New to me Barracuda with Mopar Crate 390hp low oil pressure

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Unless you have really examined the whole system and looked to find the most limited restriction, there is no way to know. The stock oil interruptor limits the flow to around 5% of the time (and less at very high RPM's), and lowers the rocker shaft pressures to a few PSI anyway. The H-S statement is unqualified so has to be taken with a grain of salt IMHO: Is it for the stock oiling system? Or for full flow cam bearings? What size is the flow restriction where their rocker shaft sits on the stand with the bolt going through it? It can be very different from the stock restriction at that point, smaller or larger.

If you read the Comp site tech info, you will learn the completely wrong info on the geometry for this system. So I am just advising to be to understand the system rather than take everything at face value.
 
Emailed Randy with Harland Sharp. He said to not worry about my 15psi hot idle oil pressure on pedestal mount roller rockers.

He is looking at photos to tell me if I've got 1.6 or 1.7 roller rockers. I think I've got 1.7 due to the relief cut out.
 
Good deal. If you are still using the synthetic oil, you are in very good shape. (You would be stunned to learn how much better a full synthetic will protect most engine parts.)
 
I’m not sure you two are on the same page(or maybe it’s me who’s on the wrong page).

I thought the engine being discussed here is a Magnum.
Magnums pushrod oil, and the metering to the top end is controlled inside the lifters.
Whether it has oe or roller rockers won’t really affect the pressure, or how much oil goes to the top end.
 
Tnx, you are right, PRH, I did not see that was the case until the OP's last post. Oooops.... Sounds like he is all set with his pressure now.

Your point about the metering in the lifters is on the mark: If there is a limiting upstream restriction setting the flow rate, then what goes on downstream (at the rocker in this case) does not set the flow.
 
Oil psi is now good. The fuel injection IAC needed reset to hold better idle. Install dual flow adjustable PCV valve. Adjusted roller rockers. Prior owner only had 4 of them in spec. One was at least 3/4 of a turn too loose. The others were right at zero valve lash.

50psi when cruising and around 15psi on low hot idle. Oil pressure jumps right up with any throttle blip.

thanks for the help. :thumbsup::thankyou:
 
Oil psi is now good. The fuel injection IAC needed reset to hold better idle. Install dual flow adjustable PCV valve. Adjusted roller rockers. Prior owner only had 4 of them in spec. One was at least 3/4 of a turn too loose. The others were right at zero valve lash.

50psi when cruising and around 15psi on low hot idle. Oil pressure jumps right up with any throttle blip.

thanks for the help. :thumbsup::thankyou:
Who's Pcv did you use?
 
Who's Pcv did you use?
ME Wagner. Excellent instructions included with the product and website.

i was right at the low vacuum setting of 6-7 so I used low idle spring set to the just 1/8 turn below the 400 engine suggestion.
Then I used my hand to fell the cruise setting, you fell the check ball bouncing, I went 1/2 then clockwise extra once the ball stopped at idle.

no oil leaks after 120 miles.

so I will increase 1/8 turn until I get oil out the breather. Then back off 1/2 turn.
 
Interesting on the PCV.... Seems like if there is no oil out of the breather, then does that mean that the PCV is now idling at the more open cruise opening? Not sure I am following.
 
Interesting on the PCV.... Seems like if there is no oil out of the breather, then does that mean that the PCV is now idling at the more open cruise opening? Not sure I am following.

Stock PCV didn’t open up enough or ar all with the large cam low vacuum at idle. I had 7” of vacuum at idle.

ME Wagner has adjustable low flow and high flow.
 
Stock PCV didn’t open up enough or ar all with the large cam low vacuum at idle. I had 7” of vacuum at idle.

ME Wagner has adjustable low flow and high flow.

Those things are worth every penny. When I first posted about them on here it caused a shot storm because of COST. The same thing that kills every MoPar guy. It’s why we don’t have anything. It’s cost first while function and value are at the bottom of the list.
 
Stock PCV didn’t open up enough or ar all with the large cam low vacuum at idle. I had 7” of vacuum at idle.

ME Wagner has adjustable low flow and high flow.
Gotcha... Well then something had to be wrong with the stock PCV valve... it will be open to its maximum flow at 7" vacuum...
 
Gotcha... Well then something had to be wrong with the stock PCV valve... it will be open to its maximum flow at 7" vacuum...

