I am embarrassed by my findings

M

Mark Pietz

Member
Ok. Getting down to ground zero by doing what I should have done many months ago. Problem with this project 4-196 is that it continually pops and backfires off idle, but will eventually pass through that zone and actually run fast. No power off the line (can't get out of its own way), I.e., not driveable. Went through the carb multiple times, new wires, cap, no detectable vacuum leaks via the normal ether test.

I just did a compression test. I thought I had looked at the plugs at one time, but apparently I had intended to do that but must have been distracted and didn't, because I discovered this thing has four splitfires in it, gapped at least 0.040". Plug #1 didn't even have the metal gasket under it. Center electrode Rich brown so not running lean, when actually ever ran.

Compression test: engine warmed up, throttle blocked wide open.

#1: first revolution 60#, then pumps up to 143 lbs after six revs.
#2: first revolution 60#, then pumps up to 130 lbs. After six
#3: first revolution 60#, then pumps up to 150 lbs. After six
#4: (first time). First revolution about 60#, then it stopped moving next rev or two, then caught up to about 150 lbs., then dropped to zero. Whoah. Did this again. It performed normally like cylinders 1-3.
Hmmm..did this a couple more times and it didn't repeat the sudden drop.
Went back and did #2 again because it was the lowest (but still ok). This time it plateaued around 100# for a few revs, then caught up to 130 lbs. As before. Did this a couple more times and results like first time.

So...are these drops for cyls. 2 and 4 evidence of the dreaded "sticking" valve? I'm probably staring at the obvious diagnosis, at least until I pull some things apart. Can't believe I didn't do this test a year ago, but we learn. :icon_gonk:

the plan was to put it up on blocks and yank the head anyway just because I couldn't find another reason, but in the end that was the real reason anyway?

Hoping to find a good shop in Auburn area that can do a valve job. For extra insurance, should I go stock valve springs or bb, just because? I won't trust what's in there.
 
Call's moore's engine supply(823-5481) and tell Bob or Rich that I sent you. They have done many IH motors and heads for me thru the past 20 years.
 
Ooops. Google'd 'em. I know where they are now. I'm wondering when I get this head apart that I'll find some busted springs, hopefully the rest of the engine is solid.
 
Mark,
yes symptoms point to a sticky intake valve. Doesn't mean the head needs to come off to be rebuilt.

Sticking valves, especially intake point to:

1) lubrication issues due to bad cam bearings. Verify with cut open valve cover. If oiling is good step 2

2) bad gas. Varnish deposits cause intake valves to stick.
Clean old fuel out and replace with new fuel. Remove all intake valve springs and clean with carb cleaner then re-oil and reassemble. Re run and drive for 20 minutes.
 
Last edited:
Idled it without the valve cover (made a mess), but everything's oiling beautifully, rockers rocking, etc. So it's on to #2. Plan was to drop the tank anyway in three weeks because there's some unknown amount of crud in it that will plug a fresh filter within about 20 minutes of idling. Simply need to fix certain things right and move on to the next thing.

This truck sat for several years and was abused before that, so varnish won't surprise. But if I go to the trouble of pulling the rockers, keepers, springs, etc. Plus holding the valve up anyway, pulling a head's no biggie since most of the front clip has already been removed. Under these conditions and with this history, wouldn't you do likewise?

I'll post pics of the progress.
 
Mark pietz said:
Under these conditions and with this history, wouldn't you do likewise?
Click to expand...

No, because it should only take a couple of hours to clean the intake valve stems. Removing the head is way more work. If the work is necessary that is a different thing but by your compression peak numbers the valve seats are fine and nothing will be gained from the extra work. Let's just say you do rebuild the head and once you reinstall it you find out that the engine needs a complete going through?

Take a look at the lifters while you are at it.

Progress in a manner that best fits your conditions. The preceding is only how I would go about the project.
 
Last edited:
Robert,
I hear you on this. I've gone back and forth on this because of needing to pull the front clip (that's a whole nuther story and not relevant here).

