What's up guys and girls? First time poster long time lurker lol. I have done hours of research on this subject and found a lot of good info here, but I still have questions. 2008 r6 on meth dual injection moveable stacks made 140 at wheels. Was done by a "builder" who I dont trust a word they say now. It dropped a valve 30 min after a rebuild. From what I found it looks like he forgot to put a shim in???? I couldn't rotate motor enough to check timing before disassembly. I checked squish when I had it apart and it was .046(in) and the head was cut. I got a slightly thinner .50mm head gasket to get squish down. To maintain ptv (.080in on tightest) I have to run like 123° on exhaust. I'm at like 111.25 on intake(to maintain ptv) should I keep this number low or bump it up? So is this a problem or just more top end biased? What's the tightest ptv you've ran personally? Should I stick with the .080 ptv on exhaust? It's a micro sprint so it lives on limiter and not much shifting usually. Gear it to hit limiter entering the turn, and lift to set car. Sorry for the long post lol I'm trying to figure out pics
RM I almost msgd you. I saw you on posts from years ago. I'm 16,100 limit as per us6a rules. I just dont know if this thing is guna be a dog or have a problem of some kind. I'm dead in the water idk what to do. Run it? Dial it back? Buy a thicker hg?
Yamaha kit manual lists minimum PTV as 0.8mm INT and 1.4mm EXH. That's safe with stock cams and rpm, I have gone quite a bit lower. I know where the limit is, but I'm not going to disclose that. 0.055" EXH is just fine and will get you some better midrange. 0.040" and 0.080" are car engine sort of specs, really.
Ok thank you! So you think I should dial back the exhaust timing a bit. Maybe try and get under 120? As long as I can maintain .055in ptv
Correct. The R6 is designed as a PTV value engine. Hit those marks as described above, don't concern yourself with the lobe center numbers, hit the PTV values for best power throughout the rev range. Mini sprints are high rpm use cases, so very high cam timing is somewhat acceptable, but you won't get out of the corner as well with the numbers you have now.
Without being a know-it-all, I am interested to know how the engine ended up with .046" (1.15mm) of squish clearance? Seems like about 50 percent more than necessary. Does the engine have non-standard pistons? And if the thing runs methanol, wouldn't you want big compression? Cause with the squish clearance you called out in the original post, you have a compression ratio of, maybe 10 to one. Perhaps even less than that.
I fat fingered the keyboard. I meant .035in but I did find .038 at the largest. That was with the original hg i put the head back on to measure it. I saw the min spec in kit and figured I could drop down some knowing squish is important. I believe I am down right to the min now .023 in. I guess the builder just wanted to be on the "safe" side? Or didnt really check? I believe they use meth because its "safer" than gasoline. It doesnt hurt that it makes a little more power, and runs cooler as well.
That was the original hg. I put a .50mm in it. I just looked back and checked I have .026 in squish. Yes it has stock pistons.
