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AMC 401 Oil Pressure low ? |
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74Bubblefender
AMC Addicted Charter Member Joined: Jun/29/2007 Location: The AMC form Status: Offline Points: 2589 |
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You said race engine...you should not expect the same oil pressure from higher clearances. But a quick spec of the pump will tell you a lot. I would also suspect different areas of that engine like the lifter bores, bearing clearances including the thrust bearing (which is often overlooked by engine builders. Often the biggest initial loss is the space between the gear top and bottom in the oil pump. Its the killer of a oil pump.
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We are just about to forge new AMC V8 crankshafts.. please check here
http://www.bulltear.com/forums/showthread.php?19564 |
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Red20
AMC Addicted Joined: Jan/29/2013 Location: Oceanside CA Status: Offline Points: 1556 |
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I agree 100% on the oil pump. I don't remember the pump gears end clearance specs off the top of my head. But I replaced the cover on a 360 once before that was out of spec. We used some wet grinding compound on a plate of glass and ran the pump housing mating surface over it for what felt like forever and took .001" off and then figuring gasket thickness were able to get the gear endplay within specs. I sometimes use Bulltear midplates between the pump casting and filter adapter to give the gears a harder wear surface to ride on. They include a slightly thinner gasket too, I believe. It was good for 10 psi at idle in one engine I used it in, if I recall correctly. |
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1969 Javelin SST "Screamin' Banana" - Totaled Feb 2018
1973 Hornet Sportabout X "yellajack" - 360/727/TracLoc DAILY DRIVER |
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AMC RICK 401
AMC Apprentice Joined: Aug/06/2014 Location: Ohio Status: Offline Points: 207 |
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We finally got the oil changed and looks like pressure is ok.
Running 20w-50 Valvoline VR1 racing oil. at 1500 RPM Idle cold we are at 65 psi at 1500 RPM Idle Hot (195 ) we are at 40 PSI as I increase RPM to 6000 pressure goes up to max 65 PSI Hot I think we are fine. We did take it to the sand drags and ran a 5.2 out of the gate and after some fine tuning we got it down to 4.89. Still tweaking fuel & timing and should be able to get to 4.7's. |
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1969 SC Rambler
1974 Jeep CJ5 Dirt/Sand Drag Racer w/401 TH400 Tube Chassis Dirt/Sand Drag Racer w/401 Powerglide "We are not here for a long time but we are here for a good time" |
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Rebel Machine
AMC Addicted Joined: Jul/03/2007 Location: Western Il Status: Offline Points: 5122 |
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Sounds like the same thing I had with my 401. 10W-30 pressure was low, 20W-50 was good. I'd bet the main bearing clearances are excessive but if you're going to run the thicker oil it may be okay.
-Steve- |
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AMC RICK 401
AMC Apprentice Joined: Aug/06/2014 Location: Ohio Status: Offline Points: 207 |
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who runs synthetic oil in their race engines and what is the preferred brand?
and at what point can I switch over from the VR1 racing oil? |
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1969 SC Rambler
1974 Jeep CJ5 Dirt/Sand Drag Racer w/401 TH400 Tube Chassis Dirt/Sand Drag Racer w/401 Powerglide "We are not here for a long time but we are here for a good time" |
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bcsideshow
Supporter of TheAMCForum Joined: May/19/2010 Location: Kenosha Status: Offline Points: 1228 |
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I run Amsoil Dominator Racing oil because of its high Zinc content.
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1969 SCRambler "B"
1970 AMX 390 Auto 1968 AMX 390 Auto 1970 Rebel Machine Project 1969 AMX 390 4SPD Project 1969 AMX 390 Auto Project 1969 Javelin 390 project 1997 Cherokee lifted 1998 TJ Lifted |
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POS #1
AMC Addicted Joined: Jan/28/2014 Location: Ohio Status: Offline Points: 500 |
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I also run and use and sell Amsoil Dominator racing oil...
and when you said clearances are within spec.. you never did mention what specs you are refuring to? like if it is from the Old Performance american style book.. well things have changed since those days.. and if you are running big clearances then you need to run 20-50 for good oil pressure.. my engine doesnt like 20-50.. i run 10-30 because my clearances are not huge like that book said to use.. BTW, i do my burn outs @ 6800,, launch @ 6800 and shift @ 7800 .. 1/4 mile at a time |
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401harry
AMC Addicted Joined: Sep/27/2011 Location: Clearwater,Fl Status: Offline Points: 758 |
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I run .002 to .0023 main clearances and for oil I run straight 30W Valvoline or Rotella with rislone ZDDP in all the old cars and the lawn tractor as well
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Rebel Machine
AMC Addicted Joined: Jul/03/2007 Location: Western Il Status: Offline Points: 5122 |
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10W-30 Mobil 1 in my street/strip 401 with TSM spec main and rod bearing clearances. Running roller lifters so lack of ZDDP isn't a problem.
-Steve- |
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73hornut
AMC Addicted Joined: Jul/03/2007 Location: Southern Oregon Status: Offline Points: 3130 |
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Most aftermarket lifters are smaller diameter then factory, complicate that with worn lifter bores.
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71 Javelin
74 Gremlin 79 Spirit AMX Rogue Valley Rumblers Like Us on FB https://www.facebook.com/groups/1602825606650796 |
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