Supernaut72

Hey all, finally getting back to work on my '67 Delta and I've come into a fresh problem. It idled rather roughly and had a noisy clacking from under the valve covers for as long as I've owned it, though it made satisfactory, smooth power under actual acceleration. Upon pulling the valve covers, I found several rocker arms which had worn with their pivots to the point of being loose to the touch, with deep matching grooves carved into the mating surfaces of both, on some specimens. Clearly time for a little R&R!

I replaced the rockers and pivots and cleaned up the pushrods and oil passages while I was at it (very messy job!), and everything went swimmingly. The engine fired up with a little timing adjustment, idled great and no longer had a worrisome, stumbling exhaust flow or embarrassing clacking. Excellent! I ran the engine maybe a few minutes before I took a break to bask in my victory.

Now comes the trouble. Two hours or so later, I go to fire the car back up, and immediately it begins popping through the carb regularly, in time with one cylinder. I investigated and found that the exhaust valve on the #8 cylinder wasn't moving at all. On the advice of the FSM, I whacked the pushrod side of the rocker arm with a mallet, and the pushrod began to move, albeit rather weakly, leaving plenty of slack between the rocker arm and its pivot. Very noisy.

I put Seafoam into the crankcase and held it at a fast idle for a few minutes, and the pushrod began to travel further, but still not with enough force to do anything but clatter against the rocker arm. With the engine off, the pushrod recedes into the cylinder head quite a ways, and I don't get that little "pop" feeling the others give when I pull it out of or push it into its bore.

The pushrod itself is in good shape and will gush oil a fair bit if the engine is run long enough to get oil to the rockers (with that spark plug disconnected of course). I found that if I gave the rocker arm a love-tap in hopes of freeing something up, occasionally the pushrod would stop moving and a healthy dose of oil would come gushing up out of the bore the pushrod goes through. I found by letting the engine sit for a period of time and then going back to it that the problematic lifter doesn't seem to pump up any slower than the other lifters, but its travel remains too short.

Hypothesis time: Since the oil return passages in both heads had years of nasty build-up in them, I cleaned them out as well as I could. They weren't bad enough to block oil flow, but enough to make me want to swab them out.
I believe I might have goofed up by dislodging and pushing a bit of gunk further in rather than extracting it, which could have found its way to a lifter and clogged it up... Even though the passenger's side oil gallery is among the first places to receive oil after passing through the filter.

Given that the engine worked perfectly, and then went on the fritz the very moment I fired it up later on, I would be very surprised if this is something as serious and gradual as a cam lobe, never mind the complete absence of glitter or chunks in the oil and no history of this particular form of lifter malfunction.
Additionally, the continued (albeit low velocity) gushes of oil through the pushrod as well as retaining the ability to push upwards with some amount of force, I'm guessing that the lifter is partially restricted though somewhat functional. After some time with Dr. Seafoam it is indeed moving the pushrod further than it was when this problem arose, but it's still not quite right.


A buddy who's big into Mopars suggested adding a quart or so of diesel fuel to the crankcase with the Seafoam, running it a bit, then flushing it all out with a couple of oil changes. I'm tempted to try this, as I've seen the results of these diesel fuel flushes first-hand, but I figured I'd ask some fellow Olds fanatics for advice in hopes of saving some guesswork. Much appreciated!

Hopefully this won't prove to be another costly or time-consuming repair. As it is this car has been monopolizing my time and money so much lately that I'm starting to refer to her as "the wife".

Oldsmaniac

I would advise against the flush with diesel. You should replace the lifters as you have proven they are troublesome. I would think they are they cause of all of you troubles now.

oldcutlass

X2 its time to pull the intake and inspect the lifters.

Supernaut72

I was afraid of that. Guess I'll be spending my next free day and a good chunk of my paycheck tackling that. I'm betting that the car is just making me pay for prioritizing some refresher work on an old Caddy over sorting out her problems. Suppose I deserved that.



