the large vent from the valve cover to the air filter housing is the most impoetant part to keep flowing.
check this engine
That depends on the compression ratio that 389 in that Pontiac has.
Tester
it says it required like 105 octane when the car came out! why do people get hightest for classics with fatty engines?
Then it looks like you’re good to go with high test. If the engine requires it then stick with it.
i don’t notice a huge difference but someone told me it would quiet the valve click down. i think it did a little bit it could be a placebo effect. i gel like the lack of ethanol probly was more responsible for
better running than the octane.
Tester
I think you mean “knocking”, pre ignition due to carbon buildup in the heads. You can try a de-carbonizing chemical treatment.
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What @Purebred said - your reference to valve click is confusing, it would be unaffected by gas octane. Does the noise happen only when you’re accelerating? Have you tried adjusting your timing? Does the engine have points? They need frequent attention, as they wear timing will change.
Hi @yadmas:
I remember filling a lot of these cars up with gas in the late 60s and early 70s. Even though there were two versions of the 389 cid, (one with a higher compression ratio), I don’t remember any one of them specifying 105 octane.
I agree that the lead in the gas back then helped to reduce detonation, so Tester’s lead additive suggestion may be useful.
You should always wipe it off. Crankshaft splash and spray will coat the stick higher than the actual level. Giving a false reading.
Remember that octane on the pump back then was based on the higher research rating. As opposed to the lower motor rating which no gas station wanted to show.
Today it’s the average of the two. Difference is about 5. So 105 back then is about 100 today.
Basically you should be using racing fuel.
Some gas stations have it. Typically about 100 so just right.
Just be prepared for sticker shock. It’s nearly double regular. But if you care for your car and it requires 100 then use it.
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I’d like to see anything that states it needs 105 (or 100) octane. The Pontiac brochures of the time just state “premium” for their high compression (10.5:1) 389 engines.
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After looking at this more closely I’m thinking the tube is wiping off the stick on one side.
I always go by the holes. If the lower hole is full and the upper hole is filled with oil I’m cool. Looks like you’re over a bit. Not enough to worry about.
If you do adjust the valve lash and you have hydraulic lifters you will need 16 new lock nuts for the rockers. The old ones usually fail after removal. It’s a Pontiac V-8 thing.
i use “instead o’ lead”. that’s usually the only available. but i’ll try one of these.
i’m decent on doing the typical driveway car work, but never really understood how octane works. so i just looked up the 65 manual for my pontiac and it says 92 for the lower compression 389 and 98 octane for the higher compression 389. 100 octane for the tripower 389. So i need to figure out which 389 i have. Not sure where i saw 105, but i did find that somewhere online. anyway, my 68 impala (307) timing was down tuned for lower octane, and if you put in super, when you accelerate you can here the click click of the valves. when you put in 87, it does NOT happen. but i had a 72 impala with 400 small block and if you put in 87 it did the same thing, but if you put in SUPER, it did not. and it got better gas mileage. In my pontiac, if you bury your foot into the gas, the valves tap dance. It seems less when i have the ethanol free 92 octane plus octane boost in it, although it could be the ethanol free.
not sure where i saw that 105 octane. its been awhile. i think what happened was i looked it up and it said it required premium, like you said, and i looked up premium octane standard from 1965 and found one that said 105 could be had. i found my manual and it says 92 for low compression 389, 98 for high, and 100 for the tripower 389. i do not have the tripower.
yes i have points. when i give it heavy gas they click. I always thought it did, but theres lots of bad info out there about what octane actual is. but i 100% can tell you that we lowered the timing of my impala 307 and it runs great on 87, but if you put in 102, and you floor it, the valves click. so im wondering if i retard the timing a little more on the pontiac, i could run better on cheaper gas. altho i already did do that a little bit. i distinctly remember though when i was younger and had a 72 400 small block, that if you put in 87 it clicked, and if you put in 102, it did it way less.
i actually dont have that. nothing goes from valve cover to air filter housing. although it says on side of air cleaner cover that the engine has crank case ventilation. must be a pontiac thing. i need to figure out which hose actual is the ventilation.
