Pinched Ring

[OX1]

Starting my own thread on this. Referencing the end of this thread.

http://classicbroncos.com/forums/showthread.php?p=2428741#post2428741

Would a pinched ring still show decent compression and/or could it
show up out of the blue? My 70 has this exact problem. HUGE clouds
of oil smoke if PVC is hooked up to man vac. Dipstick being forced
out, etc. Starts/runs perfect, plenty of power.

I had got this engine running well enough when I first got my 70
that I decided to pull and regasket. That included head gaskets
and I sure did not notice anything odd when I had it apart. Only
made it several hundred miles after that until the mosquito
control started.

This is generally what she looked like inside when it was apart.

I re-did a compr check when I got home today. These are the numbers
and the plugs. A pretty good spread @ 22 PSI, but they are all pretty
high. I can't really call any of these out for having enough blowby
to get what I'm getting.

 

[broncnaz]

Not familiar with the pinched ring idea. If a ring was pinched so to speak then when the engine is started it would most likely break. Check the cylinder walls for any scoring. But your compression numbers look to good for any ring/piston issue.
I would think you probably had intake manifold gasket that was leaking. Or maybe bad valve seals/guides.

 

[bax]

agreed....

 

[Broncobowsher]

A too tight ring tends to bind up and blow out a ring land.

You're this far into it now, better just pull the pistons and have a look.

If it wasn't already this far apart I would have strongly suggested doing a leak down test first.

 

[OX1]

Not familiar with the pinched ring idea. If a ring was pinched so to speak then when the engine is started it would most likely break. Check the cylinder walls for any scoring. But your compression numbers look to good for any ring/piston issue.
I would think you probably had intake manifold gasket that was leaking. Or maybe bad valve seals/guides.

Me either, just going by the term used in the end of the thread I referenced.
Which I guess means the ring end gap is coked up with carbon, and hence the ring has nowhere to expand. I would think this would score the cyl wall eventually and cause low compression.

A too tight ring tends to bind up and blow out a ring land.

You're this far into it now, better just pull the pistons and have a look.

If it wasn't already this far apart I would have strongly suggested doing a leak down test first.

Those pics of it torn down are right after I got the bronc several years ago. It ran halfway decent when I got it, but needed a timing chain and I was swapping in a T-18 @ the time.

I figured I might as well pull the motor @ the same time and regasket the entire thing. I only posted those pics to show what the inside looked like about 200 miles (and several years of sitting) ago.

So the motor is currently together, except for the plugs I pulled yesterday for the compression test. I thought maybe if the cause was a ring with a carboned up ring gap, I might be able to use some solvent to free it up, vs tearing it down again (or swapping it out).

At this point though, I might just call it quits on this motor and swap in an explorer motor I got a while ago.

 

[Rustytruck]

I dont see a mechanical issue with the motor but it looks like the motor is running too cold, maybe wrong plugs, too much choke or too long and maybe too light weight oil. I would do a full sea foam treatment to the engine and after running that out change the plugs to the proper autolights. I would also make sure you have a 190 thermostat especially where you live in the winter months. then change the oil to 20-40 or straight 30 weight. no 10W in these old motors. Now study your choke and make sure its working properly.

 

[Timmy390]

# 156 and #158 look wet in the pic.

Tim

 

[bmc69]

In my parlance..a "pinched ring" is one that has become locked due to carbon build up and no longer exerts sufficient pressure against the cylinder wall. The situation is usually caused by some combination of bad oil maintenance and occasional overheating; the latter also responsible for annealed rings. Its a chicken-egg situation.

It is not that uncommon.

However...the cases I've dealt with did not exhibit acceptable compression readings...wet OR dry...

 

[WheelHorse]

How many miles did you drive your '70 for before deciding to regasket it?

What's the history of the engine... looking at the information below this post, how much longer did you drive it after repairing the antifreeze leak?

 

[WheelHorse]

From an earlier thread:

Did not hot tank anything. Had not had a huge amount of running time on the bronc since I got it (mostly idling), but it had not had overheating problems with it idling to make me think it needed it. I did have very little street driving on it since I initially had electronic ign conversion problems (and timing problems with a super loose chain).

ARGGG...........................

Is it just me, or does everything you own have at least one leak (no matter how minor). Went for a short morning drive in the 70 and got on it a bit in 3rd gear (woohoo, took up to maybe 4500 RPM, really hammering her %)) and then suddenly this huge puff of white smoke comes out from under the hood.

WTF??? I use all the best gaskets/seals, let my top quality RTV sit overnight before filling (oil/antifreeze/gear oil, etc...), all new hoses, torque bolts correctly, and some stuff just refuses to seal. I think it's the thermo housing (again) where it meets the manifold, but who knows when half the eng compartment is covered in antifreeze :-[. BTW, I have exactly 3-4 hours of driving time on this engine that was pulled and completely regasketed.

