400-2v in my 73 Truck. Test was done after engine was run for about 10 minutes.Exhaust manifolds were still warm to the touch,but not HOT.

Pulled all plugs and had the pedal to the floor as I cranked the engine over. I counted to 8 on each cylinder as I cranked the engine over.

Results are as follows:

Cylinder 1.----90

Cylinder 2.----90

Cylinder 3.----60

Cylinder 4.----100

Cylinder 5.----110

Cylinder 6.----105

Cylinder 7.----100

Cylinder 8.----30

On the 2 low cylinders,I tested them at least 3 times as I thought I may not have the tester fully seated. All 3 times on those low cylinders,the numbers remained the same each time.

What might my issue be,and where do I go from here to repair this issue?

Dont know if it matters,but yesterday I pulled all the plugs out,shot each with carb cleaner as they were all fuel fouled,regapped em and reinstalled.

Today when I pulled em back out 3 of the 8 were sooty black and the rest were nice and brown(normal color)

Put a little engine oil in these cylinders. If the compression comes way up it is going by the rings.

Cylinder pressure is leaking past either the rings or the valves. I would think it's probably running pretty roughly with that much difference among cylinders. Previous poster's suggestion is your next test. Oily plugs, blue smoke, lots of oil usage indicate worn-out rings. You can also do a leakdown test, and if you hear air escaping through the carb, that's an intake valve leak; through the tailpipe indicates exhaust valve leak.
With the readings you're getting, I'd be thinking rebuild.

Well It seems the valves are culprit. I added the oil as suggested,rechecked those cylinders and both of the low numbers stayed the same. Not that it mattered but I was able to muster a high of 70 on the one cylinder and the lowest number remained unchanged.

So is it time for another motor,or would swapping a set of known good heads fix the issue?

Compression is pretty low, but consistent for all but two cylinders. Bring the suspect cylinder to TDC and add compressed air through the spark plug hole. Listen at the carb, tailpipe, oil fill and radiater. The sound of air leaking out the carb is a bad intake valve, tailpipe - exhaust valve, breather - rings, bubbles in radiator - cracked block/head or bad head gasket (unlikely in your scenario). Repeat for other low cylinder. You could also do a good cylinder for comparison on sounds. A poor-mans leak-down test. A pair of heads should fix it for a while if the rings are OK.

Just a small tidbit, but was the battery on a charger during the test. If not, results will be skewed.

No there wasnt a Battery Charger hooked up. Myself and im sure others have never heard of doing a compression test with a battery charger hooked up.

Not at all saying its wrong...Just never heard of this detail.

As I try to locate a set of heads,would it be okay to continue to operate this vehicle? I know my performance and gas mileage will suffer,but will any further harm to the engine come from driving it daily in the condition its in?

You shouldn't cause any more damage. I've know people that have driven quite a while with burnt valves. Just don't drive the crap out of it.

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You shouldn't cause any more damage. I've know people that have driven quite a while with burnt valves. Just don't drive the crap out of it.

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Drove a slant 6 for a year with a burnt exhaust valve with no problems. Valve had a good notch in it by then, but head was repairable.

1975 was the first year that nearly all engines had induction hardened valve seats. If your heads are the original ones from '73 they may have never had hard seats to begin with. I once had an old slant six that I drove with three badly burned valves and it still ran. Very poorly, but it did run. If it were mine and I wanted to keep it for a long time I would consider buying either a set of remanufactured of '75 452 heads or better yet a set of stealth or Eddy heads.

I will refer to my last post on your other thred when you concluded it was a vac leak

I said a "burnt valve"

leak down test is in order along with a valve job

so...am I right now?

Drive it till it dies. Drive the hell out of it you won't hurt a thing. It will be missing and down on power and use more gas but it won't matter a bit how you drive it. It will still miss and be down on power. In fact at higher RPM's it may intermittently pick up those cylinders.

My 1972 340 Cuda was about a burning about a quart of oil every 100 miles. It knocked under light acceleration when the vacuum advance was in. I did wet and dry tests and found the valves were shot. I had similar concerns about an accurate test, and holding the gauge in tight enough. Put refurbished heads on the car, and the oil burning and the knocking stopped. Gas mileage went up and the car had a lot more power.

I was just jokin with ya

got to rule out mech failurs before you tune

Vac leak was a big part of the problem also,you ruled that mech problem out,and the weak cyls showed up a lot better..as it was not the whole fix

It was just a guess,i have had a bunch of old worn out engines

chased a miss for a long time on some of them till I removed the heads and could see the valve

on run the poop out of it,but it can get worse and cause more damage if you want to keep and salvage any of it

a sucked/droped valve is not pretty

did you do the air pressure check and "listen" to it?

I havent done the "leakdown" test yet due to not having access to Air Tools. I have a friend with a Compressor,and plan on talking to him about helping me do this.

Before you do the heads run a can of Sea foam or other top cylinder lube threw the carb. It could be a piece of carbon holding the valve openI recently had a engine with 60 lb cyl run can threw the carb and stunk up the place but she shot back up to 135 plenty enough for a older engine