Just installed a new 408 over the weekend and have been battling a low oil pressure condition. Pressure varies from almost 0-15 @ idle to around 40 psi @ about 3K rpm. Did not want to keep pushing motor, have not driven car. Get "Check Oil Pressure" warning light on occasion.

Double & triple checked O-Ring connection. Re-used same o-ring but appears to be in good shape. Pick-up tube to oil pump connection is solid and seated flush. Used old ported oil pump then swapped in new LS6 pump. Installed autometer oil pressure gauge to confirm dash gauge. Low pressure continues.

1) Saw a recent post about a rear oil plug. Did not take notice of plug before install. Have email to engine builder, waiting for response.

2) Someone has posted that 10psi/1000rpm is suffucient. Seems very low to me. I am in that range but shouldn't be getting warning lights if it is ok.

3) If motor was built to "race" tolerances, which may mean larger bearing clearances, what kind of pressure range is normal? Still think what I am getting is exceptionally low.

4) How to remedy problem w/ distant engine builder. I can't take vehicle to engine builder for inspection/confirmation. Recommendations?

At this point I've done all I can think of. I re-isntalled the oil system. Double check connections and torque requirements. Confirmed gauge readings. Using 10-30 dino oil.

Any thoughts?

Thanks for any and all help...

 

no something is wrong, if the pump has been upgraded with the high pressure kit you should see about 65 plus psi on oil pressure at idol.
I remember something about a plug that fits inside the block, with out it in your oil pressure is next to nothing, i may be wrong but i think it is in on the back side of the block. im having a brain fart, i can not even remember the name of that valve, it's ;late and time for bed.

someone else will chime in and say what it is, and where it is at on the block.

 

Somehow you'll need to check to see that the plastic plug was inserted into the rear facing oil galley. Without it, oil pressure is very, very low.

Richard

 

They are right, the plug is most likely your problem. Also remember that there is another one at the front of the block too, at least you can check that one without removing the tranny.
These plugs are for the oil transfer galley drill/machining sites. A company makes a modification that keeps the rear one from pushing out ( there is enough clearance on the rear cover to allow this ). They put a button on the cover that keeps the plug from backing out.
Common issue on the GenIII motors, something an old school builder might not be aware of....

 

After speaking w/ the engine builder, it looks as though I will be dropping the tranny to double check that plug. The part that still still confuses me is that I still have oil pressure although is seems on the low end, but gets up to 40psi @ 3K rpm. I would think is I was missing a plug of some sort, I would be hard pressed to hold any pressure at all.

Either way, I've invested too much $$$ to be lazy about dropping the tranny. It is a PIA, but live and learn.

 

While we are on this subject guys, I was interested in doing a 408 for my truck and if i bore it & will hot tank the block will the plugs get damaged at all ?? Also would someone mind explaining where they are located at in a little more detail not really following where exactly they are located at. Also, if i did a 402 LS2 block do they have the same issues. Thanks

 

The two plugs are supposedly along the same line relative to the motor. As you look at the front of the block, the oil plug is to the right of the oil pump just inside of the front cover gasket. As you look at the back of the block, the plug is to the left of the crank, in-line with the front plug.

I know my front plug is in, but didn't look at the back plug prior to installing the motor & tranny. The back plug is supposed to be white plastic, dumbell or dogbone shaped w/ one side rounded and the other end flat. The rounded end is supposed to go in first and the flat side is what you see at the back of the block.

As far as survival of plugs, I have no idea. But I'll take some pics and have someone help me host them.

Live & Learn...

 

Gregg - do you happen to have a rollmaster timing chain?

 

Big Tex - Yes I do have the rollmaster double roller. I did RTV the shims with the oil pump install. Any other issue with the the rollmaster?

 

Double check that triangular spacer that comes with the rollmaster chain. Physically, its not perfectly triangular and will fit even if its flipped over. If its upside down, oil from the pump will partially flow from the pump right back into the pan. At idle, you'll see really low pressure but it will rise as rpms increase. You may also notice the oil gets foamy.