63super88

I just did a leak-down test on the #1 cylinder in my 394, and although being a novice to these sort of compression tests I found the results to be strange. I had thought this to be the strongest of them all. I unhooked the coil, got the timing mark to center so #1 was tdc, and hooked up the hose to the plug hole. I got the tester to 0% and plugged it into the hose, and it read just above 20% in the green area, which seems like a good compression reading, but I heard it and saw it coming out of the oil filler/pcv. it didn't come out of the rad/exhaust/throttle but I def heard it in the crankcase, does this mean its going past the ring or a cracked cylinder? i thought if thats the case the compression would be leaking a lot more? is this just typical wear of 95,000 miles on a ring? I saw a guy do a test just like this on a 394 in a '63 98 and he said that youll always hear some sound out of the breather cap hole, is he right?

rustyroger

You are right, some air is making it past the rings. Quite normal.
The good news is the head gasket and inlet and exhaust valves are sealing well.
Seems to me your engine is in fair shape (at least on #1 cylinder), why did you do a leak down test in the first place?.

63super88

forgot to mention, because I had been finding a lot of water condensation and green stuff under the cap and in the pcv, and the oil with low mileage on it looked a bit funny/thin to me so I changed the oil and tried running this test (although the cap foam element was pretty dry and might've been letting in to much cold air into the tube so I oiled it up real nice and I think it helped a little).but figured might as well do them all with the leak down anyway whats the harm. I do believe #1 to be the strongest just due to the way it burns plugs the best. its #3 and 7 I think are slightly questionable. 25% isn't bad I guess, can only hope the others aren't much higher or mechanically unsound knock on wood. i think to test for head leaks ill use block testing fluid pump in the rad filler hole to check the gases, is that type of test reliable for an older car without a coolant bottle like in moderns? ive never done these tests before but I think I know what to do, just getting accurate results from the leakdown is the tricky part, since ive got to find tdc on the rest of the cylinders without marks on the pulley. other guys said crank it 90 degrees or something but im not exactly sure what that means like as in a quarter turn on the crank or something? hard to tell what that would be. ill just try to feel them out with a wrench extension or some other probe I guess for now, I saw another guy do it like that on his same year 394. any advice or tricks for that would be helpful.

MDchanic

You are getting a normal result. Some air always blows past the rings into the crankcase - that's why the fancy leakdown test kits have gauges that are calibrated in percent leakage - because some percentage leakage is normal.

Look at a piston with rings on it, and look at a ring fitted into the bore - there is a gap in the ring. Every ring has a gap. Those gaps are a pathway for leakage to the crankcase. When the engine is running, and the air in the combustion chamber has hundredths of a second to leak out, there is no time for any meaningful leakage to occur, but when you put a steady stream of compressed air on it, you can hear it leaking through.

It doesn't sound like you did a compression test yet.
You need to do that first. The leakage information you are looking for is most relevant to cylinders with low compression (that's why you're looking for leakage). Cylinders with high compression are obviously doing fine.



Last time I was in the tenth grade, 90° meant a quarter turn.

And, yes, we're talking about the crank, which you've been referencing for TDC information throughout this job. Can you see the end of the cam with the engine assembled?

I was under the impression that we've been giving you tips and tricks this whole time.

- Eric

63super88

yea ive been hearing you loud and clear MD, your on the ball a lot with my noob questions, I do appreciate it but you and another guy said to mark it at 90 degrees from the original mark, although how would I be able to determine an exact 90 degrees away from the mark and make my own marks in close enough position to get tdc on one of the cylinders is really what I don't get, other than guestimating and feeling them out. just pulled a real stupid move though, in my hurry to start up the car and warm it up again I completely didn't notice the small breaker bar I was using was still attached leaning on the frame rail, and when I cranked it the knuckle snapped so after getting my craftsman replacement Ill start again (I seriously hope I didn't bend and or warp my balance wheel now pretty pissed actually), it was pops original one, I can hear him now "I had that thing longer than you, built my first car with it and look at it now etc etc.." I didn't get the compression tester, im running a bit low on funds at the moment so I figured just get the leakdown and do them all, whats the harm in a thorough exam, but the weather and my clumsiness aren't agreeing with me today. but when you say 90 degrees quarter turn the balance balancer its tough for me to figure out whats exactly 90, so turning it about a quarter and feeling for it is still my best bet I guess. think im done for the day, between snapping my USA breaker bar and buying a new made in commie chinaland one to replace it and the freezing cold shitty weather here in lame old Jersey im pretty demoralized. but I always like to leave it off wit the "advice" line, but what im really saying is if theres anything we missed in the discussion let me know, you know.

