Yesterday, I started my rebuilt 69 460. Started right up, when thru the 2000-2500 RPM break-in for 25 min. and shut it down. Sounded pretty good, but a little off, like the timing or something. Set the timing and it sounded better but it was dark and late, so I said I'd pick it up in the morning.

Started it up this morning to start to tune it and tweak it in. As it starts to warm up, the vacuum starts jumping, and there is a knock but it is random, every now and then, not with the stroke of the engine. I shut it down and pulled the valve cover off the side that was knocking. Turned it over with the coil off and everything looks OK, no keepers off, all valves are compressing and releasing OK, no broken springs, guideplates OK.

I checked compression and am getting about 190lbs. per cylinder. As I pulled #3's plug, the ground of the spark plug was pushed over, touching the electrode. I can't tell if something hit it, the top of the ground is not galled, or smashed, but just a little scratched, not unlike the other plugs. I looked in the spark hole with a mirror and light and what little area I could see, I didn't see anything that looked like something bouncing around in there, no dings on the top of the piston that I could see.

I pulled the pan and no caps loose, busted wrist pins or scored walls. Everything seemed alright there also. I threw a socket on all the bolts for the caps and mains and they were all tight.

There is a chance of course that I smashed the ground over when I was installing the plug. Would this make the vacuum jump and a knock occur?
I really didn't see anything else wrong besides the plug and hate to put it all back together again to find out it something that I should of looked at and didn't.

Is there anything else I could try to look at to find out what caused this, sans pulling the head? What chance do I run by re-gapping the plug and firing it up again? I hate to screw something up by running it to find out what the problem is, but it sure isn't jumping out at me.

Thanks, JD

 

You have 190psi in the cylinders which I would guess means you have failry high compression. Did you check for clearance with the piston at TDC for each cylinder? If the piston is too high, it can smack things in the chamber which of course is bad. On really high compression egniens with domed pistons, you might need to index the spark plugs for orientation of the electrodes while in the chamber. This is extreme and unlikely for a street engine but you never know.

Assuming you did all the right things during rebuild, I would guess you had a plug that was bent when you installed it, either by dropping it and not noticing(we all slip every once in awhile, just yesterday I snapped off the insulator on a plug I was removing plus I dropped one and dinged the electrode, clever me) or you somehow wedged it while installing it.

I would pull the plugs, and rotate the engine and look into the plug holes with a bigth light to make sure there is nothing in the cylinder and also to see if maybe a piston dome is a little too close. If all is clear, I would put in new plugs and try it again and listen carefully for any problems.

Good Luck,

Jim Henderson

 

Iv'e had Champion plugs fail during break-in. the electrodes just bent and grounded out, which will make a dead cylinder and a eratic vacuum readings. I've never had this happen with Autolites, NGK or anything but Champion.

Not sure about the knock, are the flexplate bolts tight?

 

Guys, thanks for the responses.

Update: I just came in from the garage, the rain chased me in and it is getting dark..

I went back through the engine again. First I turned it over by hand and didn't see anything off. I installed the starter and turned it over a few rotations at starter speed and still didn't see anything amiss.

Jim - I had the engine rebuilt by a local engine shop. They set everything up including timing the cam, zeroing the deck and balancing the rotating assy. I would think that they would have noticed something at that stage, but you never know. I hate farming out something like that but I was wrapped up in lifting the truck and installing 1 ton axles and I thought I could save a little time and spend a few extra $$$ to get it done quicker. Now I am having second thoughts.

As far as indexing the plugs, I would think that if one hit, I would see damage to more than one or all of the plugs. How would I go about indexing the plugs? Is there some sort of rubber ring or something that would allow me to put the electrode where I want it? Open end or closed end of the plug toward the valves?

oldhalftons - I have Autolite 45's gapped at .034". One of my friends stopped by and he suggested that the knock could be a result of the grounded electrode, causing a knock, erratic vacuum readings, and running bad. He thinks I'm paranoid and should not have pulled the pan and covers. I think I'm being careful...

I did pull the inspection cover and checked the bolts to the torque converter and they were tight. I gave the plate a good pull at a couple of different positions and could not detect any play, but I couldn't get that much leverage to move it back and forth. I think I could move it enough to see if it had come loose.

All said and done, I don't see anything in the combustion chamber, I see nothing loose, I can turn it over both by hand and with the starter and I hear nothing. I am going to get some new plugs, change the oil & filter, look into indexing the plugs, and (nervously) give it another shot.

I will post back and let you know what's happening. Thanks again. JD

 

The way to index the plugs, or at least one way, is to get more than one set and take a magic marker. Using the magic marker, make a mark on the insulator that indicates where the electrode is. Then take each plug and install it and note where the magic marker mark is. That will tell you where the electrode is in relation to the cylinder etc.

