72 Roadrunner with 340 oil pressure issues

[dswen22]

Alright, I tried looking in the forums for more info and apologize if a thread already exists on this, but have been stumped. The 340 in my car has 60+lbs of oil pressure on cold start and maintains about 35-50lbs on the highway, but low rpm and idle after warm it drops below 20lbs. No knocks or visible signs of metal shavings in oil. Temp stays between 170-180. when I replaced the intake I did check the oil plug behind the dist. and that was there. I am curious if maybe the pump is going bad and or they didnt use the gasket with oil pump? On that note I plan on changing out the oil pump this spring with a mellings HV, but am curious if this is something that can be done in car from underneath by dropping the oil pan? Thanks

 

[Paul_B]

I’ve always heard you need 10psi of oil pressure for every 1000 RPM. It sounds like you could be ok. Adding a HV pump will raise pressure.

 

[dswen22]

I’ve always heard you need 10psi of oil pressure for every 1000 RPM. It sounds like you could be ok. Adding a HV pump will raise pressure.

yes, ive been told this too, and maybe im just worrying for nothing about it. My fear is I dont want to grenade a 340, so being cautious and researching this winter while car is hibernating in my garage

 

[Don Frelier]

I think your fine.
Are you using a mechanical gauge?
Can you check it for accuracy?

A well maintained Mopar almost never ever has a bad oil pump.

 

[dswen22]

I think your fine.
Are you using a mechanical gauge?
Can you check it for accuracy?

currently the car has one of those aftermarket dakota digital classic setups, ( not sure how I feel about the dakota gauges, but they look stock and were in the car when I bought it). This spring I am going to test with mechanical gauge to test the accuracy.

 

[1967coronet]

Nice looking RR,
Myself I think it is a ticking time bomb.
Since I'm only 1 state away I will take it off your hands to help you out.

What weight of oil is in it ?
Most all these 70s V8s are getting a little loose even after a standard ring and bearing rebuild.
The pump and mabey a little more oil viscosity may be all it needs My old 383 used to idle near 15 warm and 35 - 40 on the road. Ran a few years like that.

 

[dswen22]

Nice looking RR,
Myself I think it is a ticking time bomb.
Since I'm only 1 state away I will take it off your hands to help you out.

What weight of oil is in it ?
Most all these 70s V8s are getting a little loose even after a standard ring and bearing rebuild.
The pump and mabey a little more oil viscosity may be all it needs My old 383 used to idle near 15 warm and 35 - 40 on the road. Ran a few years like that.

LOL I think i'll keep her around for a while. well long while as my wife loves the car as much as I do.

when I got the car late August, it had sat a while and had a 120 mile drive home. I changed the oil before driving home as it was old. I used rotella 15w40 for the ride home, changed it the next day, figured Id use that as flush and since it hadnt been ran in a long time wasn't concerned with spending the money on some oil and filters. I then proceeded to change the oil 2 more times, as the carb had an issue and dumped a ton of fuel in the 2nd fresh oil change. I now have the carb issue squared away, no more fuel dumping, it had a dual carb intake on it with 2 500 cfm carters and the rear one the accellerator pump was stuck open. I have since gone to an air gap single carb and rebuilt a 1406 edelbrock for it. Back to the oil... final oil change was Valvoline ZR1 20W50, I figured like you said, its old, might be loose. Also went from a Fram oil filter to wix. the first 2 oil changes and before the fuel dump issue, it had 45-50 on start up and was 25-35 down the highway. idle was scary at 15-20lbs. When switched to a Wix filter and the Valvoline 60+ lbs cold and 35-50 down the highway and idle 20+. I also went with a 160f stat and took out the stupid electric fans it had in it and went to a shroud with direct fan.

 

[F4R/T]

I would consider a oil change and run maybe a step up in thickness as this could be the bearings are loose . I would not run a high volume oil pump. After speaking with Bob K on my 440 years ago I was informed not to run one as you could empty the pan on the far side of the tach. Keep in mind I’m going for pure stock class not fast class.
How much fuel was in your oil when you had carb troubles?

 

[dswen22]

I would consider a oil change and run maybe a step up in thickness as this could be the bearings are loose . I would not run a high volume oil pump. After speaking with Bob K on my 440 years ago I was informed not to run one as you could empty the pan on the far side of the tach. Keep in mind I’m going for pure stock class not fast class.
How much fuel was in your oil when you had carb troubles?

