fresh 454 oil pressure dropped

[josh0325]

I own a 1990 Chevy.3/4 ton suburban and recently built a 454 to replace the gutless stock 350.  I ran it in with no issues and have probably put 4 miles on the engine.  Engine fires up and idlesat 50 p.s.I. at 900 rpm.  Today I drove it and rpm's dropped to 650, oil pressure dropped to 25 psi. Opening the throttle had little effect on raising pressure.  What are you're opinions on this.

[frotosride]

I know it may seem obvious but I'd first start with oil level, and then gage. If you have the ability to connect a mechanical gage to the block it would be best.  From there check the oil for metalics. Pull the distributor and use a drill to rotate pump before draining it to see if you get any pressure. Make sire the distributor still has the pump drive blade intact.

[bd]

This ^^^^^

What oil did you use for break-in?  Provide a little more detail on what you mean by, "...built a 454...."  What type of components comprise the valve train - stock or performance?

[Fairlane514]

50 psi cold I assume, it will then drop some as the oil heats up. 25psi at 650 isnt bad.

What oil filter are you using? Fram sucks, dont use it.

[fitz]

I always thought that 10psi of oil pressure for every 1k rpm's was fine. 

[bd]

I always thought that 10psi of oil pressure for every 1k rpm's was fine.

This is just a guideline for evaluation and works as a suitable minimum standard.  It is the sudden drop in oil pressure that is worrisome.  A sudden, 50% drop in oil pressure on a fresh engine (~4 miles) coupled with an unexpected drop in idle RPM might point to wiping lobes on the camshaft and an oil pump pressure relief valve stuck partially open from metal particles in the oil.  Hence, my question on break-in oil and valve train configuration.  If high pressure valve springs were used during break in or unsuitable oil was used, the cam could have been destroyed in the first few minutes of operation.  It never ceases to amaze how quickly a camshaft can wipe flat from too much initial spring pressure or inadequate lubrication.  This is why cam grinders recommend light-pressure break-in springs to initially "polish" the lobes to lifters.

Fortunately, the oil filter should have removed the majority of abrasive debris from the oil before it reached the bearings of the rotating assembly, as long as the filter wasn't overwhelmed with fine particles, forcing the filter bypass valve open.

[josh0325]

I'm sorry for not getting back sooner, I work about 85 hours a week.  I built the engine over the last two years.  It is a two bolt main truck engine with 781 heads and is set up with an xe262 flat tappet from comp.  Nothing too crazy just built for a little more power than stock.  It has a Melling high volume oil pump.  I changed the oil and filter.  Filter was a microguard from Oreilly, I changed over to a Bosch filter.  So far everything is fine, just caught me off guard ad rpm dropped to 660 from the normal 900 it idled at.  I dropped it in reverse and it stalled twice but fired back up.  I hope this fixed it as there was still quite a bit of assembly lube in the oil still.  Thank you for your opinions and help.

[Fairlane514]

Is it 900rpm with the choke on then drops to 660 with the choke off?  You should raise your curb idle to about 800 when hot, it may not stall when putting it in gear.

[josh0325]

My curb idle in park is set between 900-1100 rpm when cold. At 195° it drops to 850 in gear.  The break in additive I used was Risslone oil additive, and 10w30 castrol non synthetic oil.  After initial run in I change d the oil and used the same oil and hyper lube zinc replacement addditive.  When my pressure dropped to 25lbs at 600ish rpm and engine stalled that's what rose my concern.  I changed the oil and replaced with Castrol GTX, and added hyper lube to it.  I used a bunch of assembly lube on the cam lobes and lifter feet(I knew engine was going to sit for awhile). Professional shop assembled and balanced the bottom end for me.  Also, when I replaced the oil filter it didn't have any metal shavings near the top or anywhere else visible.  Hopefully I just went too crazy with the assembly lube and it clogged the filter. Only other thing I could think of was excessive bearing clearance on the crank. My build sheet says .0035" on all caps.