After an afternoon of working in the yard I finally found a couple hours to spare before dark. I threw some new Autolite plugs in my 440. These are the Autolite equivalent of the RC12YC Champion.

I'm still trying to make my part throttle ping go away. I played with the fuel quite a bit the last time I worked on it (I don't have much free time these days). I wanted to make sure I wasn't to rich. I upped the jets in the carb quite a bit before giving last time.

In 26 miles of driving I had several full throttle goes from 1st, through 2nd, and let off a bit before 3rd. I never pulled over to read the plugs right after a pull though.

Here's what #4 looked like when I got home (Autolite plug so the base is black, that isn't oil).

P1230002 by chilort, on Flickr


P1230004 by chilort, on Flickr


P1230005 by chilort, on Flickr

Here's the #8 plug:


P1230006 by chilort, on Flickr


P1230007 by chilort, on Flickr


P1230008 by chilort, on Flickr

Thoughts?

I need better pics to see the timing mark on the strap, and I need a shot down the plug....Tough to see anything in those pics. If the discoloration on the strap is right in the one pics, it shows the heat range too hot. Meaning you need a colder plug. Also, reading plugs can only be done at maximum load. You have to shut it off and read them, otherwise all is out the window.

The ignition timing can be checked by looking at the color of the plug’s ground strap and the position of the "blue line" on the strap. The blue line really indicates the point at which the strap has reached annealing temperature of the metal. Further down the strap, the more timing is in the engine....

Ideally, you want this blue line to be just below where the ground strap makes the sharp bend and above the weld. If you advance the ignition too far the blue will disappear off the strap and the strap will pick up rainbow colors (blues and greens)

What compression is the engine? The plug range is usually determined by compression....

Around 9.2:1 with Eddy heads. It is a terrible setup. Pistons are 0.100 in the hole. I tried reusing some old slugs that weren't really that worn out (long, long, long story where I was tripping over dollars to pick up dimes).

Part throttle ping can be too much vacuum advance?? did you make sure it's on ported vacuum and dial some back with a 3/32 allan wrench in through the vacuum port on the vacuum canister on the dizzy??

Been trying to clean up my part throttle ping with no vacuum advance attached.

Engine seems to want a lot of initial (19-20*) and nothing else. ...well, not much else.

One thought was that I wasn't getting enough fuel so I converted my el cheapo 750 Holley to one where I could change the jets on all 4 corners and bumped up the jets a number of sizes.

Been playing with this for a little under a year when I get free time. Mostly just trying to see what folks think the plugs are saying.

If you have a part-throttle ping AND you are using the vacuum advance, the vacuum canister is adjustable by inserting a 3/32 Allen wrench into the canister (where the hose goes) and turning it one way or another. This may not change the total advance as it adjusts how sensitive the vacuum advance is to the vacuum signal, not the total amount of advance when under a high vacuum signal. You can limit the total amount of vacuum advance by limiting the travel of the arm on the canister.

If using the vacuum advance, try disconnecting it and see if the engine still pings. If not, limit the total vacuum advance (I believe stock is 15 degrees added to total timing (initial + mechanical)).

What carb you running now?? does it have a power valve. too low a number on the power valve will not let it work at light throttle acceleration where it is supposed to and it will lean ping.
For stock applications with high in gear vacuum 1/2 is ok 16 to 17 maybe an 8.5

For modified aplications 1.5 to 3 numbers below in gear idle vacuum. Just enough to keep it closed.

So 10 in gear vacuum maybe a 7.5 (or 6.5) 8.5 in gear and a 6.5 should work great. 7 in gear and you want a 5 or 5.5 aas long as it stays closed at idle!

Holley 750 80508S that I've converted to 4150.

I believe the power valve that is in it is a 6.5.

I have about 10inhg in gear at idle.

I was told at one point that I might need a high flow power valve.

My pinging, being a part throttle deal, happens most when I actually have fairly high engine vacuum (15inhg) and seems to go away at lower vacuum levels (i.e. when I give it more gas).

How many miles on the plugs? there either new or the Enging is running very "lean"

They had 26 miles on them when I put the photos up. Now they have about 50 but mostly at idle and cruising around town. I'm about to pull a couple and take some more photos.

Edit: photos (8, 6, 4, 2)


P1230015 by chilort, on Flickr


P1230014 by chilort, on Flickr


P1230011 by chilort, on Flickr


P1230010 by chilort, on Flickr


P1230009 by chilort, on Flickr

Jets are 76 primary and 82 secondary. It came with 70 primary and the equivalent of a 75 secondary.

Engine builder's fuel guy says the plugs should look like you pulled them out of the box and you have to look for bits of aluminum to check for detonation.

Bigger squirter nozzles and a high flow PV should help.
Is it set to squirt at the slightest movement of throttle??

It may also need a more aggressive pump cam.
http://www.summitracing.com/search/?keyword=accelerator%20pump%20cams&dds=1

nozzels
http://www.summitracing.com/search/?keyword=accelerator%20nozzles&dds=1

It already has a 37 squirter.

I have a box of pump cams but it already has one of the most aggressive pump cams.

If I went with a high flow power valve what would you recommend?

hears a 6.5
http://www.summitracing.com/parts/HLY-125-165/

you may want to try a 8.5
http://www.summitracing.com/parts/HLY-125-185/

as long as your in gear vacuum is 10 it will stay closed at idle and tip in much easier

I once used a dual 10.5/5.5 on a 600 holly vac on a mild 318 and that solved my light throttle ping. course my in gear vacuum was 13??

you may have to drill the passages out a bit behind the power valve in the metering block

??
or the metering block from a 750 may work better if you can fine one to fit!

http://books.google.ca/books?id=6JIHWWW5...DOyF04qhPy1svNM

http://books.google.ca/books?id=oVZrJgUA...igJW0PgYVHppCb4

http://www.bob2000.com/carb.htm

http://www.clubcobra.com/forums/holley-tuning/101183-how-modify-your-holley-power-valve-circuit.html

lots of stuff to read out there I have a holley book somewhere i bought 20 years ago has been invaluable maybe I should update! LOL!
http://www.amazon.com/Holley-Carburetors-Design-Dave-Emanuel/dp/1884089283/ref=pd_sim_b_2

http://www.summitracing.com/parts/SAD-SA08/

I just had this same problem and solved it with a bunch of help from the guys here. This is a link to the thread https://board.moparts.org/ubbthreads/show...part=1&vc=1

I realize that the power valves are cheap and I live 30 miles away from a Summit outlet. But I don't see how a power valve is going to fix my issue. While my idle vacuum in gear is 10inhg, the vacuum where I first start to experience the ping is still around 15inhg or so. At this point, even an 8.5 valve shouldn't be contributing fuel. Right?

But when you give it throttle vacuum drops quickly. this is when you are in transision and not enough air is moving past the ventures to give the richness it needs to accelerate. the power valve supplies that fuel needed for the transision no fuel lean = lean ping


Check out the links in my April 18th post and or buy a book!

EVERY carb needs tuned to each engine.
Even if you change an intake or timing or exhaust, you still may need some changes.

My 'guess' is that it has too much initial timing and the off idle curcuit is too lean. This is befor the main curcuit is flowing ( the jets).
Do you know the idle transition-fuel sizes? Or even the idle air jets sizes? This is where you will find the problem.