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I think you're hedging here. You don't have an occasional misfire (I addressed the number of spark plug firings (pulses) above). Additionally, there is nothing 'occassional' happening here. The sound is repeatable, with a very clear 'cadence'. It happens with very specific regularity and increases as the RPM increases. Nothing occasional occurring.
Yes. Disconnect coil wire to eliminate off chance of starting (and random voltage/amperage). Eric (video) does a decent job of performing a basic compression test. Often times, many of us will perform a dry & a wet compression test. That is completely up to you. But, I will say this. If you're going to the length of performing a compression test, you'll be able to better gauge overall condition of the engine if you perform both a dry & wet compression test (since you're already spending the time to do the dry, it makes sense to do the wet at the same time). Perform the dry compression test on one cylinder. Insert ~1 tablespoon of automotive oil into the same cylinder you just performed the dry compression test - best if you can 'spray' the oil into the cylinder if possible (you will now be performing the wet compression test). Record your readings for both dry & wet for each cylinder. At the end of the day, you'll gain some insight of 'possible' issues you may have w/ (as an example) piston rings. Should the wet compression test indicate a higher compression than the dry compression test, it might suggest piston rings are failing e.g. not sealing (since the oil will act like a seal between the cylinder walls and the rings increasing the compression w/in that cylinder). There are other possible tell-tale signs of engine wear, but don't worry for the time being, perform both a dry & wet compression test on each cylinder recording your findings of each. The numbers can be addressed once you have obtained them.
I see you have aftermarket rocker arms. could one be tapping on a loose valve cover baffle ?
I would try running it with the valve covers removed (messy, I know)
with spark plugs out and not wanting to run engine long enough to get it hotter than blazes and then have to remove spark plugs and burn myself I put it on the chArger. I only have a 2/6amp charger so may take a while
in meantime does that #1 cyl and also location of most loud noise make this look more like a possible valve
I see you have aftermarket rocker arms. could one be tapping on a loose valve cover baffle ?
I would try running it with the valve covers removed (messy, I know)
i checked. The rocker arms are made to clear stock covers. And the interior baffle is good.
is there such a thing as an intermittent stuck valve or any reason an occasional misfire would happen?
what does a burnt valve do?
A burnt valve won't make an intermittent noise like your hearing. You will hear a misfire. You noise, at least what I hear on my laptop does not increase at the same rate as the rpm. It sounds like something external banging together.
The noise (clack) sounds mechanical and IMO does not appear related to the 'pulse' of spark plug firing.
I agree, also, it appears to be slapping against something. Could it be an exhaust valve (you asked) - it's possible. If so, performing the compression test helps to demonstrate if there's an issue w/ the cylinder. I am completely not following your statement regarding getting the engine hotter than blazes. Did you follow any of the videos? You need at the most about 7 seconds of engine turn-over for each cylinder. What you're stating makes no sense to me but maybe I'm missing something in your statement. You can easily perform both a dry and a wet compression test on all eight cylinders with not effects on your battery.
I still believe w/ the greatest of opinion, you need to fine-tune your wood stick probing. You have not addressed what I suggested earlier in Post #38. You realize if someone could CLEARLY make out what this sound is someone would have spoken up. You realize a PS pump rotates and is dependent on the belt to turn the pump correct? Where is it located - on the LH-side (driver's side). If you spin a bearing inside that PS pump, who knows what it's going to sound like? Who knows if or how it might malfunction and what sound it will produce. Have you done the probe yet on the PS pump? Also, I suggested testing the exhaust manifold at each of the exhaust ports. Seriously, you need to address our suggestions to continue to assist. You'll need the engine running, therefore either you put all the spark plugs back in place and start your engine w/o completing the compression test or you can complete the compression test then fine-tune your broom stick probing. 135 psi on #1 is NOT out-of-bounds.
with spark plugs out and not wanting to run engine long enough to get it hotter than blazes
How may I ask, did you follow the videos? Did you disconnect the coil? The engine should NOT be running. Again, the engine should NOT be running. You yourself asked if you should disconnect the coil wire.