rustyroger

You shouldn't have any problems using a fluid tester on an old fashioned radiator.
Make sure the radiator isn't overfull, run the engine until the thermostat opens then run the test.
It could be the car needs a long run to clear condensation from the crankcase, maybe the roads in New Jersey aren't suitable right now but It would be what I would do if any testing doesn't reveal an obvious problem.


Roger.

olds 307 and 403

A compression test would be done first. The leak down test is to pin down where the compression loss is. The goo could be weather or blow by getting past the rings. A good engine flush might help just before the next oil change. I say drive around a day or two with it in the crankcase. Their is also an air intake cleaner or combustion chamber cleaner spray that I spray directly into the combustion chamber through the spark plug hose. Similar to the Amsoil Power foam. I gained 20-25 psi on a couple of low cylinders in the 76 Olds 350 in my 94 4x4, stuck rings. Also helped oil comsumption but didn't eliminate it, you can't fix a worn out engine, just remove carbon and sludge.

63super88

I don't really think its a serious issue, just a bunch of minor annoying ones which like you say a good cleansing is probably in order. but after a 50 years and 92,000 im happy it just starts, idles and runs as good as it does. It pings here and there on heavy acceleration, and Ive been tinkering with prem fuel, 108 octane boost and marvel mystery mix and advance/decline timing. I was thinking maybe id find the source, like leaky valves on the questionable #3 and 8 maybe its not the fuel/timing but just damaged/burnt/dirty valves. (edit:it doesn't burn oil or show any of those bad symptoms just the slight ping, maybe what it really just needs is a new distributor, even swap out old points system to electronic, ive serviced the whole dist. short of pulling it out)

oldcutlass

What is your dwell and timing set to? Has your timing set been replaced?

63super88

dwell is 30 degrees and I like to keep it at that, that shouldn't be tinkered with right? the timing is like id say 2 degrees higher than the center mark on the timing indicator cause I tried to advance it just somewhat and if that's what your asking was replaced than no not much of anything was replaced on the car before I got it except the points and oil (and the tires and voltage reg maybe some fuses but that's all about it), and I have also done points/condenser/rotor/cap/vacuum advance. the ground on the distributor to the plate the points set on is barely hanging on maybe even severed which doesn't really sound good come to think of it would this affect the spark and cause some cyls not to fire as well? like I said a new one is prob the best bet might not even be cylinder/head parts but to do a distributor on a 50 yr old engine with the original dist never removed before, its tricky with that oil pump rod and such right? (I didn't really do it myself last time i did an engine had a guy do it and the engine we were working on was fully remanned little 6 cyl.)

jag1886

I would venture a guess that the crap in your breather system is just condensation caused by not driving the car enough (long enough at one time) to cook the condensed water out of the crankcase.

63super88

yep, its looks somewhat better now that I oiled up the breather element to not let so much cold moisture in, and took it for a long ride to class today, but got the car salty in the process in which I made another thread bitching about getting it salty haha. I don't know whether to feel better or worse about it. the ping is still present though, the ground on the inside of the distributor got me thinking now.

MDchanic

So it looks like there are a number of things going on here, other than your leakdown test, that you need to work on.


Right.


