Whats wrong with my motor??

Here are a few things I can think of:

Dead lifter

Arcing spark

Poorly sealed spark plug

Rod knock

Detonation

Tape from a wiring harness or something coming in contact with the fan

Coil arc

Exhaust pipe leak

if its a miss,do a compression check,mine did that when i melted a piston(not your problem),but it would run,coudnt tell from the cam,changed wires and plugs.Did a copmpression check and found a dead whole.You could have a bent valve or something in the head.

Does it do it while in the garage, or only under load (on the road)

Do the old school stethiscope test, it works.
Get a 3' piece of hose (even garden hose will work) while a helper holds your RPM's up, when the noise is present, hold one end of the hose at your ear , and with the other end hold it by each exhaust port, valve cover breather hole, waterpump etc... until you locate the noise.

I went through the same thing, I found out that one of my header primary tubes had a pin hole at the header flange.

coolblue65 said:

good idea, I wonder if Autozone will loan/have a compression guage? have to stop there tomorrow.

IF its something like a bent valve and i have to take my heads off...I will probably end up pulling the motor and building a 347!!

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Thats what i did,I needed a reason to build mine

If she's not available,you could turn the engine over yourself with a screwdriver at the starter solonoid, or a remote starter at the starter solonoid.

coolblue65 said:

hrspwrjunkie- Thanks for all the suggestions, I can cross out several of those things right away, some of your other ideas will require deeper investigating.

spark plugs... were just replaced when i redid the plug wires

Coil arc and arcing spark...wouldnt i see that in the dark? if so then thats not it....if i can't see it in the dark, then how can i look for that?

fan......has nothing to do with the fan, its electric and isn't coming into contact with anything

exhaust pipe leak...its fully welded, except the collector...will check it out but I dont think thats it...the sound seems to be coming from the engine bay not from under the car

detonation...I would only expect detonation under load no??

rod knock...not sure what causes that?

dead lifter....this did cross my mind....how could i check for this?

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Sorry it took so long for me to get back to you...work's keeping me hopping!

Are you sure the spark plugs are fully sealed? Even if they were recently installed, a piece of debris could have gotten in the way of the spark plug, making you think it is tight, but not allowing it to seal. If this is the case, chances are it will be diagnosable in the dark, but may require a mirror to look at the spark plugs from all sides. The tell tale sign is a quick burst of dimly glowing burning gas from somewhere around the spark plug.

You should be able to see arcing, especially arcing powerful enough to make a ticking sound at speed, in the dark. If you don't, that can pretty much be ruled out.

Detonation can occur even without load if spark timing is advanced far enough, but generally it won't start out light at idle and increase with speed as the faster an engine turns, the more advance it requires...unless the rate of advance in the distributor starts slow and increases to a large advance, at which point, about the only thing that could cause it is the distributor initial advance increasing. And, in this case, that sounds like it would be unlikely...but still possible.

Two things could cause rod knock: a spun rod bearing or loosening rod bolts. And a rod knock will increase in intensity as the motor increases speed.

If it is a dead lifter, what would be going on (with the symptoms you've described) would be the lifter was not pumping up which would mean it either had no seal under the plunger or it wasn't getting oil (either due to low oil or a plug in the oil distribution channel specifically effecting the problem lifter). And this too will increase in intensity as the motor increases in speed.

To diagnose the rod knock and the lifter problem, use the stethiscope method people have been writing about in this thread. I personally use a mechanics stethiscope over a piece of wood for three reasons: it can be more accurate because of the size of the contact point of the "feeler", it transmits sounds much more clearly and it is smaller and far more maneuverable allowing it to get into tight places.

I noticed you mentioned that the first thing you did was to tighten the header bolts, but did you verify that the gaskets were good? Even a copper backed fel pro can easily have the corner blown out and no amount of tightening will compensate for that. I have even seen someone install new ones and not realze that a piece of the old one was stuck to the header making an uneven gap. This type of small leak can sound very much like a rod knocking, I had this type of leak for many years, drove me crazy. I finally splurged for a set of Seal-4-Good and have not had the issue again for a few years running now.

Has the engine sat for any lenght of time. 302 and 289 have an anoying habbit of developing a lifter tick on the pass side if not started in a long while. the lifter doesn't fully colapse making it hard to locate. also you can usualy tell the difference between a lifter noise and rod bearing buy there pitch and frequency. Lifters "tap" and rodbearings "nock". lifters tap at half the frequency because the cam turns half the rpm of the crankshaft.

I suspect its a piston wrist pin slapping around. The 289 was prone to this especially when it was souped up.

coolblue65 said:

ok so here is what I got done.....all with no immediate success (except for narrowing the list).

I did the compression test, no cylinder seemed to be to high or two low, the average reading was 135 +/- 10.

So obviously I had to remove the spark plugs to do that test so I made sure to put my finger in each hole to make sure there was no crap in there, there wasn't so I reinstalled all plugs.

Next I turned all the lights off and had my buddy rev up the engine so I could try to look for any arcing- there was none.

I then tried using an old piece of heater hose to locate the sound....the hose started melting on the headers :damnit: but i continued on and I was only able to isolate the side that the sound is coming from, not which cylinder- it is the passenger side.

Pakrat- no I did not replace or even check for that matter the header gasket, just kind of double checked that all bolts were tight-which they were. I have blown a header gasket twice before and this doesnt sound at all like that (I wish it did).

So I am starting to think its a lifter or a pushrod (or even a valve), I have saturday open so I plan on pulling the intake to check the lifters and pushrods. Is there a way I will be able to recognize a damage lifter??

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That's a difficult one. Because of what you say is happening, you could look to see if there is a lifter that doesn't bleed down (by pressing down each rocker until the lifter collapses). But that doesn't mean you will be able to tell exactly because it might be partially pumped, but can't pump up the rest of the way. How deep is the tapping sound? Light and tinny or muffled and low?

An easy way to diagnose a wrist pin or a rod nock is to disable the cylinder. First get engine up to temp and figure out when it makes the noise. Then remove a spark plug wire and try to get it to make the knocking noise. Do each cylinder one at time and try not to get shocked when you pull the right wire you will not here any more knocking and go from there. If it’s a wrist pin or a rod it wont knock (when no fire) because of the lack of force from combustion. hope that helps

Graham