I still believe w/ the greatest of opinion, you need to fine-tune your wood stick probing. You have not addressed what I suggested earlier in Post #38. You realize if someone could CLEARLY make out what this sound is someone would have spoken up. You realize a PS pump rotates and is dependent on the belt to turn the pump correct? Where is it located - on the LH-side (driver's side). If you spin a bearing inside that PS pump, who knows what it's going to sound like? Who knows if or how it might malfunction and what sound it will produce. Have you done the probe yet on the PS pump? Also, I suggested testing the exhaust manifold at each of the exhaust ports. Seriously, you need to address our suggestions to continue to assist. You'll need the engine running, therefore either you put all the spark plugs back in place and start your engine w/o completing the compression test or you can complete the compression test then fine-tune your broom stick probing. 135 psi on #1 is NOT out-of-bounds.
i eliminated the power steering pump, alternator and water pump first day. Removed all the belts. If none of them turn then only thing external turning was crank pulley and flexplate. Ran it just long enough off battery that way at a cold start first thing in morning to hear that it was still there.
i did probe entire engine and each port. The video I did not post since the iPhone microphone would not pick up the end of the pole. I tried it on the microphone on front and one on side. It still only hears the same thing As before and background noise was louder than anything coming from pole. In person though I can hear.
From outside and inside the loudest place is always top driver side listening with the pole.
anyhow. I also observed the behavior of the MSD handheld. I noticed the AFR fluctuated WITH the noise. The O2 sensor is on the bank drivers side exhaust. The engine is supposed to idle at 14 AFR but with each noise goes back and forth between 13.2 and 14.0. The MSD seems to be trying to vary the timing and RPM to stabilize the behavior.
If I lock out timing at 15 degrees and check timing with a timing gun on crank to verify that MsD and engine are in sync they ARE and the noise continues. I can also leave timing lockout ON and rotate distributor and lower down to 8-10 btc and same thing. The engine always ran fun with 10 as base timing.
How may I ask, did you follow the videos? Did you disconnect the coil? The engine should NOT be running. Again, the engine should NOT be running. You yourself asked if you should disconnect the coil wire.
haha. Youre right. The spark plugs are ALL out. And MsD ATomic AND the 6AL box are unplugged at battery. if i want to charge battery faster I could put them all back in and start up and let 80 amp alternator charge it faster. But then After that I have a HOT engine. I have to wait for the pokey 6amp portable
My apologies, you stated in Post #1 you removed the AC. PS & Alt belts.
From Post #1 you said:
Started about three minutes into a drive. recently added timing control to existing MSD atomic system. Ran better than stock distributor. Ran great till today.
1) Ran great till today. Can you elaborate on this. How was 'performance' effected when this occurred? Rough engine, stalling, hesitation, misfiring, bogging down, no torque, throttle not responsive? Is there a performance 'issue' aside from the slapping/clacking noise?
2) Have you considered removing the timing control to the existing MSD atomic system you recently installed? How soon after you installed the timing control did the issue develop? What is 'recently'?
I've been following along the trouble-shooting trail, with not any more to offer than already has been. However, the nature of that noise, to me is not TIED to RPM, but RPM affects it. It almost sounds like something hollow, or bowl shaped is being knocked by something that IS tied to RPM. The only thing that comes to me is the eccentric for a mechanical fuel pump that is coming loose from the cam gear. I envision it hanging on by a bolt that is backing its way out, and it is "flinging about' in a constrained manner. Imagine a Pinata being hit with the stick as it circles, tethered, about the person with the stick.
I don't know whether this is helpful, but I'm rooting for the fix! Good Luck!!
I'll note the other thing which strikes me as odd is the fact you have the mechanical fuel pump laboring away performing no function whatsoever - correct? Since, I believe that MSD Atomic has its own (comes with) fuel pump?
Someone suggested to disconnect each spark plug wire one at a time to see if I can narrow down if the sound is indeed a valve not closing and what I am hearing is maybe a misfire into exhaust manifold.
Is that safe? How do I accomplish that? Without getting zapped by the HEI
No. Short the spark to ground instead. I tend to use a 12-volt test light (because the probe is pointy and conductive) slid BETWEEN the distributor boot and the plug wire. DO NOT PIERCE THE PLUG WIRE, just slide the greased tip between wire and boot. The test light does NOT light up. A dab of silicone dielectric grease makes this job go easier.
A small nail and a jumper wire connected to ground would do the same job.
Originally Posted by CuttyShark
Ok went down and bought one of these. It did not say it works on 70s Standard non metric threads. But does say “domestic”.
i am guessing I plug it in each spark port and crank engine with coil disconnected? Or do I hand turn engine?
Plain ol' ordinary spark plugs ARE metric. M14x1.25
The engine is cranked with the starter motor, and a FULLY CHARGED battery, possibly with a battery charger connected, so the 8th cylinder cranks as fast as the first.
Originally Posted by Vintage Chief
Mechanical fuel pump?
Maybe. The knock is too slow for anything turning at crankshaft speed, I think it's too slow for anything turning at camshaft speed. It might be something turning at cam speed, but not directly related to the cam. That'd be the fuel pump, which is only going to really squirt when the fuel pressure drops. OTOH, I've heard a fuel pump knock on my '75 Nova, and it was a lot faster than that.
