When you replaced cracked rings did you rebore the cylinders?

I took down my old 400M at 130K and the machine shop said it really didn't need to be bored. Recently sold that truck, '79 supercab gone.

I wouldn't be surprised if the 460 had cracked rings, the previous owner towed a huge 5th wheel trailer all over the country with it.

I don't guess I would mind a ring job too much but I am cheap and don't want to go through that whole machine shop ordeal again. Rings, valve guides and seals, cam bearings and maybe rods and mains, sounds like a plan. Or I could just dump a quart of oil in after a hard day's run.

 

wish a quart was all i had to dump in it after a day. this one is about two quarts an hour!

 

Sounds like R&R time. That much usage is a very bad thing. Under heavy loads and high speed any blow by will be burned almost completely by the heat (100 to 300 F increase from idle) so nothing visable. Low speed does not creat the additional crankcase pressures that will cause the blow by. I got the 460 in mine, just drove from Ocean Park WA to Chicago for work with a gross of 11500. 62 mph, 11 mpg and no oil. My engine was changed just befor I bought the truck.

 

thats not the answer i was looking for, but i am afraid you are right. thanks

 

I did have the cyl. bored when the rebuild was done. It wasn't the cheapest way out of the problem, but has given my ride a whole new life and jump in performance. You may be able get buy with doing less than a total rebuild, but don't leave any weak links while it's apart or it could cost you more in the long run.

Mr. P

 

No my truck did not have a catalytic converter. It was exempt because of its GVW package. It had a 1 ton GVWR, but was badged as a 3/4 ton.

I never did anything else to the 400 its in pieces in the garage still, just swapped the 460 in and forgot it.

 

could towing a trailer be hard on oil rings? I read superdave say on his 400 5 out of 8 cylinders had cracked oil rings and the tail pipe looked like a diesel, I know the previce owner of my truck pulled a trailer alot, and I was trying to add this all up, loss of oil, black tailpipe, maybe I have a few cracked oil rings, and that wouldn't effect the compression right?

 

Heat is hard on the rings, towing makes heat. If the ring end gap is not set correctly and the rings expand from heat and touch at the ends they are almost guaranteed to break. People seem to always get carried away with the 'more is better mentality'. So if a small ring gap is good, smaller is better, not.

I wonder if a cracked oil control ring would even show on a leak-down test?

 

My 400 had not been touched until My son and I had pulled the heads off it to start looking for the oil consumption problem.

So if there was a ring gap problem with it, it came from Ford that way.

It was just a 20 year old motor.

 

Do a compression check first. do it from full operating temp, all plugs pulled, and with each cylinder, crank the engine over with the foot to the floor on the fuel(pull the fuel pump fuse for this) take the readings dry, then add a squirt or 3 of engine oil into the spark plug hole(per cylinder test) crank the starter over a bit to clear the excess, and repeat with the compression tester installed to get a wet reading. If the compression goes up with the oil added(wet test) your valves are leaking, and possibly(most likely) your guides as well. Valve seals will usually show smoke from a dead stop under hard accelleration only. I'll back up the pcv problem as well. Change the pcv valve(cheap) change the filter for it inside the air intake filter body as well. If the valve cover actually has the wire mesh filter inside, this can be cleaned with varsol after removing the valve cover.wet/dry tests should read within 1-5 lbs difference at worst, anything more indicates a problem with the valves in a huge way.

 

This is backwards, if you see an increase in compression wet, the rings are leaking. No increase wet indicates valve leakage. Check the book.

 

well took another trip, motr starting to haze, but the same trip took less than a gallon of oil. two quarts saving. i have a local garaqge telling me that it probable had sinthetic oil or some other formulation to mask the smoke, and now that i have chaned the oil, both litterly and so to speak, it has worn the "coating" off and starting to show the true condition of the engine. i guess its tear down time. fun

 

Quote:

Originally Posted by RR4E

Do a compression check first. do it from full operating temp, all plugs pulled, and with each cylinder, crank the engine over with the foot to the floor on the fuel(pull the fuel pump fuse for this) take the readings dry, then add a squirt or 3 of engine oil into the spark plug hole(per cylinder test) crank the starter over a bit to clear the excess, and repeat with the compression tester installed to get a wet reading. If the compression goes up with the oil added(wet test) your valves are leaking, and possibly(most likely) your guides as well. Valve seals will usually show smoke from a dead stop under hard accelleration only. I'll back up the pcv problem as well. Change the pcv valve(cheap) change the filter for it inside the air intake filter body as well. If the valve cover actually has the wire mesh filter inside, this can be cleaned with varsol after removing the valve cover.wet/dry tests should read within 1-5 lbs difference at worst, anything more indicates a problem with the valves in a huge way.

"If the compression goes up with the oil added (wet test) your valves are leaking"

1 Wrong answer, if adding oil and rechecking gives a higher reading, Its the rings leaking. If it does not go up then it is a valve leaking. Common sense should tell you this even if every repair manual in the world did not.


"Valve seals will usually show smoke from a dead stop under hard accelleration only. I'll back up the pcv problem as well."

2 Also Wrong. Worn or broken piston rings would show smoke under hard acceleration from a dead stop, not valve stem seals. Valve stem seals give three visible indications they leak, you will get smoke after letting the car set for several hours or overnight and and then starting it, this will go away almost immideately. When decelerating from speed you will frequently see smoke due to the high manifold vaccum numbers this produces and if you allow the engine to idle for a prolonged period of time you will start to see smoke which will go away after a short drive. As for backing up the pcv this would be caused by the rings allowing excessive blowby into the crankcase, not defective or worn valve stem seals


"wet/dry tests should read within 1-5 lbs difference at worst, anything more indicates a problem with the valves in a huge way."

