[Fastback91]

ya just curious but all of u guys that have 351's or higher do u guys use a higher octane cause my dads 69 Camaro 307(1st owner *ORignal*) like the 289 (small block) has to take 91 octane cause of the way it was set up in the 60's

[69fastback]

A stock 289 doesn't need high octane. If it hasn't had hardened seats put in, it will need lead additive though. I run 87 in my 351W all the time. Unless you're 10.5:1, you don't need anything higher than 87, unless you're planning on running a lot of timing.

[Horseshoeing]

I have a 289 and I have to run 92 or better. I am running about 11 to 1. Its not about how big you motor is, but how much compression you are running.

[Fastback91]

ya thats what i thought just like all the bigger blocks back then had such a high compression ratio

[Horseshoeing]

Compression=more horses

[460brevill]

10.5 comp. in my i6.it want run worth doodles on anything lower than 93 oct.

[Vinyl66]

anyone know what compression i am running in my 302 w/ 289 heads? ive heard both 9.5:1 and 10.5:1

[69fastback]

Originally Posted by Vinyl66 anyone know what compression i am running in my 302 w/ 289 heads? ive heard both 9.5:1 and 10.5:1

There are way too many factors involved or someone to give an accurate number. If anybody has decked the block or heads, it'll change it dramatically. If it's been rebuilt, it could be changed because of the pistons, and there are other factors as well.

[jspagna1]

I run 1/2 93 octane and 1/2 Cam2.

[TurboLX]

107 octane here

[69fastback]

I ran 110 in my camaro. It was 13.5:1

[cgstarry]

I read recently that back in the 60's regular unleaded gas was 92 octane. So they way I am looking at it my i6 was designed for high octane fuel, so high octane fuel it shall have!

John

[Horseshoeing]

All you have to do is retime it to run 87.

[OldSchool]

Originally Posted by cgstarry I read recently that back in the 60's regular unleaded gas was 92 octane. So they way I am looking at it my i6 was designed for high octane fuel, so high octane fuel it shall have! John

They didn't have regular unleaded until 1973. The end of the "classic" cars.
I seriously doubt you require high octane in a I6, unless you have money to burn.

[zers]

What about ethanol? Any of you guys use that?

It's supposadly an easy conversion, and it's 100+ octane.

Anybody done the conversion?

[TurboLX]

E85, most drag racers use it now

[built351w]

Oh yeah well I run pure nitroglycerin!!!!! lol figured since all you guys were bragging about your octane numbers I'd just settle it one and for all....

I don't think anybody has mentioned ignition yet. Having a stock ignition vs full MSD set up changes the compression rating you can get away with. I have 10.5:1 on my 351w with cast heads and full MSD ignition, my machine shop guy told me that's the highest you can get away with and run pump gas, the good stuff Sunoco ultra 93....

[460brevill]

the early I6 was around 8 1/2 to 9 to 1 comp.they didnt require high oct.my I6 is 10 1/2 to 1 and i run the sonoco 93 too.one reason is they dont run all there gas through the same hose.

[69fastback]

It's all about compression and timing....nothing else. It doesn't matter when the car was made. If it's high compression, you can back the timing off, and run lower octane.

If you want a little more more power, you can run a higher octane, and put a little more timing in it.