[NeighborsComplaint]

I did .0035 mains on my 455. Oil pressure would dip down to 20psi at a 750 rpm idle w a Mellings M54Dvpump. I had to pull the motor a couple years later due to a leaking rear main seal and I swapped in a Butler blueprinted SD pump and billet shaft on their recommendation w the .0035 main clearances. Oil pressure jumped right up to 45 psi at idle and 80 Psi at cruise.

[HWYSTR455]

Factory large journal cranks turn into a wet noodle at RPM, flexing all over the place, which would require larger clearances. (bind)

Main saddles flex too, but obviously not as much as the crank.

Sloppy machine work is also a situation where you run larger clearances. (safer)

Larger clearances it's best to run the 80psi spring/80 psi pump.

Higher loads and larger clearances require higher viscosity oils (and more volume/flow). Basing your viscosity on oil psi readings are not an acceptable approach.

Using the above and factoring in how the engine will be used determines the clearances to be used. You can't give 'general' advice on clearances without knowing the above info.

In short, there's a range of clearances that 'can' be used, not one specific value(s).


.

[scott70]

Originally Posted by NeighborsComplaint

I did .0035 mains on my 455. Oil pressure would dip down to 20psi at a 750 rpm idle w a Mellings M54Dvpump. I had to pull the motor a couple years later due to a leaking rear main seal and I swapped in a Butler blueprinted SD pump and billet shaft on their recommendation w the .0035 main clearances. Oil pressure jumped right up to 45 psi at idle and 80 Psi at cruise.

This time around I used the butler blueprint 60-70 psi pump and a nitemare pump shaft. I did install the washer that comes with the pump . All my engines in the past have idled around 20 psi at temperature with a standard melling 60 psi pump.