Sam: although I use a 195 thermostat and like it.....I wonder if 195 is a little hot for your application.

It might be worth seeing what 180 would do.

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Yeah....Im the one who destroyed this rare, vintage automobile.....

I use champion RN9YC, 100% meth, and run a 160 stat. A 195 definately sounds to hot, maybe a 180 would work better as mentioned before. My wide band afr at WOT is around 11.0:1...still a tad rich but safer for detering spark knock.

I just wanted to clarify a few things and see where it stands, you can take this info or leave it but, hopefully this might help...


Stock for the ‘stock’ engine is actually a GR-4…

You need to run a colder plug, some info here may apply
Heat Range.


Looking up the plug using this chart as a guide
NGK CHART.

The –11 indidcated that the plug is intended to be used at a .055 gap in it’s stock application (Honda/Acura Dodge Magnum Engines, etc....)

The one thing to note is when you use a component like a spark plug that is not originally intended as a stock component for the engine/vehicle it may not correctly ‘translate’ to it’s ‘stock’ counter part (‘apple plugs to ‘mango’ plugs)… take for instance moving the electrode out a smidge from it’s ‘stock’ position, several sources have speculated that this can actually act like ‘advancing’ the timing curve since the spark from the 'new plug' now originates in a place where the flame front across the cylinder face might occur with a stock plug and the piston/crank/cam position as related to the timing of the spark if advanced a few degrees (or 5 or more).

So in this case, if you go back and try a cold plug like the GR-5 or 6 and your ping is gone, then you have found that a colder plug in the stock range was the correct choice, if you run something like the ZFR6f-11
(which is meant for the high swirl chambers in the magnum V-8’s..where turbulence occurs regularly due to the quench pocket…probably why during lower ‘boost’ you experience less pinging because the turbo is helping keep things agitated like in the new closed chamber heads…), wiht the non stock plug you are pretty much taking a ‘guess’ as to what effect the plug is having in your engine…(it could act like more advance, it could have a ‘hotspot’ on the lip of the base and creating pre-ignition …???)

Have you run a stock set of plugs as a base, then run a colder set of 'stock' plugs to see what happens (I haven't perused your old posts on the Dart Vader Build)?

Just some food for thought there buddy…

-D.Idiot

Think about this, you are fighting det at a boost level that is lower than Shaker runs. I will be willing to guess that he can run 9 - 10psi of boost with much more timing and no det while running no meth.



Shaker, how high of boost was you able to run before you had to go to Meth? What timing was you running at that level?



BTW, I would try a 160 stat.


Jess

I was looking at all the suggestions, and thought it might help to list and categorize them.

Cheap and Easy

• Colder plugs
  Colder thermostat

Moderate

• Retard timing curve
  Mess with Fuel map

More extreme measures

• Get dyno time
  Go to Methanol
  Take off head, look at combustion chambers.

Sam, I actually think you should go to the extreme measures list, and schedule some dyno time with a good shop. You have been chasing some nagging issues for sometime, and it seems like having all those snazzy instruments here would probably help you get to the bottom of the problem. You always come off as a smart guy, trying one thing at a time, and testing your results, and the dyno time would facilitate that approach for you.

I am some months ( okay, it has been years now) behind you, but I am wanting to build a very similar engine to you, and I am crossing my fingers that your gained knowledge will provide a good starting point for myself and others working on turbo slants.

Keep it up, you are inspirational.

Greg

I installed the meth injection before I even started the car with the turbo. I've since tuned it to start spraying at 8psi (full on with 7gph nozzle). The "turbo guy" at the dyno shop said to ditch the water and run 100% meth as well as a gent on the devil's own website. I've never looked back.

From my last dyno session, I made the most pwer at 21* total but backed down to 19* total because the 2 extra degrees were worth only 4rwhp and 4 rwhp. All of my track time and dyno sessions were with the motor at about 150*F.

Don't forget, I run some race gas mixed in. The 110 octane is only $1.50 more than the 94 sonoco. Cheap insurance!!

The meth drops the inlet temps about 17*F below the outside ambient temps. I installed a couple of thermocouples and checked it.

Thank you one and all for you ideas here. You guys are awesome, and brilliant. It may seem like I have been plagued with detonation for a long time. But that is not really so. I got rid of it by putting in the colder thermostat. But iI did not like the way it drove. Then, to make things seem even more involved and drawn out, I popped my achilles tendon, and could not drive the car for 8 weeks. So I wasn't doing any tuning on it at all.