Truth be told, I'm kind of leery about replacing lifters on an old engine, as I've been told that new lifters on an old camshaft will rapidly eat the lobes. Any truth to this or is this some nonsense perpetuated on the Internet? Is there any way to prevent it, like a dab of engine assembly lube on the bottom side of the new lifter?
I can afford lifters if that's what it needs, but replacing a camshaft, bearings, etc is a bridge too far for an engine that's not due for a total overhaul (and an owner who's not financially equipped for one).

Oldsmaniac

You should not have a problem with replacing the lifters. The cam is already seasoned so to speak. Cam lube on the bottom of the lifters wont hurt and fresh oil with zinc is what I would do.

RROLDSX

Why not just change the offending lifter?

Oldsmaniac

That is an option however chances are others will be problematic now or shortly thereafter. Since you are pulling the intake anyway I would change all of them. The plungers get gummed up and stick or became frozen within the lifter. The lifter can also have a broken retainer clip and come apart, or bottoms become concave.

Supernaut72

Since I had a return credit on some valve seals I went ahead and got one lifter to replace the definitely bad or stuck one, and some assembly lube. That store alone has 18 more lifters where that one came from, so I figure I'll get it apart, inspect them all for broken retainers or bad clogging or worn-down bottoms, then replace or at least clean as needed.

Only reason getting #8 working is so urgent is that I need to get this car through emissions testing (yuck) and registered and off the lot it's sitting on by year's end. Don't want to drive it around on 7 cylinders since I'm sure the bearings don't like that very much, so the only solution is to suck it up and get this lifter and any other visibly trashed ones replaced. Hopefully she'll cooperate with me on this.

Are factory original Olds 425 intake gaskets reusable with a light coat of sealer? I would think so if they're steel and haven't ever been tampered with. Worst case, I think the store down the road has them in-stock.

oldcutlass

No, the intake gaskets are a 1 time use. If your just trying to get it down the road, then your plan is fine. If you find there is wear on all the lifters, then I would bite the bullet while your there. Also inspect the cam lobes for major wear, you can look down the lifter bore holes.

Sugar Bear

The intake gaskets are not reusable. There is a raised narrow sealing area around each port that gets crushed when the intake is torqued the first time. Also check the torquing sequence, IIRC correctly it should be tightened from the end working toward the center.

Never had a problem replacing a lifter(s) and then having a cam failure.
If you think the lifter is stuck due to dirt/sludge, take it apart when you remove it and clean it internally if the rest of it is excellent.

Good luck!!! Please keep us posted.

Supernaut72

Oh. That intake gasket situation sucks, just when I had changed my mind and decided to get all sixteen lifters in order to be thorough. Oh well. It'll all be worth it eventually. At least intake manifold gaskets are readily available, plus it's the right time of year that I can just consider the whole expense a Christmas gift to myself.

Anything else I should be aware of before starting? Might try tackling this tomorrow. The FSM says that on 400 and 425 engines it's necessary to remove the distributor before removing the intake, is there any reason this is necessary on those engines but not the 330? Knowing me, even with alignment markings there's just some way I'm sure I'll stab the distributor incorrectly when I go to re-install it, if I take it out. Otherwise, the accessory brackets that bolt to the intake manifold are already off, and everything should be good to go once I drain the coolant and disconnect all fuel and vacuum lines.

Where the gasket meets the cylinder head, would red RTV be a sufficient sealant in place of the GM 1050026 sealer mentioned in the FSM, or should I use something else there?

Oh! Another question: If I get the intake off and find that some of the lifters are oversized (a potential issue I just stumbled across in the FSM that's allegedly rather notorious on pre-'68 Oldses, less common afterwards), what should I do then? From what I'm finding, replacing those mothers is real expensive nowadays... Would it pay to just disassemble, clean, and reassemble those for re-use, if I'm stuck with any? Maybe use the guts out of a new lifter and keep the oversized lifter body?

Oldsmaniac

The dist needs to come out because back of intake is tucked under dist body and you cannot get the manifold up and out. Also when reinstalling you must set the manifold (heavy!) straight down and this cannot be done with dist in. RTV black around intake water ports and on front and back seals looks better than blue or red and high tac sealant around the intake ports is recommended and often supplied with the new intake gasket if FEL-Pro brand. Would not suggest mixing components from one lifter manufacturer to another. Lifters can be disassembled and cleaned but it is time consuming.

