[dataway]

Things are starting to come together.

Checked the gap on the SP no-file rings ... I'm getting .016 - .0165" on the compression rings. (.040" over 400 ci) too tight? (noticed the service manual mentions .020" +/- .010" that seems a bit whacky)

Deck height looks like .006" ... was shooting for .005

Piston dish 11.2 cc
Chambers 72cc (with OEM valves)

Looks like I'll be about 9.9:1 at this point .... will I gain a couple of cc's with new valves??

So far so good.

[Squidward]

That seems a little tight. IIRC, instructions say somewhere between .004 to .005 per inch of bore. And the 2nd ring gets a tiny bit more. I think I was at .019 and .022 for my 30 over 400. Again, I would consult the piston and/or ring instructions.

[blykins]

Originally Posted by dataway

Things are starting to come together.

Checked the gap on the SP no-file rings ... I'm getting .016 - .0165" on the compression rings. (.040" over 400 ci) too tight? (noticed the service manual mentions .020" +/- .010" that seems a bit whacky)

Deck height looks like .006" ... was shooting for .005

Piston dish 11.2 cc
Chambers 72cc (with OEM valves)

Looks like I'll be about 9.9:1 at this point .... will I gain a couple of cc's with new valves??

So far so good.

I would be at around .019-.020 on the top ring and .021-.022 on the second ring if I were assembling.

Check gaps on the oil rails too.....I like to see .015" gaps on those.

[dataway]

I assume "no-file" rings can be filed if necessary?

[hurryinhoosier62]

Originally Posted by dataway

I assume "no-file" rings can be filed if necessary?

Yes, but be very careful to make sure you file the ends straight. Do you have a piston ring grinder? If not, buy one. They're a good investment if you plan on doing much engine work.

[dataway]

Just for the heck of it .... as I like to explore this kind of thing. I took a set of the new rings, wiped a cylinder nice and clean, put them in, squared them up, checked the gap.
(e299k40) ... again, about .016" on the top, about .020 on the second, and about .014" on the rails.

So .. installed them all on a piston, put the piston/rod in the engine, turned the crank a couple dozen times. Pulled the piston/rod back out, took off the rings, cleaned the cylinder and checked the gaps again.

After no filing, the top ring was now .018", 2nd ring was .022", rails coming in about the same at .014"

Interesting that they pick up about .002" in gap with just a couple dozen strokes in the cylinder, these were right out of the box rings, and freshly honed cylinder.

I would imagine the majority of this change came from knocking off the highest points in the hone, any preservative coating on the rings and any oxidation on the rings or cylinder walls (fresh hone meaning done a month ago)

Do you guys take into consideration this probable "running" gap when setting up the initial ring gap? I would guess in this scenario the top ring is going to settle in at about .020" after a few hundred miles on the engine. (probably a stupid question ... as I've learned from you guys that most specs/measurements are based on typical assembly procedures which would take everything into consideration)

I saw this many times setting up high revving small bore motorcycle engines, about the same change in gap/in bore, after a few hours of run time, although the run time was typically at around 10,000 rpm, in an air-cooled engine. After that the wear/gap would remain constant for majority of the engines life span (about 20 race hours), at which time other components would require attention and the whole engine rebuilt anyway.


Also .... I'm getting rod big end side clearance of about .022" ...that's measured between two rod big ends, pushed to either side. (RPM 5140 rods) ...that sound ok?

Any thing I should know about torquing the ARP rod bolts? Seems strange doing it while they are installed ... lots of side forces on bearings.

Thanks,

[blykins]

Your side clearance is fine.

The ring gap changing on a few strokes is not normal. Otherwise, your rings would just keep wearing indefinitely and never stop. I imagine that you're not squaring them up the same way each time, or trying them in a different bore. Remember, .001" in bore diameter will change ring end gap by .003".

[dataway]

Excellent ... no major problems so far. I had to touch a few of the rings to open them up some, not many so far. Not more than .002". All the cylinders seem dead nuts on at 4.160"

Side clearances holding at .021-.022.

Torque to turn the assembly over with four slugs installed is less than 20 ft/lbs.

[Cliff R]

I set all of our street engine builds at .018"/.018" and have had zero issues in that area. The "trend" in the last decade or so has been to have the bottom ring gap a little wider than we used to set them back in the day.

