Author	[Modern View]
trobin0406 07-24-2012 07:19:45 192.127.94.7 Report to Moderator	I just rebuilt my first 8N. Its a 1952, my problem was last night when driving the tractor around mowing the yard i noticed oil pressure getting around 20 hot when it was around 1500rpm. which i didnt think was bad. But i stopped to get a drink and lowered rpm to idle and pressure dropped to a hair above 0. I replaced the oil pump and had the motor completely rebuild. I filled it up with 10w30 oil. When i first start the tractor i have around 45-50 psi cold. So why do i have low oil pressure at idle? There is no knocking in the motor, a slight growling noise in the rear end but that is probably a question for another post. I just really want to get the oil pressure problem fixed before i damage it. [Reply]   [No Email]
TheOldHokie 07-25-2012 06:44:03 108.8.17.88 Report to Moderator	Re: 8N rebuild question in reply to Britcheflee, 07-24-2012 07:19:45   Quoting Removed, click Modern View to see Based on the symptoms the bottom end is likely the problem area. Did they regrind your replacement crankshaft or use it "as received"? In addition to a visual check for signs of wear or scoring get yourself some Plastigage and check the oil clearance on ALL of the mains and rods. The bearings should look pristine with an oil clearance of .001-.003 new and a max wear limit of .005. If I was payiing a shop for a bottom end rebuild I would want/expect something near the middle of the new range. Anything over .003 is simply unacceptable in my book. TOH [Reply]  [No Email]
TheOldHokie 07-24-2012 18:01:50 108.8.17.88 Report to Moderator	Re: 8N rebuild question in reply to Bruce (VA), 07-24-2012 07:19:45   Quoting Removed, click Modern View to see Yeah - maybe bump that pressure up to a whopping 5 PSI at hot idle. That would be a nice cheap way to help ease the pain of $1000+ spent on a defective rebuild. Might even keep it running long enough to sell it to some sucker that thinks that's the way it's supposed to work :evil: TOH [Reply]  [No Email]
TheOldHokie 07-24-2012 12:37:06 108.8.17.88 Report to Moderator	Re: 8N rebuild question in reply to Ultradog MN, 07-24-2012 07:19:45   Quoting Removed, click Modern View to see Repeat after me - it is not the oil!!!. The temperature in Georgia could be hot as Hades and it still wouldn't be the oil. Given that you have good cold pressure but it drops off when hot the pump, pickup, and relief all appear to be working OK. There are a limited number of places that pressure could be going and excessive main/rod/camshaft journal clearances are the main suspects. Was it this bad before the rebuild? If you replaced the oil pump and did not have the mains line bored that is a large red flag. If you paid someone to rebuild this for you take it back to them. Tell them, diplomatically or otherwise, that they botched the job and you expect them to make it right. A properly rebuilt engine should not have near zero hot oil pressure. On the other hand if you piece-mealed the machine work and did the rest on your own you are probably going to have to fix it yourself. Good luck, TOH [Reply]  [No Email]
NoNewParts 07-24-2012 11:14:03 67.240.145.25 Report to Moderator	Re: 8N rebuild question in reply to trobin0406, 07-24-2012 07:19:45   45-50 cold start 20 at 1500 warm zero at idle warm is much too much of a swing different oil won't fix this possible problems: like said, if pump/cap was replaced, and not aligned-bored pick-up cracked or holed, pulling air slightly debris holding the relief plunger off its seat wrong bearings, if it was just a bearing renew ie putting in STD bearings when 002, etc, were in there before your readings are what I see BEFORE a rebuild. Even if I just put in new rod/main bearings, nothing else, just swap in new, same size as old, readings would/should vastly improve. If somebody else rebuilt it, take it back right away, if you did it, drop the pan and find out why. On a fresh rebuild with those readings, something is wrong and the motor will fail. [Reply]  [No Email]
TheOldHokie 07-24-2012 09:40:41 108.8.17.88 Report to Moderator	Re: 8N rebuild question in reply to Doug (OH), 07-24-2012 07:19:45   Quoting Removed, click Modern View to see That is abnormally low oil pressure at 1500 RPM and dangerously low at idle. It has nothing to do with the grade of oil you are using. You still have excessive clearances somewhere in that engine. I'd strongly express my unhappines to the rebuilder. If he tells you it is normal for an old tractor and/or to use a heavier oil I would permanently delete him from my list of reliable shops. TOH [Reply]  [No Email]
Dell (WA) 07-24-2012 09:18:44 63.226.221.8 Report to Moderator	Re: 8N rebuild question in reply to trobin0406, 07-24-2012 07:19:45   trobin.......would you believe that 10-30 oil is really 10wt oil with heat sensitive additives that make it act like 30wt when hot? It is NORMAL for HOT OIL to thin and you will loose oil pressure. Its called the viscosity factor. In 1939, Ford recommended straight 30wt detergent oil, and 40wt detergent oil in very HOT climates. Yer 1952 8N is "pressure limited" to 35psi by spring loaded piston behind the BIG nut behind the water pump. Some people in search for more oil pressure will remove the NUT and piston (yes there is supposed to be a flat on side of piston) and S.T.R.E.T.C.H the spring a little bit. Me, I just 20-50wt oil in my eazy starting 6-volt 52-8N ........Dell [Reply]  [No Email]
