G72Zed wrote: ↑Mon Apr 16, 2018 8:47 pm
It's been a long time, but I actually have done a similar "Gapless" test back in 2002/2004, by no means super scientific A-B test, but it did show me some key trends, and raised a few questions.
My engine is a pump gas 10.57 CR 333 sbc (327+.040) with Sportsman II iron heads, 2.02/1.6, 750 Holley, 252 @ .50 FT cam w/500 lift, flat top pistons. Typical street sbc.
Back in 2002, I had it dyno'd and it made 396.9 Tq @ 5,600 and 482.6 Hp @ 7000 rpm on premium pump gas. The cranking PSI was 180/182 on all cyl.
Average Tq was 380, and ave. Hp was 408.4, this was from 4,100 to 7,200 RPM.
So, during the next 16 months while building my car, the engine sat on the stand, and I did some reading and looked into the "Gapless" top rings, and the trend for the "larger" gap'd second ring. I ordered the Total Seal Gapless top only (1/16) and opened the 2nd ring from .012 To .022. I pulled the heads and dropped the pan, popped the pistons out, did the gaps, the engine shop "prepped" the bores, and put it back together.
I basically wanted to crack 500 HP with a basic 327 with old Iron heads that nobody loved or wanted!! So, Dec. 2003 I go back to the same opperator/dyno, same pump gas (but winter gas) same carb/jets exhaust,plugs ect....same oil grade & amount, I kept everything the same as much as possible including water/oil temps.
It made 411.4 Tq (+14.5) @ 5,600 and 503.9 Hp (+21.3) @7,000 RPM. Averages from 4,100 to 7,200 went up to 395 Tq (+15) and 417 Hp (+9). Did the cranking PSI the same way, 200-202 PSI, up 20 PSI. BSFC was down to low-mid .40's, from the upper .40's, exhaust ports were not sticky. Leakdown test showed 1%, nothing. Dyno guy was impressed.
It's weird, even after 20k miles, the engines runs great, makes good power,really good MPG,cranking PSI still there with very/very low leakdown # (1-3%) Took it to the drag strip just for fun, ran 13 flat @ 118 mph in 3rd gear with street tires, car is 3750#'s at the line.
BUT, since the start, it's like it sucks the oil in the chambers under deceleration, and puffs blue on initial acceleration, nothing after that. Even light decel, stop, let it idle, blue smoke, then cleans up. Even taking it easy cruising, puffs on shifts. I have the good valve stem seals, no leaks, I even tapped the intake valley on the last dyno day back in 2016, it registered -1.1 Hg's, during the full pulls, no crank case pressure there. Valve cover breathers are clean, no mess anywhere.
I have gone from Brad Penn to Driven to VR1, same thing, no leaks, good power, always adding oil. Tired of fighting this. I think I will be going back to conventional rings like the AP TS, never had oiling issues in the past with this engine.
Sorry for the long post, but I am very interested in this topic.
) from the cylinder walls.