Sugar Bear

Might use only the spring and retaining clip from a new one if needed and unable to get a correct size replacement. Put the used lifters in the same bore they came from if reusing any. A used lifter on a different lobe of the cam would be of concern.

"Would it pay to just disassemble, clean, and reassemble those for re-use, if I'm stuck with any? Yes. Maybe use the guts out of a new lifter and keep the oversized lifter body?" Not the plunger.

Supernaut72

Oldsmaniac:
Yeah, I guess that makes sense, I was just curious as to why the 330 is notably excluded from that step... Same basic block and intake design, IIRC. Not that it matters, given that I'm dealing with one of the big boys instead.

I'll keep that in mind, and keep lifter components together as units. Might have no choice on the oversized ones but to tear them down and rebuild, or at least try cleaning them out without rebuilding (if this block has any). In a doomsday scenario, there's simply no way I'm paying Mondello prices for special oversized lifters or paying a shop to resize F*rd ones and futzing with pushrod lengths, unfortunately.

You're right, looking at stock photos and descriptions of Fel-Pro gaskets I notice the tube of sealer that comes with it. Most excellent!


Sugar Bear, thanks, good tips there. I would have figured the spring and clip should be items where a match isn't critical, so that'd make sense. I was hip to the rule that used lifters go back in the same bore as they came out of, fortunately by default I tend to sequence things when I disassemble them so that everything down to regular nuts and bolts go back in the same places they came from.

Got it, plunger stays with the body no matter what, even with the fat lifters. Good to know!


Thinking about the problem, and looking at photos and videos of valvetrains with truly "collapsed" lifters, I notice that the pushrods are extremely loose against the rocker, but don't seem to recede into the head nearly as much as this one. Makes sense, the plunger can only collapse so far into a "dead" lifter. In this engine's case we're talking about a very visibly low pushrod, maybe an inch difference between this rod and all the others with the motor off if I were to guess. Give or take, based on the position of the cam lobe, anyways.

Plus when I insert the pushrod it feels simply like it's smacking solid steel, rather than seating into a lifter cup; removing it, there's no soft "pop" as with the other lifters, either. It just slides up and out. Expecting to find the guts or at least the oil control plate and cup of the #8 exhaust lifter in the intake valley when I pull it off.
I'm starting to think that lifter had a broken retainer that allowed it to come apart during or after I pulled the pushrods out for cleaning and clog-checking.

The news hasn't been great up till this point given how close this engine was before this lifter failed, but I really appreciate your guys' continued help. Now that I'm past the shock/denial/here-we-go-again phase, I'm just grateful I have a great community and resource to counsel me here.

oldcutlass

Don't be surprised if the tube of RTV that comes with the gasket is dried out. You may want to buy a big tube just to be safe.

Supernaut72

I've got a pretty new tube of Red on me, just in case. Hopefully that'll be good enough in place of the included sealer, if the one they give me is no good. Sure did stick like hell when I used it to hold my newest valve cover gaskets in place, so it should be tacky enough for the job.

Supernaut72

Well, I'm glad when my hunches are correct. Pulled the intake yesterday and found the dead lifter's cup and oil control valve in the valley next to it. Also got a good chance to clean all the areas of the valley where old oil settles and builds up.

Checked the other lifters and found no reason for replacement; the wear surfaces looked like new, and they all spun freely in their bores. Got it all back together and now the engine runs much better for it.

