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02-24-2004, 09:57 AM | #1 |
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Join Date: May 1999
Location: sloatsburg NY
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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
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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, 10:06 AM | #2 |
It's a lot like a race car
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Location: Meridian, MS
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what did you oil clearances plastigauge to?
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1987 Buick T-type 1998 HD Electra Elide |
02-24-2004, 06:02 PM | #3 |
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Location: Edison, NJ, USA
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Isn't the spec 10psi per 1000rpms?
Or is 10psi low for the real world? |
02-24-2004, 06:10 PM | #4 | |
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Quote:
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 |
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02-24-2004, 06:49 PM | #5 |
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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.
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1990 Notchback: BBK Ceramic Coated Full length headers, Dr. Gas 3"- 2 1/2" x-pipe, Flowmaster 40's/turndowns. |
02-25-2004, 11:18 AM | #6 |
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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
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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 |
dude5l
Join Date: May 2001
Location: Grande Prairie, Alberta, Canada
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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.
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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 |
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I distinctly remember when plastigauging mine that the main bearing clearance should be .0015 - .003 on a 302.
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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 |
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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
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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 |
02-26-2004, 12:57 PM | #10 |
dude5l
Join Date: May 2001
Location: Grande Prairie, Alberta, Canada
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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?
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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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