Before we had all this file fit stuff it wasn't uncommon to see bottom rings come it around .014" or so, and I never once opened any of them up.

These days since we use custom forged pistons and modern ring packs, all of them are file-fit. In most cases we use Total Seal standard type, not the gapless versions. In all the years we built one engine with the gapless variety and it spit out two oil pan gaskets on the top end of the track due to excessive crankcase pressure. That engine dyno'd just fine and made great torque numbers, and no issues on the dyno with excessive pressure, but in actual use it didn't make the grade. We put traditional file fit rings in it and no more issues anyplace.....FWIW.

Good advice on checking the oil rings, Total Seal let quite a few sets get out there where they butted together tight in the bores and required some work. We saw this for a while, but the last couple of engines we've done including the one we just finished they were fine........Cliff

[BB70]

Dataway, when torqueing the rod bolts put feeler gauges inbetween both sides of the rods to eleminate the rod twisting.
John

[gtofreek]

Originally Posted by BB70

Dataway, when torqueing the rod bolts put feeler gauges inbetween both sides of the rods to eleminate the rod twisting.
John

X2!

[dataway]

Originally Posted by BB70

Dataway, when torqueing the rod bolts put feeler gauges inbetween both sides of the rods to eleminate the rod twisting.
John

Thank you .... that is just what I was worried about.

[hurryinhoosier62]

Originally Posted by gtofreek

X2!

X 3!!

[dataway]

Pistons are all in ... torque to turn the assembly is about 25 ft/lbs. with no cam and the rods are snugged down but not torqued. Waiting for some ARP lube to do the rod bolts.

[HWYSTR455]

Ring gaps are dictated by the manufacturer, and are dependent on the material. Follow the manufacturer's recommendations. There should be an insert with the rings that tell you baseline gaps for the rings.

With that said, bigger is better than too small. In 'adverse' conditions, the ends can butt, and that is not good. Adverse conditions = det, high heat (as in with N2O or forced induction), etc.

I always cut rings to allow for a 200 shot of N2O (or more). That way not only is there no chance of butting, but in the event you MIGHT want to spray it, you can and not worry.

If you do end up with det issues, especially under WOT, a small shot of N2O can help control it. It has a cooling effect (on the intake charge). Something to think about, especially if your on the edge with SCR.

.

[mgarblik]

I have a feeling I will get trashed for this post, but my experience over many years is the ring end gap is not critical to final engine performance within reason as long as their is enough gap for the application. Let me explain. I have never seen an engine fail from too much end gap. Too little, absolutely. Catastrophic engine damage if the rings butt together. Too much side clearance, same catastrophic damage as the ring lands break. As far as end gap, I remember some extensive gap testing Warren Johnson did on Pro Stock engines. They tried all kinds of end gaps on top and second rings. They had top end gaps as wide as .060 and no loss of power on the dyno. Actually found small power increases as they widened the gaps into the .035-.040 range, then little to no change up to .060. When Joe Mondello was alive he agreed with these findings in his own experiments.
So what does matter? To get accurate end gap readings, the ring must be absolutely square in the bore as mentioned. If you file the end gaps to gain more clearance, they must be filed or ground straight and all edges dressed with a diamond file or tiny stone. This goes for new rings that have not had the gaps altered. If you leave sharp edges, the rings act like little chisels in the bore. Like many have mentioned, I too like .003-.005 more end gap on the second ring. Oil rails are worth a look as mentioned, usually do not require opening the gap. If I have a target gap for example of .022" and I end up + .002-.003, I would install and never worry about it based on the research I have read. Back in the old days, I would have replaced the rings.
Dataway, I think it is great the way you are experimenting and learning all the details of your engine. I used to do these kinds of things all the time and then be puzzled for months or years about my results in the days before the internet. Good luck with your engine.

