Pump Gas Connundrum

[BBR]

Here in Amarillo I have been running 90 octane pump gas in my car. Compression ratio is 11.5:1 and a compression test is in the 183 range. Our elevation is 3600 feet and out DA's are way up in the 6500+ foot range.

So my question would be, is the pump gas they sell a low elevations likely to be ok (92 or 93 octane?) or should I think about dumping some race gas when at the tracks?

The LAST thing I want to do is puke another head gasket!!!!

[Shawn Anderson]

I know it would be more work and money to do but I got big gains from E85. My Fairlane gained .5 from the switch (but I also went from 650cfm carb to a 750) with a adding 5 degrees of timming. That was on a 10:7:1 331 small block and the stuff is way cheaper than race gas. I was switching carbs and running pump gas between tracks. Also I found that if you get e85 all over your shirt in the morning it smells good all day. Also if you forget and fill all your jugs with e85 you end up needing to find some one to take your pump gas when when you drain it out. I have found that Durangos work good for this.

[ksj2]

Maybe Bamfstr can help.I cant remember what changes he did last year and hes an altitude racer.

[BBR]

I have found that Durangos work good for this.

buwhahahahahah Thanks for the gas! haha

[Bob Holmes]

How about water/meth injection?

[Dignlif]

I run 91 in mine as well with similar compression and iron heads. At the tracks though I regularly added at least 3 gallons of 100+ depending on how much is in the 15 gallon cell, just to be safe under load.

I was wondering recently how much trouble it would be to add a 3-5 gallon cell for just race gas and just switch the fuel pump and return lines over to it for passes. Am I over simplifying this? Would there be more involved other than ensuring I properly plugged the lines on the big cell? Maybe you could do this if you have the room for another small cell out back.

[v869tr6]

For many years I ran with two tanks, used 1/2" quarter turn gas valves on each suction line to the pump and had 2 more valves to direct the fuel back to the tank it came from. Worked great with a return type regulator. Changing was as easy as opening 2 valves and closing the other 2. Saved a lot of money driving on pump and switching to race.

[Beagle]

183 cranking psi and aluminum heads, pretty well controlled and monitored AFR, advance is more under control than last year... Vizard says you are okay. We have 93 down here, but September may still be pretty warm. Have you ever heard it ping? You are kinda hairy edge for my thinking but it's also got a helluva cam by my truck motor thinking.

Does the octane booster junk (hydrazine! errr, no) have any effect on AFR? Spraying water/windshield washer fluid as far as I can tell is not a horrible idea but I've never done it. If you wanna come run down here for giggles, I can put new sheets on the beds for the Missus and kids for an overnighter if they are up for being in a house with car parts in it. lol (kinda). I'm about 15 miles from Denton's 1/8th mile strip.

[turbolaw]

Water/Meth spray is the way to go. I have a Snow Performance system. Last year at Amarilo I ran 17 pounds of boost on 89 octane fuel with no issues. See ya soon, Tom H

[BBR]

Beags, thanks for the offer. lol I've never heard it ping, but then again it makes enough noise it'd be tough to ever hear!

This is a N/A motor so I will probably just do like Rich and throw a little race gas in for a little margin of safety.

[moparman63]

im sure last year has u gun shy..lol...how bout just knock a couple degrees of timing out? mine is only 175psi,and mine has the tow truck cam.i used to spray 150hp at it down south with no timing or fuel change....but with ur big cam,u probly turn a few more rpm than my 5700..that can make the psi change a bit.lol

[CDMBill]

I run 91 in mine as well with similar compression and iron heads. At the tracks though I regularly added at least 3 gallons of 100+ depending on how much is in the 15 gallon cell, just to be safe under load.

I was wondering recently how much trouble it would be to add a 3-5 gallon cell for just race gas and just switch the fuel pump and return lines over to it for passes. Am I over simplifying this? Would there be more involved other than ensuring I properly plugged the lines on the big cell? Maybe you could do this if you have the room for another small cell out back.

Rich, I tried that approach last year, but I din't have the right valves v869tr6 mentioned so it was a manual line switch. I did have shut off valves on the supply side for each. Huge PITA as it turned out and we were concerned about fuel heating. I'll never know as as the screwed up tune and chassis masked that issue. I'm doin the revised sump this year.

[CDMBill]

183 cranking psi and aluminum heads, pretty well controlled and monitored AFR, advance is more under control than last year... Vizard says you are okay. We have 93 down here, but September may still be pretty warm. Have you ever heard it ping? You are kinda hairy edge for my thinking but it's also got a helluva cam by my truck motor thinking.

Does the octane booster junk (hydrazine! errr, no) have any effect on AFR? Spraying water/windshield washer fluid as far as I can tell is not a horrible idea but I've never done it. If you wanna come run down here for giggles, I can put new sheets on the beds for the Missus and kids for an overnighter if they are up for being in a house with car parts in it. lol (kinda). I'm about 15 miles from Denton's 1/8th mile strip.

If your combination is optimized in terms of timing water/meth will make it safe but you'll lose ET. Brian Rock's 421 was running 11.6:1 with al heads back in 06. Similar cranking compression and cam timing. He used the Snow setup for three days and then at Milan IIRC, he turned it off and picked up over a tenth. Doesn't seem like much but that year was the epic battle with Mike Crow for SB/NA which Brian won by a couple hundredths.

[CDMBill]

Beags, thanks for the offer. lol I've never heard it ping, but then again it makes enough noise it'd be tough to ever hear!

This is a N/A motor so I will probably just do like Rich and throw a little race gas in for a little margin of safety.

I'm at 11.86:1 with al heads and an efficient chamber, 28* total advance, and have run safely at low DA on Cali Chevron 91 premium. Cranking compression is a bit less than yours due to the cam timing events. At Drag week we'll see some 93' but I'll add some 100 to be safe as we're seeing increased ethanol content in pump premium, 5-10% these days, which could be a head gasket killer.

BTW 100 slows it down slightly. Oxygenated VP MS 109 unleaded makes more power but has corrosive properties and is the hardest to read on plugs I've ever seen.

[Dignlif]

I was wondering what kind of valves to use but the more I thought about it, I was thinking I could also do it with Jiffy-tite connectors so I wouldn't have to worry about leaks. A little pricey to start with the 6 x -8 connectors but would probably be worth it in convenience.

What would cause the fuel heat concern?