Probably going to try having the car smogged tomorrow. It's a 300hp 425 with the stock Two-jet carb. Adjusting the carb with the instructions in the FSM, I need a bit under 3 turns out on each mixture screw for it to run happily... No vacuum leaks as far as I can tell and the timing is good, so I'm wondering if this is about right for a 2-bbl metering fuel for such a large engine. I'm only familiar with this same model of carb on a Chev 350, where it likes 1-3/4 to 2 turns out on each screw.
I know people who run 2-bbl carbs on their 425s are probably pretty rare nowadays, but if anyone can let me know if that mixture adjustment sounds like it's in the ballpark for this engine, I'd appreciate it.

oldcutlass

The mixture adjustment is set by the highest vacuum reading on a gauge or the highest RPM attained on a meter. Just remember that the idle a/f settings only operate at idle. Once your out of the idle circuit, the screws have no purpose.

Supernaut72

Vacuum tuning sounds familiar, and highest RPM's the way I've always used that didn't involve tuning the car with an exhaust analyzer (sure don't have one of those lying around) Thanks for confirming that there's nothing unusual about tuning the mixture on a BBO. I'll double-check it with the Actron today, haven't been able to find my vacuum gauge though that'd really help right about now.

And yep, unfortunately for me the smog test on classics is at a dead idle in gear (it's on rollers, off idle for OBD1 vehicles, but only as a "precondition" on an older car if it fails the sitting-idle test on the first go-around). So, I have to figure out what the engine is happiest with, and then try to figure out exactly what *they* want, since in my experiences setting the mixture dead-on results in a really close call or a narrow failure with CO, with no cats and all.

I checked the pass/fail standards on the failed test form against other states' emissions testing programs as well as the numbers given by the manufacturers themselves for acceptable emissions levels during garage exhaust tuning, and it looks like ADEQ's numbers match the standards for what would basically be a fresh engine in perfect tune, with zero wear on carb or ignition components etc., roughly twice as strict as most places that still test 50 year old cars. Ridiculous. A mandatory exhaust check every year helps determine how the engine's burning its fuel, just wish it didn't prevent registration/renewal.

Only car I've gotten through consistently without hassle was a F*rd with a totally overhauled engine that had maybe 15k on it in total by the time I sold it. Anything original, even if it's not ultra high mileage, seems to just pass by the skin of its teeth, even when tuned properly. Maybe time to find somewhere else to live, eh?

Anyways sorry for the rant, time to release that train of thought and get on with it. Wish me luck, I'm off to hopefully get this done and over with.

Sugar Bear

Good work!!!

Yes the adjustments sound "in range" as a starting point. Vacuum gauge tuning as recommended is a good idea. Don't tighten the idle mixture screws alot, just lightly seat them. Can you also adjust the dwell and timing before inspection?

With a fully warmed engine, revving it at idle and closing the choke plate fully by hand then releasing it before stalling will often vacuum clean some of the passages in the carburetor of varnish etc. from sitting. This would be done before making adjustments.

Fresh fuel, spark plugs and a fully warmed engine also helps.

Keep us posted!!

oldcutlass

Texas has a provision where cars registered with antique plates are exempt from inspections. The registration is at 5 year intervals, pretty cool.

Supernaut72

That's pretty neat! Here, I don't believe the AZ antique vehicle plates carry any special exemptions, just the restriction that it must be 25 years old or older to qualify for one. Kind of a strange system they have going.

As for the test...
It blew 810 ppm HC over an acceptable amount of 450 at idle, but it went way down to nearly passing when they put it on the rollers up to 33 MPH. Carbon monoxide was within a healthy passing range the whole time but not extremely low like before I replaced ign components. Slightly higher during precondition.

I began to think about the slight rattly noise the tired old resonator makes, even though the exhaust sounds like a steady, healthy hum from everywhere except directly behind the resonator.

Fearing burnt or sticking valves, I pulled all the plugs expecting to see a fouled one or some evidence that a cylinder was consistently misfiring, but nope, all eight were clean as a whistle. Not bright white, of course, but a healthy off-white. In fact the one that had been dry black on the #8 cylinder (from running it with a malfunctioning lifter) had even cleaned itself right up as well after my highway run and the slog through traffic to get home after the test. Shop rag test doesn't yield much, the exhaust coming out of that resonator is a bit turbulent but it doesn't seem to suck back into the pipe at all. Engine pulls well, has a lot more power than when it's got a spark plug fully disconnected, so it doesn't seem like I've got a dead cylinder.

