New 401 Oil Pressure - Reality Check

JMSII

Ok, I am finally driving my new 401! I need a reality check on oil pressure. The 401 was completely gone through at an excellent machine shop. I installed a new timing cover, gears and dual oil filter set up (from bulltear) and dual NAPA Gold filters. At start up I get about 75lbs oil pressure and get about 65lbs cruising down the highway at temperature. Hot idle is around 25 - 30 lbs. Is this in spec? Thanks!

tufcj

Exactly what my 360 runs. Looks like good numbers to me. Bob tufcj

Wrench Man

Yep, you've got LOTS of oil pressure!, even the NASCAR engines are only running 10psi for every 1000 RPM's!

krcilek

My oil pressure runs at 40psi at high rpms but at idle its about 5psi what is the reprecussions of low oil pressure at idle? How do I correct this?

BREK

krcilek wrote
My oil pressure runs at 40psi at high rpms but at idle its about 5psi How do I correct this?

New plunger & relief spring. I would suggest a stock replacement type. I tried a high pressure spring in my amx and it was waaaaay to much 90+psi cold at idle and about 80 warm @ 3000rpm.

jeepsr4ever

Thats ok pressure..hmm I wonder where the crank was ground to. Sometimes a street grind can be large so you have a few more tenths or even millionths smaller diameter makes a huge difference in oil pressure.

JERSEYJOE

I think the AMC spec is 13 psi hot idle at 600 rpm. This is exactly what I get on just about every AMC I have ever put together. Super hot day cruising down the road at 2000 rpm about 45 psi. I have never seen an AMC motor with 10w-40 idle at 25 psi hot, I mean hot like after a 75 mph highway run. Even with a new nickel coated cover, gears, midplate, fresh bearings ect.... Just my 2 Cents.....

JMSII

Don't know what to tell you. I have a new mechanical gauge (AutoMeter with a copper tube) and it reads 24-27 when hot at idle with the A/C on. On an 85 degree day rolling down the freeway at 65mph with the A/C on the gauge in my CJ reads between 65 and 70lbs. I even went so far as to try a second gauge and it read the same. I guess I have a "fluke of the universe!"

76-cj7

When i rebuilt my 304 i had 25-30 at idle with MC's nickel plated cover. Then when i swapped in a bone stock 100k mile 360 i used MC's cover on the 360 and it gets about 15 psi at hot idle. So im assuming that it has to do with bearing clearances and this is running 15W40 rotella t in both engines

AMX69PHATTY

Are not block lifter bores a place often overlooked and not checked where the fit can open up, allow bleed off, and affect oil pressure at idle just as loose Main, Rod, and Cam bearings can ?

fast77amx

my 304 runs about 85 at idle when first start and dosnt drop till reg temp but only drops to 50 at idle then when i get on it it pegs out at 90psi gone through 2 sets of cam and dizzy gears and starting to get :(:

Dusty

fast77amx wrote
my 304 runs about 85 at idle when first start and dosnt drop till reg temp but only drops to 50 at idle then when i get on it it pegs out at 90psi gone through 2 sets of cam and dizzy gears and starting to get 🙁:

did you install the high pressure sping set? :-| thats sounds like too much pressure..... have you checked the oiling passage on the cam to make sure the cam/dizzy is getting oil?