Octane rating will have two effects, however it is relative. So if you are running at eg 1 bar boost then it's academic. If you want to run at eg 1.5 bar (with the correct supporting mods) then it will be very much dependent on what octane is in the tank. Now just to throw what our American friends call a curve ball, running the lowest octane fuel possible without risking detonation will actually give you a better burn. I run 1-1.2 bar on our 98 super unleaded. On E85 I could easily run 1.7bar on the streets. It just burns so much cooler than normal pump fuel. I could run that on the track too, however even though the E85 will handle the detonation factor, there is a very real possibility that there will be head lift at those pressures sustained on the track. We have had a couple of times where there has been coolant leaking into the cylinders due to this. However believe it or not, I have been able to drive home each time because we use a metal headgasket and they just re seal! So even though we replaced it back at the workshop, the ability to drive home especially from the track 2.5 hours away instead of getting towed is a real bonus. Now we replaced the old original headstuds with some new ARPs and wind the boost down for reliability.
Back to the question though. Sounds like the Promax kits are well worth it. Even though at the time of purchase it's a bit of a chunk of money to outlay, the savings are immeasurable vs redoing headgaskets (at best) to whole motors (at worst). That they are proven, have backup, solid improvements, and not just peak hp numbers but much nicer driveability, makes the purchase price disappear when compared to the alternatives. This is not an advertisement for Promax, nor clearly do I have any affiliation with them, just based on what I've read and what I've experienced with my own builds.
Back to the question though. Sounds like the Promax kits are well worth it. Even though at the time of purchase it's a bit of a chunk of money to outlay, the savings are immeasurable vs redoing headgaskets (at best) to whole motors (at worst). That they are proven, have backup, solid improvements, and not just peak hp numbers but much nicer driveability, makes the purchase price disappear when compared to the alternatives. This is not an advertisement for Promax, nor clearly do I have any affiliation with them, just based on what I've read and what I've experienced with my own builds.
