Now that the truck ('90 F150 Super Cab with 302/AOD) runs great I noticed that after it warms up there is an intermittent tapping coming from the distributor. I traced it down with a broom stick (the rockers sound fine) so there is no doubt about where it is coming from.
Have new cap/rotor/plugs and wires.
Not sure if it's the distributor, oil pump shaft or the new cam.
Has anyone ever hear of this?

 

There is a bushing inside of your distributor that positions the rotor shaft. Try to wiggle the rotor shaft side to side. If it does just rebuild the distibutor. You can have a little play like .003 and it is fine. Also look to see if the advance plate is loose. Sometimes the screws loosen due to vibrations.

 

Okay...waiting on new distributor, it was out of stock. I pulled the distributor and found that the top does not have any side to side slop, and the plate was tigh. But there is about 1/8" (perhaps a little less) of slop at the gear end, and a considerable amount of up and down slop. This may be normal and not affect anything, not sure.
So I'm going to try a new distributor because I have found that I have a low speed miss and occasional stall at idle while in gear.
The truck hasn't run in about 3 years so I assumed the computer was just relearning the programing. I now have a little over 100 miles since getting it running so now for more tuning.
It does fine getting up to speed and holding a steady speed of 45mph or more.
So far this is what has been replaced;
upper intake gasket, plugs/wires, cap/rotor, map, water temp, O2 sensors. Cleaned the IAC valve (just a little soot).
So hopefully the distributor rids these gremlins along with that annoying tapping!

 

So far so good!
I drove about 10 miles after warm up with new distributor and no more tapping and low speed miss is gone.
I'll drive it farther later but sounds pretty good with that cam and all these other new parts!

 

ARRRRRGGGGG!!!!!!!
Intermittent tap/rattle still there (now not sure where from) after about a 20 mile drive.
As the tap occurs it also starts running rough at idle and low speeds, upper rpm is great.
When cold it runs and sounds fine.
The change at running temp made me think head or head gasket so I checked the compression, 120 across the board, very clean plugs, no smoke, clean coolant in the radiator and no water in the oil. Water temp and oil pressure are fine.
Now I'm about to give up and spend big $$$$$ to have someone else find the problem. Been repairing my vehicles all my life and have NEVER let anyone wrench on my ride, except for the factory recall repair of the ignition switch, and I'm not a young kid either!
Has anyone ever experienced anything remotely similar to this?
Could it be the valve springs?

 

Gonna throw my 2 pesos in on this one.

If I understand correctly, you replaced the stock cam with a higher lift, longer duration, dual pattern version (along with a reman/new distributor, etc). Also, your problem only occurs after the parts are getting hot (expanding).

I didn't see it in your posts, so I'm assuming that you also replaced the lifters.

If the cam is as I described above, you may have a problem with the valvetrain geometry. I know that you said you were sure that the noise wasn't from there, but the solution may be as simple as a swapping out the pushrods with slightly shorter ones. I don't think coil bind is a candidate as you would have seen more severe problems by now. Other thoughts include a valve sticking in it's guide, excessive camshaft sprocket runout and/or chain problems and valve spring retainer/rotator sticking and/or binding problems.

If this engine is fuel injected, you can rule out the fuel pump or fuel pump arm against the cam sprocket eccentric theory as well. The last item is the oil slinger rattling or any other part of the crank/cam sprockets touching the timing cover after things warm up.

That's it in a nutshell. I hope this is of some help to you.

Regards,

Jim

 

I have a crane cam in a 300 6 and it does the same thing. I am not sure why, it seems to run FINE, but the distributor sounds poor.

 

Great idea's!
The cam runout was fine when installed. Then chain and gears are new as well. I'll check the geometry next.
Not sure what the oil slinger is though.
I'm thinking it's in the valve springs because I did not change them. The reason for the initial teardown was because the water pump went out in the early stages of a 400 mile trip and the temp guage didn't read the overheating problem. LONG story short; The motor shut down on the highway and wouldn't hardly run. Pulled a valve cover and saw a bent pushrod. So I decided to replace the cam/lifters/pushrods and timing set but didn't replace the springs. Hasn't run right since.
So next I'll attempt to replace the valve springs with the heads on the motor.

The cam specs:
Gross valve lift: 448 in. intake/472 in. exhaust
Lobe separation: 112 degrees
Duration at .050: 204 intake/214 exhaust
Advertised duration: 270 intake/280 exhaust

Not too much larger than stock, it should run fine.

 

Hi again Moneypit:

The oil slinger is a dished washer that resides between the crank sprocket and the harmonic balancer. Your engine may not have it and I don't think it would cause your noise problem.

The bent pushrod and the apparent overheating problem are intriguing. I'm speculating that the valve and/or rocker arm associated with this cylinder suffered some heat-related damage to cause this. Were there any other bent pushrods or other damage to any other parts when you swapped out the cam? Did the original timing set's marks line up properly before you took them off?

