Fastrotor

Ferodo do Marko.

Why did you leave the top hole open when you seem adamant about sealing the rest so well ? Only downside to all that dynamat covering the holes is if something needs fixing. If i had some panels laser cut to suit, and dynamat'd them and screwed in place would this be ok ? That way i'd retain full easy access to the doors..... as i know my luck if i sealed them up like in the pics !. Gary

Thanks Noel, will be good to to see it better , see how it looks with the gtr front end on there. Gary

Noel, do you have any better pics of your cars rear guard flaring ? Being black , i found it very hard to notice what you had done in your other thread, whenever that was Gary Welcome to the club.. i have a spare forged 30 sitting inside the house too.. only cause i can't afford the 26 head work yet !! Tempted to just whack it under the current 5cyl RB25 for the sprint season.

I knew the calcs must be right, but i wondered what we both did wrong in the manual calcs..... and i just worked it out. When we did the volume of the cylinder for the gap below the deck, we used the 'diameter' in the "Pi*R2*H" equation ...stupid mistake but easy to do. So its definately 8.9:1 ..... cool.... now i can calc in confidence what i need to do to get it higher. Gary

Just for interest when dynoing a fwd N15 pulsar with sr20 turbo convo that had one of these 'varex' cannons , it was making 210 fwks's open. With it closed power dropped to about a 100 But very quiet though !

Hmm seems like somehow our manual calcs are wrong.. i've used quite a few different calcs , and finally the standalone calc for comp ratio and Dynamic comp ratio from Pat Kelly , what a great little bit of software that is. They all gave over 9:1 so i guess its fine. Anyway i cc'd one cyl on the head and got 65.5cc so the actual comp works out to 8.9:1 ... which id still like alot higher , due to wanting to run 280 degree cams. Either that or get VCT on the inlet cam to raise the Dynamic comp ratio drastically down low. Gary

My Deck clearance IS 10 thou, (0.254mm) BELOW the DECK , i measured it from the deck to the piston flats at tdc. Seems pretty suspect if we enter 2.54mm in the calculator, that it shows the exact result we both manually calculated from the values. Makes me think the calc has a decimal place bug perhaps. More worrying is that it seems the motor is 7.7:1 ........ Im going to cc the heads tonight, then whack it on with gasket and tighten it all down an cc the whole lot to be totally sure. As for the deck height , there is no point measuring this one as it has been shaved down.... i need to know the original deck height to work out how much has been removed. I would have though with all the guru's on here someone would know......(and confirm our manual comp calcs) ! Gary

I just worked it all out by hand, and i get 7.7:1 same as you .! Now im worried. Engine builder says it will be 8.7:1 My results by manual were.. 3.426cc Effective piston to deck clearance 7.051cc Headgasket volume 64cc assumed head volume =74.47cc at TDC Piston bore volume at BDC (using 86.5 bore and 85 stroke) is 499.5cc Add the above value and get 573.97cc and divide by the 74.47cc = 7.7:1 Why do i get the feeling something is wrong......hopefully with the calcs !! Gary

Something is wrong for you to enter the same numbers and get a different result. Here are the exact numbers in order of putting them in. 2 86.5 85 87 1.2 64 11.5 0.254 = 9.17:1

Its really just an rb26 and your just telling everyone its a 30 ? hehe

No guessing it was yours that was better Paul, obviously. But , by how much is the real question. I'm guessing i'll get a cryptic answer, but have to ask ! Gary

Dave i wanted to know the stock rb30's Deck Height, not deck clearance. So i can work out how much has been shaved off my block. (ie deck to centerline of crank) No i used a positive value in the calc (.245mm) just as i measured it. The piston flats are just below the deck (.254mm) and the dome is above it. How did you get those values from the calc ??

what 9.5 run ? i only saw the 12 something at 95 ?? am i missing something marko ? Gary

Does anyone know for sure the stock RB30 DECK HEIGHT ??? Only reference i found on here was 230.5mm Gary