Truthfully, I don't know what the hell is knocking. I'd be all over that engine with a mechanic's stethoscope.
Am I seeing that Innova compression tester correctly? It doesn't use the nearly-universal "Industrial Interchange" quick-coupler? I thought every compression tester that had a quick-coupler used Industrial Interchange, (Milton "M" style) so that the compression tester hoses, and cylinder leakdown tester hoses were all interchangeable with one another.
Let me guess: Made in China?
Last edited by Schurkey; May 30, 2020 at 05:02 PM.
Right Ken. I was going by an earlier post where he asked if it could be the mechanical fuel pump and didn't notice Post #10 where it was taken off (and, evidently he installed a block-off plate). I just logged back in thinking I wanted to read something again & now can't recall what it was.
Oh yeah, I was thinking about the mechanical fuel pump that's why I logged back on. I was thinking of various scenarios where people have for any number of reasons maintained the mechanical fuel pump as a primary, using the electric as a secondary (basically to fill float bowls) then toggle back to the primary. Others have maintained the mechanical and just ran directly through the mechanical to the electrical; other's bypass the mechanical altogether; location of the electric fuel pump (external or internal to the fuel tank); and, one other which escapes me but is related to the ability of an electric fuel pump coupled w/ a particular type of carburetor's ability to pull fuel at the required pressure in order to maintain proper fuel pressure psi. Something w/ regards to cavitation and I just can't recall. I mean, I really am not certain entirely; but, the mechanical operates at what ~6 psi, and the electric generally around what ~30 psi? So, I'd think somewhere you'd have to upgrade the fuel lines of a mechanical system if you were pulling through the mechanical into the electric (which some have done). Since I don't know how the fuel lines are routed on the OP's system, and he said he removed the mechanical fuel pump, I'd assume he ran dedicated line from fuel tank to electric fuel pump. It's getting late and I'm tired. Oh yes, one other scenario. Aren't there two methods of running this type of electric fuel pump system: (1) no return pressure line (2) and w/ return pressure line?
I don't think it matters a lot but I always hold the throttle open when I do a compression test. I was told that as a kid and that process has followed me around for years. That won't help you find your thump though.
A burnt valve has a distinct sucking sound at the exhaust pipe I don't hear that sound but your paper trick seem to show some movement at the correct timing. I'm wondering (just a guess) if you have a bent or stuck pushrod..... Tedd
PS please let us know if you find a fix this is quite the puzzle.
1. Yes. I took the mechanical fuel pump totally off. It was only ever used to break in engine 3 years ago. It just sit there pumping air in and out. Neither end connected to anything.
2. The probing with broom pointed at 1 or 3 area of the engine. Loudest near top of block just below the Head.
3. once my battery was fully charged again I tried cranking. I heard the noise CLUNK while cranking. Since my previous efforts eliminated the pulley system, the flex plate, and there harmonic bal is free and clear to move with no binding.... and taking each spark plug out revealed the sound is there with or without firing... it is something INSIDE the engine.
4. This morning I started stripping the engine of accessories, throttle body, hoses, drained fluids, removed starter, disconnected flex plate (again checked it and looks fine. No cracks. Put a Engine lift plate on top and I am ready to yank it up and out.
5. I need an engine gantry and trolly system to do this. I borrowed one when I lived in CA but I am now in Central NY. So I am going to local metal sales and fab shop to have one welded up. Once that is ready I can take the motor to machine shop and have a pro rebuild it.
between my own process of elimination and your suggestions I basically make sure it was not an easy fix and I am confident i am doing right thing.
i am crossing country in this motorhome this summer and with Corona i may not have a job in Fall (i work in higher ed) so this MAY end up becoming my home.
Last edited by CuttyShark; May 31, 2020 at 01:20 PM.
Push rod binding on guide plate. It happen on my engine. I had to clearance the guides a tad bit. Look for a sticking push rod running it with the valve cover off.
I'm betting lifting it out of the vehicle was the easy part - getting into the motorhome looks like the real challenge. Happy for you you're moving onto the next stage.
Update: machinist (Blockhead Enterprises in Camden NY) found that the aftermarket ARP studs on #1 were coming out and stripped the threads or something. He will show me when I deliver a batch of parts. Too high of valve spring? I dunno. that was the sound! Glad it was not a rod (knock on wood)
he does not think it will need bored.
he is breaking down the rest of block today.
i ordered new Aluminum heads that have the thicker base studs.
Good Luck!!
