430 compression ratio and octane?

[RoadShark]

The manual says that my 430 has 10.25:1 compression.  I've been running 91 octane with ethanol in it.  So far, it doesn't seem like I'm having any detonation.  Anyone who's driven these things more than me have any input?  Should I be searching for 93 or adding octane boost?

[JZRIV]

Many factors can contribute to detonation...or lack thereof. Internal engine condition such as carbon on the pistons, or perhaps worn rings/valves lowering compression as well as engine temperature, carb mixture, and initial timing as well as total mechanical and vacuum advance.

Bottom line as long as you don't have detonation you are fine with 91. I've also run 89 with no problem and also 87 so you might try going down a notch and see what happens. I had a 120k mile 67 that ran fine on 87 but that was before ethanol. If you tune your engine for max performance with advanced timing that typically will keep the octane requirement up.

[Eric's.64.Superwildcat]

Hi Bill.  

 

Is you engine original or has it been rebuilt?  

 

If it is original then your actual compression is probably far from original.  If you're running premium gas (which is 91 - 93 octane, depending upon where you live) and you hear no pinging then you should be set.  I'm also assuming that your timing isn't too far advanced and that you're not running a spark plug that is too hot for the motor.  

 

Another thing that you can listen for is a 'gas rattle' under heavy acceleration.  If you don't hear a rattle then it is further confirmation that your engine is happy.  

 

I would simply purchase the highest pump octane available in my area, but stop short of octane boost.

[Pat Curran]

I never had a problem with my 430 in my 69 on premium pump gas.  I never tried regular in it though.  I would occasionally put a dose of lead additive in it but I could never tell if it helped or not.  The engine was totally original with less than 10,000 miles on it.  Sure wish you could still get the old Sunoco 260.  My 425 would fly on that gas!

[RoadShark]

Many factors can contribute to detonation...or lack thereof. Internal engine condition such as carbon on the pistons, or perhaps worn rings/valves lowering compression as well as engine temperature, carb mixture, and initial timing as well as total mechanical and vacuum advance.

Bottom line as long as you don't have detonation you are fine with 91. I've also run 89 with no problem and also 87 so you might try going down a notch and see what happens. I had a 120k mile 67 that ran fine on 87 but that was before ethanol. If you tune your engine for max performance with advanced timing that typically will keep the octane requirement up.

Thanks.  I know that combustion chamber efficiency and swirl characteristics for different engine designs can mean that one engine can get away with pump gas at 10.25 with iron heads and another design can't.  This is my first Buick V-8 so I was looking for others experience.

[RoadShark]

Hi Bill.  

 

Is you engine original or has it been rebuilt?  

 

If it is original then your actual compression is probably far from original.  If you're running premium gas (which is 91 - 93 octane, depending upon where you live) and you hear no pinging then you should be set.  I'm also assuming that your timing isn't too far advanced and that you're not running a spark plug that is too hot for the motor.  

 

Another thing that you can listen for is a 'gas rattle' under heavy acceleration.  If you don't hear a rattle then it is further confirmation that your engine is happy.  

 

I would simply purchase the highest pump octane available in my area, but stop short of octane boost.

It's bone stock.  114k miles.  Blows a little smoke on start-up.  Haven't checked the timing yet - it seems to run good.  No idea on temperature - the stock gauge isn't much help.  Definitely not overheating.

[60FlatTop]

I always use regular unleaded Mobil in any car I have. I don't experience problems. I do avoid price shopping gasoline. Generally, I top off on Sunday evening from local driving and rarely put in over ten gallons. Even if gas was $0.20 cheaper I'd save two bucks.

 

The cars have ranged from 10.5 compression down. For me to rev beyond 3,000 RPM is rare; over 4,000 in an old Buick is really missing the concept of the car.

 

The Chevy is an LT1 TPI. I will hit that one hard enough to lose vacuum and have heat pouring out of the dashboard vents, but that one compensates and has a reverse cooling system.

 

Stick with quality fuel. Your icon picture reminds me of my personal preferences since I started driving, fat cars and slim women, each used appropriately.

Bernie

[RoadShark]

fat cars and slim women, each used appropriately.

Bernie

[64Riv-King]

For a listing of gas stations in the US & Canada that sell non ethanol pure gas >>---> http://pure-gas.org/

[68RIVGS]

Never had any problems with the 430 running on whatever fuel was available, with or without ethanol, 89-94 octane.

While a higher octane, non-ethanol fuel is preferred, it is not always available, and if it is, you will pay a premium $ for it.

Back in my Wildcat days, I was working at a local airport and had access to 120 Avgas - the BBB430 performed like a scalded cat on that fuel !!

I always try and fuel the Riviera with 92 octane, non-methanol fuel, since it's not a daily driver, and gets limited use during the short summer season. I am also fortunate to have two service stations with that fuel in close proximity to me.

Edited November 14, 2015 by 68RIVGS (see edit history)

[RoadShark]

For a listing of gas stations in the US & Canada that sell non ethanol pure gas >>---> http://pure-gas.org/

Thanks - the nearest station to me is Freedom, NH.  I go there and fill up some cans to run my small engines, but filling the car up regularly isn't going to happen.

[1FastC7]

Just be careful with any octane boster product. I had a 69 Z28 with 11.0:1's. The octane boster used to jack up the spark plugs after awhile. You can always get leaded 100 octane plus cheap if you have a private airport near. Used to pay $5 bucks a gallon a few years back.