Quadrajet question

[idahovette]

Yeah @59840Surfer You may have a chance but, I'll put my money on Mike @Paladin ..... not trying to start something here, just knowing that Mike is a HOLLEY guy

 

[Snoots]

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[Paladin]

Waiting patiently for @Paladin to respond^^^^^^^^.....lol

Responded on May 30th but I'll say it again. Throw the paperweight away and GET A HOLLEY!!!!!

 

[Paladin]

Yeah @59840Surfer You may have a chance but, I'll put my money on Mike @Paladin ..... not trying to start something here, just knowing that Mike is a HOLLEY guy

SMH Some people just refuse to listen to good, sound advice because if they did all of the threads seeking info on how to polish a turd Q-jet woundn't be here because they would have gotten a HOLLEY and be driving instead of trying to fix stuff!!!!

 

[Matt69olds]

SMH Some people just refuse to listen to good, sound advice because if they did all of the threads seeking info on how to polish a turd Q-jet woundn't be here because they would have gotten a HOLLEY and be driving instead of trying to fix stuff!!!!

 

[Dave M]

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[59840Surfer]

This is not necessarily true. Well... you are technically right, but some context of the reason is probably worthwhile. Combustion temps are highest when the fuel/air mixture is stoichiometrically balanced. For 10% ethanol blend gas, that is about 14.27:1 and for pure gas, it's about 14.7:1. If you go rich or lean, the combustion and exhaust temps will drop.

The statement that lean mixture will promote hotter CHAMBER temps is correct though. What happens is that a richer mixture is basically evaporating fuel in the combustion chamber and that evaporative action is pulling heat out of the cylinder walls and piston in order to support the phase change.

In rocket engines they do the same thing by running fuel through the combustion chamber walls and then pointing some of the fuel nozzles towards the inside wall of the chamber to create a film of fuel along the chamber wall to keep the metal from melting at the 5,000+ degree adiabatic flame temps.

In aircraft engines you can adjust your mixture at cruise to lean of peak by adjusting the mixture knob until the exhaust gas temperature has peaked and then falls by about 50 degrees. This is the same thing that factory manuals have you do for idle and cruise adjustments. For idle you find peak RPM and then lean the mixture until you get an RPM drop. For cruise you lean the mixture slowly until you start getting some surging while cruising, then richen slightly. When done properly, I've NEVER seen an engine have any issues with dieseling. The problem with trying to run it richer to avoid dieseling is that you are producing more unburnt fuel and carbon in the chambers and that can lead to hot spots in the chamber that can lead to preignition and dieseling after shutdown eventually. Plus your mileage will be less than it could be.

Those AFRs were/are so hard to hit that to combat post-ignition - what "dieseling " really is - one idea was to turn on the AC compressor for 15 seconds to drag the engine to a stop.

Having localized hotspots inside the combustion chamber --- really in the squish-zone - could promote incorrect flamefront propagation and that could lead to busted pistons and hammered rod bearings if not an occasional bent rod.

Poor fuel quality - "under"-octane or poor cetane ratings were no help --- and adding alcohol to the fuel supply was not a good idea either --- it lowers the combustion chamber temps a bit by process of evaporation, and that's a good thing ---- at the loss of BTUs to spin the wheels around.

I kinda wrinkle about this though:

For 10% ethanol blend gas, that is about 14.27:1 and for pure gas, it's about 14.7:1.

.... 'cause in the days I ran a gasser at the drags I jetted for avgas and adjusted the mains to give me the best pyrometer readings - but on the weekends I ran Street-D/Fuel on alcohol, it was a lot easier to just take the jets out since it needed a LOT more fuel to get the same horsepower and then to get the best effect of that fuel, turn it up to 6:1 or so.

I don't believe alcohol in any form is a good idea for multiple reasons.


.

 

[59840Surfer]

Yeah @59840Surfer You may have a chance but, I'll put my money on Mike @Paladin ..... not trying to start something here, just knowing that Mike is a HOLLEY guy

I've met them before --- they are 90 lb weaklings and hide behind their momma's skirts.

Get me the Super Size popcorn .... and lots of butter.

 

[AuroraGirl]

Those AFRs were/are so hard to hit that to combat post-ignition - what "dieseling " really is - one idea was to turn on the AC compressor for 15 seconds to drag the engine to a stop.

Having localized hotspots inside the combustion chamber --- really in the squish-zone - could promote incorrect flamefront propagation and that could lead to busted pistons and hammered rod bearings if not an occasional bent rod.

Poor fuel quality - "under"-octane or poor cetane ratings were no help --- and adding alcohol to the fuel supply was not a good idea either --- it lowers the combustion chamber temps a bit by process of evaporation, and that's a good thing ---- at the loss of BTUs to spin the wheels around.

I kinda wrinkle about this though:

For 10% ethanol blend gas, that is about 14.27:1 and for pure gas, it's about 14.7:1.

.... 'cause in the days I ran a gasser at the drags I jetted for avgas and adjusted the mains to give me the best pyrometer readings - but on the weekends I ran Street-D/Fuel on alcohol, it was a lot easier to just take the jets out since it needed a LOT more fuel to get the same horsepower and then to get the best effect of that fuel, turn it up to 6:1 or so.

I don't believe alcohol in any form is a good idea for multiple reasons.


.

The people who run "meth" for their cars sure love that

But thats methanol, not usually or should be found in gasoline normally

 

[59840Surfer]

The people who run "meth" for their cars sure love that

But thats methanol, not usually or should be found in gasoline normally

You're right, but it's still alcohol and the BTUs are smaller that a "more viscous" fuel.

Aboard ship we burned NSFO and it was a gooey paste until it got heated enough to actually flow - even through an UnRep hose. Thickness or viscosity is a great delineator.

 

[AuroraGirl]

You're right, but it's still alcohol and the BTUs are smaller that a "more viscous" fuel.

Aboard ship we burned NSFO and it was a gooey paste until it got heated enough to actually flow - even through an UnRep hose. Thickness or viscosity is a great delineator.

I think the reason fro the methanol users was running that to cool induction temps???(Supercharged and turbos)

Also, e85 popular too (for those people)

 

[59840Surfer]

I am not sure of E-85 --- but methanol is a great chill factor because it's surface pressure is so low.

In the end --- I use my Rochesters because I can and I know them an-n-n-nd I am successful with them and they don't need tweaking when the sun goes behind a cloud.

Honestly --- in the last 15 years I THINK I adjusted the idle mix one or two times --- but I keep right on truckin' so I'm happy.

 

[AuroraGirl]

I am not sure of E-85 --- but methanol is a great chill factor because it's surface pressure is so low.

In the end --- I use my Rochesters because I can and I know them an-n-n-nd I am successful with them and they don't need tweaking when the sun goes behind a cloud.

Honestly --- in the last 15 years I THINK I adjusted the idle mix one or two times --- but I keep right on truckin' so I'm happy.

Methanol will destroy everything you love about your carburetor

 

[AuroraGirl]

I've met them before --- they are 90 lb weaklings and hide behind their momma's skirts.

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[Ricko1966]

You'll notice,I liked @Paladin s remark get a holley not because I agree. I just admire his persistence.