RedRascal

I am disgusted. I build my 5.3L LS engine using a 2007 Silverado engine as a donor. I carefully assembled the engine using new or refurbished parts, used a Melling high volume oil pump and started the engine today for the first time and had NO OIL PRESSURE! I shut the engine down and connected a mechanical gage at a port near the oil filter...still no oil pressure. Did I FU the o-ring connecting the oil pickup to the oil pump? Can this be replaced with the engine in my PU truck WITHOUT dropping the oil pan? Is there any other explanation for no oil pressure other than a leaking joint between the oil pickup and the pump? I would appreciate any feedback if anyone else has experienced this. Thanks in advance!!

RB04Av

Possibly so. It's too dark out for me to see for sure though.

Yes and no... kinda depends on your definition of "dropping"... it's damn near impossible to do it with the pan still bolted to the block (I'd say "impossible" except that there might be some wise-a$$ that will post up that s/he did it) but the pan doesn't have to come "out". If you lower an inch or an inch and a half you'll have plenty of room to work.

Of course, but that's probably the least painful one, the one I'd investigate first.

Somebody posted a scan of Melling's instruction sheet. Actually there are a couple of posts of a couple of scans of a couple of different instructions. The definitive one shows 3 configurations of the pickup tube; the ones that will send you into the weeds if you're not careful only have 2.

Oil pumps all have the same bore for the pickup. There are 3 pickup styles: straight, "tapered" or "flared" depending on which direction you're going in your description, and "stepped". The stepped one is obvious; the outer, larger portion is something like .87" OD, and the inner, smaller section (where the O-ring goes) is something like .84". The "tapered" type has the same quantitative difference; the end of the tube is .87" and it necks down to .84" right past the bead that seats against the pump casting. The straight one is just exactly that: .87" all the way.

The stepped and tapered ones both take the thick O-ring. The straight one takes the thin one. DO NOT try to go by color!!! There are / have been MULTIPLE colors of both sizes, leading to enormous confusion. The important characteristic is SIZE, NOT color. The correct O-ring should be a nice tight fit, with a drop of oil or light smear of grease; it should require a little effort to put in, but once started, should slide in easily. It should NOT just drop in: if it does, you have the thin one where it should be thick. It should NOT stay outside of the pump bore and refuse to go in: if it does this, you have the thick one on it but need the thin one.

I HIGHLY recommend this little doodad right here. Billet BarBell (saccitycorvette.com) Note that the page is improperly named. You may find, with some pickups, that you'll have to grind a flat on one side, because the flange of it is too big to sit next to the tube. Not a real big deal. The other side has a bolt from the factory. I've never seen any nuts associated with it.

The barbell won't cause low oil pressure at the point you describe measuring. It will only allow dirty oil to bypass the filter. One thing that will though, is the oil gallery plug at the front of the motor, right next to the pump. The cam retainer plate is another potential culprit.

Jimbo1367

Forgive me if this has been gone ever already ( didn’t fully read entire post-yet)

did you remove the oil pump? Did you properly align the new pump with shims or alignment tool (I.e. SaccityVetres s tool) ????

I hope you didn’t just bolt it on like a typical SBC or BBC.

RedRascal

Thanks to all that replied. I suspected the o-ring from the beginning and the responses seem to confirm that as a prime suspect. It has been long enough since I rebuilt the engine that I cannot remember the o-ring that I used or, the configuration of the pickup tube. To answer Jimbo's question: Yes, I used an alignment tool and centered the pump rotor utilizing shim stock "as seen on TV".

WE TODD DID

iTrader: (2)

The pan is really easy to remove from the trucks if it's 2wd. Just remove the crossmember under the pan, unbolt the rack and drop it down, and the pan practically falls out.

joyridin'

iTrader: (1)

Since the engine was rebuilt, was the galley plug installed in the front to the right of the oil pump when you are looking at the engine? My machinist removed it and threw it in a bag. I never realized what it was until I couldn't get pressure when priming the engine. If it isn't there, the oil will go through the pump and return to the pan before it ever sees the oil filter.

RedRascal

Sadly, in this case, the engine is in my old truck that has a Fatman frontend which has a solid crossmember.

RedRascal

Good info! I has been some time since I built the engine. I clearly remember making sure the rear "dumbell" plug was in. I don't remember installing a plug up front. It could be that I forgot to do it or it was so routine that it was not a memorable event. I sure hope that is the problem. Thanks for the tip!

joyridin'

iTrader: (1)

How do you like the front end? Is it airbag, coil spring, or coilover? I was looking at the coilover version for the front of my 68 C-10.

RedRascal

I have a 53 Ford F100. I wanted great ride comfort so I went with the Fatman front suspension with air bags and a ridetech air management system . I went back and forth between airbags and coil overs and you would be well served with coilovers. I kept the rear leaf springs using slipper springs on a 72, 9-inch axle with auxilliary air bags for ride height. If I get the engine oiling issues straightened out, I want to try and wear out the 53.

tblentrprz

Did you try to prime the pump with oil through the driver side plug towards the front?

MixedE36

Did you fill the oil pump and prime the engine?

RedRascal

Yes, thanks for the reminder.

RedRascal

Ye, and thanks for the reminder.

RedRascal

Joyridin'
I have spent some considerable thought on the engine since your post regarding the front oil gallery plug. I clearly remember installing a new rear dumbbell plug because I read "horror stories" about rebuilders forgetting to install it. I do not recall installing a front gallery plug. This means it was so routine that it did not create a memory or, it did not happen. I am hoping for the second option. I don't recall having any issues with the oil pickup o-ring and I don't believe that is the problem; however, if the front plug is not the issue, the o-ring will be my prime suspect.

MixedE36

After my build, it took quite a bit of cranking prior to me building oil pressure. I cranked it without sparks plugs to eliminate cylinder pressure. Pulled the fuel pump fuse as well.

WE TODD DID

iTrader: (2)

I don’t believe it would be the pickup oring, but you could easily rule it out by adding 3-4 quarts of oil bringing the level up to the oil pump. See if you have pressure. If you do, you’ll know that’s it. If still no pressure, pull the timing cover off and look at the plug.

joyridin'

iTrader: (1)

As i mentioned, I never gave it a second thought as the place that machined the block pulled it out. He said they pull them out to make sure that oil galley is clean. It made sense, I just never thought about it and the plug is in far enough you don't notice it.

On another note; I bought a cheap $15 12v oil/fuel pump off ebay. I removed the screw in galley plug and plumbed the pump outlet into that galley hole. After about 15 seconds, my gauge showed 50 psi of oil pressure. I let it run until the pump got seriously hot and oil was coming out of the pushrods. I figured by that time, it was well primed.

cmysix

iTrader: (2)

Never had to drop the pan on my LS2 corvette

LS CHEVY II

iTrader: (2)

Not required, just a money grab cash scam to buy shims etc, plus it voids the melling warranty.

OP, sounds like the plug or barb. Sounds like you may know the galley plug was pulled at the shop.