whats the proper way to get the most accurate PSI reading from a cylinder? How many times should the engine be cranked around? or do i keep going until it stops at the highest psi? tried reading the instructions but it doesnt really say much. Also.. Whats an ideal PSI average for a stock 305 engine?

 

I'd say it should only need 3-5 pumps, but I wouldn't be surprised if it needed as much as 7. They say to do the check while the motor is warmed up, but I've never seen a difference in cold readings. Biggest thing is to have a good battery and/or charger hooked up while doing the testing and have the throttle open as much as possible. Compression ratio, cam, and altitude change the actual reading you get, but I'd guess it to be in the range of 180-210psi. Ideally all cylinders read exactly the same, but they will vary. You could put some oil in a cylinder, preferably to coat the entire cylinder wall, and see if it reads higher. If it does read higher with extra oil, you probably have yourself some blowby.

 

So i just keep turning it over until it stops then? thats what i did one 1 cylinder as a test run and it read 178 or something.. I was like WTF because i thought it was suppose to be around 120 or something. I just got the battery charged so thats all good.. didnt hold the throttle open though

 

I'd say crank until it goes no higher, but take note of how many cranks each takes as they should all be within at least one crank to get the same reading.

 

before starting, remove all 8 spark plugs, and have the battery fully charged.
In reality, you'll see pressures below 180. If you're seeing 140s, fine. Especially if you live at higher elevation. Anything under 100 is trouble.

 

Alright.. So i removed the spark plugs.. 2 of them had the milky oil on the tips.. so that meant there was oil in the cylinder... so those 2 worried me the most.. so i did the compression test on 1 of them and it came out at 170ish.. So is it possible for the water/oil mix to get into the cylinder with a blown intake gasket?

 

Milky oil on plug is usally a blown head gasket or cracked block/head.

When doing a compression check you should get about 70% of total compression on the 1st crank and crank it a total of 3 compression cycles.

Total compression number depends on your pistons/heads/cam but all numbers should be within 10% of each other.

I just tested my 383 stroker after 3k miles on it and my numbers were 175-180 running 10:1 pistons. Most stock motors I've tested run around 155.

If you have heavy carbon buildup on a stock motor or some milky goo that stuck in the cylinder your numbers will be higher.

 

I did the 2 cylinders that had the liquid in it and compared it to 2 other cylinders i did..

Here are results ive got so far.

2 liquid cylinders: c.6: 170 psi c.4: 160 psi

and the other 2 random cylinders i did: c.1: 165 and c3: 167ish

The stuff in the 2 cylinders wasnt milky.. It was actually water/coolant because some of the water got sucked into the compressor hose and i emptied it on my hand it was infact coolant.. no oil.

Im going do the rest tomorrow because it got dark on me

 

How does your oil look?

You shouldn't have any coolant in the cylinder.

If oil is ok you might get away with just a head gasket change. The 4 numbers you have so far are pretty tight. Pull the head to see what's going on.

 

I posted my problem in another thread.. but ill just re type it here..

The other night i was putting the car back together after a valve seal change.. I put all the plugs in but didnt tighten them.. so they were all loose.. i wanted to see if there was any knocking or whatever from the valves.. While it was running.. i noticed the color of the oil while i was adjusting the valves.. it was a light milk color.. i instantly went and turned off the car.. in the 30 seconds or so i had it running.. it completely drained my whole coolant overflow tank and radiator which was full to the top of the cap.. It all went into the oil.. Didnt overheat or nothing..

Thats what made me do this test to begin with because i wanted to see if there was a head gasket problem because people have told me it was the intake manifold gasket

 

I redid the 5 cylinders with all the same resolutions..

C1:165
C3:142(ouch.. but i believe i know why its low)
C4: 160
C5:154
C6: 165

I believe the reason why C3 is low is because when i did the valve seals.. the rope got stuck in the cylinder..I cut the rope and burned it out.. Its still probably in the process of clearing out.. and the ring is probably stuck because when it runs.. it runs kinda rough then runs fine once it warms up. So far 3 spark plugs have been coated in burnt nylon because of that.

hmm.. I will do the other 3 tomorrow

 

Now that i looked at some other peoples compression results.. my lowest compression psi is higher then some other peoples highest compression number..

Not too bad for a 220k engine...

So far.. Do you think the head gaskets are alright from the numbers?

 

Alright.. So i only got 7 cylinders because my battery started to die and i was getting compressions like 90 when last night it was 145

Heres what i got:

Driver Side:
C1: 165
C3:143
C5:152
C7:155

Passenger:
C2:155
C4:160
C6:155
Battery died for C8

Lowest one was C3.. I explained that a few posts up.

Alright.. Would this indicate a blown head gasket? Tell me whats up.

 

If you blew a head gasket, two cylinders next to each other would read low or at least that's the most likely happening.

 

Here's what you can do. Take all the rockerarms loose so the valves will be shut. Take the valve core out of the compression tester hose and screw it into the cylinders you suspect a problem with. Hook an air hose up to the compression tester hose (it should click right on) and listen for where the air is going. If you hear it in the radiator you have a bad head gasket. Chances are you do.

 

I dont have access to an air compressor at the moment..

there wasnt any 2 cylinders in a row with low readings.. Dont head gaskets usually blow after overheating? and doesn't the coolant leak slowly into the oil? The radiator and overflow tank were completely drained in 30 seconds into the oil.. It started and ran just fine afterwards. The symptoms for a head gasket dont match up right to me.

The previous owner loosened some of the intake bolts but didnt torque them down right.. He just used a regular socket wrench.. would that cause anything?

 

Did you lose all you coolant right after installing the intake?

Intake water leaks can but don't always go into the cylinders.

To lose coolant that fast it's more likely that your intake gasket is leaking.

You can have a blown head gasket and only 1 cylinder reads low but that low should be less than 100.

Try pulling the intake and look at the intake gasket. If that's the problem you should be able to see it. Plus you can clean any of the milky goo that's still there.

Have you flushed out the motor realy good since making a milkshake with the oil?

 

That drastic of coolant loss could be a crack inside the engine too. You could hook up a coolant pressure tester to the radiator and do the opposite of what TylerP suggested. Pull all the plugs out and have a listen.