This past weekend I ran at 40 degrees timing, then after 2 runs dropped to 38.
My MPH was lower than I wanted, but that might be due to shifting the cam short(6500)
Can anyone look at my plugs?
It's hard to see the timing mark on the straps

520 CI 4.375 stroker, 10.1 CR
https://www.summitracing.com/parts/hrs-720152-08/overview/
Trick Flow 240s, opened to MW size
2" headers, 337 intake ported to the heads MW size

You probably need to put in one new plug, in #7 cylinder, in the staging lanes close to pulling out for a time trial and shut the motor off after the run and pull that new plug out before driving it back to the pits and post a picture of it on here
What brand and spark plug part number are you using now?
How in the heck did you get a BB Mopar motor to make 520 C.I. with a 3 3/4 stroke

Hi Cab.
The plugs are NGK BKR6EYA
The correct stroke is 4.375

For a head with a modern chamber like the Trick Flow 240, 40° is way too much timing IMO. It will be happier and faster at somewhere between 32-34°. Most of my Indy stuff likes it on the lower end of that.

What fuel are you using?

You are rich at an idle by quite a bit.

You are rich at cruise.

Can't see WOT with the shell on.

The timing marks on the ground wire are hard to see in those pictures. If that's pump gas, the timing on most looks slow. On one or two it looks close.


The plug in the third picture looks like you are a bit slow on intitial timing and it looks like the timing curve itself is a bit long and slow.

You're not ready to do clean cut plug reads yet. You can certainly clean up the idle and transition stuff first and then move to WOT tuning.

Timing mark is about half way...it might like the extra timing because it looks to be too much fuel (rich condition).
Can you tell us what carb, jetting, hood scoop, carb spacer, ignition your using?

It's very rich in the areas that are visible in the pics.

I am running 90 octane on the street, throw in a gallon of 110 to the existing 8ish to go race.

I have an AFR on it when the exhaust is on, it runs low 12s on cruise, high 13s at idle. at full open its in the high 11s.

I set the idle for highest vacuum, any leaner and it gets a stumble off idle.

It's been hard to get any 1/4 mile track time to play with the timing, the different timing marks on the straps confused me.

There is an 1/8 mile track close, but, the prep is so iffy, the top ends vary with how bad the tires blow off.

My setup now has a Mighty Demon 850, no spacer, no hood,running a 14" non- drop down air cleaner.

The ignition is MP kit with a FBO box.Saturday on my last run, the engine was hottest (210) and it broke up on the top end. It hasn't ever missed a lick, fuel pressure was at 6.5 lbs, so thinking maybe the heat had something to do with the breaking up? The advance is all in by 3000 rpms. Initial is 20, advances another 20 degrees. It loves the initial, may be time to recurve?

Before the hood was removed, the plugs seemed cleaner. The air must be doing weird things to the boosters.

There is a fiberglass hood with a hemi scoop coming in the near future.

The motor will pull hard past 7000 rpms, with stock oiling I don't want to rev that high, thus the 6500 self imposed shift points. Might be leaving some HP on the table though shifting it too soon. Better than rods on the pavement though.

The closest chassis dyno is 2 hours away, but, it might be time to just bite the bullet.

Thanks for all the input!

If anyone is interested, one of the runs is @1:30
https://www.youtube.com/watch?v=JiJQ8q4R...0hyFdaZMrZymReM

Carbs tune is way off call me and I can walk ya through stuff or fix it for ya.............

Not to hijack the thread but Dom...are you ever going to get a web site? I ask because the chance of me joining Facebook is in the zero range.


Also, I'm using 8/32 X 3/16 long brass set screws for PVCR in my 5 emulsion BLP metering blocks. Those set screws will actually back themselves out and turn sideways in the power valve restricter channel!!

It's happened more than once. Am I using screws that are too short, or should they have a flange on them.

No time for a web site and would never get anything done so Dominic Thumper on FB is where it's at for now. I use 8-32 1/8 with zero issues........

Just thinking out loud, could running no hood make the carb go rich?
Here are plugs that come out of it with the hood still on.

To my untrained eye the looked alright.

The plugs on the left look better.

The only way for anyone but you to see your WOT tune up is to take the shells off the plugs and post a picture of the porcelain.

For your WOT here should be a .060ish wide ring at the bottom of the porcelain and the rest of the porcelain should be clean. We can't see that with the shells on.

On pump gas, the timing line/mark on the ground strap should be just past the corner heading towards the shell.

So the timing mark on some of them looks close.

Running the hood helps keep the air going into the carb. more consistently than with no hood
You already knew that though, didn't you
Put it back on now
You will have to retune the carb. with the new glass hood with the scoop
The old plugs with the hood on are a lot like I like to see in my motors
On your AFR readings I like to see mine leaner than yours are, I like and tune for 14.5 or leaner at idle, 12.8 to 13.6 on light part throttle cruise and around 12.5 to 13.3 at WOT depending on the fuel being used at that time, these are with the motor, trans and rear end at running temps for normal driving
As far as total timing I haven't found any BB Mopar motors, race or street and strip, that liked or ran faster with anything above 36 degrees :shruggy
Most of them liked and ran the best at 34 degree total timing with my timing lights the way I see them
That is with the timing marks on the timing cover and balancer verified as being actually zero at top dead center also