My 50 Plymouth idles about 15-20 psi and about 40 psi driving. The oil pump is new, the rest of the motor, unknown mileage. Posted using the Full Custom H.A.M.B. App!
I wouldn't worry about it if it was about 5 or 10 psi or so at idle, as long as it increased with higher RPMs.
I know you didn't ask but there used to be "oil reducers" that you inserted in the oil galleys going to the cam bearings? Essentially oil " jets". Evidently old mopar flat sixes tended to run too much oil past the cam bearings. I don't know if this was the result of a design problem or just worn parts. Where I live I have a friend who tried everything to raise hot idle oil press mopar flat six. New oil pump, heavier oil, removed pan and cleaned pan and screen, etc. all to no effect. Found a set of these reducers SOMEWHERE and that did the trick They came packaged on a card.
The manuals of the period note not to be alarmed by low oil pressure at idle, and in top gear look for 10lbs per 10 mph. should top out near 45 to 50 for an engine in good shape. If you have 30 at 30 and above you are ok on an experienced engine. There is a caveat. If you have the Chrysler full flow oil filter ( a cast metal piece mounted to the side of the engine on a triangular mount, a fouled filter will effect oil pressure and flow. If you have the bypass, style, sheet metal can with visible supply and return lines, if these foul they go to bypass mode and do not effect pressure or flow, they just bypass the filter. Also on the drives side of the engine near the oil filler tube is access to the bypass pressure valve and spring. It is common for the springs to break and result in low pressure. Also the plunger can foul and get stuck in position effecting pressure. So if you have no unusual noises in accompaniment to low gauge reading at idle and it kicks up to 30 at cruise should be liveable. You can also check your gauge by adding a cheapo after market gauge, just to be sure how low, low is.
Factory spec 45 - 55 PSI @ 40 MPH. I wouldn't worry too much as long as you have at least 10 at idle (hot) and 30 on the road.
Thanks alot for all the info another question is are these motors supposed to sound like a tractor at higher rpms?
Don't know many tractors that run at high rpm most are governored for a max of about 2000. So maybe a better description of noise. Fan roar, exhaust, piston slap, spark knock, lifter noise???
The thing sounds like its hammering going down the road when i got the motor i pulled the pan cleaned everything up and put a new oil pump in i also noticed that there is new pistions rodes and bearings in it so im not real sure were the noise is coming from
Yes ! run it thinking of a diesel engine.... Low RPM, TQ..... You can help it by adding electronic ignition.... Langdons stovebolt sells a mini HEI that I used and really made a difference, but L-6's love 1300 rpms....LoL its true.... When a normal engine stalls out, the L-6 is makin power and smiling..... 1800 with points mine reminded me of a Farmall.... That went to 2200rpms with HEI... but over that, probably shouldn't be there long.... runnin straight pipes, at an idle, she should lope like a Harley.....
My 39 Plymouth truck (with 54 plymouth engine) runs at about 50 psi at moderate RPM, about 15-20 at Idle.
The engine should be very quiet at any speed if it has a good muffler. Not sure what you mean. I have seen them completely worn out, with broken pistons, low oil pressure, still running and hardly making any noise. First check the valve adjustment. You have to jack the car up, take off the right front wheel and remove an access panel in the inner fender. Then you can take off the valve covers under the manifold and get at the valve adjustment. Correct setting .008 intake .010 exhaust. If you do a lot of high speed driving, or in a truck, increase the exhaust clearance to .012 Should be adjusted with the engine hot. I like to have the access panel out. Go for a drive, jack up car, take off wheel, remove tappet covers, start engine, check all the intakes, check all the exhaust. Make a note of any that need adjusting. Shut off, adjust, start engine, check again. Before you say I am "nuts" the engine only idles at 400 RPM and does not throw around much oil. Once the valves are set correctly you only need to check them every 10000 or 20000 miles and might need to adjust 2 or 3 of them slightly. If they are way off, as yours may be, you can set them cold, drive the car for a few days, then recheck hot. There should be NO noise if the lifters are adjusted correctly. Maybe a very slight ticking if you set the exhaust at .012, even that should be impossible to hear with the hood shut.