3 Wrong. Dry test readings should all be within about 10% of each other, if they are not, that is why we do the wet test, to see what area needs our attention.(see 1) If all cylinders read within 10% of each other at temp. then you almost certainly do not have a problem unless the pressure is below 150 psi on the average low comp. motor. Higher than 9 to 1 comp. will produce significantly higher numbers but remember the 10% rule when comparing readings between cylinders and all will go well. If there is more than a 10% difference and the wet test shows no improvement on the low cylinders then you will know you have some sort of valve sealing problem on those cylinders. If it does improve then you have a ring problem. If two adjacent cylinders are low and show no improvement wet, then it is head gasket time. Most all of the other info within the quote is on the money.

Now I'll tell you where I have found a problem on 460's. I have run accross several of these monsters sucking oil from the lifter valley into the intake ports because of a mismatched fit between the intake and head. Two of these motors were virgin and three had replaced intake gaskets but all of them were sucking oil through one or the other bank of cylinders but not both. Four of these motors are still suffering from this problem although to a lesser degree. All of these motors have all of their original intakes and heads and none of them has any warpage of the intake or surfacing of the head. I also just bought a spare intake from the salvage yard to inspect and it shows that it was sealing by the barest little bit (less than half the width of the sealing bead on the gasket) and was in fact sucking a tiny bit of oil into the drivers side runners. The pass. side was sealing by a mile. In spite of evidence showing this might be a fairly common problem I am unable to find anyone else who has run across it. On my personal truck I am using one quart of oil every 110 or so miles, I have only seen smoke once from the tailpipe, I was hauling a bobcat with my foot on the floor, the cat. con. is imaculate inside and functioning properly, I see a light cover of sooty buildup, similar to a diesel in my tailpipe and in 2 years and 10,000+ miles my plugs show very little at all, nothing obvious. I have no blowby problems at all and excellent compression readings. This particular vehicle showed an actual increase in oil consumption after I replaced the intake gaskets. before replacement it would go 260 miles on a quart of oil. The truck has HD Emissions because it has a GVW over 8600 lbs and I am pretty sure that is why I never see smoke, just the sooty tailpipe but why no fouled plugs. The truck has no leaks at all now and hasn't for sometime (almost as long as it took to find them all). Well thats my experience with high oil consumption, I know where it is going but neither I nor my machinist has figured out why, I guess next I check and see that the head is aligned on the block properly and that some idiot didn't put it together without the dowel pins. Oh well, I'll report back when I solve the whole puzzle.

Mike

 

Thanks, this definitely sounds like something we need to know more about.

I assume that when you did the compression check on your engine it didn't indicate any problems? Have you noticed a rough idle or any other symptoms associated with a vacuum leak?

 

HardScrabble Thanks, this definitely sounds like something we need to know more about.

I assume that when you did the compression check on your engine it didn't indicate any problems? Have you noticed a rough idle or any other symptoms associated with a vacuum leak?

Hello

I hope you all can follow this as I haven’t slept in two days, it probably will seem as if a drunken idiot wrote it.

It never gave any signs that it had a vacuum leak and it never fouled the plugs but it always used a lot of oil (at first about 1 qt every 220 or so miles, now about a qt every 100 miles) and was definately not leaking it, when I had the intake off recently to fix a water leak between the intake and head I noticed pass. side bank intake ports were wet with oil. The first thing I thought of was either an excess blow by problem or a missing pcv baffle but the way the pcv system on this truck is connected it would affect both sides equally because the pcv connection comes off of the upper intake and a check there revealed the barest trace of an oil coating. Compression is great on all cylinders and they are all within 3 psi of each other. Upon 2nd inspection of the intake and gaskets I noticed that the intake was barely sealing to the gasket on the pass. side, the gasket only made contact by about 1/3 the width of the sealing bead that surrounds the port and the ports were very wet, the driver’s side was sealed by the full width of the sealing bead and the runners were dry. I obtained another intake from a salvage yard that shows evidence of a similar problem and a look at the heads on the donor truck showed the same problem but on the driver’s side bank instead. I took the salvage yard intake to my machinist and he is curious enough about this that he is not charging for his services while we figure out and fix this problem. I guess I'll get my original intake back off of the truck in the next couple of days so he can have them both for comparison purposes and a thorough warpage check. When I installed the intake so I could use the truck for work, oil consumption was double what it was before. I noticed that the Fel Pro gasket it calls for are slightly thicker than the McCord gaskets that were on it before so I am assuming the thicker gasket is exacerbating the problem. I also recently noticed oil seeping up past the intake gasket on the pass. side. Checking with various parts houses, some say this engine had a valley pan in 89 and others call for the conventional intake gasket set, can anyone who had or has worked on a virgin 89 460 w/HD Emissions in an F250/350 tell me which type gasket it used for the intake gasket as even my local dealers have not been a lot of help. The motor home version, which is HD Emission, calls for the valley pan, which has me wondering as it is supposed to be thinner and a thinner gasket may very well make the problem go away.God help me if it is not the intake or gasket as then we likely find out the heads were surfaced at some time and at an incorrect angle to the block or intake surface or too big a cut was taken off which unless I miss my guess would narrow the valley and cause the same type of problem as too thick an intake gasket, it would cause the intake to ride up too high in the valley and loose it’s seal around the bottom of the port. At least the last choice is a cheap, easy fix (except for head removal and installation that may be necessary to diagnose it). So many things to check, so little time.
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All feel free to ask or suggest as many heads are better than one.<o></o>

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