Pump Gas Connundrum

[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?

[TheEngineWorks.com]

You should be more then fine with that cranking compression on 92/93, been doing it for a LONG time, with many engines.. Toss some pump swill in it, and have fun! When you say your cranking compression is 183 range, I assume that is peak pressure, after multiple revolutions. Mine is well above that, and I'm not gonna get into what it is, but I fully expect to have nothing in my tank but pump gas..

I didn't see it but I guess you have aluminum heads too..

[CDMBill]

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?

Some folks have reported that running the fuel back and forth into a small volume, like a five gallon cell, add heat to the fuel from the pump, the lines, rails etc. without the addtional fuel mass to cool it down, add in a hot trunk based location and who knows?

BTW Rich, with iron heads you have a very different knock threashold than thos of us with aluminum heads. Often a full point of compression lower.

[moparman63]

just err to the safe side enough to make you confident in your rig.that car has come light-years along since last summer.

[c2xejk]

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

Quick question. On a water/alcohol injection system, do you need run braided SS lines (like for fuel lines) to be NHRA legal?

I will likely be running at least water injection and likely a 50/50 water/alcohol blend and wondering if the rubber hose is sufficient or if I need to convert it to braided SS.

Thanks

[BBR]

just err to the safe side enough to make you confident in your rig.that car has come light-years along since last summer.

Tell me about it. I was just flat unprepared last year and had very little confidence in the car. This year I've worked many of the bugs out and feel much much better about the car's prep.

I checked DA's at all the tracks yesterday around 9:30am and all were virtually the same at 2400-ish feet. I'll just monkey around with it on Sunday and see where I'm at and it probably should be a good indicator for the rest of the week.