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Does this mean that in order to approximate 1967 premium fuel, I'd have to find current 95 octane fuel? Costco premium is shown as 93 octane.
Unfortunately, yes it does. Another problem is that today's engine oils tend to result in excessive wear to non-roller camshafts. The zinc was removed due to catalytic converters.
If your car pings on hard acceleration, you need higher octane. You know what pinging sounds like? If it pings all the time, you need an engine overhaul? Or, you can retard the ignition slightly. That will affect performance and fuel economy a bit, but not much in a car that old.
One last place to look if you get pinging is distributor function and timing in general. Are vacuum and centrifugal advance working properly?
1967 Tempest was one of the prettiest cars ever made. You have a kinda rare one with the Sprint straight 6 with an OHC engine. While the straight 6 wasn't rare, the Sprint version wasn't seen much. Your engine makes 215HP at 5200 rpms, torque is 240lbs per GM Catalog. The compression ratio is 10.5:1. That pretty much means you can run 90 octane rated gas as a minimum. BUT, and you knew there had to be one, that engine is designed around leaded gas. The tetraethylene (lead) was used as a lube for the valve seats besides being a great and cheap octane booster. Using unleaded gas will cause you issues over time. The issue will be the valves beating themselves into the valve seat. You'll very slowly start to lose power. Unless you've installed steelite valve seats, valve recession will be an issue eventually. You can prolong the effects by using VP Fuels Octanium which has a small shot of Tetraethylene in it. You also need to know that tetraethylene is a wear agent. In the old engines that used the leaded gas, engine life was something around 80,000 miles and it was due to the tetraethylene. It's like throwing a handful of fine sand in the oil every 3000 miles. The molecule that causes the wear is smaller than 40 micron so an oil filter is NOT going to capture it. So keep the oil changed. I would suggest using Pennzoil 10w-30 yellow bottle motor oil. It's beats any synthetic at high heat deposits and is 3 times more stable than any synthetic based motor oil out there per ASTM D 5800, which is a volatility test.
Octane increases the compression ratio. The higher the compression ratio, the better the horsepower of the engine. .
Higher octane allows higher compression ratios, which can increase engine horsepower. Now the trend is toward direct injection, knock sensors, and variable timing.
As someone who has built, fixed, rebuilt and raced cars my entire life I can tell you this. Unless there is substantial carbon build up on top of the pistons or you have the timing advanced too far. You are not getting pinging on the Costco 93 in a 10.5/1 motor. I'm running 93 in a 80 cutlass with an old school SBC swap. 11.2/1 C/R with iron heads and it doesn't ping or knock. Generally you can get up around 11.0/1 with pump 93 and iron heads. A touch more with aluminum.
Do you know what knocking and pinging sound like in older cars. Find an old metal coffee can and put a handful of marbles in it. Shake it up... That what it sounds like.
If you are hearing this then you need to determine why. Octane is not the fix but a band-aid.
Do not let gasoline that contains alcohol set in the carburetor because it will dissolve the little rubber seal on the (needle and seat) and cause your carburetor to over flow which is a fire hazard, A can of seafoam will help with the engine performance and the lead additives you can add to your gas are also recommended for the older cars which used leaded gas.
What is your car doing, or not doing, that you are thinking the octane is the culprit?
Quote:
Originally Posted by TrapperL
1967 Tempest was one of the prettiest cars ever made. You have a kinda rare one with the Sprint straight 6 with an OHC engine. While the straight 6 wasn't rare, the Sprint version wasn't seen much. Your engine makes 215HP at 5200 rpms, torque is 240lbs per GM Catalog. The compression ratio is 10.5:1. That pretty much means you can run 90 octane rated gas as a minimum. BUT, and you knew there had to be one, that engine is designed around leaded gas. The tetraethylene (lead) was used as a lube for the valve seats besides being a great and cheap octane booster. Using unleaded gas will cause you issues over time. The issue will be the valves beating themselves into the valve seat. You'll very slowly start to lose power. Unless you've installed steelite valve seats, valve recession will be an issue eventually. You can prolong the effects by using VP Fuels Octanium which has a small shot of Tetraethylene in it. You also need to know that tetraethylene is a wear agent. In the old engines that used the leaded gas, engine life was something around 80,000 miles and it was due to the tetraethylene. It's like throwing a handful of fine sand in the oil every 3000 miles. The molecule that causes the wear is smaller than 40 micron so an oil filter is NOT going to capture it. So keep the oil changed. I would suggest using Pennzoil 10w-30 yellow bottle motor oil. It's beats any synthetic at high heat deposits and is 3 times more stable than any synthetic based motor oil out there per ASTM D 5800, which is a volatility test.
Quote:
Originally Posted by IMBACKAGAIN
As someone who has built, fixed, rebuilt and raced cars my entire life I can tell you this. Unless there is substantial carbon build up on top of the pistons or you have the timing advanced too far. You are not getting pinging on the Costco 93 in a 10.5/1 motor. I'm running 93 in a 80 cutlass with an old school SBC swap. 11.2/1 C/R with iron heads and it doesn't ping or knock. Generally you can get up around 11.0/1 with pump 93 and iron heads. A touch more with aluminum.
Do you know what knocking and pinging sound like in older cars. Find an old metal coffee can and put a handful of marbles in it. Shake it up... That what it sounds like.
If you are hearing this then you need to determine why. Octane is not the fix but a band-aid.
Thanks for the information.
I've only had this car about a month. I'm still getting used to what kind of noises the engine makes. They are definitely a lot different than the noises that my Honda makes. When I got the car, it had about half a tank of premium fuel in it. It seemed to run OK on it, but with the next tank, I included a bottle of STP octane boost. Didn't seem to make much difference in sound. When that tank was empty, I tried a bottle of the Gumout octane boost with the next tank. Seems to run about the same. I'll just fill up with straight 93 octane Costco fuel on the next tank and see how it goes.
I had a similar car some years ago. It ran OK on Amoco premium. I guess if the current car was actually knocking, it would be pretty apparent.
TrapperL - My parents had a 1967 Tempest. It was a cool-looking car, even if it was a four-door sedan. It had the base 326 with 2-speed automatic. My current car is a 1967 Firebird Sprint. Here are a few photos of it.
If you can find gas with no ethanol in it, you would be better off with that gas, IMHO.
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