Since the valve cover, tappet cover, and pan gaskets all leak a fair amount, these parts need to be pulled and new gaskets installed. I guess the real deciding factor would be if I find cam bearing material in the pan, then all bets are off. :sad: if not, then maybe going your route makes sense after all. I know what a b*tch it is to bend over the engine bay on a Scout II and dick around with stuff in the heads. That's my real objection. Once I get the keepers and springs off, and the remains of the o-ring seals, do I just work the valve up and down and spin around while running a suitable cleaner into the guide? My preference for solvent is xylol, which I use to remove the residual gum and varnish from parts that carb cleaner simply won't strip.

Otherwise, the compression numbers didn't look that bad. About 28 years ago I rebuilt a non-ic 196 "by the numbers" and compression ranged 140-145, so I think the 150s are probably carbon. 130 isn't great, but probably not bad either. And that initial spin generating consistent 60# is not bad.

Looks like I'll be pulling a pan first.
 
Whatever you use (spray carb cleaner) make sure they move like glass after douching well with good oil engine oil. Should fall by their own weight and offer no appreciable resistance when side loaded.


Check for bent push rods too.
 
I have fed a small rope thru the spark plug hole as an aid to keeping the valves up when doing this type of work.
This works so much better than other things I have tried.
 
sdowney717 said:
I have fed a small rope thru the spark plug hole as an aid to keeping the valves up when doing this type of work.
This works so much better than other things I have tried.
Click to expand...

The rope does work well but the air fitting works plenty well.

I don't do anything but place piston at tdc and the valve can only move 3/8". You will need full movement of the valve to clean up the guides so the rope won't work in this case
 
With the rope you can turn the crank and lower the piston.
Then when your done, turn the crank back up which pushes the valves shut to attach the retainer.
I dont always have air pressure to work with where I was working. I always worried about the air spinning the crank.
 
Well, well, well...

Robert's assessment (varnish) or michael's (flat lobe/lobes).

And the winner, for now, is Robert. Today I got my gas tank back, boiled out, and coated inside. Replaced all 20+ feet of vapor recovery vent lines, new 2" hose that connects tank to filler (that other 1/2" hose next to it had the p.o. Virus - heater hose! :yikes: ), new sending unit, which even works, and
yada yada yada. Installed the tank, added a factory skid plate, about 3 gallons of gas, and fired her up!

It never popped or backfired through the carb despite my attempts to get it to do so. So I backed it out, and it even had power. Got brave and took it up the street. It has square wheels and squishy suspension, but it did drive and I got it through the gears. Not the power of a 345but it's a runner! :ciappa:

now for the root cause: was it that almost 1" of rust sediment and varnish in the bottom of the tank, even though I poured fresh gas into it? Was it the egr (I installed a block off plate today at the same time, but the egr was disconnected and closed. Hmmm...probably not). But I discovered that the main hose that goes from the charcoal cannister back to the plastic vapor recovery tank in the left rear quarter, was disconnected at the tank. So without now going out to check, does that line go to direct manifold vacuum? The plastic nipple on the recovery tank has a teeny hole, which must be where it controls the vacuum going to the gas tank. So was that line making a big vacuum leak and the real cause of the popping? :confused5:

in any case, all's fixed back there and it runs fairly quietly. Now up onto the blocks and on with the project.
 
Mark,

just to clarify. Neither michael or I are in competition with each other when we suggest a possible corrective action to a member. We just try our best to help.

We both are pleased when things get fixed no matter who's advice happens to help..

Glad things seem to be getting better for you.:yesnod:
 
Robert,
I don't see any competition at all, just two differing sets of options of what could be wrong. For me, I was glad to hear opinions of what could be wrong, and was prepared for "any of the above". Although I have to admit, I had my fingers crossed that all the work and $$$ I spent on the tank, hoses, sending units, aching muscles, etc. Would bring results. But it could have just as easily gone the other way.

The only irritation in this is that I put about 5 gallons total in the tank, the gas gauge needle rose like it should, then today the needle is bottomed at empty. So although I have a new sending unit, there's something else going on now. May have to drop the tank to figger it out.
 
You must log in or register to reply here.
Back
Top