Hello I am new to this forum. I have a 2000 Dodge Ram 1500 with 5.2l magnum motor. The truck has 286000 miles and the bottom end started knocking. I had purchased a 5.2L from a 2002 Van which I was told was rebuilt at the tech school in St Petersburg, Fl. Now I am unaware how long the individual had the motor on his engine stand but I had it on mine for a little over 2 years covered up. I decided to finish the motor up by putting new double roller timing chain and gears, timing the motor, setting the rocker arms and torqueing to proper specs while timing was set to V8 and TDC. Now I did not check compression before installing motor in my truck ( I know My mistake along with the rest) I was trying to get my truck back up as quickly as possible. I did spin motor over with everything unplugged to prime oil pump but again after I had motor in truck. Although it never did build enough pressure to move the gage. So when I did attach everything back and attempted to start I notice the engine spun over rather freely as opposed to to having good compression. So I checked the compression finding that the compression was only between 55-60 psi on all cylinders. I did attempt putting oil in cylinders and rechecking the compression which did improve to 90 - 150 psi but upon trying to start I run battery down and had to charge it. Here's where everything went wacko after charging the battery I tried to start again and compression was back to 55-60. I have tried spraying seafoam in cylinders for 3 days but no improvement. Now my questions are is there something I missed? Is there anything I can do other than taking motor back out and tearing it back down? Thanks in advanced and I apologize for the length but I am trying not to forget anything

 

Need to re-verify cam timing. If that's good, then, I think you got lied to.... and the motor is a worn out core, not a fresh rebuild. Either that, or whomever did the rebuild didn't do a very good job. The compression jumping so dramatically with some oil in there, leads me to the conclusion that it's just a worn out core.....

 

I would have checked into this! Look a the cylinder walls through the spark plug hole or get a bore scope. If you don't see a fresh clean cross pattern it's a worn out motor.

 

Thank You both HeyYou and Morparite I will check this out. I am leaning to the same although I didn't want that to be the case.

 

Hi Again, Update and more questions. I pulled motor back out of truck and just purchased a used motor and put in it to get me back up. I have since pulled down the motor and found that the reason I had no oil pressure is that there was no pickup tube for the oil pump. I had heads checked they are pulling vacuum and appear they have been rebuilt as it has new valves ,seats, springs. A check of the cylinder walls show fresh cross pattern in each cylinder walls. I have cleaned everything up bought new Felpro Gasket kit and against my better judgement went ahead and put heads on installed the intake, set the valves and turned over the engine to check compression I have only checked number 1 and all I got was 30psi. Here is my question the Felpro Gasket headset has 2 of the same gaskets causing the drivers side to be installed in reverse will this cause my compression issues? as I cannot find anything else wrong visually

 

Were the lifters put in a container of oil and purged of air before being put in the motor? Did you prime the motor like you did before? Verified the cam timing is correct? Just out curiosity what kind of pistons are in it? bowl tops(stock) flat/valve cutouts? Do you know if the block was decked or the heads shaved?

 

Long ago, and far away, a buddy of mine bought a 'reman' engine, only to discover it had rather low compression...... Leakdown test showed it was all going past the rings. So, tore it down, measure things out, and found stock sized pistons in a .060 overbore block. That motor was NEVER going to build any compression.....

 

Hi guys , thanks for the response. Yes I pulled all of the lifters and put them in oil for like 2 days, I did prime the motor as far as I know the pistons are stock and as far as the head and block I honestly cannot say the machinist I took the head to check didn't say if they had been shaved he did look them over and pulled the vacuum. He believes the heads are good but that the valves setting could be the problem only if I was to back off of the bolts and the compression jumped up this was not the case it stayed the same. When I put the new oil pump and pickup tube in I ?did check the tightness of everything it all appeared to be in very good shape. You are right HeyYou, I hate to ask this question I have never down a leak down test what do I need to do this? What about the Head gaskets is this Normal I have never done this in the past with head gaskets? THANK YOU BOTH for everything

 

Need a gauge set, and a significant source of compressed air.... (something not everyone has....) Gauge set has two gauges on it, one is input pressure, the other is cylinder pressure. With the cylinder at TDC on the compression stroke, screw the gauge into the spark plug hole, turn on the air. You will be able to HEAR where the air is leaking out, and the gauges will give you the percentage of leakdown. I like to run input pressure at 100 PSI, so the second gauge is pretty much a direct reading of leakdown. 80 PSI on the cylinder side gauge, 20% leakdown. Supposedly, anything less than 25% is "acceptable", and no more than 10% difference between highest, and lowest cylinders. I like to see 15% or less. Keeping mind, on a fresh rebuild, the rings won't be completely seated yet, so, greater than 20% shouldn't come as a surprise.

Head gaskets are gonna both be the same. You just turn one 180 degrees for the other side of the engine. Should have which side is up printed/embedded on the gasket somewhere. Install them that way, and all should be well.

 

Thanks for this I do have a supply for air I will have to pick up a gage set. As for head gasket set I had to flip the drivers side over with the writing down to get it to seat on the block. Neither side had any writing stating this side up it through me off. I just went out and pulled the timing cover and verified the timing with number 1 cylinder on top of compression stroke. Cam dot at 6 and crank dot at 12 not really sure what else it can be other than rings.