Detonation, 10.7 ratio and 91 octane isn't working. ****UPDATES ****

[firefighter3931]

I pulled the vacuum line yesterday and took a 175 mile drive today. The part throttle ping is gone, but I still get some at around full throttle. Until I make some internal changes, I may need to run a few gallons of 110 Sunoco in a tank of 91. That ought to raise it to 95-96 octane.

Good work....you're moving in the right direction ! 

Now, you need to get that wideband installed and get some AFR readings at WOT to see if it's a lean condition and decide from there where to go 



Ron

[b5blue]

I ran a 509 for 6 years in my 440, forget vacuum anything, keep ignition system flawless (Firecore plug wires? Heat range of plugs?) and tune for WFO till you get it. It was VERY picky about fuel brand and this was pre ethanol, you may need octane booster.   

[Cooter]

I pulled the vacuum line yesterday and took a 175 mile drive today. The part throttle ping is gone, but I still get some at around full throttle. Until I make some internal changes, I may need to run a few gallons of 110 Sunoco in a tank of 91. That ought to raise it to 95-96 octane.

Exactly where I am at with the Challenger engine. That is why I rec. that you swap out known comp. lowers like head gaskets. Once you go so far with tuning, it really gets down to too much static Compression. only way round it is to lower it.

[Kern Dog]

I have been reading up on "Quench". Pretty interesting stuff.
With flat top pistons and a closed chamber head, it goes like THIS: As the piston rises up on the compression stroke and closes in on TOP dead center, the incoming mixture compresses and gets pushed away from the flat portion of the head and toward the pocket where the valves and spark plug are. This sudden movement away from the one side of the head causes turbulence while cooling any potential hot spots. This "Quench" effect is most effective in a limited range. Once the distance between the piston and cylinder head get too far away, it begins to become less effective.
The above is a summary of the many, many articles, posts and threads that I have read. I am often a trusting person, but I still am amazed and a bit unsure to fully accept it. I currently am .56 from the head at TDC and many sources state that quench is lost at .060 and larger distances.  This logic means that even with detonation at 10.8, if I switch to a thinner head gasket to get the piston closer to the head for better quench, I will actually detonate less even with higher compression? Can you see how someone that has never personally experienced this can be skeptical? Sure, some of this is a money issue. I could spend money on some .027 Cometic MLS gaskets, a bigger cam with new lifters, timing set and gaskets....Spend almost $600 to learn that everyone is right. The .027 thickness would get me to .044 from the head which is dead center of Ideal for quench. It also would put me right at 11 to 1 compression. I'm sure that anyone else in my position would be skeptical, right?

[justcruisin]

Right, no guaranties, best bet, work with what you have, get the wide band in and dial in your fuel and ignition, see where you end up with your current set up.

[HPP]

Or you could spend $450 for a water/methanol injection, bolt it on in an afternoon, and use washer fuild instead of Sunoco 110.

Yes, with an assembled engine, I'd be skeptical to change as well. Anytime I've used quench, it was designed in from the begining. But I was also able to produce power and mileage figures from using it that rivaled many new vehicles for mileage and produced power from a milder combo that was compareable to many more expensive builds. It is an effective and practical way to increase compression efficiency that is used in many late model engien designs.

[Kern Dog]

My air cleaner is up against the hood as it is now. I'm using a dropped base too. I am guessing, but wouldn't the water/methanol injection involve some sort of carburetor plate delivery? If it were port injected, that may be interesting.

[Cooter]

"Quench" ain't worth two pinches of puppy sh*t if running shi*ty fuel. Today's "91" is like yesterdays 87....

I can dump TODAY'S 100 Octane in the Chally and notice a difference right away. 93 To 100 and notice an imediate difference? Yeah, I'll buy that 93 "pump" fuel is actually 93 octane.

[HPP]

My air cleaner is up against the hood as it is now. I'm using a dropped base too. I am guessing, but wouldn't the water/methanol injection involve some sort of carburetor plate delivery? If it were port injected, that may be interesting.

It does require a delivery nozzle to be added to the system, however there are options to its mounting. If you have a single plane intake, you could mount it directly into a plenum wall. If it is a dual plane, then you would want a plate to enable it to spray into both sides. Although I suppose if you were so inclined, you could put two nozzles in place. You also can put it upstream of the throttle plates, but that method may be best left to efi applications.

The appeal of the injection is that it is on par with loading your tank with 116 octane. If your on the edge of detonation, it will not only solve that issue but because of the cooler, denser charge, can also step up horsepower as well. Reports of an additional 5-35 horses and torque inscreases of 25-50 lb ft over optimal none injected tune ups are not uncommon.

[Kern Dog]

I have the Edelbrock RPM intake. It is a dual plane. I wonder if I could drill and tap for fittings....One for each plane. I have never considered such a thing, but it does sound interesting.

[HPP]

You mightwant to talk to them about specifics of yourset up. I haven't comeplted mine tobe able to give youpin point advice. Google Snow Performance and you can find plenty to read.

[Musicman]

I have the Edelbrock RPM intake. It is a dual plane. I wonder if I could drill and tap for fittings....One for each plane. I have never considered such a thing, but it does sound interesting.

Snow uses/sells a spacer plate that goes under the carb, but if done "correctly" it should be possible.. You just need to ensure an even non-biased dispersal.

[Kern Dog]

I looked at some kits on the Summit racing site.
I have no room to use a plate system. The air cleaner is so close to the hood, the clearance could be measured with a feeler guage.

