Engine builders - a little advice please

[tubman]

Many of you have seen my thread about the '51 Mercury engine I've had for 20 years. I put it on my test stand and it had excellent compression (95 to 110 lbs, this after sitting 20 years and at 900 ft elevation, no less). I was real happy until I turned it over with no plugs, and couldn't even get the oil pressure gauge to even wiggle. Over the last couple of days, I transferred the engine from the test stand to a regular engine stand, removed the pan, flipped it upside down and removed the #1 rod cap. What I found was a good looking journal, and a bearing shell with some embedded material. I used to "Plasti-Gage" to check the clearance, and got .0025, but the "Plasti-Gage" was irregular. (I did not take any pictures of this; sorry)

I was lucky enough to find a set of standard bearings at a killer price about 2 years ago, which I bought. I got one of the new inserts and used used the "Plasti-Gage" to check it out. This time I got .002, and the "Plasti-Gage" was nice and uniform, Here are some pictures of the second check; for some reason, the journals look a lot better in person than in the pictures.

At this time my plan is to replace all 8 rod bearings with new ones (assuming they are all in the same shape as #1). I will then remove and check the oil pump. At this time, I believe I have a stuck relief valve.

My questions are : If the rest of the rod journals and bearings look like #1, can I just replace them, or should I "Plasti-Gage" each one. I ask this because it seems to me that I should try to minimize the times the caps come on and off and the price of "Plast-Gage" these days. Also, given the condition of the rod bearings, should I pull off main caps and check them, or just leave them alone? Again, I hate to disturb anything that's been together this long.

There are a couple of other things to consider. Earlier today, I got a call from the machine shop saying the block and crank I am going to use for my 258" Hot Rod engine are good, and they are going to commence building it. Trying to build one flathead on a fixed income is tough enough, let alone going all out on two. Thus, I'd like to minimize the cost of this one. Also, I am 73 years old, and doubt I'll put even 10,000 miles on it before I go. This engine is slated to go into my '51 club coupe, which is usually used in a leisurely manner. However, I don't want to do anything to jeopardize a "std.-std." Merc crankshaft.

This is them first flathead I've done in about 50 years. Back then I didn't have any problems with them, but maybe I was just lucky. Since I can't take a couple of hours off and get another engine at the junkyard for $35 any more, I'm trying to be real careful with this one. Any advice, criticism, or comments will be appreciated.

[tubman]

While I'm at it, I"m going to post some pictures of the bearing shell I removed and some shots of the inside of the engine. I haven't done any cleaning, and it looks good to me.

[Binx]

I can't explain the lack of oil pressure, but if you've disturb the crud in a motor (which yours does have), it will find its way into the bearings. I don't think the bearings you show are bad and should be replaced given the plasi-gage readings but now that you know crud is getting into the bearings, it may be a good idea to take it apart and clean it up including the crank.

Lonnie

[deuce_roadster]

If I had an engine half apart that was gunky like that I would take it completely apart and have everything cleaned and re do whatever needs it. The bearings look to me as if contaminants have started to attack them. Time to check EVERYTHING.

[Ol' Ron]

And while it's apart, you could bore&stroke it install a cam. Only kidding.
However, The bearings look usable, I've used worse, but befor you tske evrything apart, why not throw sone cheap oil in it and find out why you have no oil pressure. Be a shame to have a bunch od new bearings in it and no oil pressure. Maybe the gear on the cam slipped. I get 30-40 lbs on a 12 volt battery and no plugs

[flatheadmurre]

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Im with Ron on this one find out why the oilpressure is missing first.
With rod bearings looking that nice the mains will most likely be even nicer.

[scooder]

I'd yank the oil pump and have a look to see if there's any issue, and the gear on the back of the cam. Could be a real simple fix, you won't know unless you look.
If I found some thing wrong in those parts, I'd fix that. If it was a real obvious issue, say a sheared gear pin or the like. I'd then strip that engine an clean it properly, check conditions of the other bearings and such, replace if needed, build it back up and run it.
I couldn't fire it up knowing that nasty crud is on the pan. If you get some on your fingers and have a feel, I would be surprised if you get no gritty feeling, it's like there's tiny flakes of rust mixed in. This is fairly normal in an engine that's been run a fair amount (like your engine) and that been stored for a long time. That old crap in the pan is full of nasty acids and stuff.
Martin.

[JWL]

Given the limitations of disposable income I would have fixed the pressure problem first. If that fix did not indicate a long standing problem I would have looked at the mains and if they look good, I would shake the rods, clean the easy and obvious gunk, and be "on the road again" if nothing looked irregular.

