I wonder at what point in his life Dave Moss suddenly woke up one morning, decided he was now an expert needing to give his advice to the world???
Stock head gasket is 3 layer, sounds like someone has been in the motor before. If your deck height measurements and head gasket measurements are right, your motor had from .030-.036 squish with that head gasket. That's probably as tight as you want to go.... I would cc the heads and get your comp ratio before you machine the head surface.
.030" is far too tight in my experience, I'd mill the cylinders to get in the .036-.038" neighborhood (measuring with a depth gauge as you did) with 3-layer gaskets and call it good. Below that the pistons start to get bright spots. I've seen .003" variance in deck but never .006" that I can remember. Something seems fishy. That old thing about measure twice, cut once.
You are correct Mike, someone has been in this engine previously. There are ID marks on some of the parts. Do you know what the height of stock head gasket would be? Since I have it apart.... I am giving due diligence to upgrades. I don't want to spend much money but I want to do it up rite.
Either someone machined the cylinders (which is odd to me) or the pistons are already aftermarket or at the very least not stock sv pistons.
I just checked my brand new stock head gasket and its 0.038" - .039" or .99-1mm. (I do everything in metric)
I'm a "meticulous machinist". I measured 16 times or more on Each cylinder and at as many points as I could get. LOL If I do the deck... there will be very very little variance. I guess I'd better measure everything I can..... and check under all the rocks. someone has been in there before and I thought that same thing when I measured the deck height. Perhaps they replaced a cylinder. As I mentioned on the 1st and only engine I worked on. I set the deck at .005" with a stock head gasket. No issues but I never pulled it apart.
I hate those digital things. LOL Compressed thickness is what I need to determine where I need to set the deck height. Thanks for the help though. Is that a 3-part gasket ?? I'm trying to ascertain the origin of the .017" (crushed thickness) gasket I removed, whether it was purchased or modified to size.
Yeah I don't have the compressed thickness...shouldn't be to far off as the outer 2 layers aren't that thick. Yes its a three part gasket.
As the crushed head gasket...I have one front my recently expired motor. These numbers don't add up but its what I got. Each layer was .0008 with the total thickness of .030.
Stock base gasket - .010 Stock head gasket - .030 Your deck height variance is double of what I have ever seen before. .030 quench band is very very tight. We have gone tighter before, but not for long, and you'll never have to clean the carbon off the pistons. With stock rods .030 is just flat dangerous in my opinion. .040 is a good safe "tight" starting point with stock rods. Down to .036 is doable, though you are pushing it.
That is a strange head gasket size if someone had a custom one made. I would bet its two layers of the stock gasket, When they have been in there for a long time, especially with studs squeezing above them 36ft lbs, they have a tendency to become one without a solid brass/metal gasket separating them. The two outer layers normally net around .018 which is why is such a common home improvement mod, taking .012 out of the quench band.
You're almost .010 off. Which is why people give you shit when you make "factual" statements about motor building. I know you mean well, but people take this advice very seriously and invest a lot of money in doing so, throwing around numbers and statements as facts just doesn't go well with the guys who are here sharing real, solid, proven numbers. Luckily your reputation proceeds you, and Gene is smart enough to know who to listen too. I really don't even mean to be a dick, but if you hadn't posted that photo, and said .039 for a stock head gasket your putting someone in the position of catastrophic failure. Which reminds me, what happened with your motor? You mentioned U4.4 being your problem? Ive used that fuel in motors up to 16:1 without issue, surprised it could have caused you any problems.
So you start saying that the facts I put out are wrong and then accept the fact because I posted a picture. Read my post. I stated a brand new unused head gasket is .039. I didn't state anything more than that as fact. If you read that I said something more that would be not my problem. Was it an SV650 that you ran U4.4 up to 16:1 or was it some other motor? I ask because I'm told due to the thermal design of the motor its not like current modern motors hence the restriction in fuel. On my motor the current theory is that my wide band o2 sensor failed and gave me crap information. And then during live tuning I missed an important clue that the o2 sensor was crap so I kept going leaner and leaner trying to get it between 12.7-13. I ended up then leaning it out so bad it did what all lean motors do.
I never accepted the fact. You showing the picture showed us all you have no fucking idea what you are talking about and made it easy to dismiss. And a brand new unused headgasket is not .039. You stated it as fact. Its not. You were wrong. Your inability and lack of knowledge does not make it correct.
