Engine problem with 63 L84

[Michael G.]

Yesterday, my 63 FI engine was getting noisy, so I adjusted the valves. The engine is stock, except for roller rockers. I set the intake to .008, the exhaust to .016. After adjustment it was very quiet, smooth, and ran very well. I then drove it about 60 miles with no problem; it performed as expected. I then stopped for dinner for about an hour.

After dinner, I got in the car and turned the key and the engine backfired through the plenum very strongly. I stopped it and examined the engine and found the number one plug wire loose and arcing to the distributor. I put it back on and started the engine. The engine ran, but had a noticeable vibration, one that was not there before the backfire. It ran poorly, for about twenty miles back home.

At home I lifted the hood with the engine running and heard a knocking from under the plenum, not unlike the noise I heard when I bent a pushrod last year. I shut it off and took the valve covers off. There was no evidence of a bent pushrod and all of the valve gaps were still in spec.

After putting it back together, it still vibrates.

Anyone got an idea of what I'm dealing with here?

Thanks,

[Domenic T.]

Re: Engine problem with 63 L84

Mike,
I don't have the book in front of me but I remember the valve gap to be much higer than .008 & .016.

DOM

[Dan H.]

Re: Engine problem with 63 L84

Michael, you might want to check the plug wire that came off, ohms etc. Might be pulling a dead cylinder now, internal break in the wire.

[Michael G.]

Re: Engine problem with 63 L84

Dom, those are the settings I use in both my cars. They're different from the manual, but are from a paper authored by Duke and John some time ago and quoted here many times. I used them last time I set the valves, with no issue. Thanks

Dan, I'll check the wires and the plugs.

Thanks,

[Ken A.]

Re: Engine problem with 63 L84

I'd look for a bent rod, if your FI unit leaked into number 1 cyl. Run a quick compression check.

[Monte M.]

Re: Engine problem with 63 L84

Mike,
Like Ken said, double check the push rods for number 1 ctlinder. Check to make sure the #1 wire is still good. Change the number 1 spark plug out. If none of this seems to help, go back to the basics.

Start the engine and get a pair of insolated pilers and pull each wire off one at a time to see if any cylinder makes a significant change. If the wire was not firing #1 and it ended up with excessive fuel in it, when it ignited it popped pretty good. This may have affected something.

If none of that works, check your injector for the number 1 cylinder. The backfire may have blown something on it or messed with it in some way.. It might be a reach, but you have to check everything. If you do not have a spare injector, swap out a couple on the engine to see if the problem moves with the injector.

There are still a few more things to try, but for now this should be enough to keep you busy.

Let me know how it turns out.

Monte

[Dan H.]

Re: Engine problem with 63 L84

Michael, a good back fire might damage your cranking signal valve making the engine run rough. Just a thought, good luck!!!
Dan

[Michael G.]

Re: Engine problem with 63 L84

The Fi unit shouldn't have leaked gas into the cylinders, it has an electric anti-siphon valve to prevent this. I don't doubt that some fuel could have collected in cylinder #1, though, from lack of ignition spark (hence the backfire). Whether it was enough to bend a rod, I don't know. The engine seems more out of balance than I ever seen caused by just one cylinder "missing". It doesn't bog or stumble on acceleration, like I would expect with a "miss". I don't know the exact sound of a rod knock, but this could be one.

I'll check the compression, plugs, wires, and inspect the #1 push-rods again. If that doesn't work, I'll also sub-in a good cranking signal valve, though, I won't be able to get the valve from my blue car until Sunday. I have a new extra nozzle-block somewhere, so I'll try to find it.

Thanks,

[Duke W.]

Re: Engine problem with 63 L84

Everytime is see "roller rockers" I cringe.

My first question is why did you bend a pushrod last year?

Unless the engine runs away and well exceeds 7000 that's almost unheard of with a Duntov cam and OE valve train.

Duke

[Michael G.]

Re: Engine problem with 63 L84

Hi Duke, the push rod bent because the engine rebuilder used valve springs that were too strong. Several rocker studs also pulled out of the heads. We discussed it here (It was actually more than a year ago). I replaced the springs with standard ones and now have put about 4,000 miles on the car since. It's been fine since, until now.

[Joe C.]

Re: Engine problem with 63 L84

The Fi unit shouldn't have leaked gas into the cylinders, it has an electric anti-siphon valve to prevent this. I don't doubt that some fuel could have collected in cylinder #1, though, from lack of ignition spark (hence the backfire). Whether it was enough to bend a rod, I don't know. The engine seems more out of balance than I ever seen caused by just one cylinder "missing". It doesn't bog or stumble on acceleration, like I would expect with a "miss". I don't know the exact sound of a rod knock, but this could be one.

I'll check the compression, plugs, wires, and inspect the #1 push-rods again. If that doesn't work, I'll also sub-in a good cranking signal valve, though, I won't be able to get the valve from my blue car until Sunday. I have a new extra nozzle-block somewhere, so I'll try to find it.

Thanks,

A dead cylinder will give you a rod knock. Do a cylinder drop test to find the dead cylinder.

[Michael G.]

Re: Engine problem with 63 L84

Joe, thanks, I'll do a drop test tomorrow. My guess is #1....

[Carmen R.]

Re: Engine problem with 63 L84

Hi:

I was having an issue with a rough running engine this weekend. Instead of pulling off ignition wires off, one at a time, I used a timing light to check each wire for a spark. I don't know about you, but I received enough electrical tingles in the past. I don't enjoy them.

Haven't figured out signatures or avatars, yet.

63 L84

[Monte M.]

Re: Engine problem with 63 L84

Mike,

As far as the rod knock goes, it will sometimes even be a double sound. Meaning two quick knocks. Typically putting it under a load will make it loader.

Get a piece of hose three or four feet long.. Garden hose or something a little smaller. Put one end to your ear and put the other end on the intake by the number 1 cylinder. then, move it down to the head and continue down to the block and pan. See if the sound changes. This might point you in a direction.

It is going to be really hard to hear. You can take the fan belt off to quiet it down to hear better. you can run it safe for a few minutes with no water running through the water pump. If this persists, remove the fan from the car and run the belt just on the pulleys. This will allow the water to contine to circulate. You can run it this was for as long as you might need to. This is the best was to reduce noice to be able to hear better what is going on.

Best of luck,
Monte

[Michael G.]

Re: Engine problem with 63 L84

Duke, sorry to make you cringe unnecessarily, but , the rockers are "roller-tipped" rather than full rocker rollers. As you have explained previously, the rollers on the tip are probably are not required, due to the normal tip geometry. I figured that they were superfluous, but didn't hurt, so I haven't changed them yet.

Monte, I've got a stethoscope. When the problem first cropped up, I used it to listen to the valve covers, and plenum and a few other random locations. Oddly, I found that the noise is strongest on the top of the plenum, when I place the scope in the middle, on the drivers side of the flag. I will try the test you suggested.

I can't work on the car today, so will continue my testing tomorrow.

Thanks,