Again this is speculation, but it's possible the valve/guide under the bent pushrod got too hot, binding occurred and now shows up as the noise when the engine warms up. A vaccum gauge may help confirm this when the engine starts running rough. Also, if the rocker arm associated with the bent pushrod was damaged (warped/bent, etc), it could cause some clearance problems too, leading to the noise.

The valve springs could definitely be weak from age and being overheated as well. I hope there was no other cylinder head or other damage as a result of the pump going south. Your compression readings seem a bit low, but I don't know what the compression ratio specs for that year engine and operating altitude are.

Correct preload on the lifter plunger should be about 0.030 to 0.040 inches with the lifter on the base circle of the cam and the rocker arms torqued down. Don't know if your engine has adjustable rocker arms, but that would be great as you could adjust them with the engine running and maybe solve your problem.

lastly, check for a possible exhaust leak around the exhaust manifolds, since they can cause a similar tapping noise when warm.

I'm curious what you find. Hope it's something simple.

Regards,

Jim

 

No other bent pushrods and the timing marks linded up to the TDC for the #1. Nothing else seemed out of the ordinary.
I tried hooking up a vacuum gauge at the top of the manifold, seconds after getting a 22 reading the motor dies as if it were choked, unhook it before it dies and it stays running. Still digging......


I am waiting to get my tax refund then I will buy a new set of Crane rollers and valve springs for about $250. If that doesn't do it then a set of GT40P's are next.

 

Now this is gettin interesting!

Have you tried pulling any codes from the computer?

Also, was the noise the same, better or worse after swapping distributors?

From your last post, it sounds like you had the vacuum gauge hooked up, motor pulling about 22 in Hg, motor starts to die, hose pulled off fitting creating vacuum leak and then the motor recovers. Is that an accurate description?

Where were you reading the vacuum signal from (the multi port fitting on top of the manifold near the throttle body?) and did the motor run better after you pulled the hose off than while it was hooked on there before it started to die?

I love a good mystery!

Jim

 

I had a code for the MAP sensor which was replaced but no new ones. The noise is exactly the same as before the distributor swap. Yeah I pulled the single vacuum line from the tree at the top and it does run better, with the higher idle.
I just got back from a long drive and got the knocking going pretty good and traced it again, to the valve cover, right above the pushrod that was bent (#5 int.). I'm fixing to pull that cover again and have a better look at it now that I know where it is coming from. At least I don't have to pull the manifold to get to it!
I just hope it's not the head.

 

Hello amigo

From everything we've talked about, it sure sounds like #5s valvetrain is the culprit. When you pull that valve cover, I would look for a galled rocker arm pivot ball, bent or partially pulled out rocker arm stud, cracked or broken valve spring(s) and/or retainer(s). Lastly, it would be nice to know if the valve(s) move freely in their guides without too much side to side sloppiness (tougher, I know) and whether the valve stems are bent or not. Of course, the rocker arm itself where the pushrod sits and where it contacts the valve should be thoroughly inspected.

If you can safely run the engine with the valve cover off, I'd be curious to know if that cylinders pushrods rotate "normally" and whether the rockers are getting oiled as well as the others (with the noise present).

I realize, after reading some of your responses to other posts, that you obviously know your way around a motor. I hope that one of these suggestions help you find the problem.

Good Luck!

Jim

 

Now not too sure where the noise is coming from. Pulled rocker cover today and inspected the rocker that had the bent pushrod. Has some wear under the fulcrum and an offset wear pattern at the pushrod dimple, no other marks. Swapped that rocker for one at the #8 cylinder to see if the noise moves then would know for sure if it was the rocker. Well the noise is still at the rockers for the #5 cylinder, AND at the upper intake manifold, where it mates to the lower between the 2nd and 3rd runner!
Possibly an injector?
When an injector goes south can they make a knocking after warm up? At idle it's just intermittent, at a steady elevated rpm (1500 or so) it is constant.
Is there a way to test just one injector for this?

 

You may be on to something.

Yes, injectors can make a slight ticking sound when operating. If one was to go bad, it could explain the noise and operational problems (maybe more than one is contributing to the stalling). As for testing it, I don't know of any other way than removing it and bench testing (flow/operational tests). I know that the electrical circuit to them can be tested with "noid" lights and some other hi-tech equipment, but as for the mechanical condition of the injector, the only other way to check would be to substitute a new or other known good injector. I'm crazy enough to try and take it apart and see if I can fix it!

Man! I hope that's all it is!. Maybe you can swap it with a nearby injector and see if the noise moves. Since you didn't have any other codes show up, I guess you can rule out any vacuum leak gremlins around the manifold(s), even though I can't see them causing the noise.

Stay with it!

Jim