High octane in a mostly street car

[prplcar]

I was thinking about trying VP 103 octane this summer or that race gas mix your own additive. Just wondering if it will be worth the expense or just expensive exhaust. I have Badger cast pistons and 9.75:1 compression ratio, Edelbrock top end and don't want to blow anything up. Motor makes close to 500 hp as is on 89 octane and am looking for more on race day. It's a 440, .030, single 800cfm, duel plane.

 

[Bb70charger500]

You got around 500hp out of a 440 with only 9.75:1 comp what parts do you have on it? Heads cam so one I'd like to try to duplicate what you did . And on the gas I'm not much help I don't know

 

[Meep-Meep]

9.75:1 may not warrant the higher octane. Do a cranking compression test also to make sure you don't have some crazy high number. Depending on cam I'd expect somewhere around 170 PSI and that should be good with 91 (if you have it). If you have a pinging problem then try looking for the source. Fuel mixture, timing, etc..

 

[66Satellite47]

Compression ratio is something that really needs to be measured (deck height, dome/dish, head gasket thickness, ACTUAL chamber volume) to know where you really are. At 9.75:1 with aluminum heads no need for race gas. Good quality 91-92 is fine, 89 might be pushing it, go with best pump premium you can find. I presume it runs OK now.

 

[62 Dart Convertible]

Higher octane fuel will not produce more power unless you don't have enough ignition advance in it now on 89 to hold off pinging. If your running full advance (total around 36 deg BTDC) and not pinging, then save your money...

 

[IQ52]

You got around 500hp out of a 440 with only 9.75:1 comp what parts do you have on it? Heads cam so one I'd like to try to duplicate what you did . And on the gas I'm not much help I don't know

540 HP 440 with 8.9:1 compression.

http://www.forbbodiesonly.com/moparforum/showthread.php?64775-Pop-s-440-is-near-ready-to-dyno&highlight=pop%27s+440

 

[terzmo]

I run 93 on my stroked 440...anything under 10.5 should run 93.....100+ octane for that compression is a waste of money...Building a 472 hemi with aluminum heads...10.25 compression and will run 93 octane.

 

[Cranky]

If everything is right, there's no need for the 103 but if you do have some slight pinging, one gallon added to a tank of pump gas should do the trick. I like to run some initial timing and in the summer I'd get slight ping when outside temps were close to the 100 mark and engine temps were approaching 190. One gallon of av gas did the trick for my basically stock 71 340 Cuda. Keep in mind that high octane gas just burns slower....

 

[prplcar]

No pinging, even with 87 octane. I can get up to 91 without ethanol or 93 with. Just wondering if more would be worth it. Motor is nothing to fancy, just a 440 .030 over with a Edelbrock top end kit(cam, heads,intake) matched 800 cfm Thunder series carb and domed pistons. Not sure specs they were in the motor when I got the car and did not have money to change when I did the rest. Thanks for the input and interest.

 

[Meep-Meep]

No pinging, even with 87 octane. I can get up to 91 without ethanol or 93 with. Just wondering if more would be worth it. Motor is nothing to fancy, just a 440 .030 over with a Edelbrock top end kit(cam, heads,intake) matched 800 cfm Thunder series carb and domed pistons. Not sure specs they were in the motor when I got the car and did not have money to change when I did the rest. Thanks for the input and interest.

As stated, save your money unless you have a pinging problem.

 

[Bigal75]

You only use the octane required. If you want to try higher octane you can also try AVGas. It's cheap compared to race fuel and is excellent quality. Don't let anyone tell you that it's no good for cars. That's BS.

 

[66Satellite47]

"Motor is nothing to fancy, just a 440 .030 over with a Edelbrock top end kit(cam, heads,intake) matched 800 cfm Thunder series carb and domed pistons. Not sure specs they were in the motor when I got the car and did not have money to change when I did the rest."

If you have domed pistons, at some point you really should measure everything to get the actual compression ratio. Depending on the dome cc's, with 88cc Ede heads you're probably in that 9.7 - 10.2 range. Then you can be more confident of the octane needed. Is the total timing in the 32 - 35 range? Should work OK on 91 -93 good quality premium.

 

[383man]

Higher octane fuel will not produce more power unless you don't have enough ignition advance in it now on 89 to hold off pinging. If your running full advance (total around 36 deg BTDC) and not pinging, then save your money...

This is right on the money. I hear so many guys think that just putting race gas in your car will give it more power and its not so. The high octane will let you build the eng to make more power by running higher comp and more timing and so on. But just putting race gas in the car will not make it faster or make more power.

My 440/493 is 10.6 comp with aluminum heads and it runs great on 92 pump gas. In fact I have never had race gas in the car but I built the eng to run on pump gas. Race gas will let you make the mods to make more power. Ron

 

[Kern Dog]

Marketing and bench racing often lead impressionable newbies to think that high octane gas makes any engine more powerful than before.
NOT true.
If the engine runs fine on 85, 87, 89 or 91, there will be absolutely no gains from the higher octane fuel. I'll admit that I love the small of leaded 100 or 110 fuel when burned in my car. Smell alone is not worth paying double. That phrase works with situations other than just cars, too.