I have a 1998 5.7 vortec motor (that has had the block swapped for a 383 stroker. ) and i am having a power loss issue. Once up on plane with no issue i can hold her there for a few minutes then she looses power (probably 40%) and at the same time the alarm sounds. Its a 4 bbl carb motor (changed from 2 bbl when sroker block installed). All guages read fine. I also just discovered that my oil dipstick was spitting oil out of the top pretty bad. Can a loss of crankcase pressure cause such a loss of power and also set off an alarm. Oil pressure stays at around 40 all day.

any insight greatly appreciated.

Thanks

Brian

temp stayed down. oil pressure stayed up? u need to find out why alarm sounded. u sure it isn't fuel flow? check pick up in tank.

Sounded like fuel psi at first, and then read the oil out the dipstick deal.

Assuming it has the stock Merc crank breather set up on the vc's, then I would say check compression. Sounds like the motor may have a ring/piston sealing issue.

You have the classic symptoms of such, so again, ck your compression.

Compression is good. 180 - 185 in most. Two fronts a little closer to 190. There's probably only 150 hours since new stroker block so internals should be good.... I also thought about fuel... got 5 to 7 psi steady. Its a single electric fuel pump running right up to a split line for a holly 4 bbl carb. I know on the big efi motors you need like 45 psi at the rail but on this motor I assume 5 to 7 is ok?. And cant see how low fuel pressure to trigger an alarm... I was under impression only overheat, low oil pressure or low gear oil could trigger alarm. I see this engine has sort of half a computer (early days of ecm i guess) can that thing throw codes? I learned on newer stuff like 7.4 MPI and up where you can connect a reader but didn't see a port on this one.

thanks so much for responses guys i really appreciate it!

Brian