Going to try steam-cleaning the valves and cylinders once more for good measure next time I go to work on it, but it seems more like an issue of the fuel not having time to fully combust before leaving the cylinder, unless the engine is spun up a bit, as in the precondition...

Maybe a slipped harmonic balancer ring is giving me a bogus timing reading? My Chevy has that same problem so I'm aware of the possibility. Base timing set too retarded, with factory-recommended ported vacuum advance coming into the equation when the throttle opens a bit, would result in the engine expelling some raw fuel before it can fully burn, but primarily at a dead idle, I'd imagine. Especially since I'm running slower-burning mid-grade at the moment. Wouldn't be surprised if it scored a little better with regular 87, in its current state.

Might also explain why the engine stalls completely if I retard the timing any further, and spits out the carb intermittently if I hold the idle up to keep it running at that setting. Even though the timing mark seems to indicate that I should be able to get away with doing that. Hmmm. Looks like I'll be verifying TDC next time.

Just like that, a glimmer of hope is restored. Ha!


Just saw your post, Sugar Bear! Yep, stopped by a local speed shop that specializes in classics and they kindly helped me ensure my tuning was set to "Tucson specs", as they called it. Unfortunately none of us thought about the possibility that the timing is out, despite the mark saying otherwise. With a cold engine, I'll be rotating it to find TDC and check or make a new mark on the balancer, and go from there. Dwell's been checked and re-checked, it's right at 30 degrees

Didn't know about the vacuum-cleaning trick, that's a good one to keep in mind! The carb is a fully rebuilt unit, but after sitting around for the better part of a year that definitely couldn't hurt.

Got the last few gallons of a full tank of Chevron mid-grade in the tank now, just bought it last week too (to give an idea of how inefficient the motor's been running prior to all this tuning, as well as how hard I've been running it on the highway before and after the tests). All ignition components are good, so at this rate I'm pretty well convinced my timing is out. Thankfully the mark is consistently incorrect; it doesn't bounce around or anything, just sits at what now looks to be the wrong position.

oldcutlass

There is no difference on vacuum advance between ported and manifold once the carb is out of the idle circuit. What is your dwell/timing set to now?

Supernaut72

Then perhaps the centrifugal advance is doing the trick, when the engine is off-idle? It still "failed" during the part-throttle precondition, but it was much, much closer to a passing level than sitting at 550 RPM in gear.

The timing is "set" at 5 BTDC with vac advance out of the equation, just like the book says... However this doesn't mean much if the balancer isn't reading right, which is what I'm starting to suspect.
Dwell's 30 degrees, also what the manual calls for.

On the subject of ported/manifold advance, I've read that Oldsmobiles in particular were odd in that they did not use manifold advance except for some special cases in the late '70s. When I got the car, the vacuum line was hooked to the carb port as well, so when I replaced the carb with a same-model unit, I hooked it back up exactly how I found it. Of course I've also read a write-up on ported/manifold advance elsewhere on this site that claims manifold vacuum is correct for cars of this period, instead...

--
Oops, found it again and then read all the posts below, including yours, confirming that ported is the proper factory original way, and the claims that ported is better for exhaust emissions. On the carb port, it will stay.

Oldsmaniac

In NJ the old cars could not pass the smog test unless timing was retarded. Used to do like 0 degrees TDC. Engine had no power but very low HC as well. After the test put things back to normal and drive for another year.... Thankfully, Antique Plated cars need no smog test or inspection now.

Supernaut72

Yeah, I've heard about dialing the timing back that far to pass on HC, as well as the late '70s cars with the spec actually calling for the timing to be set ATDC, which makes me wonder if my balancer mark is off just so that I'm actually running somewhere way far ATDC at idle, just before the point of stalling the engine completely, which then advances to a reasonable level when the engine is off-idle (accounting for the drastically lowered emissions and the return of smooth power, even if it may not be as much as the engine's capable of).

Surely there's such a thing as too far ATDC when retarding timing for the sake of emissions, to where it begins to eject a portion of the fuel charge through the exhaust, right? If so, this thing must have really slipped.

