DETONATED MY ENGINE

[Anonymous]

Hello, amazing site. I've spent quite a few hours reading already. I'm hoping for some insight regarding a recently rebuilt engine that sadly had two piston ruined by detonation, pre-ignition, or just plain running lean (those are my deductions/ and the extent of my mehanical experience is about 3 years and running). Perhaps the destruction of an engine, I spent $1600 3 years ago to have rebuilt, will help people learn from my inexperience. Here's some pics of pistons 2 and 3 in my 200ci (now out for a rebuild)

http://oldeconolines.com/dm1.jpg
http://oldeconolines.com/dm2.jpg
http://oldeconolines.com/dm3.jpg

The engine is in a 62 econoline travelwagon, which I've done quite a lot to make run such that it would be dependable.... oh well, live and learn. To outline a few of the upgrades, I replaced the smaller radiator with a fresh 240 radiator, Had the carb rebuilt (a motocraft carb I am told is for a 200ci : D9JL 9510JH 9170 1109) AND RE-JETTED, I also put a pertronix ignition in the dist along with a "flame thrower coil" (I believe the dist is from a 65?-that's the cap that works).

So I've got pistons 2 and 3 trashed. My thinking is this must somehow be caused by the carb, dist, or both. I'm not sure whether the carb or dist are high or low vacuum. I had the setup tuned (so I thought) by a regular shop, and they claimed the carb and dist were compatible. I don't think the water jackets on pistons 2 and 3 are clogged, or that there's any crack in the head. Perhaps there's some vacuum leak in the carb, not sure.

To be safe, my current plan (would love to consider other suggestions) is to replace both the carb and dist (I need to keep costs down so I'll probably look for inexpensive options now- like a 1940 carb rejetted- and go for a upgrade to a webber type later). I printed out the article on the Duraspark conversion, and I can do that. My essential questions are:

1) has anyone ever seen pistons 2 and 3 burn because of running lean?- Has anyone seen this situation before?
2) what id numbers can I reference to ensure I get a high vacuum Duraspark and a High vacuum 1940 carb? (or a another stock type carb)
3) any other suggestions as to what caused the piston destruction and what I can to to get set up so I won't end up a thousand miles from home with a blown engine?

I would mention also, I never heard any abnormal noises from the engine that would suggest detonation or a serious engine issue; with the exception of one occasion last summer when decelerating on a long haul, the engine started ticking loudly. I let it rest for awhile, restarted it and the ticking had reduced significantly; let it rest a bit longer and the ticking was gone. I chalked it up to a stuck lifter and got back on the road. Never having driven a late model vehicle prior to the econoline, I always assumed the way the vehicle accellerated as being the nature of the beast; but I've always had to be carefull on takeoff to avoid the bucking bronco effect or killing the engine; I am now deducing this was cause the carb was jetted too lean. For the record, the rebuilder omitted valve guides from the original rebuild, which was causing fouled plugs, so he pulled the head and did the valve guided about 3K into driving the new motor. Since then the plugs were in my opinion normal grey-brown, perhaps tending somewhat to white. Any help will be greatly appreciated....... thanks.......

 

[Mercury Mike]

Ouch. That's a tough thing to happen. What was the timing set at? What distributor were you using? What carburetor exactly? Autolite 1100 or Holley 1940? (The 1940 usually has the motocraft stamp on it, I think).

 

[Lazy JW]

Howdy and welcome!
Regardless what distributor you choose I highly recommend mapping the curve ON YOUR ENGINE!

This isn't difficult but does take some time.

First, verify TDC on you timing pulley.
Next, mark the pulley in 5 degree increments up to at least 45º BTDC.

Then, using a timing light rev up the engine to see where the advance actually goes. If you have the vacuum-only advance you will need to buy/borrow a little hand pumped vacuum pump to see how much vacuum gives how much advance. Then you can insert a "T" fitting into the vacuum line and run a tube into the cab to observe actual vacuum while driving. Then you can deduce how much advance you are actually running.

With a mechanical advance, unplug the vacuum advance and just rev it up until it stops advancing, recording the amount of advance every 500 rpm. Then, let it idle. Using the hand pump on the vacuum advance, pump up the vacuum, observing how much advance is produced for a given amount of vacuum. Write all of this down on a chart/whatever.

Now you can tell exactly what is happening by using a tachometer and a vacuum gauge.
Have fun.
Joe

 

[cfmustang]

I thought it was 1 & 6 that tend to run lean/hot on our sixes since they are on the ends of the log.

On mine, those two cylinders were actually a little oblong compared to the rest so I had to have my cylinders bored out.

 

[Anonymous]

The carb has *motocraft* stamped on the side (for a 200ci : D9JL 9510JH 9170 1109)- it looks almost exactly like a Holley 1940, but I'm told was an "industrial carb", like I say, I think it was jetted too lean I could check the jet diameter. The Dist has "FoMoCo" stamped on the side along with the number 12127. I had the timing set just to the right of center on the scale atop the pulley; I think it was 6 or 8 BTDC. I got furthe evidence today to suspect the carb is a high vac, and the dist a low vac.
At this point, my main concern is to find a cont-effective way of getting things back on line. I'm open to a 32/36 carb if I can find a decisive way to match a dist. I am not familiar with different models of the Duraspark, and wandering the junkyards leaves me feeling as likely to bring back useless junk as anything......
I could undertake the suggestion regarding the vacuum advance test when I get the motor back from the rebuilder, but I'd just as soon save the time and get the right dist/ carb compo in from go......thanks ..... David

 

[Lazy JW]

... I got furthe evidence today to suspect the carb is a high vac, and the dist a low vac...

Which tells me that the carb was pulling max advance to the distributor, hence the detonation.

This thing is almost 45 years old. Even if you do find the "right dist/carb" there is no way to know what's happening unless you dial it in. But you may get lucky. Or not.
Have fun,
Joe

 

[The Plankster Prankster]

Never having driven a late model vehicle prior to the econoline, I always assumed the way the vehicle accellerated as being the nature of the beast; but I've always had to be carefull on takeoff to avoid the bucking bronco effect or killing the engine; I am now deducing this was cause the carb was jetted too lean.

been there, done that!! thats too much timing advance. i guarantee it!!! my truck has had problems with the advance sticking, and thats exactally what it does. you can reproduce it every time by putting a check valve in the vac advance line, thus always having full advance. your problem is definately caused by too much advance, either a bad setting or an advance that advances too quickly. in my experience, your fuel/air mix has nothing to do with it
--josh

 

[LaGrasta]

I'm curious as too how many miles was on the engine since it's rebuild.

I'm running my advance somewhere around 25°. I have about 19lbs of vacume and it idles and runs super.

To set it, I kept retarding it until the pinging stopped and left it there. It's been about 3 years now. With less advance, I have hardly any power.