I don't know the chamber configuartion of your engine, but by knowing where the electrode sits, you can figure out if you have interference(in a really tight chamber) or more usually you can tune the engine for a tiny bit more power by setting the electrodes of all the plugs to the "optimum" rotation in the chamber. Essentially you index to "match" a set of plugs and have them in the best flame path.

Indexing is unlikely to indicate a problem in most engines. It is really a tuning trick, but can be used to avoid interference in really tight chambers with domed pistons. To make the most of indexing, you need to know what the combustion chamber looks like. If I recall correctly most people turn the electrode so it faces the incoming fuel air mix from the intake valve. It has been a long time since I worried about this so it would be best to do some reading if you get serious.

Good Luck,

Jim Henderson

 

Update: I put the plug that was damaged back in and the ground was closest to the piston as it reaches the top of the stroke. If I understand this correctly, this is the worst position it can be in for clearance, but the best position as far as burn because that position leaves the gap pointed in-between the valves.

I got some new plugs (Autolite 45's), and gapped them to .034". I marked all of the plugs and put them in until I found one that pointed away from the piston. I then started to swap plugs around until I got all of them within plus/minus 45 degrees of the optimum position.

Put everything back together, changed the oil and filter, and fired it back up.

Let me see if I can explain this right. It starts right up but runs in 15 second intervals with the following two conditions:

Interval 1. 15 seconds with the vacuum gauge jumping from 5 to 15 in. rapidly. No knocking. Running bad, Then....

Interval 2. 15 seconds with the vacuum gauge jumping from 0 - 20 in. same rate as 1., rapidly. Occasional knock occurs during this interval. Barely running. Using a mechanic’s stethoscope, I listened for the knock and is the loudest at cyl. # 3, the same cyl. the plug was bent. The knock sounds like someone tapping on the valve cover with a screwdriver. (This is sounding uglier and uglier!)
It died a couple of times during the test in this interval.
Then....Back to Interval 1.

I pulled #3 plug out and fired it up. It made a steady knock while running but I really couldn't tell anything by the sound (inexperienced ear).

Now I am thinking maybe a collapsed lifter (new Comp Cams), bent pushrod or bent valve. What'cha think? I ran the engine and was looking at the valves operate and didn’t see anything not working or gimping. Is there anything specifically that I can look for? Is there anyway to check the lifter, valve and pushrod without taking the heads and manifold off?

Thanks for hanging in there with me, JD

 

I've never heard of someone having trouble with the piston making contact with a plug in a 460. Unless you have some highly specialized domed pistons, with a really high CR, like 14:1 or unless you had the deck squared and they took off a ton, I just don't see it happening. That being said, I have no explanation for having a bent electrode on a plug, especially for only one plug!! That is strange. I will ask around and see what I can come up with. Have you told your machinist and see what he thinks??? Also, a bent pushrod would not hurt the spark plug. I guess theoretically a bent valve could if it were turned right when it closed, it could whack the plug.

 

Thanks for the info, bigsnag. Man, I hate a mystery! I called the engine shop but it was too late, I'll call them tomorrow from work. I am leaning towards I hit the plug on the installation and by chance, it's the same cylinder that is having the problem.

If one of the lifters never pumped up, would it make the engine act like it is? I will start pulling pushrods tomorrow night and see if I can see anything.

 

Some ideas...

The jumping vacuum may indicate just rough running or it may indicate a vacuum leak in the intake or maybe a valve not working properly. After shutting down, and cooling off, did you retorque the heads and intake? At least on older model engines this was a "traditional" thing to do after firing it up the first time. Some newer engines or methods don't need this.

Another idea, are you sure your plug wires are hooked up to the correct plugs and that your initial timing is pretty close? We all goof every once in awhile and swap a plug wire. This could cause the symptoms you are seeing, except for the bent electrode. Might also be a bad wire, bad distributor cap etc.

You never did mention what compression you are running. The pressure you did mention seemed kind of high, 190psi, but then like I said I am not real familiar with the 460 other than just maintaining the one I have. So are you running popup/domed pistons? With a 69, there is a potential that you are, so that is why I am asking.

What are the cylinder pressures now after having the problem? Maybe something broke in #3 and a pressure check may indicate that for you.

Good Luck, and post what you find so we can all learn.

Jim Henderson

 

Well, I just got off the phone with the rebuilders. They think it's a lifter that is not pumping up or defective from Comp Cams. They said to get some 50W oil and add a qt of 90W gear oil and a can of STP to try to get it to pump up. Does this sound right??? I would think you would want thinner oil to get into the lifter easier.