There was a lot. Luckily I had noticed it right away and didnt run it much at all. The genius who "rebuilt" the carbs prior to me owning the car did a number on those carbs... I just decided a one carb setup would be simpler and easier to work with, and the dumping fuel issue went away with the 1406 edelbrock and new intake. I dont plan on pushing the car hard at all, the occasional wheel spin here and there is about it. From what I noticed, it seemed to like the ZR1 valvoline 20W50 with wix filter.

 

[MWbirdLOVER70]

I’ve always heard you need 10psi of oil pressure for every 1000 RPM. It sounds like you could be ok. Adding a HV pump will raise pressure.

Maybe the motor was built lose like some drag motors. I’ve run the same pressures as you. And yes 10lbs per 1000 rpm rule

 

[HEMIB]

mine runs 18 to 22 idle 50 to 60 highway 10w 30 hydraulic lifter 392 340 stroker never had any problems HV pump

 

[MWbirdLOVER70]

LOL I think i'll keep her around for a while. well long while as my wife loves the car as much as I do.

when I got the car late August, it had sat a while and had a 120 mile drive home. I changed the oil before driving home as it was old. I used rotella 15w40 for the ride home, changed it the next day, figured Id use that as flush and since it hadnt been ran in a long time wasn't concerned with spending the money on some oil and filters. I then proceeded to change the oil 2 more times, as the carb had an issue and dumped a ton of fuel in the 2nd fresh oil change. I now have the carb issue squared away, no more fuel dumping, it had a dual carb intake on it with 2 500 cfm carters and the rear one the accellerator pump was stuck open. I have since gone to an air gap single carb and rebuilt a 1406 edelbrock for it. Back to the oil... final oil change was Valvoline ZR1 20W50, I figured like you said, its old, might be loose. Also went from a Fram oil filter to wix. the first 2 oil changes and before the fuel dump issue, it had 45-50 on start up and was 25-35 down the highway. idle was scary at 15-20lbs. When switched to a Wix filter and the Valvoline 60+ lbs cold and 35-50 down the highway and idle 20+. I also went with a 160f stat and took out the stupid electric fans it had in it and went to a shroud with direct fan

 

[MWbirdLOVER70]

There was a lot. Luckily I had noticed it right away and didnt run it much at all. The genius who "rebuilt" the carbs prior to me owning the car did a number on those carbs... I just decided a one carb setup would be simpler and easier to work with, and the dumping fuel issue went away with the 1406 edelbrock and new intake. I dont plan on pushing the car hard at all, the occasional wheel spin here and there is about it. From what I noticed, it seemed to like the ZR1 valvoline 20W50 with wix filter.

Love the ZR1 and went to Purulator and same scenario and got more oil pressure. Ditched the Castrol/Fram days and went new route but always ran 20W50

 

[WileE]

Car is a real beauty !! Looks like you got a 71 grille in it ? Maybe add the bird head to it ?

 

[dswen22]

Car is a real beauty !! Looks like you got a 71 grille in it ? Maybe add the bird head to it ?

Technically it’s a satellite cloned to roadrunner, bought it this way so to me it’s a roadrunner, I’ve always wanted a 71-72 RR, it’s my favorite, this was close enough for me ;)

 

[dswen22]

Maybe the motor was built lose like some drag motors. I’ve run the same pressures as you. And yes 10lbs per 1000 rpm rule

This kinda makes sense, has a pretty lump cam in it.

 

[Bird 426]

I have the same oil pressure as yours with a HV pump. I have been using 10-40 Lucas classic hot rod oil. Been this way for going on 4 years, 418 stroker. Your engine should be fine, drive it, you will be disappointed if you do all that work and nothing changes. Don't ask me why.

 

[dvw]

If it has a standard pump, a HV will increase the pressure. It’s simple. The HV flows more volume. Be aware that some HV pumps have pan clearance issues at the back corner of the pan.
Doug

 

[toolmanmike]

I haven't read every word posted above but what kind of a gauge are you measuring the pressure with? Also, how many miles are on it? Low oil pressure, hot, at idle, is usually worn bearings.

 

[terzmo]

I think 20 at idle is fine. Are you also going to a larger pan with HV pump? Just out of boredom I would swap a mechanical gauge in to compare.