low oil pressure

1SILLYGT · 02-24-2004, 09:57 AM

Someone please help, I recently swapped a 351w into my 90GT and I spun a bearing. I pulled the crank had it cut with matched bearings and I also added speed-pro pistons and eagle rods. now when I start the car up i have about 10 lbs of pressure at idle. Does anyone have any suggestions for me. Please

tireburner163 · 02-24-2004, 10:06 AM

what did you oil clearances plastigauge to?

richd · 02-24-2004, 06:02 PM

Isn't the spec 10psi per 1000rpms?

Or is 10psi low for the real world?

420nitro · 02-24-2004, 06:10 PM

Quote:

Originally posted by richd
Isn't the spec 10psi per 1000rpms?

Or is 10psi low for the real world?

yes but you still would like to have at least 20 pounds at idle though.
It sounds like you have alot of clearance, so you can run monster boost or spray.

Did you try to put thicker oil in?
You can also put in a high volume/ high pressure pump?
Or it could be that your pump is going bad. Does the pressure build when the engine revs?
If all else fails, when you check the pump check the clearances again.
good luck

429mustang · 02-24-2004, 06:49 PM

Did you plastigage the clearances when you were installing the crank? When I had my crank ground I still made sure the bearings going in were the right size before it was too late (they were within specs on the tighter side which was good), but I wasn't about to trust the guy who helped me load up my block/parts at the machine shop. I'd look into the pump and even the oil pressure sending unit, you could always buy one and try it, then if it doesn't change anything then return it.

1SILLYGT · 02-25-2004, 11:18 AM

yes the rule is 10 psi per 1000rpm but i would rather be safe then sorry. the pressure does increase as i accelerate but the engine makes a slight knocking noise. I added some 40 weight oil but that did not help. I originally had the stock oil pump in the car, but after the problem i went out and bought a high pressure pump(not yet installed). I didn't plastigauge anything, what would be the specs for that? thnaks for the help

LX5liter · 02-25-2004, 05:38 PM

I just replied to your other thread before reading this one, which answered some of my questions, but brought up new ones. Does it knock all the time, just cold, or only on deceleration? I believe the clearance should be .001"-.003". Check and make sure the proper bearings were put in as well like 429 said. It should be marked right on the bearing.

stang_racer20 · 02-25-2004, 07:39 PM

I distinctly remember when plastigauging mine that the main bearing clearance should be .0015 - .003 on a 302.

1SILLYGT · 02-26-2004, 10:56 AM

just to answer your question lx5liter, it only knocks during deceleration. I actually pulled the motor the other day and removed the crank. All of the rod bearings are fine, but it looks like the #1 and #5 main bearings are worn and the crank itself has some marks. The motor only has about a half hour of drive time.im gonna plastigauge it to check the clearances this weekend. but the only explanation i can come up with is that they were bad bearings or a bad crank. the whole motor was freshly assembled with almost all new parts. Im getting really frustrated. I want to hit the streets

LX5liter · 02-26-2004, 12:57 PM

Only knocking on deceleration usually means a rod bearing. When you re-assemble the engine, make sure and plasti-gage the rod clearances. What about the wristpin bushings, is there any play in them?

02-24-2004, 10:06 AM	#2
tireburner163 It's a lot like a race car Join Date: Aug 2000 Location: Meridian, MS Posts: 4,130	what did you oil clearances plastigauge to? __________________ 1987 Buick T-type 1998 HD Electra Elide

02-25-2004, 11:18 AM	#6
1SILLYGT Registered Member Join Date: May 1999 Location: sloatsburg NY Posts: 28	yes the rule is 10 psi per 1000rpm but i would rather be safe then sorry. the pressure does increase as i accelerate but the engine makes a slight knocking noise. I added some 40 weight oil but that did not help. I originally had the stock oil pump in the car, but after the problem i went out and bought a high pressure pump(not yet installed). I didn't plastigauge anything, what would be the specs for that? thnaks for the help __________________ 90 GT 351W long-tube headers, flowmaster exhaust, off-road h-pipe, 3.73 gears, hurst short throw shifter, GT-40 heads, demon 650 carb, speedpro pistons, eagle rods, comp cams

