thesiren74
Well-Known Member
Sounds like converter bolts hitting something.
200 psi is way too high for pump fuel, and no way 'carbon build up' will push it up that high. Try another compression gauge first. And an actual 9:1 compression ratio and moderate to big cam won't end up close to 200 psi cranking pressure... maybe 145 psi. So I really suspect your gauge is off, and if so, it may be masking some cylinder pressure variations. You said 'most' of the cylinders ware at 200?
The only other way to get such high cranking pressures is the timing is waaaaay advanced. That would have to have happened during assembly. If the engine has been running OK, then that is not logical (and things won't fail more advanced).
The exhaust note when you went around back is sputtering and fluttering, like the exhaust valves are not closing properly all the time, or some cylinders are misfiring. So if the cylinders' compression are OK (which is still unknown based on those not-logical compression readings IMHO), that points to valve leaks or intake leaks or cam/valve problems. The sound at the end has a distinct miss going up with RPM's so 1-2 cylinders are not firing right at all.
So was this running OK before?
OK, that is all OK and very consistent. BTW, having a new gauge does not mean it is a good gauge. That is why I suggest trying another gauge as a check. For you to truly have those high compression readings, you would need MUCH higher compression ratio, OR the intake valves lifting very differently than they are supposed to (like all the intake pushrods bent or all of the intake lifters collapsed or all of the intake lobes wrecked), or the cam timing advanced a couple of teeth. None of that matches well with the symptoms.When I said most were at 200 PSI, that was just me being lazy. All of them are actually different readings, but all are close to about 200. The lowest reading I had was like 190, and the highest was about 205 PSI.
OK, that is all OK and very consistent. BTW, having a new gauge does not mean it is a good gauge. That is why I suggest trying another gauge as a check. For you to truly have those high compression readings, you would need MUCH higher compression ratio, OR the intake valves lifting very differently than they are supposed to (like all the intake pushrods bent or all of the intake lifters collapsed or all of the intake lobes wrecked), or the cam timing advanced a couple of teeth. None of that matches well with the symptoms.
I am keying in mostly on the exhaust note, which really sounds like a couple of cylinders missing when you rev the engine a bit at the end.
One other easy thing to try: If you have a voltmeter, place it on 'ohms' and measure the resistance of each spark plug wire end to end; for standard resistance wires, they all should be between 3,000 and 10,000 ohms. Sometimes they can get hot and fail and since you had one burn out, the rest are suspect.
Did you observe anything when you looked at the plugs?
Use a stethoscope and poke around on the different engine components while it is running and see which area is the loudest of the knock.
Even check the transmission areas too while running, that sound travels through everything.
Distributor, intake, valve covers independently, timing chain cover, fuel pump, oil filter area, block, oil pan.
Infra red heat temp gun can check the exhaust temps for each cylinder at the header tubes once the engine warms up. If you have a cold cylinder that could lead you to your problem.
Especially if one of your cam lobes started going flat. Need to use the Zinc additives for the high lift hydraulic lifter cams of this era. Today's oils don't have the Zinc, and cams can go flat, especially in a higher performance setup.
Yep, I use a big screwdriver or a 3' wooden dowel... both make great stethoscopes.This is what i would do first! if you have a shop broom, and it has a wood handle, remove it from the brush and us it as your stethoscope. or go to the lumber yard and buy you a Wood Dowel, 1/2 diameter,4-6 foot long and us that as your stethoscope.
How was #7?Ok guys, I just fired it up and got temperature readings off of all the cylinders, and cylinder 5 was a bit lower than the others. with the engine running, cylinder 5 was at about 300 to 350 degrees, while the other 7 cylinders were at about 400 to 450. I don't think number 5 is a dead cylinder, but something is definitely up with it.
are you thinking wires for 5 & 7 are mixed up?How was #7?
Wouldn't be the first time, it's an easy mistake to makeare you thinking wires for 5 & 7 are mixed up?
Wouldn't be the first time, it's an easy mistake to make
I dont know if it would cause the knocking, but who knows
Have not heard anyone talk about what kind of oil pressure you are running at now, at startup and after warmed up. 5 psi oil pressure at idle is not enough although better than Zero. Sounds like a lot of valve train noise in the video, that is the first thing that shows up when you are experiencing low oil pressure.
What does the oil look like when you pull the dipstick and wipe it on a white paper towel. Black and Grainy or clear like brand new oil ??? Next pull the oil filter and cut it open, you can zip around the base of the oil filter 1" up from the bottom and let the can fall off. Have a drain pan there to catch everything that comes out of it, then you can see what it has trapped out of the system before it sends the oil though the engine again. If that filter starts plugging off it will reduce your oil pressure.
Also take a magnet to the paper filter from the inside of the filter to see if it picks up any steel from parts wearing out. Seeing steel slivers in there is not a good thing, and there will be some black sludge in there too.
Can drop the engine oil out too and see what comes out of the pan.
Put fresh oil and a new oil filter and fire it up again and see if things quiet down a bit. If all checks out OK so far but still making noise, you can add 1/2 pint of Lucus Engine Oil Treatment to the oil and try again (the thick stuff like Honey . . like the STP) this should quite things down a bit as a test. Will help you determine if it is internal engine bearings or valve train, or an external item like a cracked flex plate at your torque converter.
Still have not heard that you have checked out that mechanical fuel plump yet, they will still pump fuel with the arm going loose inside sending the noise and rattle all the way down the camshaft and up through the valve train. Just think about the "Beat" of your knock, it is not like a sound that all 8 rods are slapping at the same time. It's is more like a single "Beat" of the Eccentric on the cam hammering the loose Plunger Arm on the fuel pump sending the noise down through the cam and into your block.
Can also pull the distributor cap off and see how much left to right turning distance you have on the distributor rotor. More than stock distance travel when turning left to right tells you things are getting wore out down below there, all the way down to the oil pump and distributor drive gear and bronze bushing in the block.
With the Distributor cap off with the rotor on, you can put a socket with a ratchet on the big bolt on the end of the crank at the pullies. See how many degrees you have to rotate the crankshaft before the rotor on the distributor starts to turn. Clockwise, counter clockwise, see how many degrees. If excessive can help zero you in on your problem.
Also what does the transmission fluid look like when you wipe the stick on a white paper towel, nice and cherry red or dark brown and burnt smelling ?? Could be issues at the front pump of the trans just behind the torque converter, things getting wore out . . . So yeah someone asked what does it sound like when you put it in gear, better or worse ???