jsawduste wrote:I would not rely on internet experts to answer such an important question. But then you could do it yourself. It is`nt that hard. I would think your machine shop should be able to measure it.
I believe the H802CP pistons have a ~15cc dish but that was the figure I also heard about for the 677P pistons that I used in my stroker. I cc'd them using the plexiglass method and they came out at 17.5cc so the static CR of my stroker ended up being 9.25 instead of the 9.5 that I'd planned. Moral of the story is you won't know for sure until you cc the pistons yourself.
jsawduste wrote:I really wish there was a true answer as to what DCR and octane combo can be run. I have researched this to death and have come up with no answer.
Yeah join the club. SilverXJ and I are also in the same boat and as we've all discovered, there are too many variables to give a definite answer.
jsawduste wrote:You have the exhaust and intake manifolds right on top of each other. Not to mention the ports themselves beside each other. By the time the intake charge enters the combustion chamber it is already well heated.
Perhaps Leee could make us a cross flow head of aluminum ?
Absolutely right. You can get 3rd degree burns on your fingers if you touch the intake manifold runners and it's all due to the non-crossflow head design. I've found the intake runners to reach as high as 160+*F. I insulated the underside of my intake manifold and that helped some, but the manifold still becomes well heat-soaked in slow-moving traffic (burns are only 2nd degree now instead of 3rd).
An aluminium crossflow head would have been the ideal solution but that would only have been possible if Hesco had also redesigned the bottom end, perhaps going for a single overhead cam design (or even DOHC). I guess Hesco baulked at that idea due to the potentially high cost involved.
jsawduste wrote:Dino, this is the one type of information I am referring to. I would bet that the refineries in your country create there fuels using different additives then we do here in the states. Much of it driven by government mandated emissions laws that I would expect are not the same as yours. So to say that your 91 octane burns the same as ours would be speculation. Let`s be careful and compare apples to apples when handing out advice.
I wouldn't be at all surprised if they use different fuel additives in the UAE so your point is well taken. I know that until fairly recently the fuel contained 10% MTBE but I don't know if they're still using it. Call it another variable that makes the question of DCR v octane even more difficult to answer.
jsawduste wrote:Even something as straight forward as the degreeing the cam can have a change in how an engine operates. Manufacturing tolerance stack up, parts choice and assembly practices in itself can make a huge difference. What if you used a brand x timing set up and I used a brand z ? The only sure way to compare would be the actual measured cam timing via a degree wheel and a dial indicator. That is, if we both measured the same way. I can tell you my cam is really 3.5 * advance when it was supposed to 4 *. Many cams have a buit in advance/retard as part of there make up. So a Crane at 4* and a Comp at 4* may not even be close.
Yeah, there's no doubt that variables you mentioned do affect the DCR and that makes it even more difficult to answer the OP's question. SilverXJ and I have tried to draw upon our experience with our own strokers to help answer his question but as you've rightly pointed out, there are a lot more dots that have to line up for the OP to run his stroker on 87 octane.
Sorry for the long post but this has become a good debate.