I don't know what you mean by hammering at high speed. If you had a bad rod it would have come thru the side of the block by now. OK if it is a rod knock STOP and rebuild the engine before you blow it up. Could also be a broken piston. This is common on old, worn out engines. You don't give us much to work on like make, model, year, engine size, condition, miles, symptoms.
Spark knock? Overheating engine/ over advanced timing/ lean mix/ combustion chamber deposits/ low octane gas oh and inappropriate gear.
Spark knock happens on a hard pull at low RPM. Not likely on a low compression flathead on today's gas. It is impossible to tell without more information but if it is not valve adjustment it may be piston slap or rod knock. If it is either of those, STOP before you blow the engine.
I am going to throw a thought at you. Years ago I rebuilt my Hudson 202 flathead 6. It runs well, but had a what sounded like it had a rod knock at idle. I took the big screwdriver and held it at the bottom of the engine and heard no knock. Then I placed the screwdriver on the head bolts. There it was, the noise came from top end. So I did some research and found that the replacement head gaskets were only big enough for .030 overbore. I put .060 oversize pistons in and the damn pistons were hitting the head gasket, not much, but just enough. I removed the pistons and increased the chamfers by .050. Installed the pistons, and no piston knock at all. Now to your engine, could the same have happened to your flathead 6? It sounds like it was rebuilt, so you may want to check this out.
The motor is for a 1948 desota is the 25 in block and i just got confermation from the guy that i bought it off of said it was rebuilt about 3500 miles before he pulled it to stuff a 350 in to get mpre horse power and its a 237 cubic in if im not mistaken hanks for all the input and it also has 2 inch exhaust from the manifold to a thrush glass pack and 2 inch to the back of the car
You have so much good info on the old mopars Rusty......then you start nitpicking on the stupid shit, why? Nobody thinks a flat engine exists...... Edit, of course an opposed 6 does.
Frankie almost everyone on this board refers to a flathead 6 as a flat 6. Somehow they know Fords are flatheads, everything else is flat. I rag on them all the time for this. So for once somebody got it right, I thought I owed them a compliment on it. There IS a reason for getting things right. How many threads have you seen filled with hopeless hope because the original question was wrong, did not say what the person intended to say, or was all mixed up? YOU know the difference between a flat 6 and a flathead 6. I know the difference and 1951custom knows the difference. But not everyone does.
This thread is a good example of getting bad, incomplete information and trying to be Sherlock Holmes and figure out the answer . First question, what is the oil pressure supposed to be on a Chrysler flathead six. Simple answer. 45 -55 PSI @ 40 MPH Next question, is it supposed to sound like a tractor? Uh oh, I don't even know what he means. If the muffler is blown it will sound like a tractor. Is that what you mean? Next question, I hear knocking or banging at high speeds STOP this is not good. May be a bad rod or broken piston which will kill your engine if you keep driving. See what I mean? At this point I don't know what is the matter and evidently, neither does the questioner. If we had all the facts maybe we could figure something out. Latest nugget of info, the engine was recently rebuilt (according to the previous owner). Well I wouldn't put too much stock in the word of someone trying to sell a used car but there it is. That is all I can say with the limited info available. Does it have a good muffler? What kind of noise is it? How loud? If you can hear it inside the car, and the muffler is good, and the valves are adjusted, there could be something seriously wrong inside the motor. Every bit of info helps. If the info is wrong, incomplete, mixed up, who knows what is going on.
I had a 230 L-6. It was exactly like I stated, before and after Langdon HEI.... Some old timers around had the same engine, bought new and always loved how good it sounded.... They where never designed to run at 2500 rpms. They are luggers, and over 1500 start to take on Farmall characteristics sound... Mine was a fresh rebuild, and ran great... Anyways, I think we are beating a dead horse, this guy got his answer and has moved on....
Sorry to disagree but the factory that made them says the Dodge flathead six develops max HP @ 3600 RPM. They will rev higher than that, 4000 - 4500 in stock form. Not recommended for long periods but they will do it.
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