Dry Compression Numbers

[Dana67Dart]

What do you all think.

273 2bbl standard compression and standard cam, solid lifters, no excess lifter click except on #6 or #8

The engine runs fine, it was rebuilt 28+ years ago but only has about 25-30,000 miles it. One of the heads was pulled 10-15 years ago and a the mechanic commented there was crosshatch pattern on the cylinder walls still visible. Most of the 25-30,000 miles was in the 10 + years before the head was pulled.

#1 110 psi
#2 107
#3 112
#4 120 (more like what I would have expected)
#5 107
#6 110
#7 110
#8 112

They all seem low to me.

I was thinking maybe the rockers were adjusted too tight??? (I have not touched them yet)

Or maybe the rings never broke in properly???

Or is this just old loose engine from the 60s with a below average rebuild?

 

[teringer]

if you have been running unleaded gas without harden seats in the exhaust you need a valve job run a straight edge across the valve tip looking for high ones from sunken ones the exhaust valves will be tight

 

[Marcohotrod]

Was the engine warm, carb wide open, good battery? Check the valve lash, ticking can be loose, not tight. Many of us run unleaded without seat inserts on old mopars.

 

[AJ/FormS]

Maybe a lazy tester?

My 69 FSM says 120 to 150 with no more than 20psi min/max
Other than low, it doesn't look that bad.Actually looks pretty decently even. #4 could be an anomaly.
I would get a second gauge, if I thought the engine was lazy.

 

[Dana67Dart]

My recollection was the engine was cool to cold, (I was changing the spark plugs and hate getting burned on the manifold.)
Compression gauge was new. (my trusty 30 year old one wont seal around its hose any longer)
all spark plugs were out.
throttle wide open.
new battery fully charged.
5 compression cycles per test.
repeated #2 #4 and #5 to verify results


After I got the plugs in I remembered that I should have done it hot and wet to get real numbers but didn't want to pull the plugs again (old and lazy)

 

[AJ/FormS]

I crank until I get at least 2 consecutive same numbers on a warmed up engine; Or until it's only building 3 or less psi, per bump, or there's obviously something wrong in a hole,lol. .

 

[Dana67Dart]

Check the valve lash, ticking can be loose, not tight.

I thought the tick would be too loose, but was thinking if the rest were too tight the valves might not be seating completely and leaking a bit. (but I guess if that was the case I would have burnt valves really quickly)

I'm sure there are no hardened seats in the heads and I'm sure they are the OE heads
Dad didn't replace anything unless he had to

 

[rustycowll69]

you don't wet the cylinders except to verify leaking rings.

 

[Dana67Dart]

One of these days Ill pull the plugs hot and buy an oil can to get a wet measurement.

 

[Dana67Dart]

My 69 FSM says 120 to 150

That's what I have seen on SB fords in the past and what I expected to see

 

[Dana67Dart]

No one has mentioned the crosshatch visible after 10 to 25K miles is that normal?

 

[toolmanmike]

No one has mentioned the crosshatch visible after 10 to 25K miles is that normal?

Normal.

 

[rustycowll69]

No one has mentioned the crosshatch visible after 10 to 25K miles is that normal?

normal is a relative term. that cross hatch was normal 40 years ago, probably(for cast iron rings). Nowadays it's probably more common, but 45 years ago, I had my SB honed with a torque plate and a Sunnen Power Honing Machine to near mirror finish for moly rings. That baby's rings sealed like you wouldn't believe.
cross-hatch can be overrated. It used to be said to be important, but what may be the most important is a straight, consistently round bore for best ring sealing.

 

[stixx]

No one has mentioned the crosshatch visible after 10 to 25K miles is that normal?

In today's modern engines you will still see crosshatch after 100K miles (due to better oil and fuel injection).

 

[moper]

Get some mechanics gloves or the right extensions and do it hot. It's probably fine and you're worrying about test results from an improper test.

 

[toolmanmike]

normal is a relative term. that cross hatch was normal 40 years ago, probably(for cast iron rings). Nowadays it's probably more common, but 45 years ago, I had my SB honed with a torque plate and a Sunnen Power Honing Machine to near mirror finish for moly rings. That baby's rings sealed like you wouldn't believe.
cross-hatch can be overrated. It used to be said to be important, but what may be the most important is a straight, consistently round bore for best ring sealing.

Mopars blocks had a high nickel content and are quite tough. The crosshatch sticks around for many miles.

 

[66jim]

remember to factor in elevation. I see your in northern
Colorado

 

[MOPAROFFICIAL]

"Warmed up" it could pick up 5-10 psi.

 

[QuickDart360]

My 1975 360 out of a chrysler cordoba still had all the crosshatch in all 8 bores!! Being young and dumb had it bored .30 over. For more cubes go figure!!

 

[sireland67]

The real question is how does it run?
If it runs fine, no blue smoke or ticking leave it alone.

 

[Dana67Dart]

The real question is how does it run?

It runs fine, one cyl has a tick I haven't adjusted out, I was just surprised by the numbers. No smoke etc

 

[AJ/FormS]

If they are solid lifters, don't be adjusting the tick out!
There is a spec for lash adjustment that creates the tic. When it stops ticking the valves are in trouble. It should sound like a little sewing machine under that hood with all sixteen ticking
I forget the spec, but if I had to guess; .018int and .023ex,hot, would be a good place to start.

 

[Dana67Dart]

If they are solid lifters, don't be adjusting the tick out!

Yes solid lifter. and yes it sounds like a sewing machine except for one cyl which has a distinctive "I'v got excessive clearance"click and you numbers sound righ to me too. Ill confirm in shop manual

 

[AJ/FormS]

OK good, I was worried for the valves there for a second,lol.