[heff]

i searched the archives, and didn't find any answers...i'm hoping someone can answer this time this problem is posted.

specs:
70 pontiac 350 block, .030" over
#16 small-valve heads, cut .010"
nos steel head gaskets
summit 2801 cam, installed straight up
comp cams lifters
melling m54d pump, i took it apart and cleaned everything and deburred passages
hardened steel pump shaft
King full groove mains
King rod bearings, they looked 'coated' when i got them
i can't remember what kind of cam bearings, but the oiling holes were lined up
no cam fitment problems
smoothest break-in i've ever seen, no leaks or car getting hot or misses or anything
i cleaned all oil galleys and washed engine about 6 times before assembly
break-in oil wasn't metallic, didn't look unusual other than being slightly gray, which i chalk up to assembly lube, eos, and cam lube.
oil looks good at this time, like 300 mile oil should look
CAT 10w40 oil, no additives at this time
engine has about 300 miles on it right now
close ratio muncie trans, 3.73 rear


i replaced the electric oil pressure sender before i installed the engine, and i also have an autometer 100psi mech gauge hooked up with a copper line. when the engine is warm(180 degrees) the oil pressure will bounce around from 45-50psi-60psi when i'm running around 3000rpms. idle the pressure drops down to around 30psi, bounces up to 35-40psi, then might drop back down to 25-30psi...touch the throttle and it goes up to 45-50psi, maybe higher. this happens with both guages, so i can rule out the elec. guage being faulty. this didn't happen with the previous build on this engine, with summit 2800 cam and automatic trans.
so...is this something to do with the oil pump, bearings, cam lobe, lifter problem, or due to the lift of the cam? i saw all these as possible problems on other posts, but no clear answers....just guessing. is this something i should worry about, or what? the car has yet to get hot...it hasn't gone over 190, and i've driven it in all kinds of traffic. i'm using a delco filter, i'll probably go back to motorcraft or wix after this oil change tho. the oil pressure climbs when i accelerate, it's just when i'm at a steady rpm...if i go to 4200rpm the oil goes around 65psi. so...anyone got any kind of answers?

[chiphead]

My street/strip 400 does the exact same thing. After the oil gets hot and thin (10w-40), engine at 205, the oil pressure gauge (connected at dist port) is fluttering between 45-55 PSI at 3000-3500 RPM. Quickly, like the gauge is connected to a lie detector or some *****. bee-boo-bee-boop. WTF is this I'm thinking. Am I about to blow up?

I think its the relief ball in the damn oil pump. I blueprinted the pump, but didn't mess with the relief. So I'm pretty sure its the relief ball/spring dancing around in the bore. Not sure if this is a reliability issue, as I run my engine really hard. Same behavior- 20 PSI hot, touch the throttle and its 45 PSI. As soon as I romp on it, the oil pressure goes to 55-65, so I'm good there. These new oil pumps have some sort of design issue with the pressure relief system.

[snakepod]

I'm having the same issue with a recently built 406. Only happens when fully warmed up. Using Rotella and EOS. The Engine builder said that this was not a problem.

[heff]

i'm not too worried about it...as long as the pressure goes back up and stays steady when i'm hammering on it...i just wonder what causes this...i'm thinking airation of the oil maybe...the guages get that little bit of air in the sending unit and that's what it is...but then you'd think the air pressure would be the pressure as the oil, unless it's bleeding out of the line somehow...who knows

[Formulabruce]

Originally Posted by chiphead

My street/strip 400 does the exact same thing. After the oil gets hot and thin (10w-40), engine at 205, the oil pressure gauge (connected at dist port) is fluttering between 45-55 PSI at 3000-3500 RPM. Quickly, like the gauge is connected to a lie detector or some *****. bee-boo-bee-boop. WTF is this I'm thinking. Am I about to blow up?

I think its the relief ball in the damn oil pump. I blueprinted the pump, but didn't mess with the relief. So I'm pretty sure its the relief ball/spring dancing around in the bore. Not sure if this is a reliability issue, as I run my engine really hard. Same behavior- 20 PSI hot, touch the throttle and its 45 PSI. As soon as I romp on it, the oil pressure goes to 55-65, so I'm good there. These new oil pumps have some sort of design issue with the pressure relief system.

mine does same thing (455) had same pump, since I had a big leaking problem, I had the pan/pump apart many times on the engine running rig at the machine shop. I ended up going to a AC Delco parts place and getting a standard pressure pump,( ended up a NOS melling lol) took it apart and measured spring differences and seat difference, gears etc. I ended up with basically a stock pump to eliminate like 85% of the fluctuation. seems odd that less pressure on the ball would be better, but its quite a bit smoother and has 35 at idle and jumps up to 50 at 4K which is plenty.I cant see taking away horsepower with uneeded pressures if your clearnaces are good.