Cylinders Low In PSI ? (HELP)

[BigDog98]

Re: Cylinders Low In PSI ? (HELP)

OK, thanks. A leak test requires a compressor and a leak test gauge. You probably can rent these things, but you will need a source of electrical power near the boat to run the compressor. Also, be careful when doing a leak test. . . If you don't get the cylinders at their top dead center (TDC) location, the engine could rotate violently when you apply pressure to the cylinder. Also, if you forget to relieve the pressure prior to rotating the engine to the next cylinder's top TDC the engine will rotate violently as well (I've done that )

Valve jobs usually involve grinding the valve edges and the valve seats to get a nice fresh and properly angled surface on each. This type of work is pretty straight forward for any machine shop.

The high psi numbers can mean that there is fluid of some sort in the cylinders . . . Or the gauge itself is inaccurate. Anyway, best to proceed with the leak test at this point.

Yes I have a compressor and a buddy of mine has a leak down tester so I will borrow it from him. Ok so if its a valve problem then i guess i can just take them off and bring it to any local machine shop. And i am aware of the (TDC) meaning when cy1 is on its compression stroke. I was told that i can just jam a screwdriver in the number 1 cylinder and rotate the engine till the cylinder hits the screwdriver and thats how you know if its in (TDC) Correct me if i am wrong. And as far as I know there is not any liquid in the cylinders because when i did the test then i would have saw water or and liquid being pushed out from the spark plug hole. But like i said correct me if im wrong. And based on this you could tell me if its a good idea for me to do the test on my own.

 

[BigDog98]

Re: Cylinders Low In PSI ? (HELP)

How do you adjust valves to get higher compression?
Valves closed at TDC is most compression you can get. Water in cyl can increase compression. I am suspect of bigdog compression guage/technique due to variable readings.

Bigdog: consider getting a mechanic to do leakdown test. Maybe $100 ? Most important to get correct diagnosis at this point. TPenfield is right you could get hurt trying leakdown yourself. in long run, this will save you money by not chasing wrong problem. Just my opinion.

I have a bit of knowledge of how its done by the power of the internet. I honestly thin i can manage it myself because i have everything to get the job done by the power of friends. My main question is if i can do the test with the engine winterized? Let me know

 

[BigDog98]

Re: Cylinders Low In PSI ? (HELP)

Before you do a leak down test yourself if you do, search for threads on the subject and have some reading. It might be confusing if not done before.

Yup thats the plan!

 

[BigDog98]

Re: Cylinders Low In PSI ? (HELP)

we dont know the history of this engine (maintenance ect.) if valves are out of adjustment and not opening all way (exhaust side ) could potenially lead to elevated compression readings.

im just looking at the basics before tearing down and i am buy no means asaying anyone is wrong.

low compression could be anything

i agree a leak down test would definatly be a good next step also may want to try another gauge as was stated before.

also fluid entering cylinder could drive the compression up as was stated earlier

was the fuel disconnected before the test i dont recall if it was.

If im way out lunch and let me know and ill back off

sorry if im causing confusion here

No need to apologize. I understand you loud and clear. I will get all the equipment and then i will do the test. I am just still trying to figure out if i can do the test with the engine winterized? But other then that just stay tuned for the next video and then this one will be more detailed and better. I dont think there is liquid in the cylinders because when i did the compression test there was no liquid being pushed out of the spark plug hole.

 

[achris]

Re: Cylinders Low In PSI ? (HELP)

Yes you can do a leakdown test with the engine winterised...

 

[tpenfield]

Re: Cylinders Low In PSI ? (HELP)

Yes I have a compressor and a buddy of mine has a leak down tester so I will borrow it from him. Ok so if its a valve problem then i guess i can just take them off and bring it to any local machine shop. And i am aware of the (TDC) meaning when cy1 is on its compression stroke. I was told that i can just jam a screwdriver in the number 1 cylinder and rotate the engine till the cylinder hits the screwdriver and thats how you know if its in (TDC) Correct me if i am wrong. And as far as I know there is not any liquid in the cylinders because when i did the test then i would have saw water or and liquid being pushed out from the spark plug hole. But like i said correct me if im wrong. And based on this you could tell me if its a good idea for me to do the test on my own.

Well, you have a timing mark on the front of the engine (harmonic balancer) that will be a whole lot better than the screw driver. The key is to get it TDC on the compression stroke and not the exhaust stroke. That is pretty easy, since the valves will be slightly open on the exhaust stroke and fully closed on the compression stroke. So, if the #1 cylinder does not hold air at TDC per the timing mark, it is a fair bet that you are on the exhaust stroke. So, in that case, you just need to turn the engine 1 revolution with the breaker bar.

The trick will be to get each of the other 7 cylinders on their TDC compression stroke. Fortunately on a V8 engine those points are at 90 degrees of rotation. You just follow the firing order around the engine. I usually put additional timing marks on the harmonic balancer with paint or chaulk to make it easy to rotate the engine 90 degrees to the next cylinder's TDC.

As stated there are articles on the Internet to cover all of the details. Again, be careful . . .

 

[ONEGA]

Re: Cylinders Low In PSI ? (HELP)

I have a bit of knowledge of how its done by the power of the internet. I honestly thin i can manage it myself because i have everything to get the job done by the power of friends. My main question is if i can do the test with the engine winterized? Let me know

Water drained from block, that's all you need to worry about for now.