Most stock PCV valves have a poppet weight and aspring acting on it, at the beginning of it's travel. The vacuum will lift it off it's seat at about 2" and it gives some flow at 4-6" of vacuum. At 6" vacuum the poppet contacts the spring and now it is fighting both it's own weight and the spring as it rises. At the top of it's travel it begins to close off, not completely, but to a flow of 1.3-1.7 cfm or so. With the oem spring it reaches that point at 14" or so.

The lighter spring and adjustable ME Wagner will allow less vacuum to pull it to it's full travel, whereas the oem spring won't.


TSM chart pulled from a AMC forum. here is the flow rating in cfm:

16"+ 1.3-1.7
14" 1.5-2.0
12" 1.7-2.5
10" 2.1-2.8
8" 2.4-3.4
6" 2.7-3.7
4" 3.2-4.2
2" 3.3-4.4


Idk- what or why. But I’ve got zero oil leaks, good idle, no smoke. Whereas before I had oil coming out of the Valve cover breather.
 
if you don't mind me asking ? What heads and exhaust system are you using ?

The largest MOPAR Magnum heads and prior owner said they were machined for 2.20 or 2.02 exhaust valves. Idk if that’s even possible. I can verify it has 1.7 ratio roller rockers and she sounds like a big cam. Exhaust is full length TTI headers.
 
The largest MOPAR Magnum heads and prior owner said they were machined for 2.20 or 2.02 exhaust valves. Idk if that’s even possible. I can verify it has 1.7 ratio roller rockers and she sounds like a big cam. Exhaust is full length TTI headers.
Most likely 2.02 intake valves
 
The R/T heads came with 2.02 Intakes and the R/T logo would be right under the 1 and 8 exhaust port, which is probably covered up by your hedder flange. if that's what you have.
The Magnum Head exhaust flow isn't the best, that's why Mopar suggests using big 1 7/8" hedders. There is a big difference in using a maximum flow muffler, like a dynomax ultra flow, and a turbo type or anything else with less flow.
It's like the motor is fighting itself, and it is. You don't want to smother a Magnum, it has it hard enough. Just the idle, is so much better when it's free.
 
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I got the sales invoice for the 390hp crate.

Is there options to have a headshop enlarge them exhaust ports? That’s what the prior owner said he had done. Larger exhaust valves
 
I got the sales invoice for the 390hp crate.

Is there options to have a headshop enlarge them exhaust ports? That’s what the prior owner said he had done. Larger exhaust valves

No reason to make the exhaust valve or port any bigger. It’s too damn big as it is. Don’t know why they are doing that.
 
Gotcha... Well then something had to be wrong with the stock PCV valve... it will be open to its maximum flow at 7" vacuum...

I `m wondering , are you guys talking about intake vacuum or crankcase vacuum ?? -big diff. !
 
quote"These are some off brand gauges and the Optima battery is now 11 years old so when its gear at low rpm the volt meter is bouncing and the lights flicker as the electric fan is pulling power. I know that volts can cause irregular meter readings on some gauges. Could the cheap gauges and/or low battery volts be throwing out the very low oil pressure reading? This is my best hope.end quote
Sounds like you have a sending unit type aftermarket oil pressure gauge,use a real mechanical oil pressure gauge.
The fact that its dropping that much though does show a lot of of oil by passing either worn bearings or the roller tappets aren't correct
 
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Most stock PCV valves have a poppet weight and aspring acting on it, at the beginning of it's travel. The vacuum will lift it off it's seat at about 2" and it gives some flow at 4-6" of vacuum. At 6" vacuum the poppet contacts the spring and now it is fighting both it's own weight and the spring as it rises. At the top of it's travel it begins to close off, not completely, but to a flow of 1.3-1.7 cfm or so. With the oem spring it reaches that point at 14" or so.

The lighter spring and adjustable ME Wagner will allow less vacuum to pull it to it's full travel, whereas the oem spring won't.


TSM chart pulled from a AMC forum. here is the flow rating in cfm:

16"+ 1.3-1.7
14" 1.5-2.0
12" 1.7-2.5
10" 2.1-2.8
8" 2.4-3.4
6" 2.7-3.7
4" 3.2-4.2
2" 3.3-4.4


Idk- what or why. But I’ve got zero oil leaks, good idle, no smoke. Whereas before I had oil coming out of the Valve cover breather.

You obviously know more about this subject than I do , but my store bought "from autozone" pcv opens full at idle , and stays wide open to about 4200 , no partial opening anywhere . Couldn`t watch it on up in the rpm`s when I hammered it . Never had oil coming out the breathers before, even when she was an oil leaker , 5'' of ''crankcase'' vacuum now.
 
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