[yamaha_wv]

Well the problem is i dropped in a junkyard 3.8 out of a 95 mustang. When i first started it up. the lifters were tapping extremely bad but after a couple seconds they continued to build pressure and act normal. Well after i finished putting the car the rest of the way together i went to take it for a test drive but when i started it the lifters kept a steady tap, but with normal oil pressure on the factory guage, but when it reached operating tempature the oil guage went to nothing and the lifters got extremely loud so i shut it off. So i went to the zone and bought a mech oil pressure guage and put it in place of the factory guage just because the factory guages arent always correct. When i started the motor, oil pressure went straight to 100(max on the guage) at idle. i figued when my oil pressure went to 0 was because of the relief valve? and where would i start too look for a cloggage? Also i have a low miles 96 block and heads, could i possibly swap the crank and pistons from the 95 into the 96? the rods and pistons are a different setup. any info would be awsome. thx

[JTs03v6]

The motor should have come with warranty?? If so take it back.
As far as swap pistons and crank...the block will need to be machined. And if they are both stock pistons they will not work because you will need oversized pistons to allow for the block to be bored and honed correctlly.

[stephen]

Normal oil pressure is 40-125 psi with the engine hot and at 2500 RPM.

If the oil pressure is lower than that the engine has major problems.

[stephen]

Originally Posted by yamaha_wv i figued when my oil pressure went to 0 was because of the relief valve? thx

It's possible the relief valve stuck open. It's located inside the engine timing cover on the front of the engine. If you remove that cover you could clean it out and replace the relief valve and spring.