Supernaut72

Think I've found the final piece to the puzzle. While finding TDC and re-marking the balancer, I moved the engine back and forth by hand and noticed a considerable amount of slack in the rotor's movement.

I re-timed the engine and then tried the shop rag test again, this time really trying to stuff that sucker into the exhaust pipe, and sure enough, on every stroke of the engine, the exhaust would blow out, and quickly suck back in before the next blast of outbound exhaust, rinse and repeat.

My working theory now is that the timing chain and nylon-coated gears, at 122k miles, are due for a change. Due to stretch and wear, maybe even a skipped tooth, the cam's gear is probably lagging behind the crank just enough that the exhaust valves are closing after the piston has already begun its downward intake stroke, resulting in an extremely brief reversal of exhaust flow from each cylinder. This'd explain why all the spark plugs are perfectly healthy and the car makes acceptable power off idle, and yet the exhaust makes sounds consistent with valve issues and loves to shake at idle.

I'm now on the lookout for a deal on a timing set on RockAuto, preferably a double-roller if the stock timing cover will accommodate it. Any particular brands and chain dimensions I should be aiming for with this goal in mind?

oldcutlass

Cloyles is a good brand for a double roller. Should be available on Rockauto or at your local parts store.

Sugar Bear

Try to figure out if the balancer has slipped before removing it.

Another forum member had a good suggestion, take a picture of the cam and crank gear marks before installing the front cover for later when you start to wonder; were they lined up correctly?

Supernaut72

Thanks, got it! Looks like I'll be going for one of their sets.

Sugar Bear, I still do believe the balancer slipped a bit as well, as with the #1 cylinder at the very tippy-top of its travel on its compression stroke, the mark machined into the balancer was indeed off from where it should be. New mark made a heck of a difference in how the car ran, but unfortunately with valve timing retarded that much, it didn't make the difference I was hoping for this morning.

That's a really good idea! As it is I have a habit of taking pictures of things before and during disassembly so I know how they're supposed to look when it's all put back together, but I'd never thought to snap some photos during re-assembly to prove to myself that everything I touched got set up properly. Almost invariably, after buttoning up engines and transmissions that I perform internal maintenance on, I start to question my work. Doubly so if something is amiss with it after putting it back together.

Supernaut72

Looks like my new timing set is not expected to be here until the 30th or so, and since I've resolved to not run the engine any more until this is done, it looks like I've got some time to prepare, or God forbid, tear my attention away from Oldsmobiles for a while.

Anybody here done a timing chain on one of these engines and have some tips for breaking down the front of an engine that's never had more than the water pump off before? Particularly regarding the balancer/hub, but any other interesting did-you-know facts would be useful for a first-timer working with a "first-timer" engine. Especially since the manual is a little vague about the effort required at some steps (literally, "step x: remove crankshaft and cam gears and chain"). No mention of which parts are a tight press-fit, if certain things should be or *need* to be heated before removal/installation or if that matters, etc.

I'll be stopping by the car briefly on Christmas day to spray the hub and lower timing cover bolts with PB Blaster so they'll have a good while to soak. Not that any other bolts have been at all difficult or seized thus far, thankfully. Just like to take precautions so I don't wind up fighting one odd stubborn bolt when I'd rather be getting the job done!

Anyways, I hope everyone has a wonderful Christmas! I somehow forgot that it was right around the corner until I went to order the parts and noticed the shipping delay. Probably a sign to take it easy for a while.

Supernaut72

Got the timing chain done with, after a couple of afternoons' commitment; had a devil of a time with the timing cover's lower seal, but I got it all together and so far, no leaks detected (knock on wood).

The job eliminated an appalling amount of chain slop and made a noticeable difference in how the car runs. Much less side-to-side engine shake at a slow idle now, but still a little-- Not sure of the cause, whether this is how 425s are with original, well-worn but unbroken motor mounts, and/or the fact that the heavy counterweight AC compressor is out of the car at the moment. I'm wondering if some sort of counterbalance is the reason that non-AC cars had the alternator swapped to the passenger's side, unless that was just the Olds engineers trying to mix things up for the sake of looking more symmetrical.

