Ford 460 blowing dip stick out

That's not great. What were the wet #s?

My stock-block 347 liked to push the dipstick out of the tube when I ran it hard, ever since it was new. I figured that it was a case of some blow by, coupled with no vacuum on the PCV system. After the block split down the middle, and I replaced it with a Boss block, it quit doing it. I read somewhere that, since there is a lot more material around the bores (it can be safely bored out to 4.166", and I'm only at 4.030"), and the block is high-nickel iron, the cylinders deflect much less, and there's much less blow by. 

That said, I'm going with the idea that the increased airflow into the engine has revealed that the rings were already ready to be a problem. 

I don't think those compression numbers sound too bad for an old American v8, especially when you consider the throttle was closed and all the plugs were in. The way you did the test wasn't "optimal" but I wouldn't call it "wrong" or disregard those numbers because it sounds like the method you used was consistent from one cylinder to the next. The range from highest to lowest compression look good to me. You should do a wet test to see if it jumps way up. I can't remember the spec with certainty, but I think you want a 10% or less increase. 

If the price is right I would buy it regardless. 78 is my favorite body style for ford pickups. Stick some new rings and rod and main bearings in it, a gasket set so it leaks less, and go enjoy 7 mpg of American greatness.

The 460 in our leMons car was doing the same thing- blowing the dipstick out of the tube- in addition to having a very nasty habit of actually blowing out the intake manifold gasket ends- these are the seals, front and back, that seal the bottom of the manifold to the block.  

Our "solution" was to build up a low-mile 460 that I pulled from an RV for a couple hundred bucks.  It's worked great so far.  

Curtis helped us a lot with that build- he really knows his stuff on BBFs.  I still have the old dipstick-blower sitting in my shop and am debating overhauling it.  I don't recall as it had a LOT of miles on it- maybe 80,000?.  But it would blow out that intake gasket with regularity, every race.  

The one thing that I was never quite sure about was the valves on that engine.  This is why: we replaced the head gaskets with MUCH thinner ones than stock (like, 0.020" vs 0.060") to try to get a little extra compression and quench.  When we did this, I never checked or set the valve lash.  Now, the 460 is a hydraulic lifter engine, but there's still a procedure for setting lifter preload (which I _did_ do on the new 460).  

I suspected (and still do) that the tighter lifter preload, due to the thinner head gasket, may have caused some blow-back into the intake tract, possibly pressurizing something in there and into the crankcase and causing the gasket and dipstick to blow out.  The engine used to run a bit hot, too- likely as a result of the valves never seating properly.  

Ok, I forgot about adding oil too. Maybe I will have time this weekend to try again. I had limited time last night and didn't think to plan out what I needed to do. 

My dad told a friend he wanted $4k for it, HOWEVER, it is the only rust free Ford in the state and it has new tires, shocks, brakes, etc... Original 66K mile truck with only an exterior repaint in its past. I also will likely get a family discount.

singleslammer said:

Ok, I forgot about adding oil too. Maybe I will have time this weekend to try again. I had limited time last night and didn't think to plan out what I needed to do. 

My dad told a friend he wanted $4k for it, HOWEVER, it is the only rust free Ford in the state and it has new tires, shocks, brakes, etc... Original 66K mile truck with only an exterior repaint in its past. I also will likely get a family discount.

Want to do a compression test after the kids go to sleep?

We can but the truck is currently at my Dad's I can certainly bring it over though. 

jstand said:

In reply to singleslammer :

Third, if there is good vacuum at the pcv port and no difference with or without the pcv valve in place, then pull the valve cover to check for sludge build up. The returns may be sludged up and restricting vacuum from reaching the bottom end leading to the pressure that is blowing out the dipstick. 

While low probability, it’s a lot easier than rings, and would be the first engine to have clogged returns in the head.

 

Again, I must disagree.  There is effectively zero vacuum at WOT when he is experiencing the problem.  A lack of vacuum isn't a viable diagnosis since there isn't supposed to be any in the first place.  If its blowing a dipstick because the 5/16" line (with a PCV valve restriction) has become blocked, the problem isn't that the tiny flow of PCV has stopped, its that there is too much overall blowby.

If you are overfilling your swimming pool with a fire hose and trying to drain it with a garden hose, the problem isn't the garden hose.

