I have read many forums on here and other places trying to locate my problem. I know this is an issue that has been covered over and over but my situation seems somewhat unique. Thank in advance for any help. I have built 10 or so of these now and kinda stuck.

Sent my lm7 to the machine shop for a refresh. They tanked the block, honed the bores, all new bearings, and rings. Gapped .028/.028 for my turbo application. While they had it I told them to assemble the shortblock for me, so I picked it up with no front or rear timing covers, just crank and rods torqued. Standard clearance bearings all the way around.

I bring it home, install new cam and thrust plate. Reused timing set and oil pump. Added the windage tray and pickup tube. 100% sure I used the correct o ring and it went in smooth with no problem. I filled the pump with assembly lube as I always do. New gasket on front cover. Put a new rear main seal in the back cover, double checked to make sure the barbell was there (it was). Reused lifters from another engine I had that had cracked a water jacket. They looked great. Finished up assembly and put it in the truck.

I am running the turbo oil feed off of the oil cooler location, using the stock style block off plate that I drilled and tapped for 1/8” npt. Just set the engine in without mounting turbo or crossover. Took the oil feed line and ran into a jug and have a mechanical gauge ran from the original oil pressure sensor port. Pulled spark plug and spun it over to half *** prime it. Put the plugs back in and finished wiring so I could crank it for first time.

Engine fired right up and never built oil pressure. Ran for 10 seconds or so. So I check the feed in the jug, not a drop. So I added a quart over fill and let it run for 15 seconds. Nothing.

I pull the oil cooler feed plate off, and fired it up. Oil gushed out of the left hole on the port. Seems like really good pressure. Made a large puddle in the 3 seconds I let it run.

I’ll add that it hasn’t leaked one drop of oil anywhere up until I pulled that plate off. So wherever the leak is (if there is one) it’s leaking out and returning to the pan.

If I have good pressure at the filter but not at my gauge, common sense tells me the issue is somewhere past it. But my issue is I’m not getting one drop of oil from the oil feed line to the turbo. To pressurize that line I’m guessing it will have to build pressure throughout the whole motor? If the barbell is in place, where could 30psi be leaking out? Either way I’ll be pulling this thing back out.

thanks for any help.

 

Is the barbell installed?

 

yes it’s there.

 

Is the little freeze plug installed on the front of the block?

 

Yes, machine shop put a brand new one in. I double checked

 

I'm not exactly sure if this is correct but I believe the block off plate is between the oil filter inlet and outlet. Maybe a clogged filter or something like a plug in the theaded tube for the filter, or even barbell in wrong/seal pinched..?

Maybe look real close at the oil filter and inlet and out let.

But still doesn't really make sense oil would pour out the block off but not come out a small hose attached to the block off unless it's just making just enough pressure to flow out a big hole and not a smaller hole (line)

 

Can also pull the plug out of the front of the block that is closest to the oil pump and hook up a gauge there to confirm if youre getting any pressure.

Could also be that the oil pump is cavitated. Had that happen a few times and had to rev the motor to get it to start pumping. Have had it happen with a couple oil pumps and one power steering pump over the years.

 

I saw a guy on here once who drilled and tapped the factory block-off plate where oil cooler goes, and put a fitting there...maybe oil lines to turbos...don’t remember. The fitting went in practically all the way to the back, blocking off oil flow from the engine. Took him a while to figure it out, basically same scenario as what you have here. Worth a shot.

 

thts what I’m saying. The issue must be after the oil filter because it’s not building enough pressure to force it into the feed line. As soon as I get home I’m gonna jump back on it. Pull the motor back out.

I thought maybe the lifters aren’t pumping up but that wouldn’t cause a 0psi situation I wouldn’t think? For as much as I’ve left it idle, I haven’t heard any knock or funky noises. Which it’s open headers so there’s that

 

just fire it up and crack the throttle a few times with no oil pressure? I’m super nervous about it but willing to try anything. I’ll be pulling this motor more than limey anyway

 

Drain a quart or 2 from the tank. Then plug from the front side of the block. Hook uo a long hose and funnel and feed the 2 quarts in there. Or get an oil priming adaoter for the spin on filter (kent moore has it) and pressure feed it with an electric pump.

 

I hear you but yes sometimes you have to do that or you need to prime the oil pump through the oil gallery plug up front so that you don't have to rev it.

You need to do the idle rev/flair right after starting it right when you see no psi and there is still assembly lube all over everything. If you've already ran it a bit I would be a little nervous about revving it too. But when I have had cavitated pumps it didn't take much of a rev, just a light rev to get the pump to suck up enough fluid to seal the internals of the pump up enough to make it start functioning properly. Having oil on the pump gears seals them together to allow the pump to suck up fluid. Sometimes they get dry and the pump won't suck up the oil.

 

It takes about 30 seconds to fully prime the system and could be up to a minute before its circulating throughout the engine.... Just food for thought...

 

preciate your input. I let it run for over 30 seconds to make sure I wasn’t losing my mind and worried about nothin. Still zero pressure. So gonna yank it back out and go from there. I’ll update for those interested

 

Definitely let us know what you find

 

Can u actually cram the barbell in backwards? Didn’t think it was plausible but now I’m wondering.

 

Technically, I believe you can, never tried it but that I'm aware of the passage way is the same diameter all the way in and the barbell is the same diameter, so it could technically go in backwards.

Here's a couple of diagrams with the barbell and can give you a better idea of what's going on in that area. I'm not sure if it being in backwards would affect anything or not, or what it would do. Never ran across that one.

 

thanks for the diagrams, and the help. I didn’t think it was in backwards. But had to ask. This is frustrating no kiddin

 

What oil pan do you have on the engine? If it has the check valve in the pan that could be the problem.

 

Alright, pulled the motor. Barbell is there, and installed correct

the little oil galley plug next to the oil pump is there, too. All external plugs are there

right before I pulled it I removed the filter. Spun the engine over with no coils plugged in and oil came out of the port that fills the filter. I had an extra set of hands to bump the starter over while I watched. Oil did come out, though I’m not sure if it looked like a strong flow. I can’t say much for the oil past the filter, I just know my mechanical gauge still has read 0psi @ the stock sensor location at the back of block and my turbo oil feed still hasn’t put a drop of oil into my bottle.

Since I can’t find a glaring problem, while it’s out I’m gonna go with a standard volume melling pump and O-Ring, as well as lifters.

maybe the bypass on the pump is stuck or it’s just worn out causing a low flow situation. Don’t know