Bought this flathead Ford back in May of this year. It's always had low oil pressure, about 20-25# when cold 5-10# when hot. The other day I was road testing to see if my new plug wires solved my miss(they did). Had been running down the road at about 50 and slowed to make a turn. Had to wait a minute for an on coming car. When I heard this rattle from the engine. Lasted about a second or two then repeated once more just a moment later. Sounded like all the rods were knocking. I looked down at my Oil pressure gauge and it was sitting on 0. Then as quickly it jumped back up to 10#. What the he** happened? Everything seems to be back as it was but it sure startled me. My next question is can you replace the oil pump without pulling the engine?
I doubt if an oil pump would be intermittant. More likely to be relief spring or some thing in the pickup. On some engines the relief spring is in the pump and in others it is in the main galley. I think I could change change my pump from the bottom but I would never do it because I am 66 and don't work well upside down.
This is what I would do and I'm assuming this was/is an older engine and not a fresh rebuild. Drop the pan to see if it's loaded w/sludge. It probably is to some extent so clean it all out and then remove your intake and clean out the probable sludge in there as well. Flush w/kero and I would install a new stock oil pump and p-up (at least clean up the pickup really, really well). If you are running the stock top mount oil filter, clean it out and remove and blow out the lines. Also, clean out or replace your breather cap and install a PCV valve to help reduce the sludge. After putting it all back together I would run some 20w-50 detergent oil in it for a bit (maybe a 20 minute drive), drop the oil, and then install the regular 30W non-detergent oil a flattie calls for. This should clear the oil passages and bring up the oil pressure so you quit knocking. It is not unusual for a flattie to drop to 5 lbs of pressure at hot idle. Oh, and by the way - doing this on your back is a bummer - befriend someone with a lift!!
I have no idea how long this engine has been running. The prior owner was unable or unwilling to tell me. The engine dose not smoke, show an blow-by, nor has it used any oil in the last 1000 miles or so that I can tell. The plugs look just exactly like the literature says a properly burning plug should look. I have a synthetic oil in it right now as I recall 5W 40. I have not checked the compression since I got it. The engine is a 85 horse 24 stud with a 12V conversion. Didn't run worth a crap when I got it. Installed new points and sent the Dizzy off for adjustment. Rebuilt the carburetor and just replaced the plugs (NKG B6L) and plug wires. Seems to run smoothly now but that clatter startled me.
You might want to try some straight 30 weight and see if your pressure comes up a bit. Synthetic 5-40 is pretty thin stuff.
Ebbsspeed has this right - your flattie was running on straight non-detergent 30W oil probably before the synthetic was put in - the oil is thin and would cause the problems you encountered. It will also find any and every leak you never had as well - just the nature of the beast I guess .... I would still do my suggestions above but wait until the "off-season" and run straight 30 non-detergent for now - your pressure should be OK with that.
Old wifes tale !! Flatheads don't need non detergent oil. 90% of those that have been in use in the last 20-30 years have been getting detergent oils. Non- det. has been not easiely available without a bit of looking for the last 20+ years. HOWEVER unless you are running in a very cold area don't use 5- anything straight 30 or 20-50 is what I've been using in 90% of what I've been driving in the last 40 years. Flatheads to Corvairs to SBCs.
Well the reason I went with the synthetic was the weather. 70 days over 100 degrees here in Texas. The 30W when hot ran about 5 psi and the 5W 40 brought it up to 10#. Would have put 50W if I had found it.
Could someone explain why a 10w30 wouldn't be a good choice? Why a straight 30w when there are new-fangled oils nowadays? It's what I've been running on a stock model A and what I've run on my flathead in the past. Am I wrong?
Do not run non detergent oil. I totally disagree with the old idea that the engine would run better with it. If there is a sludge problem then the odds are its because it was running on non detergent. The new oils are by far superior to the old ones. I have never run multi viscosity oils on my flatheads. Straight 50 valvolene racing oil which has zinc. Change it every 500-1000 miles.
there are alot of posts on this.but to sum it up real quick. no zinc(or very low #s) and really low phosphurs in todays shelf oil. all our old engines need this stuff to survive. straight 30 is ok aslong asit has the old ratings.
