dkatz

Is one able to run a 1970 olds 455 engine on 95 unleaded gasoline. If not what is to be done short of a valve seat job.

kevinkpk

yes. I wish I could find 95% for my 455

joe_padavano

I've run older 60s Olds motors on unleaded in daily drivers for decades with no major problems. At the worst, just install hardened valve seats the next time you need to do a valve job.

kevinkpk

I do wonder if he is using avgas, although I've not seen in awhile 90 low lead in aviation gasoline, still, iso octane is what he says 95%, should be fine in his 70.

Olds64

Do you mean run 95 octane fuel or actually mixing 95% unleaded and 5% leaded fuel? If you are currently mixing a little bit of leaded fuel in to your tank every time you fill up then I would just run straight unleaded. Like Joe said, it shouldn't hurt too much. Just put hardened seats in next time you tear the heads apart.

joe_padavano

I assumed 95 octane, but note that he is in South Africa. The US-spec octane rating system is not used worldwide. Numbers may not correspond.

kevinkpk

Iposted the 95% as gasoline is iso-octane, and normal heptane. Octane rating is a percentage of actually octane, so 95 octane is 95% iso, and 5% normal heptane (less ethanol, and that actually is an octane rating, but I am not into corn squeezins)

kevinkpk

I should have added blends of hydrocarbons are also used in octane rating.

dkatz

Sorry guys I should have specified 95 Octane. We get three types of gasoline/ petrol in South Africa. 93 Octane lead replacement petrol, 93 and 95 Octane unleaded. They are doing away with the lead replacement soon. I will then be left with a choice of 95 and 93 unleaded. I was wondering if an additive is necessary. I like the idea of doing a valve job at a later dates and getting those heads to breathe...........

kevinkpk

I've not had any issues with unleaded in my 70 455. I cannot remember how long ago it's been since leaded gas was removed, and unleaded was all that was available, I am thinking before 1980?

yogi442

I know out here in the Northwest leaded gasoline was removed in the mid 70's. Unleaded was designed to run all motors whether they ran on leaded prior. I have a built 455 and run on 92 octane which is highest we have here. No problems, but for occasional usage I do put octane boost in the tank with a fill up for little better performance. The 455 is a 68 that we put in my 66 442. Even the built one in my 76 Cutlass which is dual carb'd runs on unleaded premium with no problems.