Gapless Top Rings

[CGT]

I know this has been discussed/debated on here in the past. Nevertheless, looking for personal experience, opinions, class racing engine builders with possible before and after's etc.

[MadBill]

We've got a 700 hp 379" SBF road race engine equipped with 2 ring Wiscos and TS Gapless® top and low tension oil rings (1.0/2.0 mm) down for a refresh after 5 seasons, ~ 45 hr. total.
New, the short block rotating torque was 6-8 lb-ft. and leakdowns were between zero and 1.5%. They now run from 0.5 to 2.0% and the bores look perfect. (Note to self: check current rotating torque.) The very used 4 stage oil pump easily pulls 20+ inches of vacuum but we dial it down to ~12"Hg. to play it safe.
A lot of guys don't like Gapless, saying 'we didn't make any more power with them.' but I haven't heard anyone say they made less and if nothing else, it makes it less fiddly to gap them. (The 0.005" over set I put in my 0.010" over 4.450" BBC came in at ~ 0.035" and Keith at TS said: 'absolutely no problem, run it.")

[groberts101]

Every single engine I've ever used gapless rings on feels fresher longer. Also makes at LEAST slightly more manifold vacuum and gives extra tuning flexibility when you know how to take advantage of that higher manifold vacuum. Carb is easier to dial in and consistency improves. Less blowby so combustion space stays cleaner while pushing less out the pcv and breather/s.

[ptuomov]

I’m speculating that gapless rings don’t really help by directly sealing the combustion chamber better, but they do help by better scraping the excess oil off the bore walls. Some of the excess oil gets thru the conventional ring gap. Does this make sense? If it does, you’d expect a messy wet-sump engine to benefit from gapless rings more than a well-developed dry-sump engine. Also, if oil scraping is the benefit, gapless second ring starts making sense. Nutz or not?

[groberts101]

I don't know about the gapless design directly affecting oil contamination since the typically included napier 2nd ring in premium ring sets handles that task just fine.

Ask how any engine equipped with gapless rings makes more manifold vacuum than same engine with conventional gapped rings(even if gapped on the tighter side of toletance) and it's not hard to understand that they DO actually seal better. Same with cleaner oil.. how does that occur if they don't seal up a little better?

I'm about as cynical and pessimistic as they come when it comes to advertising claims.. but becomes much harder to question the obvious once you've used them many times. They work very well and I will use them whenever possible for as long as I can and tell everyone I actually like about them as well. And seeing as they can be had in just about any possible custom made configuration.. seems possible to use them almost exclusively on everything from small bore weedeaters to big bore caterpillars.

[ptuomov]

Wouldn’t the conventional napier style second ring still have a gap that lets in oil? I’m talking about oil everywhere wet sump disaster that floods the bore walls.

[statsystems]

Lots of people say their gapless rings burn oil.

I use them on everything that doesn't get gas ports.

[Walter R. Malik]

I know this has been discussed/debated on here in the past. Nevertheless, looking for personal experience, opinions, class racing engine builders with possible before and after's etc.

Usually the crankcase pressure build-up takes a few seconds longer if there is no crankcase vacuum pump involved.

[ptuomov]

Lots of people say their gapless rings burn oil.

I use them on everything that doesn't get gas ports.

Do the people who use a gapless top ring also believe in leaving the second ring gap larger?

[dfarr67]

How about in a daily driver application- say a working truck 1/2 ton?

[grant6395]

The info I got from Matt Hartford was that any engine will seal better and make a very slight amount of low to midrange torque( up to 7500 ish). But an engine that spins like our comp engines will loose power up top, due to the design of the gappless ring. My guess it upsets ring seal at upper rpm. Used many sets on alcohol engines with great success . Probably due to the fact they were carbureted and too fat at idle. ( oil contaminated)

[statsystems]

Lots of people say their gapless rings burn oil.

I use them on everything that doesn't get gas ports.

Do the people who use a gapless top ring also believe in leaving the second ring gap larger?

I do.

[Walter R. Malik]

Lots of people say their gapless rings burn oil.

I use them on everything that doesn't get gas ports.

Do the people who use a gapless top ring also believe in leaving the second ring gap larger?

Actually, ANY gap at all is larger than "Gapless".

I usually gap the 2nds at what I would normally gap a regular top ring.

[MadBill]

Also, if oil scraping is the benefit, gapless second ring starts making sense. Nutz or not?

Here's my short version of Gapless history and rationale:
1. Gapless top rings invented ~ 50 years back.
2. Materials of the time weren't up to the requirements, so..
3. The gapless ring was moved to the second groove.
4. More recently, material science caught up with the top ring environment and the gapless was moved back up. Strangely, the second ring gapless is still an option. I say strangely because current thinking is that the second ring must not seal compression, in order to ward off top ring flutter.
5. Illustrative tale: I recommended a friend use TS Gapless rings in the rebuild of his 1969 Alfa Romeo. All the work was meticulous, the bores finished by a top-notch race shop to Total Seal's specs. The leakdown numbers were zero across the board but, apparently due to cylinder wash while getting the DIY Mega Squirt injection dialed in, oil consumption was found to be ~ 500 mi/qt. It improved somewhat over the next few thousand miles, but a slight (but mortifying for an otherwise 95 point restoration) smoke plume followed it everywhere.
When torn down for inspection, one cylinder was found to be badly scored, but the gapless rings were installed in the second groove and all four top rings were in anywhere from two to five pieces. This engine had not been abused in any way and although only 9.0:1 CR, was always run on 91 octane.
I don't know if this was a 'second groove' Gapless set, or was a mis-installed top groove one but I am 100% certain the ring failures were due to flutter caused by the inter-ring pressure build up. The engine was rebuilt this time with factory replacement pistons, rings and liners...

[user-30257]

Simply put, gapless rings allow you to use a thinner ring, any power you may have gained was probably from less friction. But then again adding an extra ring to the ring groove makes a heavier ring pack and a stack up of tolerance.
Why not just order the right piston and the thinner ring, and forget about gapless. If you are using gapless for better ring seal find a better machine shop, or get better at preparing bores.
You need a flat ring groove and a flat . As far as blowby, I have seen refreshed engines to reduce blowby make no more power and been slower at the track..

But take what I say with a grain of salt. I'm a nobody.