1976 F-250 2WD super cab, 8 ft. box (155" wb), 460, factory 4 speed, no A/C, new dual exhausts, camper special, hi miles but rebuilt engine 15 K miles ago.

Just bought this "beast" two weeks ago to pull a trailer or haul a slide in on a budget. Bought from grandson of original purchaser, used on farm to haul heavy trailers and a slide in camper too. Runs pretty well, good oil pressure, clean coolant, runs on the cool side of the gauge, tons of torque compared to what I'm used to, but smokes (dark) some while running, a blast of smoke when started up from sitting when cold, all from passenger side exhaust pipe.

I know I need to do a compression check to verify rings, valves, or valve stem seals. I'm traveling this weekend, so will take a week or two to do this, but would appreciate some of the wisdom of you experts on a plan of attack. PCV is oily and need to change. Found a vacuum leak I need to fix.

I've not done a compression check in 30 years, since I had my first 63 Galaxie 289! First, pull all plugs. Do I ground the coil center lead on this early electronic ignition truck or just pull the center lead off? Second, test each cyl. compression and record. Third, run some oil around each cyl, one at a time and retest for comp. to check rings, right?

Any other wisdom on this "smoking on one side" thing would be appreciated.

 

Moved to 460 engine forum.

 

You're on the right track with the compression test method. I prefer to disconnect the primary wires to the coil. Pull the positive lead and nothing will spark.

Hopefully you'll get lucky and you may just have some worn out or disentigrated valve seals. That's an easy fix you can do with the heads on. Pull a valve cover (I'd do the passenger side first) and make sure they're all still in one piece. Poke them with a little screwdriver and make sure they're somewhat pliable.

 

Thanks for the confirm, Scott.

I bought this thing for next to nothing, and my 17 year old son and I now have a plan.

I'll let you know what the results are.

Tom

 

Finally performed comp check on my old 460. I got what appears on the suface to be good results, getting between 129 and 138 on each cylinder. I pulled the passenger side valve cover and yes, there are valve stem seals visible inside each valve spring, but they looked like they had all "ridden up the shaft" of each valve stem and did not appear to be sealing on the base of the head. What is supposed to keep the valve stem seal down on the head inside the spring? Do I have the wrong valve stem seals? Do they seal anyway when the valve spring is compressed and they are forced down on the head when the valve is fully open? Is there a ridge around the base of each valve stem seal that is supposed to be seated on a lip on the head? The rubber on each valve stem seal looked to be flexible and functional. Back passenger side plug had more oil on it than the others, some were tan, some had some blackening, but this was true even on some of the drivers side plugs where I'm getting much less smoke.

I'm really confused now! Supposedly I've got OK rings and valve/valve seats, right? Hey, I've got good compression! Or am I into some issue with an oil ring being put in backwards, upside down when the engine was rebuilt 15 K ago? The inside of the engine was very clean, so it must have been rebuilt fairly recently mileage wise.

Any further wisdom from any of you engine experts would be appreciated as I am stumped.

 

More thoughts.

I read the responses to "funky460"s question entitled "mysterious oil usage" with oil burning but no smoke being potentially caused by a leaking intake manifold. I have an Edelbrock performer on mine, and I've not checked, but I believe an Edelbrock carb also.

Could I be getting some leakage from my intake manifold causing some oil burning?

Another thought: my master cylinder power booster appears to be doing next to nothing. Seems I've read of master cylinders sucking oil from somewhere (probably the master cylinder), but I'm not using oil in my brake system. Brakes are solid, but have very little (really no) power assist. I may be getting far into left field here, but want to be sure all the cards are on the table in this discussion.

 

It sounds like you have good compression. Given that, I'd try a leakdown test next although it sounds like you've isolated your problem cylinder (#4). Even with those good compression #s you may have a broken oil ring but it's more likely that you have a worn valve guide.

About the valve seals, it's normal for the rubber type to hang up towards the top of the valve stem. Don't worry, they still do their job like that if they're still in one piece and not hard. They act as sort of an umbrella.

I doubt you brake booster problem has anything to do with your oil burning issue. It sounds like it's time for a new booster/MC. It's always a good idea to relpace them as a set.

 

Thanks again for your wisdom, Scott.

Would a leakdown test help me get a better idea if it was a bad oil ring or a bad valve guide? Is it not true that a leakdown would indicate air leaking either into the middle of the engine below the pistons (sorry, I'm not a mechanic and don't know the term) or out the valve stem?

It would be nice to know ahead of time from pulling one or both heads that this repair would solve the problem. I can do the head removal and replacement myself. If it's an oil ring, it may be time to kiss this truck goodbye, considering how few $ I've got in it in the first place.