The bottom line is that his crankcase pressures are too high.  The only thing that can cause high crankcase pressure is blowby.  He has a ring seal problem.  

In reply to Curtis :

Thanks for all the good info. I ordered a cheap endoscope and will check for obvious scoring. 

I might try the seafoam (whatever cleaner) trick but if the scope doesn't show major scoring, I will plan to install new rings and bearings.

singleslammer said:

Compression checks came back good. Range was 112 - 126. Thoughts?

Small stock cam and 9:1 compression I would like to see higher numbers than that, but as you mentioned it was done with plugs in and throttle closed.  I can't find factory spec right now but I would say a wild guess of 135-ish hot?  You might find that its close to what you have if you do the test again, but my guess is that you'll find 6 cylinders that rise to 135 and two that stay around 100.

the 10% rule really only applies to the peak pressures that a cylinder can trap.  Its possible that your 112-126 numbers were because 6 of the cylinders COULD trap 135psi but with the throttle closed they never saw it.  That is to say, if you do a compression test with duct tape over the intake, they might all show an even 100 psi which looks good and even.  But give them WOT and  you might see suddenly that 6 of them jump to 135 and two stay at 100.

This is why compression tests just show trends.  Part of what causes ring seal is pressure getting in behind the rings and pushing them out against the walls, so it doesn't show much as far as real world operation.  Leak-down tests are a bit better but still not an accurate indicator.  Now, if you combined that all with an oscilliscope, you might see how the spark energy is trending based on running cylinder pressure and match it up to the cylinder's compression test numbers, but that is a lot of diagnosis for what we pretty much already know is bad ring seal.

Having said all that...

I would honestly buy it, put a new breather and PCV on it, and keep a rag behind the seat to clean up the oil that sprays everywhere when it starts looking like there is enough smoke that it might catch fire.  :)

singleslammer said:

In reply to Curtis :

Thanks for all the good info. I ordered a cheap endoscope and will check for obvious scoring. 

I might try the seafoam (whatever cleaner) trick but if the scope doesn't show major scoring, I will plan to install new rings and bearings.

I thought seafoam was snake oil until I tried it.  Its pretty awesome stuff.

We did the vacuum line trick with a can of seafoam on my buddy's 4.6L and the stuff that came out the tailpipe was pretty insane.  Sparks and soot and small european countries.

I would do that and also pour a bit in each spark plug hole and let it drain into the crankcase for a day.  Dump the rest of the can in the crankcase and follow the directions.  Might not do a thing, but its $10 of hail mary and might really help.

If you do new rings, expect some increased smoke for a while.  Cylinders don't wear evenly.  With the thrusts on the compression and power strokes being sideways, they sometimes get a little egg-shaped.  It might take a while for the rings to wear into that shape.  Worst case scenario is that they're too far out of spec and you have to bore and hone... or find a low-mileage junkyard core and swap longblocks.

It smokes white a bit while driving. I meant to mention that after yesterday's testing

In reply to Curtis :

What are your thoughts about valve tappet preload being off?  Anything to that causing crankcase pressures, you think?  

Curtis said:

singleslammer said:

In reply to Curtis :

Thanks for all the good info. I ordered a cheap endoscope and will check for obvious scoring. 

I might try the seafoam (whatever cleaner) trick but if the scope doesn't show major scoring, I will plan to install new rings and bearings.

I thought seafoam was snake oil until I tried it.  Its pretty awesome stuff.

We did the vacuum line trick with a can of seafoam on my buddy's 4.6L and the stuff that came out the tailpipe was pretty insane.  Sparks and soot and small european countries.

I would do that and also pour a bit in each spark plug hole and let it drain into the crankcase for a day.  Dump the rest of the can in the crankcase and follow the directions.  Might not do a thing, but its $10 of hail mary and might really help.

If you do new rings, expect some increased smoke for a while.  Cylinders don't wear evenly.  With the thrusts on the compression and power strokes being sideways, they sometimes get a little egg-shaped.  It might take a while for the rings to wear into that shape.  Worst case scenario is that they're too far out of spec and you have to bore and hone... or find a low-mileage junkyard core and swap longblocks.

