70 440 Main Bearing Question

[charge70]

I'm rebuilding the 440 in my 70 Charger.What should I use for main bearings,1/2 groove or full groove?I have both available to me,I know these were originally built with 1/2 groove bearings but that was 50 years ago and things change.All opinions welcome.Thanks,John.

 

[turbine68rt]

I used fully grooved mains in mine but if I could do it again they would be half grooved. My understanding is it's beneficial for rod bearing oiling but sacrifices potential pressure. Clevite has a chart illustrating pressure loss using a 180° groove as the baseline up to 360°.

 

[Nate S]

1/2 groove was used because the downward force on the mains is very high and by their nature, journal bearings do much better as the area increases, much beyond a linear improvement. The groove gets oil to the rods, if clearances are good half is sufficient.

That said, there are configurations that seem to want the full groove. Those configurations will have to do more with surviving lots of power than any sort of long life.

 

[ruffcut]

Agree with half groove bearings. My engine builder recommended half groove and he's been building Mopar engines since 1963. He just might know a little something! ruffcut

 

[66Satellite47]

I think it depends on what the usage of the car will be. For a street application that isn't MAX performance, I'd use the standard 1/2 bearings with proper clearance. I have used full groove on all my drag race motors. The drag motors were all high RPM with larger clearances and high volume oil pumps.

 

[charge70]

This is a stock rebuild street motor that will not see any track time

 

[66Satellite47]

This is a stock rebuild street motor that will not see any track time

Then a 1/2 groove main is just fine, be sure to check the clearance.

 

[dvw]

My race motor runs 1/2 groove to 7300 with no issue. To be honest never had any issue with either type. The important thing is to have enough clearance. Which on a performance motor in my opinion should be .001" per inch of journal diameter. Race motors I add .0005" to that number. I'm also a thin oil advocate. 20W50 has its place but it would be in something with very high load and high oil temperature. If that's the case an oil cooler is a good addition. Keeping the pick-up covered is mandatory. If you are doing any high G maneuvers a modified pan should be in the mix, street or not. A baffle in the pan never hurts anything. Its a good safety measure.
Doug