I didn't retorque the heads or manifold after break-in, the rebuilders just said to start it, bring it up to 2000-2500 RPM and go back and forth slowly between this range for 25 min. Change the oil and filter and I'm good to run it. I think the gaskets they used do not require retorquing but I will ask them directly tomorrow.

I went through the wires three times, using a comp gauge to see cly 1 coming up, then brought up the '0' on the damper, then 15426378 starting with 1 where the rotor is pointing, counterclockwise. The cap and dizzy is a brand new MSD unit with a 6A box. Wires are new Accel 300+.

Compression is 11.0:1, TRW L2443F-60 forged pistons, cam is Comp Cams Xtreme 4X4 FF X4 270H-11 270/278 226/234 554/574, with Crane Energizer 1.7 roller rockers.

The comp has been 190# in all cylinders before, after and during this whole ordeal. My comp gauge will not resolve enough to see a difference between cylinders. It reads exactly the same on all cylinders along the bank that is making noise.

I think I am going to take the valve cover off and watch 90psi of oil shoot out of my pushrods as I watch the valve train. I’ll rig a shield to try to cover the rockers. What’cha think about the thick oil theory to pump up the lifter(s)?

I hope I got my signature working, there’s a link to my truck with more specs on the engine. Here it is unless I didn’t get it…

http://www.superford.org/?vID=5010

Thanks, JD

 

A bad lifter does not explain the electrode on the spark plug. That would be my main concern!!! That electrode getting smashed could be (and probably) is the source of all of your problems. As soon as it gets bent over, that cylinder no longer runs properly. One bad cylinder can cause problems with vacuum etc. BTW, I have never heard of a Comp cam and or lifter being bad out of the box.

 

A wild guess on heavy oil and lifters... Maybe since the engine is "new" the theory is that you don't have a problem with sludging so thick oil will make it to the lifters. Then the thick oil will resist getting squished out of the lifters during operation.

I wonder why the rebuilder is not taking a more active hand in debugging the problem. If something in the cylinder is out of spec or banging around, the damage may increase which would cost them more in warranty, assuming there is one.

Haven't done any serious engine mods in years, but occasionally cams and lifters etc do fail shortly after startup. Could be bad metalurgy, inadequate lubrication, out of tolerance dimensions which slipped past QA. There have been cases of even modern factory cars having bad valve trains early on.

If I had built the engine, I would be getting to the point where I would consider pulling the head and intake and measuring stuff. Try the oil trick and see what happens, maybe you'll get lucky.

BTW, is this engine going to run on street gas? That is pretty high compression for the low octane stuff we get now a days.

Good Luck,

Jim Henderson

 

Just a update:

The oil thing did not work, no surprise. As I fooled around trying to figure out what's wrong, the noise is progressively getting worse. I talked to the rebuild shop and they are going to honor the warranty and come out to my house to take a look.

I will post with their conclusion as soon as they take a listen. I am tired of chasing this problem, I will let them handle it. I should be plumbing brake lines now, not monkeying with the engine.

Jim - I have some Mobil 93 in it now, I really can't tell if it is pinging yet as the gremlins are making to much noise in there. Up the street from me they sell both Sunoco 100 and Av-Gas. I will be experimenting with advance curves and gas options soon (can't wait for that one!).

Thanks for all the help. JD

 

Update: Mechanic just left, stopped to eat supper and post. The shop has changed hands but they are going to honor the previous owner's warranty.

We fired it up after two weeks of sitting and it sparked right up, vacuum jumping from 5-25in., knocking right away. He says it's lower end, maybe a wrist pin. Wants me to pull the engine and take it down to the shop.

I want to take a look and see what happened or at least was is damaged or not damaged before I let him have the engine.

Started to pull the manifold and stopped to check the #3 plug: It lost .022" gap (from .034 to .012). Something has got to be hitting it but there is no scratch marks on it. Hmmmm.....

No bent pushrods

I'm going out now to check the rest of the plugs, pull the lifters and then the head off. I'll go from there.

A couple of ???'s

1. Would a busted wrist pin make the vacuum go nuts? I can see the noise and running poor, but that vac. gauge is jumping!

2. Can I just pull the piston and rod out without removing the engine. The pan came right off and there is a lot of room between the axle and crank, not so much between the a/c housing and head on top though...

3. I would still like to check the lifters. They will be in question until I get them checked somehow. The 'bad lifter' therory is gaining popularity with some and now I would like to test them to rule this out... Is there a way to test them on the bench? Can I just pump them up in a can of oil by hand to see if they're holding pressure?

Listening to it, it sounds like every plug wire is routed to the wrong cylinder and I am running the lowest-grade, watered-down gas in town, and it has a gremlin banging on top of the piston with a ball-peen hammer. I'll post back when I get the head off....gotta find him....gotta find him....

 

loose connecting rod bolts or ?