Re: [AMC-list] AMCRC event, and...

[Frank Swygert <farna@xxxxxxx>]

Glad you had a good time at the meet. Sorry about the oil problem though!

I looked at the oil circuit diagrams in several TSMs. Only the old 196 relief circuit makes any darn sense to me! It bleeds oil off directly back into the pan. The 196 pump with oil filter has the relief in the pump cover, and just dumps oil back into the pump. So does the relief on the 232 pump. Well, if you have a good volume of oil in the pump already there's not going to be a lot of pressure relief! You, however, are using the block mounted relief valve, not one in the cover.

I do have some suggestions.
1. Increase clearance at the pump cover. Simple enough -- thicker gasket.
2. Reinstall the original bypass filter. Again, easy enough, only cost is for a new filter.

See what kind of pressure drop you get with one or the other. Another suggestion would be to increase the size of the relief hole, but that would be a last resort since it can't be returned to normal. A shorter or lighter spring (maybe cut one of the too heavy ones you have down?) might be all you need too.

I do recall that my old 196 held excellent oil pressure (60-70 psi at highway speeds), but it never held more than 20 psi at hot idle. The only real change you've made is in the pump, so I'd try that thicker gasket and get 0.006-0.010" end gear clearance again. I don't think the filter will help as the L-head versions originally didn't even have a filter. Maybe they used a different pressure relief spring without a filter, but I don't think so. The filter kit was a dealer installed option in the late 40s, and I don't think the kit included another pressure spring. I know there were aftermarket kits in the 30s and 40s that didn't, it's possible the dealer kit did.

Oil pump end gear clearance on the 232 oil pump is spec'd at 0.001-0.003 with 0.003 desired. On the V-8 the 75 TSM says 0.002-0.006 with 0.006 desired. I'm thinking that the old 196 would have a greater end clearance simply because of the older technology involved in building the thing. Remember, it's basically a 1941 engine, so state of the art late 30s engineering and tooling. BIG difference between pre-WWII and post! The pump was probably made to pump a lot of oil even with a big clearance, and now that you've tightened it up to modern specs it's REALLY putting out! I couldn't find any end gear specs for the 196 oil pump. The TSMs say the pressure relief is 50-58 psi, aluminum model was 60-65. You shouldn't be getting over 60 psi at any time with the engine hot at mid level speeds, though it may go up a bit more at high speed (mine would go up to 65-70 when it wasn't too hot out at 65-70 mph, but not under those speeds).

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Date: Tue, 29 Jun 2010 23:33:14 -0700
From: tom jennings<tomj@xxxxxxx>

Got back from the AMCRC meet Sunday night. I was there only for
Saturday, I'd visited a friend in Oakland Friday, drove up first thing
Sat. morning. Saw Joe Fulton, we got into a drunken brawl and the
police came as usual. Umm just kidding. Met Steve Fox, but no one else
who'd admit to being on this list!

I took some pics, I'll upload 'em somewhere soon.

Well I got back Sunday night, but my ride home did NOT go well -- lost
oil pressure pulling out of a rest stop onto I5, the desolate section.
I will spare you the incredible nightmare I had with SoCal AAA, it's
too traumatic to talk about still and I ain't no delicate flower.
ANYWAYS. Car got towed how to LA. $$$$. I killed the engine within 1 -
2 seconds of the light coming on.


I assume I sheared the woodruff key. I'll find out when I get the pump
out. So depending on what the problem turns out to be, I have two
possibilities: deal with and fix it, or restore the oiling to stock
configuration. But I think I have another more basic problem...

This motor should not have 60 - 80 psi all the time. It's 60 psi at
700rpm idle, hot, 10W30, even now with 1600 miles on it. It can only
be one of two things:  too much pump volume, or a restriction in the
load side of the oiling system.

Volume: I did two things that increased volume: blueprinted the pump,
and eliminated the bypass filter (which bleeds oil right into the
sump). But it's hard to believe dropping the gear end clearances from
.009" to .002" did THAT much improvement, nor that the bypass filter
with it's 1/8" brake line bled off THAT much oil. I assume the
blueprinting is the larger effect. I wish I knew.

Restrictions: I would be worrying that the machine shop did the cam
bearings wrong, but I recall distinctly the machinist telling me
without me asking that the oil holes in the bearings lined up OK (I
told him to watch for the wrong parts, eg. the 61 oddball year
bearings). I personally looked at the front one. If the crank or rod
bearings were installed wrong, it would have died long ago. Top end
gets plenty of oil.

The bypass plunger and spring should only be operating at "high
speed", 2000, 3000, or whatever. At idle, the pump shouldn't be able
to put out enough volume to lift the plunger. There should be enough
flow through all the journals etc for the pressure to not get up that
high.

So why do I have 60 psi at idle? Was I an idiot to "blueprint" it
without knowing whether there was a volume problem or not?

Should the pump be physically stressed putting out 60, 80 psi all the
time, normal or not? Is that too much stress on a dinky 1/8" thick x
3/8" wide woodruff key? (Yes it was a new key.) Is my earlier bypass
spring problem related somehow? Maybe I stressed/fractured it then,
and it's just failing now. It went out as I revved it to 3000 in 2nd.

If the woodruff key is simply marginal, I could use a harder key, or
mill the shaft and gear for a larger key. Two different gauges both
read the same oil pressure, for the record.



--
Frank Swygert
Publisher, "American Motors Cars"
Magazine (AMC)
For all AMC enthusiasts
http://www.amc-mag.com
(free download available!)


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