396 casting #3855961 no oil pressure

[budd01]

so i have a pickup in my shop with a 396, low oil pressure and a couple dead cylinders, the dead cylinders are 2 and 4 so i'm hoping it's just a blown gasket between them, as for the low oil pressure, it starts at 60 and goes down to 5 and the lifters are rattling , i'm thinking it has the wrong cam bearing and main bearing, can someone help me with what the difference is between the early 396 and later one, thanks, lawrence

[Livrat]

From the code "IVH" it appears you have a 65-68 Impala 325HP engine orginally equiped with a Holley carb
The early Big blocks had a grove in the rear cam journal and rear cam bearing to send oil to the lifters, the later ones the block was groved behind the cam.
Since you said that the lifters were ticking and there were two dead cylinders I would suspect you have a flat cam as big block were not know to blow a head gasket, as for as the low oil pressure since it has 60lbs cold and drops to 5 hot, I would suspect the crank and bearing are just worn out

[budd01]

thanks for the reply, ok i forgot to mention this, the engine pumped most of it's oil out the dipstick tube the day the owner drove it to my shop, when it was installed they used a PVC valve in one cover but just put an oil fill plug in the other valve cover, so i guess the crankcase became pressurised forcing the oil out the dipstick tube, the dipstick tube is an after market unit that goes way down in the pan, that is the reason i'm think a blow head gasket, maybe

[bowtie72]

Now this is just my opinion. The oil pressure problem could be a check valve in the oil pump. I had the same problem with a small block. Had good oil pressure when warm ( high oil viscosity) but after reaching normal operating pressure It went to about 5 psi. (normal oil temp). Fresh motor everything new. Swapped out oil pump problem fixed. Your pressure comes from the pump, not the cam bearings. Every pump has a relief valve set to a pressure or they would never build pressure. Your lifters are ticking because they are not getting enough oil. The miss in the cylinders could be coming from flat cam (bad cam lobes), head gasket(big blocks aren't prone to doing but not impossible). I think a leak down test would be the easiest way to trouble shoot. If you pressurize one cylinder and hear air in the other then a head removal would be in order. If you pressurize and hear no air between cylinders I would check cam. Hope this helps!

[budd01]

heres an update, the compresion numbers are:

1) 125 2) 0
3) 145 4) 10
5) 145 6) 125
7) 145 8) 150

the cam numers are measured at the push rod:

IN EX

1) .210 .215
2) .222 .221
3) .220 .213
4) .220 .218
5) .211 .227
6) .140 .218
7) .208 .217
8) .215 .220

here how i measured the cam.

[dmack91]

On the oil pressure issue, my money is on worn out bearing (either cam or crank). Had SB307 that was "rebuilt" without replacing the cam bearings. Same issue - good oil pressure when cold, but dropped to 5 when hot.

For the compression issue, if you go to a decent auto parts store (I got mine at NAPA) you can get an adapter that threads into the spark plug hole and then you can hook up an air line to it and pressurize the cylinder. Do this at TDC on the compression stroke (both valves closed). With the air hooked up, listen for escaping air. If it comes out of the adjacent cyl, you probably have a head gasket or cracked wall issue, out the dipstick tube would be past the rings (or where the rings should be if they are broken), out the exhaust is a stuck exhaust valve, out the carb is a stuck intake valve, etc.

I had a 460 lose compression. Did this route and found I had a broken valve spring that wasn't allowing the valve to close fully.

Good luck with the diagnosis.

[dos0711]

Keep us updated please!

[budd01]

a little update and another question, as it turned out the main bearings were wrong, the crank had been turned .010 but the bearings that were installed were standard, the head gasket had blown between 1 and 2 cylinders and into the crankcase which caused all the oil to shoot out the dipstick tube because there was no vent, just a PVC so the only way to releave the pressure was out the dip stick tube.

heres my new question, when i went to install the o-ring for the canister oil filter i found it did not want to sit right, so i pulled the canister oil filter adapter, maybe it not really called an adapter?, i found these two o-rings, i want to keep the canister so what do i need to install the adapter correctly?