 

tjgraf,

Are you familiar with scientific adage, "Occams Razor"?

Before you get complex, make sure drain holes are open in pass side head allowing oil to return freely to pan without lingering & getting sucked down valve guides while umbrella seal is up at top of valve stems.

If possible, double PCV engine w/ 1 valve in each rocker cover. Insufficient internal venting causes top of engine, & sometimes entire engine to "pressurize". It forces oil out any hole it can find, like valve stems, or back thru vacuum ports which actuate PCVs.

Also if your PCV gets vacuum off center, front, carb, base plate, you may want to pull hose & make sure that port is still way open & free flowing.


I've worn few 460s out. If eng was reasonably cared for, not seriously over heated, & is relatively original OEM stock, chances of broken ring & other serious internal problems aren't very likey. I'm not saying that's a rule, such problems tho are usually the exception.

 

Thanx Pete.

Good thoughts on the oil drainage from the valve cover/rocker area. I'll check it out. Engine was surprisingly clean when I had the cover off over the weekend, but you never know about this stuff. Will also double check vac source to PCV. The PCV vents the valve cover that is on the side that is burning oil, so I'm not sure a second PCV is necessary on the other side, but hey, I'm up for a simple fix!

A Ford mechanic buddy of mine at work today swears that the valve seals snap over a lip on the head casting and don't ride up and down inside the spring on the valve shaft like I was seeing. I'm going to see if I can somehow push the rubber seal down on a lip if it's really there. He may be thinking about a different engine. I can't remember if the stem seals on my old 63 Galaxie 289 popped over a lip or if they were just push on like Scott says they are above. It's been too long!

 

All of the stock oriented Ford engines I've been into (which covers pretty much all of the modern designs after the FE) had the rubber umbrella style valve seals. Even all the stock Chevys I've rebuilt have had the same style valve seals. None of these seals had a provision to positively "snap" onto the head. They all just float on the valve stem. Keep in mind, I'm referring engines that were made in or before the 80's. I've never cracked open a cam cover on my DOHC 4.6 to see what style it uses.

I'm betting the style of seal your machanic friend is referring to is the nylon positive-type seals commonly used on high performance engines. Somewhere along the line Ford may have switched over and used these in production engines. I know for sure the GT-40 5.0 use these type.

 

I changed stem seals in an 88 460: These seals push down over the top end of the guide. They have a metal band to keep them in place (ie, to keep them from riding up the stem). Your 76 might use something different - the 88 seals only applied to engines back to 85 or so.

I also rebuilt a Ford 2.8 V6 - the seals there also stay put on the guides, though they didn't have bands.

 

OK guys. I've done a buch of research on the valve stem seals thing prior to changing my seals yesterday on the passenger side only. As it turns out, I use this truck so little, I didn't notice that the drivers side exhaust pipe is also emitting some oil.

My son and I went to Penn Tech in Williamsport last weekend for their open house. While there, we stopped and discussed this situation with the Ford ASSET instructors. These guys know Fords! One instructor was a Lincoln mechanic for 15years and really knew his 460's. It turns out that you can use either umbrella seals or the positive seals with the metal rings on the top (compress seal on valve stem) and bottom (compress seal on valve guide) as you have all indicated in your messages.

So the son and I did the passenger side head yesterday with the seals that have the metal rings. Seals in there were umbrella seals and appeared to look pretty good, once again verifying that the engine was rebuilt roughly 16 K miles ago. Very clean inside rocker cover.

After done, fired it up, took it for a spin and yes, it still burns oil just as bad on both sides of exhaust.

Remember, my compression was even all around and OK from test a month or two ago.

Never did leak down test. That is the next job to do to determine if it is valve guides or oil rings or ?. Yes, I also need to put a factory Ford PCV on it, and maybe a second one on the drivers side too as one of you indicated.

Someone early on mentioned that a leak in the intake manifold could cause oil burning, maybe it was in an earlier thread - don't recall for sure.

I'm ready to pull intake, pull heads, pull engine, or whatever it takes. This is a father - son education project here. But I want to be intelligent in the order I do this to avoid unnecessary work!

Your thoughts?

 

tjgraf

What about the valve guides?

I have two sets of 460 heads for cores and the guides are bad in all of them. The oil gets past the guides and right into the cylinders it goes.

 

How much oil you using? My 460 was using as much as a quart every 60 miles when I took it down. It had been apart before and someone/somehow the ring gaps on the oil rings where lined up. I also had good compression and good power. Went ahead and rebuilt engine, things are good now. Only time mine would smoke was when you shifted.