I've attached the datalog (EBL Flash-II) of some detonation I have been unable to find the source of. It is audible and I can watch it on the WUD at the same time. I get a rash of pinging when I go to WOT, and another series of knock events when I let off the gas. If I try to immediately recreate the effect it won't occur. It seems to happen after a short period of lighter throttle and lower RPM. The knock events still occur according to the WUD, but must be less because they aren't audible.

I have pulled TONS of timing to no avail. I have checked mechanical timing and verified it absolutely. I have checked that the latency of the distributor module matches my timing light. I have changed to a new distributor (small cap from large cap), new plugs, etc. It has been there from the time I started tuning the car on $6E.

This engine sat for 11 years. The cooling system is disgusting. I have flushed it half a dozen times and rust still comes out. When I pulled the knock sensor absolutely nothing came out the hole. It was plugged with rust. I have a theory that perhaps the cylinder head cooling is very poor. And when I rev up the engine it helps cool the heads and reduces the detonation for a short time. It burns no oil - new stem seals. 190 compression on all 8. Also doesn't seem to occur at all when cold. Nothing audible or recorded in the WUD. I'm running a 170 thermostat and fans set to 190/180.

I'm more curious than anything since I'm swapping the engine in not too long. But I would really like to nail down a cause for my own education.

GD

 

A lot of rust buildup in the heads cooling jacket can insulate it from the chambers.

Is it possible that the wrong water pump is installed? The newer serpentine setups use a reverse rotation pump. While V belt system use a standard rotation pump. Switch them and the pump will pump, but not as well as it needs too.

RBob.

 

I swapped to the serpentine system a few years ago and when I did I bought a (cheap $17 Autozone) water pump for a serpentine model because of the change in rotation. I did buy a REALLY cheap pump because of all the rust though.... I figured it would probably kill it in short order but it actually has been fine. Maybe my problem is a really cheap water pump? I did know about the reverse rotation after reading up on the swap so I'm 100% sure I got a serpentine model. But for $16.99 I'm not entirely sure the quality is adequate. Hhhmmm that's an interesting thought. But I'm not sure I want to "waste" a quality pump just to find out if that's the actual issue. I was planning to replace it with the engine just to get as much rusty junk out of the system as possible.

GD

 

i have a used stewart stage 2 pump layin around somewhere (i think lol) if you wanna try it. Pay shipping lol

 

That sounds like just the ticket. I'll send you a PM. That would rule it out and neither break the bank nor worry about contaminating it with rust. I can do a flush at the same time with whatever aggressive chemical I can find to chew up the rust.

GD

 

Well I swapped in the Stewart stage 2 water pump, drilled a few extra holes in the thermostat for the additional flow, and the detonation persists.

I also just replaced the engine mounts with poly (old one's appeared original 1986 and they were TOAST). Moved a few things around that might have been hitting the engine or exhaust - heater pipe, and adjusted the right side header to y-pipe flange, and a couple brake lines. When I rev the engine it barely moves at all. Maybe 1/8" if that.

I pulled a spark plug (#3) and checked the piston top and so forth for carbon deposits and saw nothing of note - looked pretty clean actually. Exhaust valves were grey ash colored - no dark carbon or oily residue. Very dry and clean overall. Engine burns little to no oil and has solid, even compression - around 190 psi, and all cylinders within 5 psi. *Edit* - performed the compression test again with the gauge at my shop (Snap-On) instead of the one at my house - all cylinders about 160 psi. 190 did seem high based on what I've read. Wanted to rule out something stupid like someone installing the wrong thickness HG in the past, etc. Looks like it's normal.

Here's an updated log file, and a screen shot of an area around 3600 rpm, 95 MAP where the retard hit 13 degrees (reduced down to 7 degrees SA). When it does this you can feel the power loss. AFR is at 12.7 commanded, wideband says it's closer to 11.5

Anyone have suggestions?