Don't even get me started on the D20 rear bearing cover with all the shims. STILL leaking (not bad, but a visible drip now and again), even after covering both sides of each shim with a light coating of spray on gasket.

I did finally use "the right stuff" on the 9" 3rd member (after the 3rd try). Maybe I should use that stuff on everything now, but it sure ain't cheap. (not that the Permatex copper ultra is cheap either).........

Thanks for listening......................;D

Original thread from 2009

 

[73azbronco]

I would take the heads to a shop and have them check the sealing and valve guides and seals. If they find definite issues, you probably have the answer. Your in for a penny, might as well make sure the heads are a non issue before moving on. Considering a valve job is relatively cheap compared to opening the bottom end up. Or worse, do nothing to heads, pull the bottom apart to find that's OK...

 

[OX1]

How many miles did you drive your '70 for before deciding to regasket it?

What's the history of the engine... looking at the information below this post, how much longer did you drive it after repairing the antifreeze leak?

I've got maybe 200 miles total on it since I got it (90% of that after the regasket). Engine barely ran when I got it. It had a leaking 750 double pumper on it and a really loose timing chain. Once I found the bad chain, I did compression and leakdown test and everything came out good.

That is when I decided to regasket (since front of motor needed teardown anyway). After that I had a huge problem with the thermostat housing leaking, and overheating problems until I put in a new alum radiator and stock shroud.

About maybe 30 miles ago (and several years), I was just driving along, not even under accel and huge clouds of oil smoke started pouring out exh, almost instantaneously.

I have been messing with alignment recently, as I figure I need to do motor, so I might as well tear out front axle at the same time (do caster). I also need quite of bit of sheet metal work on inner fenders, so it will be a good time to do all that. (I am also currently installing a 2 post lift I got used about 10 years ago, now that I have a shop, which will make it easier to do engine/axle/sheet metal).

So not much real history on the engine, but it did run real well for over 150 miles. It still runs really good. Starts right up, perfect idle, plenty of power. Very odd it is doing what it is doing. It has to be blowby, as it is now starting to blow out oil seals in back of intake (so now oil is leaking on back of engine, which just started recently). PCV is disconnected and just running to back of inner fender (vac line for PCV on carb plugged), but opposite valve cover has breather type oil cap, so normal type crankcase pressure should be relieved, if thats what I had.

I would take the heads to a shop and have them check the sealing and valve guides and seals. If they find definite issues, you probably have the answer. Your in for a penny, might as well make sure the heads are a non issue before moving on. Considering a valve job is relatively cheap compared to opening the bottom end up. Or worse, do nothing to heads, pull the bottom apart to find that's OK...

I have a supposedly low mile explorer motor I will probbaly run with the carb.
Never heard it run, considering building a hacked engine running stand so I
can run it outside the vehicle and do compression, leakdown, and check oil pressure.

Old machinest friend who used to run dirt cars claims they would just start them
right on the floor. He said with no trans or attachment on them, they would just sit there,
even revving them. I have my doubts, but it could be an interesting video. ;D

 

[Jdgephar]

Old machinest friend who used to run dirt cars claims they would just start them right on the floor. He said with no trans or attachment on them, they would just sit there,
even revving them. I have my doubts, but it could be an interesting video. ;D

Physics tells me for each action, there is an opposite reaction. Rotation on the crank is going to try to force the block the opposite direction. I'd want something holding it in place, other than just sitting on the oil pan?

 

[Seventee]

Old machinest friend who used to run dirt cars claims they would just start them
right on the floor. He said with no trans or attachment on them, they would just sit there,
even revving them. I have my doubts, but it could be an interesting video. ;D

OX, I ran a 400/C6 on my garage floor. It sat surprisingly still, even when revving. Not sure how you would start it without a transmission attached though, unless you build a special plate to hold the starter.

 

[broncnaz]

Ive run straight sixes on the floor no issues although I wasnt about to rev it up very far.

 

[73azbronco]

I've seen it as well, no rocking because in reality, no torque is being applied.

 

[OX1]

OX, I ran a 400/C6 on my garage floor. It sat surprisingly still, even when revving. Not sure how you would start it without a transmission attached though, unless you build a special plate to hold the starter.

Ive run straight sixes on the floor no issues although I wasnt about to rev it up very far.

I've seen it as well, no rocking because in reality, no torque is being applied.

Thats funny to hear the confirmations. I'd guess they at least had a bellhousing on it for the starter, like you said 70.
Does not seem to apply to a starter, when tested on the ground though.

 

[bmc69]

Thats funny to hear the confirmations. I'd guess they at least had a bellhousing on it for the starter, like you said 70.
Does not seem to apply to a starter, when tested on the ground though.

if you want to rev it quickly, of course it wants to rock the opposite direction. I make up a crude starting stand using 6x6s and 4x4s and some long drywall screws.

 

[bax]

You? Make up something crude? Surly you jest!

Ok I set that one up for you

 

[OX1]

You? Make up something crude? Surly you jest!

Ok I set that one up for you

Physically or verbally?