 

[BigDog98]

Re: Cylinders Low In PSI ? (HELP)

Water drained from block, that's all you need to worry about for now.

what do you mean? I have drained all the water from the block and filled it up with antifreeze.

 

[BigDog98]

Re: Cylinders Low In PSI ? (HELP)

Well, you have a timing mark on the front of the engine (harmonic balancer) that will be a whole lot better than the screw driver. The key is to get it TDC on the compression stroke and not the exhaust stroke. That is pretty easy, since the valves will be slightly open on the exhaust stroke and fully closed on the compression stroke. So, if the #1 cylinder does not hold air at TDC per the timing mark, it is a fair bet that you are on the exhaust stroke. So, in that case, you just need to turn the engine 1 revolution with the breaker bar.

The trick will be to get each of the other 7 cylinders on their TDC compression stroke. Fortunately on a V8 engine those points are at 90 degrees of rotation. You just follow the firing order around the engine. I usually put additional timing marks on the harmonic balancer with paint or chaulk to make it easy to rotate the engine 90 degrees to the next cylinder's TDC.

As stated there are articles on the Internet to cover all of the details. Again, be careful . . .

Ohh ok so for the number one cylinder i should just turn the engine to the timing mark and then each other cylinder i should just turn it 90 degrees from each other by there firing order? And that is how i get every cylinder on there compression stroke (TDC)? Also do you think that i can get the valve cover off for more visibility? Do the bolts from the valve cover usually need to be torqued down after? Thanks

 

[ONEGA]

Re: Cylinders Low In PSI ? (HELP)

what do you mean? I have drained all the water from the block and filled it up with antifreeze.

I mean that you don't have to worry about winterizing the motor which has to be taken apart anyway. Just make sure it won't freeze as we may expect temp drop down at night to low 30's in the area later this week. I wouldn't even bother filling it with antifreeze.

 

[achris]

Re: Cylinders Low In PSI ? (HELP)

what do you mean? I have drained all the water from the block and filled it up with antifreeze.

Ditch the antifreeze, just leave the block empty...

Antifreeze it a waste of time and money, and actually adds to the damage risk....

 

[BigDog98]

Re: Cylinders Low In PSI ? (HELP)

I mean that you don't have to worry about winterizing the motor which has to be taken apart anyway. Just make sure it won't freeze as we may expect temp drop down at night to low 30's in the area later this week. I wouldn't even bother filling it with antifreeze.

Too late for that. I decided that because i never winterized the engine then i should do it this year since we are expecting a very low temp.

 

[BigDog98]

Re: Cylinders Low In PSI ? (HELP)

Ditch the antifreeze, just leave the block empty...

Antifreeze it a waste of time and money, and actually adds to the damage risk....

Too late for that !

 

[achris]

Re: Cylinders Low In PSI ? (HELP)

Too late for that !

No it's not... Just open the block drain plugs and it's gone...

 

[BigDog98]

Re: Cylinders Low In PSI ? (HELP)

No it's not... Just open the block drain plugs and it's gone...

Yea but that would be a waste of 2 gallons of anti-freeze that where 6 bucks a gallon!!
I will just keep em in the manifold and risers for now. We will see if i will need to drain 12 bucks into the bilge.

 

[BigDog98]

Re: Cylinders Low In PSI ? (HELP)

How much PSI do i put in the cylinders and do i only test the bad ones or all the cylinders ?

 

[achris]

Re: Cylinders Low In PSI ? (HELP)

The tester comes with instructions. Up to you if you want to do the good ones... Might be nice to do them all, and have a baseline for the maintenance log...

 

[tpenfield]

Re: Cylinders Low In PSI ? (HELP)

How much PSI do i put in the cylinders and do i only test the bad ones or all the cylinders ?

Many procedures talk about 100 psi, but that may be more than you need and beyond what your compressor might be able to sustain. I run about 50-60 psi . . . still plenty of pressure.

Test all of the cylinders.

 

[jcbache]

Re: Cylinders Low In PSI ? (HELP)

Seems to me no matter what the leak down test shows, those heads are gonna have to come off. Wet test showed no appreciable change. Big question for me would be did you have decent oil pressure before you started all this and did you hear any chicken cluckin' in the pan ( bottom end noise)? Was it smoking more than usual, and if so was it burning oil or was it steam? After the heads are off you can check out the cylinder walls. You'll be able to spot damage from a bad ring ( which I doubt, this is a 350 chevy, not a 2 stroke outboard). If the cylinders look good, you had good oil pressure and no bottom end noise then I bet your problem is in the heads and or head gaskets. Soak everything in PB Blaster for a day or two before you dive in. Good Luck.

 

[BigDog98]

Re: Cylinders Low In PSI ? (HELP)

Seems to me no matter what the leak down test shows, those heads are gonna have to come off. Big question for me would be did you have decent oil pressure before you started all this and did you hear any chicken cluckin' in the pan ( bottom end noise)? Was it smoking more than usual, and if so was it burning oil or was it steam? After the heads are off you can check out the cylinder walls. You'll be able to spot damage from a bad ring. If the cylinders look good, you had good oil pressure and no bottom end noise then I bet your problem is in the heads and or head gaskets.

Well no there was no noise and i always have good oil pressure 40-60psi. or at idle is about 20psi.