[ieatdrt]

Let me give you some specs first then I'll explain:
408W stroker
10.8:1 compression
Autolite 3922 plugs
MSD 6AL w/MSD distributor
Compcams XR274R solid roller 274/280 adv. dur, .602/.608 lift
Performer RPM AirGap intake
Edelbrock 800cfm Thunder AVS
93 pump gas

I think my car hates me. It will ping off idle when I'm letting out the clutch,then intermittenly while cruising, which is probably just being drowned out by the exhaust. I can swing the initial timing from 8-16 deg. and it remains the same, although it stumbles like crazy at 8. It seems to quiet down the most around 12 deg., but the ping is still there. Cruising at 2000rpm and mash the throttle and it takes off like a scalded cat, after the wheels stop spinning. I just can't get the darn thing to stop pinging. I've even drained the tank and put in fresh gas. I've installed an adjustable vacuum advance, and installed a vacuum advance limiter that I can adjust as well. I've also tried both ported vacuum and full manifold vacuum sources. Nothing makes a difference. I have a F.A.S.T dual band AFR monitor hooked up and monitor both banks simultaneously. I've got it running pig rich, cruising around 12-12.5:1 so I know it's not a lean condition. The idle is about 14:1, which is just fine maybe a tad rich. I'm currently putting in about 12 on the vacuum canister. It idles great with about 10-12" vacuum. Just pings and runs like crap up to about 2000-2200 rpm. Never had trouble dialing in a car before, really stumped on this one. Generally speaking if you're pinging you pull out some timing then go from there, but it just won't respond.

Any help is appreciated and I'm thinking 10 initial is a good place to start without chance of pinging. I know there are alot of similar setups out there, maybe somebody ran into the same issue.

[S1att3r]

i is possibly a burned valve. my car is doing it too.
just my 2 cents.

[ieatdrt]

I'll do a compression test tomorrow, but it's a brand new build. The engine has only about 15 miles on it, and that's from driving around trying to tune it and break in time. Brand new AFR 205's.

[S1att3r]

then i doubt its a burnt valve but a compression test couldnt hurt a bit.

[rocky289]

Just to prove a point, you could try some 100 octane.

[ieatdrt]

I'll throw some in today, what's burning me is that it doesn't respond to pulling out timing.

[cindys_sn95]

how was your deck clearance? how thick is your head gasket? if you quench is to great it will ping like crazy. best quench is .035-.045.

[ieatdrt]

The quench is .0355, .0035 above the deck and .039 compressed head gasket thickness. I can try a thicker head gasket.

[ieatdrt]

Tomorrow I'll pull the plugs, and read them. See what I'm getting, and maybe purchase the head gaskets to help open up the quench and lower CR slightly.

[cindys_sn95]

if you had + .035 deck height and .039 gaskets, yea thats to close. going to be hard to find a gasket .070-.080 thick, unless you go copper.

[ieatdrt]

No, no, it's .0035 and .039, that gives me a quench of .0355, which is within the .035-.045 area. I was thinking maybe a .041-.047 gasket which would bring me into the higher end of the quench range. Although I don't want to go too high or that will also cause ping also, not enough quench. Yea, .004 quench would probably put my piston through my head.

[cindys_sn95]

what chamber size? what piston? thats really strange.

[ieatdrt]

58cc chamber with Probe SRS 10674 pistons, which are a -22cc reverse dome. I'm going to play with it some more today. It actually get's worse when you back out the timing. I leaned it out a bit and brought the timing up to 12 initial 10 on the can. And it responded positively. Still has a slight ping just when the clutch is released, but not while cruising. I'm thinking of swapping the mech. adv. bushing out to keep the total down, and bringing the initial up to 14 and see how it responds. I may swap my 800 avs for my old performer 750 and see how it responds too. Oh and the plugs were all looking good, medium tan color.

[ieatdrt]

Here's the piston.

10674 - Ford 408/418W -22.0cc Reverse Dome SRS Pistons

[The Greek]

With the initial, centrifical and vacuum advance all in, at whatever RPM that this occurs, (Should be between 2400 to 3200 RPM, depending on the type of transmission) the total amount of timing advance should not exceed 52*BTC. Without the vacuum advance connected, total advance should be between 36 to 38 BTC.

With a manual trans, all in should be at a higher RPM than with an auto trans, say about 3000-3200 RPM. Is the advance coming in too soon? Have you tried a colder heat range plug? Are your plugs projected tip? Try a set that has a recessed tip. This may help to keep the ground strap from retaining heat and acting like a glow plug.

The compression ratio is a bit on the high side for 93 Octane, but with aluminum heads, you may be able to get by if the timing advance isn't coming in too soon and/or if the plugs aren't retaining too much heat.