I have a head scratcher to run by the forum. As many of you may remember, I had an issue last summer where I had a couple frost plugs on my 77 CVX20 Jet (with 460 ford) that were rusted out and leaking water rapidly into the bilge. Some of the local club members were gracious enough to help out with getting the motor pulled and new frost plugs put in, last November. In the process, we also put in new spark plugs, new valve cover gaskets, had the exhaust off and cleaned all the sand and muck out of the water jackets in the motor, changed the oil & filter, and installed a remote oil change kit. Didn’t change out the plug wires, cap, rotor, or points – just put in the new plugs.
A couple of other things to add – the floor was replaced over the winter and that was a dusty and dirty process that the motor was exposed to, since the engine cover was off. A new in-line fuel filter was put in place, as well as an in-line fuel shutoff value (neither of these were in place before). Also put in a new audio system, and new carpet. I don’t want to leave out any details, as more info is hopefully better in trying to figure this out. Boat had not been out on the water since last August, and was put away with a full tank of gas from August which was given some Stabil last October or November, at winterization time.
Went out for the first time this year a couple weekends ago, with Jim Barrett on Lake Mtka. The boat idled pretty well, but I could detect a little bit of a Miss in it. The first big thing I noticed was that the boat was slow to plane, and I could only get about 40 mph (not the normal 60). I could only get about 4000 rpms also, not the usual 4800 – 4900. Later in the day I was also starting to get an odd 'knock' type sound when trying to get up on plane. Sounded to me like something hitting the inside of a valve cover??? That happened about 12 – 15 times probably - just a single knock at a time, over the final couple hours of our outing. Toward the end, I did not want to risk any damage and I just idled back to the boat ramp. The boat was fine at idle, it just didn’t like being under load later in the day..
This past Friday, I was doing some diagnostics and noticed that the 3 & 4 cylinder were reversed in the firing order (#3 wire was going to #4, & #4 to #3). I changed those wires on the distributor. The other thing I noticed was that the manual indicates where the #1 cylinder is on the distributer (rearward middle connection), and the direction that the distributer turns. So at that point you can know what wire is going to the #1 cylinder, and just follow the firing order around to make sure all is correct. In my case though, my #1 wire was 2 ports over on the distributor from what the manual says is supposed to go to cylinder #1. Not sure how that can be, but all I can say is it has always run perfect and nothing has ever been moved since I’ve owned the boat (8 years).
So, Saturday afternoon Jason and I go over to a local lake to test the boat (with the 3 & 4 wires the way they should be in the firing order). I has also drained the old gas and put in a fresh tank of new gas, just incase. The boat idled fine, but when you attempt to plane and put any kind of load on the motor, it starts backfiring right away. Jason checked the timing and determines that it is at 30 degrees BTDC, rather than 10 degrees like the manual recommends. Jason loosens the distributor hold down screw and tries to adjust the timing to get it to specs, but the distributor is stuck, and doesn’t want to move. We hit it with some liquid wrench, but nothing doing – it is stuck. The distributor is aluminum and the thought is that the unlike metals (dist & intake) create a reaction that contributes to the distributor becoming stuck. I Googled the issue, and there was quite a bit written about people having the same issue as mine. General concensus was to hit it with lubricant (like PB Blaster) for as much time as it takes to free it up, but not to reef on it to break it loose, as it will break off and you will have more issues.
So we left the lake thinking that the timing must be the issue. Jason emailed me this morning, and I will just insert his text here: “I did a little experimenting with my old Mercury Montclair yesterday. It has a 390 Ford V8. It's a different engine than the 460 but has the same firing order and timing spec (10-14 BTDC). Anyway, I changed the timing from 10 to 30 to match your boat and it actually ran smoother. So, Even though your timing is off, I don't think it's causing the backfiring and ruff running we were hearing. Especially since we never moved the distributor in the first place. It would still be nice to get the timing right, but I think there must be something else off. I also swapped the 3 and 4 cylinders to match how your engine was. It still ran ok but was ruff. I didn't rev it up but I did not hear any knockingâ€.
This certainly seems to make some sense that the 30 degrees doesn’t matter, since it always ran fine before, and we never changed the timing (the dist is stuck and wont move).
So I am now turning to the forum to see if anybody has any great insight or ideas as to what I may be experiencing. We never touched the distributor last year when the motor was out, just put in new plugs and labeled / re-connected wires to them. Obviously it ran well with the timing where it was, and with the #1 wire moved over 2 spots (not sure what to make of all that). Could be a bad plug perhaps? Cap, rotor, & points have been on there since I’ve had it, but I was taking the approach that if it runs well, don’t mess with it. New fuel filter put in-line, why would that matter. Carb is a large Holley, and was rebuilt professionally a few years back when I was having some vapor lock problems. Mechanically all looks good with the carb – choke seems to be functioning fine and the secondaries seem to open fine when giving it the groceries. Plugs in at least 4 of the cylinders are really hard to get to with the motor in, and the exhaust connected. So they have not been removed to look them over. I am really at a loss. Jason or Jim, please throw in any additional details I may have missed.
Did somebody perhaps steal my good running 460 at the Mpls boat show, and put one in it's place that had problems?
Sorry for the length of this, but it has turned into kind of a long story. Thanks for any insights or ideas you guys might have.
