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AMC 401 Oil Pressure low ?

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6PakBee View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote 6PakBee Quote  Post ReplyReply Direct Link To This Post Posted: Jul/08/2017 at 7:38am
Originally posted by FSJunkie FSJunkie wrote:

...I tore it apart and found that Mopar had installed standard size main and rod bearings on a crankshaft that had been machined .010" undersize....


I am finding this very hard to believe.  :shock:
Roger Gazur
1969 'B' Scheme SC/Rambler
1970 RWB 4-spd Machine
1970 Sonic Silver auto AMX

All project cars.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote 6PakBee Quote  Post ReplyReply Direct Link To This Post Posted: Jul/08/2017 at 7:40am
Originally posted by jcisworthy jcisworthy wrote:

Its the oil pressure relief valve spring pressure.

The 401 I just had on the dyno had about 20 PSI at an idle and mid to high 50's peak.

I made the spring pressure adjustable by drilling and taping the spring retainer screw in the filter housing, if that's what it is called.

On first start up it had 200 PSI !! so we shut it down quickly and I changed it up to about factory tension. That gave me the 20/55-60 on the dyno. That was close enough to make pulls and get numbers out of it and I was gun shy to make changes on the dyno after that so I left it.

After I got it home and ran it on my new run stand I was able to tune it to 30 PSI at an idle, 1200 rpm's and 80 PSI open. This was all done by turning in the bolt which added spring pressure. 

Clearances on the rods and mains are .0025 with .0015-.002 lifter clearance, using EDM lifters and 5W30 oil.

https://www.youtube.com/watch?v=8ENn_3NlTtk&t=4s


Stock pump and filter housing (other than the mod to the relief valve)?
Roger Gazur
1969 'B' Scheme SC/Rambler
1970 RWB 4-spd Machine
1970 Sonic Silver auto AMX

All project cars.

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Post Options Post Options   Thanks (0) Thanks(0)   Quote jcisworthy Quote  Post ReplyReply Direct Link To This Post Posted: Jul/08/2017 at 7:58am
Stock pump and ported factory housing
Specializing in dyno services, engine building, and cylinder head porting

rbjracing.com
Phone Number 518-915-3203
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Post Options Post Options   Thanks (0) Thanks(0)   Quote FSJunkie Quote  Post ReplyReply Direct Link To This Post Posted: Jul/08/2017 at 11:43pm
Originally posted by 6PakBee 6PakBee wrote:

Originally posted by FSJunkie FSJunkie wrote:

...I tore it apart and found that Mopar had installed standard size main and rod bearings on a crankshaft that had been machined .010" undersize....


I am finding this very hard to believe.  :shock:
Believe it. It was a service replacement engine, a remanufactured long block. Hecho en México. It did way better than the one it replaced, which only went 6,000 miles because somebody at the remanufacturing plant neglected to remove the plastic plugs from the oil galleries that are used during the cleaning process. It ran just fine, but overheated all the time because of the friction. 

Remanufactured engines are a no-go. 
1955 Packard
1966 Marlin
1972 Wagoneer
1973 Ambassador
1977 Hornet
1982 Concord D/L
1984 Eagle Limited
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