[blykins]

Originally Posted by mgarblik

I have a feeling I will get trashed for this post, but my experience over many years is the ring end gap is not critical to final engine performance within reason as long as their is enough gap for the application. Let me explain. I have never seen an engine fail from too much end gap. Too little, absolutely. Catastrophic engine damage if the rings butt together. Too much side clearance, same catastrophic damage as the ring lands break. As far as end gap, I remember some extensive gap testing Warren Johnson did on Pro Stock engines. They tried all kinds of end gaps on top and second rings. They had top end gaps as wide as .060 and no loss of power on the dyno. Actually found small power increases as they widened the gaps into the .035-.040 range, then little to no change up to .060. When Joe Mondello was alive he agreed with these findings in his own experiments.
So what does matter? To get accurate end gap readings, the ring must be absolutely square in the bore as mentioned. If you file the end gaps to gain more clearance, they must be filed or ground straight and all edges dressed with a diamond file or tiny stone. This goes for new rings that have not had the gaps altered. If you leave sharp edges, the rings act like little chisels in the bore. Like many have mentioned, I too like .003-.005 more end gap on the second ring. Oil rails are worth a look as mentioned, usually do not require opening the gap. If I have a target gap for example of .022" and I end up + .002-.003, I would install and never worry about it based on the research I have read. Back in the old days, I would have replaced the rings.
Dataway, I think it is great the way you are experimenting and learning all the details of your engine. I used to do these kinds of things all the time and then be puzzled for months or years about my results in the days before the internet. Good luck with your engine.

I will "amen" all of that.

During my stint at Valvoline, I had to do calculations to see how much end gap was necessary to actually cause blow-by. The engine lab had dozens of engines running at all times, in order to recreate different running situations, including high-mileage engines. You could get into some DEEP ring end gaps without causing issues.

[gtofreek]

I totally agree with everything mgarblik said! Well written.

[hurryinhoosier62]

Originally Posted by mgarblik

I have a feeling I will get trashed for this post, but my experience over many years is the ring end gap is not critical to final engine performance within reason as long as their is enough gap for the application. Let me explain. I have never seen an engine fail from too much end gap. Too little, absolutely. Catastrophic engine damage if the rings butt together. Too much side clearance, same catastrophic damage as the ring lands break. As far as end gap, I remember some extensive gap testing Warren Johnson did on Pro Stock engines. They tried all kinds of end gaps on top and second rings. They had top end gaps as wide as .060 and no loss of power on the dyno. Actually found small power increases as they widened the gaps into the .035-.040 range, then little to no change up to .060. When Joe Mondello was alive he agreed with these findings in his own experiments.
So what does matter? To get accurate end gap readings, the ring must be absolutely square in the bore as mentioned. If you file the end gaps to gain more clearance, they must be filed or ground straight and all edges dressed with a diamond file or tiny stone. This goes for new rings that have not had the gaps altered. If you leave sharp edges, the rings act like little chisels in the bore. Like many have mentioned, I too like .003-.005 more end gap on the second ring. Oil rails are worth a look as mentioned, usually do not require opening the gap. If I have a target gap for example of .022" and I end up + .002-.003, I would install and never worry about it based on the research I have read. Back in the old days, I would have replaced the rings.
Dataway, I think it is great the way you are experimenting and learning all the details of your engine. I used to do these kinds of things all the time and then be puzzled for months or years about my results in the days before the internet. Good luck with your engine.

EXCELLENT post, Mike.

[dataway]

Originally Posted by mgarblik

Dataway, I think it is great the way you are experimenting and learning all the details of your engine. I used to do these kinds of things all the time and then be puzzled for months or years about my results in the days before the internet. Good luck with your engine.

Takes me a quite a while to explore all the nooks and crannies ... pictured below is the only engine I really know well. Developed these for 15 years, until they had twice the OEM hp and would survive at 14,000 rpm. Ended up building my own exhaust systems (Hossfeld bender), my own intakes, ignition system, a dozen different custom piston designs (Arias) and ring sets, custom Ferrea and Manley valves, totally reworked oiling system etc. Left the porting to experts, and had Langcourt in GA do the cylinder work, but other than that, I literally fabricated, machined, or modified every single part in these engines. Ended up making about 124hp / liter (26hp / 209cc) using 2 valves per, and rocker arm valve train. I still have people call/email me from all over the world asking for info on them .... much of which I've forgotten already and I have to look at my notes.

Anyway.... yeah, pre-internet ... things were a pain. Most of my racing/building career was done with the internet readily available, huge resource, and as evidenced by my posts here, I've come to depend on it for information, advice and help from other people.

One thing I have learned for sure, is it's very unlikely I'm going to think of, discover, invent, or realize ... something about an engine, that someone before me hasn't realized already .... so ask the guys that have worked on them for years, it saves a lot of time and money.