Right now I'm double-checking the tune-up specs in the FSM, and I'm unsure whether this is a typo or not, as it contradicts every tune-up chart I've seen until now. It claims 7-1/2 degrees initial advance for a LOW COMPRESSION 2-bbl 425 as well as all other V8s, but 5 degrees for a High Compression 2-bbl 425. Usually I see it listed the other way around, with the L.C. engine being the only V8 with 5 degrees initial. Either way, the less advance the better for the purposes of emissions testing I suppose.

It seems that everything is set properly, slow idle is right on at 600, and the Actron tach's needle is much more steady than it used to be, so the engine doesn't seem to be suffering from full-on misfires anymore. Due to conflicting information telling me 575 or 600 rpm based on the fact that my car is technically "AC-equipped", I opted for the higher figure.


Guess we'll see if all this work was worth it, come daylight. If it's a narrow failure that looks like it might have been caused by just a sliver too much oil consumption, I'll retard the timing to 0 BTDC and maybe flush the oil and swap to 10w40 from the 10w30, though I haven't noticed any worrisome oil consumption thus far. Fingers crossed.

oldcutlass

Glad its running better and hope you get past the smog checks. I bet the engine can get away with a the 7.5 degrees, if you look at what the 66 settings are. Remember these settings are just a guide not gospel.

Supernaut72

Well, bit of bad news. Failed again, had a friend check compression and turned up 75 PSI on cyl #4 and #5. Consensus seems to be burnt valves or some really nasty, hardened deposits on the valves of those two cylinders (based on the continued cleanliness of the spark plugs of those cylinders). Will be performing a TDC air pressure test to check for air leaking through the exhaust pipe and/or carb to be absolutely sure before I do anything of course.

Might pull the heads if I do find air leaking past valves, and then go from there. At the least I'm planning on two new valves per low cylinder, maybe a new set of valve springs and seals all around. Probably going to leave the guides alone since oil consumption doesn't seem to be an issue, and hopefully the seat work won't break the bank. For now I'll just have to take it to its new resting place and figure out my next move.

Sugar Bear

If the problem is leaky valves, new valves may not be needed, the old ones are often able to be refaced. It depends on how thin they are. About the seat work do you mean the refacing of them or going with hardened seats? Hardened seats are probably not necessary if you are on a budget.

Replacing springs is a good idea. I have wondered how they are affected if fully compressed for years in an engine that has been sitting.

If the leak is in the rings/pistons a solvent left in the cylinder for a few days could free and unclog stuck rings.

Keep up the diagnostics! Good work!

Supernaut72

Got the heads half-pulled today. I felt around in the #5 combustion chamber and the valves feel intact, so a refacing may indeed be all that's needed, hopefully.

I'd been reading about hardened seats and the conditions that really require them, and yeah I think I'm going to stick with the originals if at all possible.

Really though, what a horrid job! Even with a helper we absolutely could not get the driver's side head off. Following the manual we left the exhaust manifold attached to the head, and I really paid for it. The thermal exhaust diverter looks like it got kind of mangled against the frame after hours of trying every which way to work it free and the exhaust manifold connection flange would not fit past the engine block.

Also, since the manual said to leave the dipstick tube in place during removal, that got pinched a bit and pulled forcefully from the engine... Hopefully not damaged. Would have probably cost me eight pushrods had I listened to its instructions to leave the rocker arms in place during removal. After deciding we'd done enough damage and decided to ignore the service manual's faulty info and remove the exhaust manifold, we got the four tab-locked bolts out... Then found that the middle bolt was some extremely weird size, a 17/32 socket matched it perfectly but it was a cheap 1/4 drive socket that broke when we tried to undo the bolt.

