ok Recently i installed a new oil pump because my old one went bad(pressure releif valve was sticking), and was blowing oil out the oil filter seal, luckily i noticed it before anything bad happened, so as the story goes..

I replaced the oil pump with a DM-55HV with a new pickup and driveshaft. Then i filled the motor with valvoline 10w40 conventional, the car seems to run fine but my oil pressure readings are really strange, for example the other night it went down to zero, and stayed there while the car was running, i drove it home (about 5 minutes away) and it stayed at zero the whole time, i shut the car off and let it sit 4 30 mins and i started it up, now it was reading 30 psi, that is what it is at on average, only the pressure does not increase with rpm, and after driving for a while it drops to about 25.

ok here is some more info:
I checked everything and no leaks
The pump came with a notice that said it is a high volume high pressure pump, and it came with a different (non colored)spring, to use if a lower pressure was desired, and said to replace the (colored spring).when i talked to a few people, and they said that i should use the non colored spring because it was the stock one.oh and the oil pressure sending unit is new

Is it possible that the pump is leaking internally? any way to check this?

What else could it be?

Anyone know what the psi is for the colored and non colored spring?

I really got to get this problem figured out..


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87 IROC-z 305 TPI
Borg Warner T-5 fresh rebuild
10-bolt 3.73 Richmond gears rebuilt GM posi,
formerly BW 9-bolt w/3.45 gears(broke it)
Ported Plenum and Runners Homemade AFPR
ACCEL 8.8 wires, High output coil,and cap & rotor
Bosch platinum + 4 plugs
Ram Air w/ K&N filters,
MAF sensor screens removed, TB coolant bypass
Polyurethane tranny and torque arm mounts
No Cat, Dynomax Headers & catback w/custom tips
K&N oil filter,Mobil 1 synth,Factory Oil Cooler, Futura GLS Super Sport tires 265/50/15 rear and 235/60/15 front mounted on 86 monte carlo SS rims.

406 siamesed TPI in progress

 

This may sound like a stupid question..but I've seen it..

Are you sure the pump mounting bolt is tight?



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ASE Mechanic/Machinist/Smog Tech

1999 NBM Trans Am
1986 Chevy 3/4 ton pick up
1981 corvette
1995 Kawi ZX6R
and 2 POS commuters...

R.I.P. #3
"He can see air"

 

yeah that sucker is torqued in there to specs

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87 IROC-z 305 TPI
Borg Warner T-5 fresh rebuild
10-bolt 3.73 Richmond gears rebuilt GM posi,
formerly BW 9-bolt w/3.45 gears(broke it)
Ported Plenum and Runners Homemade AFPR
ACCEL 8.8 wires, High output coil,and cap & rotor
Bosch platinum + 4 plugs
Ram Air w/ K&N filters,
MAF sensor screens removed, TB coolant bypass
Polyurethane tranny and torque arm mounts
No Cat, Dynomax Headers & catback w/custom tips
K&N oil filter,Mobil 1 synth,Factory Oil Cooler, Futura GLS Super Sport tires 265/50/15 rear and 235/60/15 front mounted on 86 monte carlo SS rims.

406 siamesed TPI in progress

 

My guess is that your oil pressure guage is messed up. Probably your sending unit. When I bought my '86 TA the guy told me that he just replaced the oil sending unit because the guage kept reading 0 psi.

Second guess, something happened with the new pump and you were actually holding 0psi and the 5 minute drive home ate up your bearings and that's why you're holding such low oil pressure now.

As for the pressure drop after running awhile, that's normal. I have a Melling 55HV pump in my 355 and when I start it cold it holds 55-60psi .... but after running for awhile when the temp gets to about 185-195 I've had mine drop down as low as 45psi.

As the story goes... you only need 10psi for every 1000 rpms that you're running. My 305 ran 25-30psi all the time. Of course the engine had over 200,000 miles on it.

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1986 Trans AM
355 TPI
4 Wheel Disc Brakes
9 bolt Borg Warner Rear (2.77's....oh joy) :P
6" rods, approx. 9.7:1 Compression, Stock TPI (soon to be ported), 24#/hr LTI injectors (cleaned and flowmatched by Cruizin Performance), Hedman Shorty Headers, 3" exhaust with 80 series flowmaster, SBC 993 heads completely redone and modified for 1.6 RR, 1.52 RR (for now), Comp Cams XE262-14 TPI Cam, Holley AFPR, TPIS airfoil, MSD wires, MSD 6-AL Ignition, Hypertech 53,000 volt coil.

Track times to come.