8:1 compression and octane ratings

[Rob]

Good Day

My series 3 has the 8:1 compression 2.25 motor. From what I understand, it is a european spec and over there 90 octane gas is the norm. What is the preferred fuel for this motor?

Anyone have experience with running 87 in an 8:1 motor? Is ignition retiming or carb tinkering an option or should I just stick to the more expensive premuim gas?

Thanks, Rob
83 88

[rick.m]

Hi. I have a TURNER HEAD 8T0 1 AND A 2.5 CAM AND A WEBER AND I RUN REG UNLEADED AND IT IS FINE , HAVE NEVER RUN HIGHER OCTANE. I CHECKED WITH richard turner in england and was told to run reg,. gas . all the best. rick.m

[ANDYD]

Hi Rob,
I second that, I ran 8 : 1 compression head with a Webber carb, it ran great on regular.
Cheers,
Andy :D

[DaveB]

Another opinion, but not necessarily correct...

I usually run mid grade or premium, with timing advanced about 3 degrees further than stock. This seems to give me the maximum power I'm going to get from the engine. Doesn't ping or run on, and runs very smooth. It's about 7.5:1 with a 2 barrel weber.

I can run regular, but find it idles rougher and tends to run on at shut down. So I give it 90-91 octane at least every second tank.

Dave

[Rob]

Thanks for the feedback... looks like I'll have a few options to try-out!

Regards, Rob

[Greg S]

I have a 2.25 with an 8:1 head. I used to run premium fuel all the time and it ran fine. I changed to regular at 87 octane and it runs fine.

I got better economy with premium but it wasn't worth the extra money. I didn't notice any change between the two other than about a 2 mpg improvement with the premium.

Greg S