Since I couldn't find a replacement anywhere, now I have to special order a socket to proceed any further on that head. Hopefully nothing turns out to be damaged too badly when we finally get that stubborn, heavy hunk of iron out. Talk about Murphy's Law. At present I'm seriously regretting embarking on this disaster, but then I don't have $900 to pay a shop for this work so I'm stuck doing it myself. Hopefully a shower, several beers and some sleep will put me back in a condition to tackle this. Better news tomorrow I hope!

Sugar Bear

The middle bolt should be the same size as all of the others 9/16", if it is the original one. Try using a six point 14 mm socket even if it must be tapped on to the bolt head. The head of the bolt may be slightly smaller due to rust.

Don't be surprised if that bolt breaks, if so drill it and tap it once the head is off.

About the dipstick tube, hopefully it was pulled out of the block and not broken off in the block. If it was pulled out it is no big deal just put it back. If it was broken off you will need to get the broken piece out of the tube that is in the block. Do this while the head is off as there is more working room.

Keep up the good work!!!

Were you able to do a leakdown test?

Supernaut72

Tried a 9/16" socket on it, as well as a wrench, and both were way oversized for it (not the slightly-oversized feeling of the correct size on a rounded/damaged bolt head). Of course, 1/2" was too small to fit, as well as 13mm. Might have tried 14mm and found it to be a tad too small or a little too large to torque on without fear of rounding the bolt, don't recall. Might be worth revisiting with that size. Interestingly, there was a metal lock tab on the passenger's side middle bolt, the driver's side middle bolt did not have one. The bolts all look about the same age and condition though, so that's really got me stumped. The 17/32 looked like it was going to work perfectly until the socket itself broke unfortunately.

Had a little luck with a weird wrench with an odd-shaped swivel end that's supposed to clamp down on the bolt when you apply torque to it, I moved the bolt a bit with it but I decided not to press my luck with it since I don't want to round the bolt off. At the least, it looks like it may not be stuck in there too badly. I've been giving it liberal doses of PB Blaster so maybe it'll come out with channel locks or vice grips if it comes to that.

I'll have to investigate the dipstick tube once the head is out of the way, as the bottom of the tube doesn't appear jagged or broken, but I haven't gotten a good look since it came out. The bottom looks flared out rather evenly all around, so hopefully it wasn't sheared or anything. Worst case I guess I'll just brute-force the remaining bit out of there and find a replacement.

Lesson learned, I'm going to second-guess the manual in all major matters from now on, I will not advise anybody listen to that manual when it comes to removing cylinder heads. Far better to remove the exhaust manifolds and rocker arms first, even if it is a little cramped to be undoing lock tabs and fitting a ratchet down next to the manifolds.

And thanks, it's been a back-breaker so far but I'm saving a ton of money by going this route even if I might have to replace the dipstick tube.

Didn't get around to doing the leakdown test since my helper was a little pressed for time and wanted to get right into it... Might still perform the test on the other bad cylinder (#4) before removing the passenger's side head bolts. Based on the weird sounds coming from the exhaust pipe, it definitely sounds valve-related, guess I was in denial of that and thinking it was an internally rotted resonator or muffler or entirely the timing chain's fault in order to save myself from doing this, but my hands are tied if it somehow turns out to be worn rings, however unlikely that is.

Sugar Bear

Since a leakdown test could not be done, if the heads are taken to a machine shop ask them to vacuum test the valves before anything is disassembled. If the cylinders with low compression show leaks and the cylinder walls look like the ones with good compression, the problem is probably in the valves vs. rings/pistons. A test can also be done by pouring a liquid into all of the intake ports with the head on its side and watch for leaking out of the intake valves and then turn it on the other side to check the exhaust valves in the same manner.

Supernaut72

Good tip, thanks! When the driver's side head was partially removed I did get a pretty good glimpse at the bores of cylinders #3, 5, and 7 (#1 was too close to the top of its travel to see the bore though), and all of the visible bores on that side looked the same... Will wait until the head is fully removed to get a closer look of course. All of the pistons also looked nice and clean as well, though the piston of #1 had a small, light carbon spot in the dished area. Not a problem cylinder, just interesting to note where the carbon deposits were.

With any luck it's just poor valve sealing, we'll know for sure as soon as we can get those things out.