMENDATION GUIDE
Speed Pro 1st Rings

Moderate Performance (.004 per inch of bore diameter)
Drag Racing, Oval Track (.0045 per inch of bore diameter)
Nitrous Oxide - Street (.005 per inch of bore diameter)
Nitrous Oxide - Drag (.007 per inch of bore diameter)
Supercharged (.006 per inch of bore diameter)

Speed Pro 2nd Rings

Moderate Performance (.005 per inch of bore diameter)
Drag Racing, Oval Track (.0055 per inch of bore diameter)
Nitrous Oxide - Street (.006 per inch of bore diameter)
Nitrous Oxide - Drag (.007 per inch of bore diameter)
Supercharged (.006 per inch of bore diameter)

Notice: Most of the second ring gap recommendations are larger than the top rings. Recent testing has proven that a larger second gap increases the top ring's ability to seal combustion. This larger "escape" path prevents inter-ring pressure from building up and lifting the top ring off the piston allowing combustion to get by. Many engine builders have reported lower blow-by and horsepower gains at the upper RPM ranges with wider second ring gaps. Also, almost every new car made is using this inter-ring pressure reduction method to lower blow-by and emissions and to increase engine output.