[firefighter3931]

I looked at some kits on the Summit racing site.
I have no room to use a plate system. The air cleaner is so close to the hood, the clearance could be measured with a feeler guage.

Change the intake manifold 

You can easily fit a Holley Street Dominator single plane with a 1in spacer using a drop base air cleaner assembly under the stock hood. 


Ron

[Kern Dog]

I have read that the intake you speak of is a decent piece. The Performer RPM I run has it beat on power though.

[firefighter3931]

I have read that the intake you speak of is a decent piece. The Performer RPM I run has it beat on power though.

Actually, the Street Dominator makes more horsepower than the RPM dual plane.....it did in every magazine article i've read. I also compared both on my own 446 when we had it on the dyno and the Holley SD was the clear winner. 


Ron

[Kern Dog]

Man, I'm lucky that I have had the time to mess with this!
Short of pulling the engine and installing some dished pistons, the "fix" according to some sharp guys seems to center around the CAMSHAFT.
I have asked about this on other web forums. I've received some good advice and some stuff that made me wonder...
Hensley: "You need a thicker head gasket ans a smaller cam" Really? Wouldnt a thicker gasket reduce quench and increase detonation?
Comp Cams: "That '509 cam should be fine, you just need to use a thicker head gasket to lower compression" Again...what about quench?
Mancini:  " Yeah, a bigger cam would help. So would a thicker head gasket."

Hardly anyone in over 200 responses in various threads here, on Fabo, FBBO and Yellowbullet has thought that a thicker head gasket is a good idea. One constant though is to CHANGE THE CAM A more aggressive cam will have the ability to bleed off more cylinder pressure AND deliver more power.
I did a cranking compression test and got some interesting info: 220 in the highest hole, 210 in the lowest. This confirms that the engine is trapping faaaar too much pressure. A bigger cam is a must. Using an online calculator, my static compression is 10.73 and my DYNAMIC compression in 8.99. Experts say that an engine needs to be below 190 cranking compression and have a dynamic ratio below 8.0 to run fine on 91 octane.

Here is a cam I am considering. It is a hydraulic roller.
http://www.hughesengines.com/Index/products.php?browse=category&level0=QmlnIEJsb2NrICA0MTMtNDI2LTQ0MCAoUmFpc2VkIERlY2sp&level1=Q2Ftc2hhZnQ=&level2=Um9sbGVyLCBIeWRyYXVsaWM=&searchmode=partnumber&partid=24186

The duration isn't a whole bunch more than the 248 of the '509 cam, but it has a 110 LSA and a nice increase in lift. I will be using 1.6 ratio aftermarket aluminum rocker arms in a kit I bought from Mancini racing.

[justcruisin]

Good to see you have done plenty of research before handing over the gold. I'm sure with a drop in compression via the cam you will have a sweet runner. Fwiw, the dynamic on my engine is 8.2 with a cranking compression of 180 and it runs fine on 91 all though I choose to run it on 93.

[firefighter3931]

Look at response #3 in this thread and you'll see someone allready suggested that the cam was your problem   



Ron

[Kern Dog]

Yeah... I can be a little slow to catch on sometimes.
In the past, I have often made impulsive choices that proved to be wrong for me. Right here and now, I'm trying to cover all the bases to make the right decision. While many have suggested a cam change, NOBODY has spelled out the one that worked for them. I'm sure that others have engines similar to mine. I wish that I could hear from those guys!

I called Hughes this morning but their guys were all at INDY for some Mopar show.
I guess it will have to wait until Monday.

[firefighter3931]

Give Dwayne Porter a call 802-951-1955 and tell him what you got and how you drive the car. He can spec you a cam and it will run fantastic. Dwayne specializes in BB Mopar and is a master cylinder head porter and cam guru. 

I'm pretty sure he's going to tell you it's detonating because of the midrange cylinder pressure which is a product of a tight LSA and too short of a duration@.050 which is closing the intake valve too early. 


Ron

[Kern Dog]

Thank you for the referral. I have tried the number twice in the last 3 days. It rings and rings....He must be REALLY busy! I'll try again tomorrow.

[Kern Dog]

I got to talk with Dwayne today. What a helpful guy.
I couldn't squeeze a specific cam recommendation from him even though I tried. He did agree that a cam with a later intake closing would help.
First off, he was surprised at the cranking PSI #s I had. He said that THIS build shouldn't have #s that high with the long duration of the '509 cam. He suggested trying another compression guage. I told him I was installing 1.6 ratio adjustable rocker arms. He liked the idea and suggested to REcheck the cranking PSI afterwards. I asked about the effects of retarding the cam to delay the intake closing. He liked that too and again suggested to check cranking PSI.
Dwayne talked a lot about tuning the distributor to slow the advance curve. He said that a slower curve would result in reduced performance but would also reduce spark knock.
He thought that the real cure to the detonation would be to cut the block to allow the pistons to sit at zero deck. Then, have the valve side of the pistons milled .040 to reduce compression. This would improve quench while reducing compression. I'm not willing to pull the engine out anytime soon, so I'm going to focus on the cam and ignition.

[firefighter3931]

Dwayne is sharp, no doubt about that !  Did you degree your cam in ? I've been wondering why it has so much cranking pressure as well ?  If it wasn't degreed in properly ; the cam could be too far advanced and closing the intake valve too soon. 

If you didn't want to open the engine up a meth injection kit with a street dominator intake manifold would be your easiest route. Lots of guys run high compression on pump gas with meth and it works fantastic. 


Ron

[flyinlow]

Just curious . When does the methanol system inject? Just acceleration? How big of a tank do you need to cover a full tank of gas?