We shoved new pistons and rings in a 30,000 mile block that I didn't even dingleberry hone.  Just broke the top ridge.  The thing didn't even smoke a bit.  I'd expect a 60,000 mile engine (the OP's) would be similarly fine with new rings and done.  

Still, 60,000 should only be about half-life, worst case, for the factory rings.  I wonder why such bad blowby already.  I bet the seafoam (or whatever solvent you care for, I've done PBlaster and ATF and diesel fuel myself) works.  

volvoclearinghouse said:

In reply to Curtis :

What are your thoughts about valve tappet preload being off?  Anything to that causing crankcase pressures, you think?  

Doubtful.  If anything, that would trap less mass in the cylinder and cause less blowby I would think.  Too little preload and you wouldn't get full valve opening.  Too much preload and you wouldn't have full valve seating.

I guess in extreme cases of too much cam and not enough compression, a light preload might increase cylinder pressures lower in the RPM band, but not over and above what it would normally see.  That is to say it might recover some of the pressure that was lost to the mismatched cam/compression choice by artificially reducing valve event duration.

volvoclearinghouse said:

Curtis helped us a lot with that build- he really knows his stuff on BBFs.  I still have the old dipstick-blower sitting in my shop and am debating overhauling it.  I don't recall as it had a LOT of miles on it- maybe 80,000?.  But it would blow out that intake gasket with regularity, every race.  

 

You're too kind.  I'm just an avid builder of old-school iron.  That, and the stuff I usually buy is so clapped out that I have developed a keen sense of what the failure is.  

I'd redo the compression test properly but wouldn't bother with a wet test.  Every cylinder improves with a wet test, good, bad, or indifferent.  Instead, make each compression check the same number of revolutions.  I do five or six "hits" on the compression gauge for each cylinder.  If the gauge rises to a crappy number after two "hits" and stays there, it's usually a valve issue.  If the gauge builds up to a crappy number bit by bit with each "hit," the rings are gone.

I'm with Curtis 100% on the ring seal diagnosis. For the dipstick to be blowing out it has to be outflowing the PCV (which is tiny) and the vent (which is comparatively huge). It's a ring seal problem no matter how you slice it. Compression numbers aren't good, but also aren't smoking gun terrible. Removing the plugs and opening the throttle would only cause those numbers to go up, but as said given that you have a fairly tight spread i'd call the test skewed-low but still valid. I personally wouldn't bother repeating the test with oil or any other way because there's only so much a compression test can tell you (it's just one data point) and what it has already told you is enough: That the problem is not attributable to a single cylinder or small number of cylinders. From that you can extrapolate that to 'fix' the ring seal  you'd basically need to take the whole thing apart. 

I don't really feel like you HAVE to fix it. You can do the easy thing and just increase your vent flow. Put vents on both valve covers instead of just one and see how it goes. If it's not to the point of seeing actual smoke/fog flowing out of the breather vents than the worst thing you're likely to experience as a side effect of more vent flow is an odor, and if you don't smell it already you're probably fine. 

Also, given what youve said about the condition and price on the truck, i would absolutely buy it.

Ok, thanks gang. Is it a bad idea to throw a nipple on the dip stick hole to stop oil from escaping? I realize this might cause the valve covers to leak (more) of a seal to blow out but if I do this with the added vents, it might be enough to bandaid the issue for a bit.

In reply to singleslammer :

If you ditch the PCV valve and put another breather on it, you may not need to worry about it blowing out the dipstick. I certainly wouldn’t try to hold anything in via the dipstick tube... it’ll find it’s way out, and main seals are a bigger headache than a dipstick tube...

Maybe a short chain for the dipstick, with a clasp so you can undo it when you need to check the oil?

Or (overkill) an aftermarket dipstick.  A few companies sell a braided dipstick tube with a tight-fitting handle.

IIRC, those years of BBF the PCV is in the filler cap on the front of the driver's side valve cover, right?  Or was that early enough that the PCV was in the pass side rear breather?

Either way, they should each have a big hole in them.  Fill both of those holes with breathers and keep a rag around for cleanups.  PCV does a lot for oil health, but given all of your blowby and the subsequent loss of oil to burning and pushing some out the breathers, you'll be replacing oil every once in a while.

It has the valve in the passenger rear with a breather on the front. Is leaving the front one on is likely good enough with just adding a breather to the rear?