johnnyz

HELP!!! I've toasted 3 motors already and don't want to toast a 4th. But it did take the 3rd motor going down to find that my oil pan is being sucked dry! I have a 1984 350 Chevy block with 400 heads with everything stock otherwise. The motor is in a boat and at running 3000-3500 rpm after about 20-30 minutes completely empties the 5 quart oil pan. Had great oil pressure until the motor ran dry.

What is the problem? Is there a problem with 400 heads on a 350 Chevy with oil restrictions? I have no idea what else it could be.

We rebuilt a 1981 350 Chevy block with the 400 heads twice. First time motor redone with rebuilt heads, all new bearings and new stock oil pump. Great oil pressure, real low motor temp then all of a sudden the oil pressure dropped and all the crank bearings overheated running 3000 rpm for about 30 minutes.

2nd time, same motor combo (1981 350 Chevy block with the 400 heads) with different crank and new oil pump. This motor lasted 12 hours before #8 connecting rod went out.

Thinking that perhaps the block had a cracked internal oil passage, the 3rd motor had a different 1984 350 short block that was running for 4 years. Put the 400 heads on with yet another new oil pump. After about 30 minutes running between 3400-4000 rpm all of a sudden the oil pressure dropped again. I checked the dipstick immediately and there was no oil. I looked in the oil filler holes in the valve covers and saw some puddles of oil but not allot. After about 5 minutes, the oil was back in the pan.

Each time, the motor was completely disassembled, cleaned completely and put together properly. New OEM stock oil pump with 5 quart pan each time!!!

Any ideas please? Thanks in advanced for your time.

mudmaniac

It sounds like the 1 common part has been the heads, lose them they must have a problem with oil return. That is the only thing that makes sense.

MDTAHOE

The oil return holes in the heads must not line up properly with the block causing a extremely slow return to the pan

old dog

i guess it could be the head's but i would check the retutn holes in the head gasket's ,i have put 350 head's on 400's and vise versa and havent had this problom .except in a badly slugged up engine ,