Now that I can drive again, it simply runs much better at the high temp. So, this injection thing is a step back to try and cure the problem a different way without compromising driveability.

In this case, the easiest thing is just to go with 100% alchohol injection. That is just a simple fluid change. But I would rather fix it with plugs first if I can. I like the idea of being able to buy cheap, readily available windhield washer fluid at pep boys, and run regular gas. I will never know until I try.

And, the timing may not be right for the transition from NA to boost. I need to mess with that. I will read DI's link on spark plug choices. Plus, one of the gurus on the injection forum said to go up at least one size on the injection nozzle. So I am going to try that. I wish I knew what the timing curve is like on the stock Buick Grand Nationals. That would be very informative.

For what it is worth, when I checked the plugs, they were shiney silver. Sparkley clean! It is like the windhield washer fluid takes every bit of everything off of them, even the stock bluing, or whatever is on them when new. So reading the plugs seems out of the question. I imagine the combustion chamber is kept just as clean, with all the carbon being knocked off the valves as well.

Sam

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That's why most old mechanics 'de-carbon' and engine by running it up to full operating temp, crack the throttle to high rpms, and pour a cup of water into the carb bore...it' just steam cleans all the build up out the tailpipe (hope the cat. convertor doesn't plug up... or a big wad of carbon wedges into the exhaust valve...)

Good Luck Sam, it's just the experience of the journey in figuring out your unique build that will make the thrill of accomplishment worth it when you finally get it all sorted out...

-D.Idiot

DI, When the dyno shop did the very poor tunup on the car a year ago, they started with a stock set of plugs, and never changed them. When I changed them out, I went with Dan's extended tip plugs and liked them alot. When I wanted to go colder with that type, but could not get colder extended tip plugs, I used these ZFR6F-11 as per Dan's recommendation as being the closest thing you could get in an extended tip plug that was colder.

For what it is worth, the dyno shop simply dumped too much fuel, and took all timing advance out to try and kill detonation. They never approached it from spark plug angle, which seemed sophomoric to me at the very least. I got back a car that ran worse than when I took it in. I spent alot of money on a venture that kind of turned me off on the entire dyno approach.

I can see the logic of speculating that extended tip plugs have the effect of increasing the advance on the timing if the flame front is already a few degrees across the piston bore at fire.


In studying the NGK chart it looks as if the GR-5 is the same in every important design feature as the stock plugs except for the size of the hex. The ZFR is 5/8" and the GR is 3/4". Also, as I looked down the page, I saw the V power plugs. Any experience with those? I seem to remember someone saying they liked them. It kind of broadens the spark kernel somwhat maybe. I am going out this afternoon to get a few item, and spark plugs is on my shopping list. Maybe i will try the v- power type if Advance has them in stock.

Sam

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I am a bit confused by the NGK chart.
Which plug would be the longest tip and the coldest plug? And in the V-Power? Of course for the Slant6.

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67Cuda,FAST EZEFI,340cu,CR=10.25,RollerCam&Rocker (XR268HR,#20-810-9)(#1622-16)(EddyRPM#60779,#7576), (MSD6AL,#6425) A904, GearVendorsOD, 8 1/4,3.55:1, ClassicAir

GR4 should be a V-power plug. That's pretty much all I use.

I agree with DI that going back to the stock type plug in a colder range would be a very sensible place to start.

I would start with GR5 or GR6 and maybe go colder from there.

Lou

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Home of Slant6-powered fun machines since 1988

According to the chart the GR4 is a hot plug and the GR6 is a cold plug. Is the chart wrong?

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67Cuda,FAST EZEFI,340cu,CR=10.25,RollerCam&Rocker (XR268HR,#20-810-9)(#1622-16)(EddyRPM#60779,#7576), (MSD6AL,#6425) A904, GearVendorsOD, 8 1/4,3.55:1, ClassicAir

Get some Champions RN9YC and gap them .025 to .030. (I'm at .030)

They're nice and cold!

Bren, You are right in your interpretation of the heat range numbers. The problem is that many of those plugs you can come up with in theory are not actually made. As it turns out, the book lists nothing colder than a GR45. I had to go to the ZFR7F-11 to get a colder plug.

If that is not cold enough, I will try Shaker's Champions.

Sam

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rn9yc`s are to stock plug for high compression 340`s and rv9yc`s are there match in the small plug heads