That old bearing is beautiful.

[tubman]

Thanks for the input. I have logical reasons for doing what I did. When it became obvious that I didn't have adequate oil pressure, I decided the first order of business was to find out if this was caused by a long term internal problem, or a result of sitting for so long. When I decided I needed to pull the pan, you will notice I pulled it before I turned the engine upside down. I did this specifically to prevent anything in the sump from dropping into the engine. I specifically decided to pull a rod cap off the first journal, because it is the furthest from the oil pump, and rod bearings are usually more susceptible to failure than mains. Now that I have determined that the problem was not long term, I am going to pull the oil pump. That is today's task. I checked with my old "Motor Manual", and they have a procedure for checking out the oil pump. At this point, I am leaning towards a stuck check valve; we will see. If there is no obvious problem with the pump, I plan to make a fixture such as G.M. described to make sure the pump produces enough pressure. Once I get a known good pump reinstalled, I plan of running pressurized oil through the port in the back of the block with the pan off the engine to see if there are any unusual internal leaks. I will find out what's wrong. Once I have the problem solved, I will thoroughly clean the inside of the engine, replace the rod bearings and reassemble it.

A couple of things I find curious. First, a couple of you mentioned that the old bearing shell looked good. I can easily see the junk embedded in it, so I will be replacing them. I already have a new set of standard bearings. What concerned me more than the appearance of the bearings was the fact that the "Plasti-Gage" was quite irregular when flattened, This indicates to me that there is uneven wear on the old bearings. It showed .025 clearance with the old bearings. With one new shell, it showed .002 clearance. It seems to me that if I replace both shells, I will reduce the clearance another .0005, resulting in rid bearing clearance of .0015; since the factory spec calls for .001 to .003, I figure this is close to perfect.

The other thing is that I have pulled many engines apart over the years, and this one is by far the cleanest inside I have ever seen. Perhaps the angle of the photographs is bad or something, but this is one clean engine. I have been very careful of everything I have done so far, and am quite confident I can clean it adequately.

[HP Hunter]

Those baerings look good, I would check or change the pump while its apart though. That clearance is not enough to give you no pressure? You may have a relief valve sticking?

Harry

[JWL]

You might have missed the message from Ron--check the drive gear on the back of the cam. The pump must be turning to produce output.

[Scott H in Wheaton]

Also, I don't think sitting for a long time will cause a no pressure issue.

if it doesn't have pressure its because something is wrong, and it was wrong when the engine was stored.

[flatheadmurre]

With a broken pin in the pumpshaft or loose gear on the camshaft it may turn enough from friction to produce flow but slip when pressure needs a bit more power.
Stuck reliefvalve or broken spring ?
Just to cross them off the list one by one until you find the issue.

[Ronnie]

Good tutorial here
http://www.enginebuildermag.com/2009...mp-technology/

R

[tubman]

Originally Posted by JWL

You might have missed the message from Ron--check the drive gear on the back of the cam. The pump must be turning to produce output.

This, of course, is one of the things I will be checking. I don't think it will be a problem though, as later flatheads, unlike earlier ones, have a flat machined on the shaft and gear to prevent slipping. Also, when I had the engine on the test stand, it had good oil flow, but little pressure. Since there don't seem to be any bearing clearance problems, I expect I will find the problem is with the oil pump or the drive.

[deuce_roadster]

Couldn't the relief valve stuck open from sitting a long time and then being used create a situation where there would be some flow but no pressure? I guess I have a different definition of really clean. Good luck, I hope it works out for you. I would be afraid of more of the stuff you see embedded in the old bearing shells coming out of the crankshaft and other passages and getting into the new bearings. You certainly will find what is causing the oil pressure issue, and be able to make it run. My guess is the pump itself.

[Ronnie]

The relief valve is closed in the static position.

R

[Mac VP]

Probably not the problem but don't rule out the front oil galley pipe plug (6026 in the drawings). If it were missing you'd have zero oil pressure.

[tubman]

I spent some time yesterday cleaning the engine up before I do any more mechanical work. Luckily, no grit or rust flakes in the pan. There is about an eighth inch of what feels like axle grease in the sump. What looks like "gunk" on the pan baffle is actually a black "stain"; it has no substance, just a color change. I hope to get the pump out today, but that may not happen, as it's going to be in the low 80's (!) here in north central Minnesota today. Sounds like a good day to fire up the Corvette and go look at the leaves!

[Diavolo]

Just a thought but what if all the oil drained out of the pump and it can't prime? Could pull the cover off and cram some grease in the pump, also check for engagement into the idler gear to the cam.