I read somewhere in these threads that these engines have a low compression ratio because they were built to run on low octane gas( i think he said like 78 octane)because that's what they ran in the 70's.He went on to say this is the reason they run hot because they can't burn all the fuel,meaning that the engine is essentially on choke constantly.
the unburned fuel then goes out the exhaust,This might explain why mine backfires so much.It blew the muffler appart first,now the Y-pipe is coming apart!!If this is all true what can I do about it?Is there a way to lower the octane of the gas you buy?

 

The lower the octane number the easier it is for the fuel to ignite. An incomplete burn could be due to several reasons such as air fuel ratio, timing, combustion chamber design, ect. not the octane rating of the fuel.

 

Even regular was better than 78 in the '70s.

I remember reading the operators manual for my dad's GI GMC trucks. They had some low compression, I almost want to say in the 6's. They spec'd 67 octane. This was from 1952, but man, 67? The 534 is a product of 1950s engineering, but not early '50s.....

534's are obsolete, and you are learning why....

 

I don't know about that , because we had 3 T950.s all 1964s bought new one 534 5x4
and two with Cummings 5x4. I usually drove a diesel and the gas job will blow the doors
of the other two and that inludes Macks Petes etc. You didnt even need the aux trans
they started talking around 3000 rpms tough on gas maybe 3mpg, never broke never
failed, so for $0.30 a gal nobody cared. sam

 

octane was actually much higher in the 50s/60s thanks to tetraethyl lead...

 

if you find you have no problems with timing, leaks, fuel pressure, etc. that is causing your rich condition, and you think it may be from the octane (probably not, but I'm no engineer) increase your compression. you can shave the block and heads, run a domed piston, or blow it with a turbo or supercharger, get it up to 11, 12: 1 and you wont have a rich condition, or a lack of power!