You are right but I was/am concerned of possible sludge problems using a detergent oil cleaning things out in an old engine that had only seen non-detergent oils. It was said the previous owner gave him no info on the engine so what I suggested was to be safe and "to error on the side of caution".
If you suddenly switch to detergent oil all the accumulated crap will start to loosten up and float around potentially causing alot of problems. Same is true for "engine flush" or kerosene or diesel fuel flushes. The general rule is to stick with non-detergent unless you manually clean everything up first, then run only detergent oil from that point forward.
Fairly easy to flush everything down pretty well by rmoving intake and pan... Stuff to look at: The pickup, as noted, and side and end play of gears within pump A flathead with a good pump will pull some running oil pressure with plug missing from main oil gallery. Early and late differ slightly in pluggage, and the front plug especially seems to be commonly missed by builders. The intermittant raises another worry...gear on rear of cam that drives the pump could be losse and starting to rotate on its post...you can see how lovely thay would be as it starts to wear away the shaft. Some have D-shaped hole and shaft to prevent this, some do not. An outside chance given the interchangeability of everything would be totally wrong choice of pump/pickup parts for your pan, giving a pickup smashed against the floor or just skimming the top of the oil.
Sorry to get off the topic of the original post. I use a zinc additive for that stuff. I just figured the multi viscosity would be better for starting.
non-detergent 30 wt on shelf at Wal-Mart, been there for years, ya just gotta look hard. also many air-compressure oils are "S" rated and suitable for gasoline engines.
The synthetic oil you are using has probably loosened up old sludge and deposits. You can help clean things out by draining and filling with kerosene start up for a minute or two drain and refill a couple of times and then use whatever oil you choose.
You know the oil on the dip stick does not look all that dirty. It's still clear enough to see the writing on the dip stick. Lots of good info here. Believe I'll try some of these remedies.
When you find the problem let us know so we can benifit from your experience. I would try warming it up and turning in both directions while watching the oil pressure gauge.
Decided to try the easiest thing first. Changed my oil to Valvoline 50W Racing. Cold run up 50/55#, running down the road 20/30#, hot idle 10/15#. All the readings are about double what they were last month, but it's 30 degrees cooler also. Think I'll just leave it as it is for now and see what happens. I'm not happy with the car, it's beautiful but stock and I'm a Street Rodder, KNOW WHAT I MEAN?
I am working on a flathead for a customer 1935 ford 5w.Just to let you know, the pressure relief valve and spring is under the intake manifold.If you pull the intake there is a plug towards the front of the engine if you pull the plug out you will get the spring and valve.I pulled teh one out of this 35 and streched out the spring and it did have a little more pressure.The intake is fairly easy to get off and napa has gaskets available. Chris
you asked about replacing the oil pump....pulling these off is a PITA when its on a stand and you can access everything. also there is the driver gear and access panel that i cant recall if you can get out while it has a fly wheel on. usually you have to pour solvent down in that gear area to help melt the sludge thats holding the pump in.
That's and old wives tale about detergent oil loosening everything up. Use a 20/50 oil which is detergent. It has all the ZDDP you will ever need. But pull the pan a clean up any sludge, especially the pick up tube. I would go with a new oil pump too.
IMHO,,, It is not an oil problem, but a mechanical problem, like relief valve, clogged pickup, or loose clearances. I also don't think you should use what's known as non- detergent oil. It CAUSES sludge. If it were me, I would contact one of the experts at a major oil company and get a straight story on lubricants. Then I would check out the above. Good luck!
I have to agree with a lot of what Bruce says #17. My Flathead would do the same thing as you mentioned in your post...next to no oil pressure at idle using 15-40 went to zero several times, the engine had only a few thousand miles on a fresh rebuild by the previous owner..So I dropped the pan engine in the car ('51) put in new pump same result. and went to 20-50 0il ....finally pulled the trans and flywheel pulled off the oil pump idler gear and discovered the drive gear on the cam was cracked,thus turning on the cam shaft....like Bruce said, there is a small flat or "D" in this gear to line up with the flat spot on the cam. I replaced the gear making sure it was lined up properly on the cam. I think a lot of people don't realize there is a flat spot and just tap the gear on the shaft. That was 15 years ago, the car is still running strong...I keep the drive gear as a reminder and paper weight next to my computer
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