trobin0406 07-24-2012 11:48:18 192.127.94.7 Report to Moderator	Re: 8N rebuild question in reply to Dell (WA), 07-24-2012 09:18:44   So should i drain the oil and try a 40wt? Yesterday in Georgia it was in the high 90s so i know the tractor was working hard. Would stretching the spring stabilize the oil pressure? I would like to try the easiest thing first instead of having to tear the tractor all apart again. [Reply]  [No Email]
Dell (WA) 07-24-2012 17:40:35 71.217.20.96 Report to Moderator	Re: 8N rebuild question in reply to trobin0406, 07-24-2012 11:48:18   trobing0406.......what does 6-qts of 40wt detergent oil cost??? $12? (dunno, I haven't had to buy oil lately) You can always try some panzzer pizz. (tink STP of Andy Grannitellii and Mario Andretti fame) ..........Dell [Reply]  [No Email]
jackinok 07-24-2012 12:45:28 162.58.82.135 Report to Moderator	Re: 8N rebuild question in reply to trobin0406, 07-24-2012 11:48:18   my opinion again,your building up pressure to 45 lbs cold before bypass valve and spring opens. stretching it wont increase pressure hot.it will give you higher oil pressure cold maybe ,but the spring doesnt lose its tension.a straight weight oil may help, i use straight 40 weight in mine, but if its varying that much,after a rebuild,i think you hve bigger problems,again my opinion. [Reply]  [No Email]
HCooke 07-24-2012 08:41:25 70.195.0.73 Report to Moderator	Re: 8N rebuild question in reply to trobin0406, 07-24-2012 07:19:45   I would replace the 10w30 with 15w40 oil. [Reply]  [No Email]
jackinok 07-24-2012 08:32:36 162.58.82.135 Report to Moderator	Re: 8N rebuild question in reply to trobin0406, 07-24-2012 07:19:45   did you replace the pump or rebuild the pump?two different ball games.If you replaced the pump without having the block line bored you could wipe out your new bearings. If you had it rebuilt it had to be done properly or you will have low pressure obviously. One thing that I personaly believe contributes to low pressure is the fact that there are no cam bearings in these,but thats just my belief,no proof. While these will run for years sometimes on very low oil pressure,if you had yours rebuilt by a shop i would let them find the problem. [Reply]  [No Email]
trobin0406 07-24-2012 11:44:52 192.127.94.7 Report to Moderator	Re: 8N rebuild question in reply to jackinok, 07-24-2012 08:32:36   The pump was rebuilt. I had to buy a good used crankshaft because the old one was way to worn. I then brought it to the machine shop where they matched it to new bearings. I can believe after all that it would be a bearing issue. Should i attempt to remove the oil pump and start checking for problems there? [Reply]  [No Email]
old 07-24-2012 12:55:59 209.86.226.32 Report to Moderator	Re: 8N rebuild question in reply to trobin0406, 07-24-2012 11:44:52   Do you run it year round??? If you only use it in the summer I would switch to a 40W oil. If you run it year round I would go with say a 20W-50 oil and see how that works out. I have one tractor that I run a 60W oil in but it only gets run in the summer and it as far as I know has not been opened up since back in the 50s if it ever has been opened up and it is a 1935 tractor that my grand father owned and I have had 5 generation of my family on it [Reply]  [No Email]
jackinok 07-24-2012 12:34:25 162.58.82.135 Report to Moderator	Re: 8N rebuild question in reply to trobin0406, 07-24-2012 11:44:52   first,IN MY OPINION, i would drop pan.next make sure oil pickup tube is not loose thats sort of common.then pull oil pump.look for scoring where gears have eaten into bottom cover.if you can see where gears have worn you likely have excess wear there you can sometimes fix this by laying a piece of 600 grit or so sand paper on a piece of glass and carefully honing out marks. next start checking bearings with plastiguage. better to have them dry of course and dont turn engine with plastiguage in cap.youll likely find a bearing shot or worn.maybe even one or more badly scored if you didnt get oil journals good and clean.Again my opinion but ANYTIME you change the crank block should be line bored. again this is my opinion,your engine might run a long time but it shouldnt have these issues.Did you check engine bearing clearances with plastiguage when you assembled it? [Reply]  [No Email]
trobin0406 07-25-2012 06:28:49 192.127.94.7 Report to Moderator	Re: 8N rebuild question in reply to jackinok, 07-24-2012 12:34:25   I will try pulling the pan in the coming weeks to see if i can find anything that you have described. I didn't assemble the bottom end so i don't know if it was measured using a plastiguage or not. I will definitely ask and find out. [Reply]  [No Email]