02-25-2004, 05:38 PM	#7
LX5liter dude5l Join Date: May 2001 Location: Grande Prairie, Alberta, Canada Posts: 603	I just replied to your other thread before reading this one, which answered some of my questions, but brought up new ones. Does it knock all the time, just cold, or only on deceleration? I believe the clearance should be .001"-.003". Check and make sure the proper bearings were put in as well like 429 said. It should be marked right on the bearing. __________________ Good luck! Brad R. 1992 L.X. 5.0 coupe MODS: A few little bolt ons New Best time ...11.60 @ 128 mph @ 2000+ ft altitude. Rice Haters Club member #39 Users rides #2542

02-25-2004, 07:39 PM	#8
stang_racer20 Registered Member Join Date: Jun 2003 Location: Wisconsin Posts: 348	I distinctly remember when plastigauging mine that the main bearing clearance should be .0015 - .003 on a 302. __________________ 92 Mustang GT, 347 Stroker(Forged Steel Crank/Rods-Balanced, Forged Aluminum Dished Pistons), Trick Flow Track Heat Intake, Trick Flow Twisted Wedge Heads w/ Stage 3 port/polish, 80mm C&L MAF, FMS 30# Inj., BBK AFPR, Trick Flow Stage 2 Cam, Trick Flow 1.6R Rockers, BBK E.L. Headers, Flowmaster Cat-Back, MAC CAI, FMS Pulleys, Griffin Alum. Radiator, MSD Pro-Billet Distributor; AOD, Dynamic 3300 Lockup Converter, B & M Super Cooler, B&M Ratchet Shifter; 3:73 gears.

02-26-2004, 10:56 AM	#9
1SILLYGT Registered Member Join Date: May 1999 Location: sloatsburg NY Posts: 28	just to answer your question lx5liter, it only knocks during deceleration. I actually pulled the motor the other day and removed the crank. All of the rod bearings are fine, but it looks like the #1 and #5 main bearings are worn and the crank itself has some marks. The motor only has about a half hour of drive time.im gonna plastigauge it to check the clearances this weekend. but the only explanation i can come up with is that they were bad bearings or a bad crank. the whole motor was freshly assembled with almost all new parts. Im getting really frustrated. I want to hit the streets __________________ 90 GT 351W long-tube headers, flowmaster exhaust, off-road h-pipe, 3.73 gears, hurst short throw shifter, GT-40 heads, demon 650 carb, speedpro pistons, eagle rods, comp cams

02-24-2004, 09:57 AM	#1
1SILLYGT Registered Member Join Date: May 1999 Location: sloatsburg NY Posts: 28	low oil pressure Someone please help, I recently swapped a 351w into my 90GT and I spun a bearing. I pulled the crank had it cut with matched bearings and I also added speed-pro pistons and eagle rods. now when I start the car up i have about 10 lbs of pressure at idle. Does anyone have any suggestions for me. Please __________________ 90 GT 351W long-tube headers, flowmaster exhaust, off-road h-pipe, 3.73 gears, hurst short throw shifter, GT-40 heads, demon 650 carb, speedpro pistons, eagle rods, comp cams

02-24-2004, 06:02 PM	#3
richd Registered Member Join Date: Jul 2001 Location: Edison, NJ, USA Posts: 125	Isn't the spec 10psi per 1000rpms? Or is 10psi low for the real world?

02-24-2004, 06:49 PM	#5
429mustang Registered Member Join Date: May 2001 Location: westerville, OH USA Posts: 618	Did you plastigage the clearances when you were installing the crank? When I had my crank ground I still made sure the bearings going in were the right size before it was too late (they were within specs on the tighter side which was good), but I wasn't about to trust the guy who helped me load up my block/parts at the machine shop. I'd look into the pump and even the oil pressure sending unit, you could always buy one and try it, then if it doesn't change anything then return it. __________________ 1990 Notchback: BBK Ceramic Coated Full length headers, Dr. Gas 3"- 2 1/2" x-pipe, Flowmaster 40's/turndowns.

02-26-2004, 12:57 PM	#10
LX5liter dude5l Join Date: May 2001 Location: Grande Prairie, Alberta, Canada Posts: 603	Only knocking on deceleration usually means a rod bearing. When you re-assemble the engine, make sure and plasti-gage the rod clearances. What about the wristpin bushings, is there any play in them? __________________ Good luck! Brad R. 1992 L.X. 5.0 coupe MODS: A few little bolt ons New Best time ...11.60 @ 128 mph @ 2000+ ft altitude. Rice Haters Club member #39 Users rides #2542

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