Port sizing for 3.0 race motor

[3literpwr]

Trying to finalize some details for my rally car and wanted to help solidify some port sizing. Current specs so far are 3.0 95mm JE 10.8:1 pistons, 46mm itb's, twin plug, arp rod bolts and stock rods, and more than likely DC60 cams... I was planning to port the heads to 40mm intake and 38mm exhaust...

Thanks
LP

[Henry Schmidt]

Originally Posted by 3literpwr

Trying to finalize some details for my rally car and wanted to help solidify some port sizing. Current specs so far are 3.0 95mm JE 10.8:1 pistons, 46mm itb's, twin plug, arp rod bolts and stock rods, and more than likely DC60 cams... I was planning to port the heads to 40mm intake and 38mm exhaust...

Thanks
LP

Port shape is more important than size but your formula is pretty close.
We built 3 rally engines for a series in Europe with almost identical specs (10.4 rather than 10.8). One actually learned to fly winning the championship the first year.

[3literpwr]

Good looking trio... My 911 won't be ready for the Rally America season opener Sno*drift in two weeks, but I will be flying in my old open class mitsu. I hope to have the 911 ready by late 2014. Oh and my wife is co-driving!

[Lapkritis]

Originally Posted by 3literpwr

Good looking trio... My 911 won't be ready for the Rally America season opener Sno*drift in two weeks, but I will be flying in my old open class mitsu. I hope to have the 911 ready by late 2014. Oh and my wife is co-driving!

Which # do you have for the VR4? I had #1974 (white like yours) and sold it off to Connecticut about 9yrs back. Heck of a sleeper with a ported o2 housing, 3" turbo back and the frequency valve bleeder mod.

[3literpwr]

Im pretty sure its #241... I sold it a few years back, but am driving it at Sno*drift in two weeks... Car made 300hp 360tq on 34mm turbo restrictor @ 18 psi and overall a good rally car despite a slow steering rack and crapy ratios for a restricted rally motor.

PRS rally car - a set on Flickr

[Lapkritis]

Just flipped through your Flickr album - gorgeous build. I used mine for commuting and time-trial ice racing with long term plans/pipe dreams to build out as you did. One trip to a 1/4 drag in Quebec and killed my second gear synchronizer... that's when we decided to part ways.