Doesnt an alarm come on for low oil pressure?

Anytime the oil pressure drops below 8-9 psi the Guardian system will sound the horn and reduce the engine power per the Merc Tech Line.

I know I get bashed sometimes for saying that not all "recreational engine builders' are ENGINE BUILDERS", but how many of you would perform your own brain surgery or give a go at building a computer chip??
No good professional engine builder can teach you everything you need to know to build a reliable endurance marine performance engine on the internet in a few posts! It takes us knowledgeable builders usually 20-30 years to learn most of what we need to know and we don't know it all!

Don't have enough time to go into exact technical reasons why we don't recommend any hydraulic roller lifter besides the stock GM big block hydraulic roller lifter or the Morel replacement. Most lifter issues come from other problems and not the lifters themselves, however some aftermarket hydraulic roller lifters and designs have problems and the results can be disasterous! You think they will warranty your loss because their lifter did not "GET APPLIED CORRECTLY!"

Watch your replacement camshafts base circle size. If it gets to much smaller than 1.200" it can put the lifter in a position where the loss of oil pressure can result, especially with cam valve lifts of .600 or more.

Best Regards,
Ray @ Raylar

The Crane 26535 lifter that Crane recommends for the GM 496 (2001-2006) and which was spec'd for the GM HP3 race engine has the same roller cam contact surface to inner oil land distance as the stock 496 lifter based on the lifters I have. Picture of the Crane lifter and the stock lifter side by side attached. So if that is correct then the Crane 26535 and the stock lifter have the same minimum cam base circle limit regarding oil pressure loss. My problem is that the base circle on my cam is too big causing the Crane lifter to expose its roller slot to the lifter oil galley by approximately 0.032"at max cam lift allowing oil pressure to escape past the roller anytime the lifter is at max lift position. See attached graph for oil pressure versus rpm for both the stock and the Crane lifter in my engine. The stock lifter's roller is completely shrouded (no roller slot) so no oil pressure problem at max lift with my ~.6 lift cam. My cam is supposed to have a nominal base circle of ~1.246 (never messured). The HP3 Gen I race engine cam base circle is 1.203 (0.610 lift) exhaust and 1.218 (0.598 lift) intake. Both cams ran fine in my engine with the stock lifters.

I'm putting the stock lifters back in the engine and sending the Crane lifters back to Crane to confirm they are the right 26535 lifter.