If your timing is set to 2° past the center (5°) mark, then it's set to 7°.
If your engine is high compression, it is designed to run at 5°, on RON 100 octane fuel.
Modern fuels in the US are rated using the AKI index, not RON, and a RON 100 octane is roughly equivalent to 95-96 AKI octane, so unless the pump at your local gas station says "96" in big letters on it, you're not giving it enough octane.
(If you have a 9:1 low-compression engine, it will probably tolerate about 92 octane).

If you are already running too little octane, and you further advance the timing (to 7°), then you are taking a situation in which the silent detonation (occurring when you can't hear it pinging) which is already destroying your engine, is now even worse.

If you have pinging, you need to increase your octane and retard your timing until the pinging stops completely, or one day you will notice your engine running roughly, and wonder why all that smoke is coming out of the oil breather.

If the pinging is being partly caused by carbon deposits, it appears that some have had success removing them with aftermarket throttle body cleaner sprays, sprayed into each spark plug hole and allowed to sit for a few days, or with Seafoam added to the tank (when it's at a quarter full or less) and drizzled into the carburetor. Do that, too.







It's not. He's asking about your timing gears and chain.
The gears wear badly (the later ones are coated with nylon, which chips off), which retards your cam timing.


So this is a very original car.
That means that you will get your best results following the instructions in the original Oldsmobile Service Manual.


Not exactly. It can cause the car to stall or run really badly intermittently, often without any apparent rhyme or reason.

You should fix that. Use any sort of a very fine braided wire.
If all else fails, very fine soldering wick, designed to soak up solder when disassembling circuit boards, may work well.



You need to fix this as your first priority.

- Eric

63super88

well I already understand the octane problem i run 92 octane prem, usually a 104 or turbo 108 octane booster and 4oz of marvel mystery oil. I had gotten a tip on a previous thread a little while back about the ping to advance the time to prevent it but I guess that person was wrong. im gonna decline it some, and throw a 108 booster in it cause last time I filled it I got 3/4 tank and added some marvel (maybe a couple oz too much but eh), is this a good brand, is there a brand youd recommend if at all? and definitely retard the spark 2 1/2 degrees like that page from the manual says? PS a link to the online resource for that orig service manual would be great, I remember looking into it once but lost the link, thanks!

MDchanic

Really? I'd use a stronger word than "wrong" myself.
If anyone actually recommended that, he was an idiot.



There are a number of fairly common substances that can be used to reduce the tendency to knock, including toluene and xylene, but these reduce the lubricity of gasoline, and can damage rubber seals, so are not the perfect solution.
I have no idea what's in most of the auto parts store additives, and, frankly, I don't trust them. Years ago, I tried them all, and didn't feel that any of them worked.
I recommend Octane Supreme, which I've bought from Wild Bill's Corvettes, and which definitely works, and definitely contains lead (because it definitely left good old fashioned lead deposits on my spark plugs).



WildAboutCars has a wide variety of Oldsmobile manuals available for free, including the 1963 fullsize Service Manual.

- Eric

oldcutlass

As Eric said, the wire needs to be fixed, and the dwell of 30 is perfect. When does it ping, partial throttle like up a hill, or floored? Have you looked at what your total timing is with and without vacuum advance? If the timing set has never been changed, I would make that my next project.

63super88

thanks for the manual and info, i remembered my account and all once I clicked the link. well it really only pings in the heavier accelerations, but im not exactly drag racing the thing though you know, just a little heavy footed at the stoplights when I feel like testing out my last settings. the mix I use in the gas (prem 92+ off-shelf turbo 108 booster+ 6oz marvel)has noticeably helped id say.

ill double check dwell, set timing at spec 5 and slightly declining say 1/2 degree until she likes it, not going under 2 1/2 degrees, firmly test driving it in between until she likes it. (although I do remember trying to advance/decline it every which way at this dwell before but wasn't really strict on it like this science experiment im on now). ill get a compression tester hopefully tomorrow, and maybe get around to it Friday afternoon.

For compression test: warm engine till cold light out, take out all plugs, test one at a time for 3-4 turns, record results, compare to specs right? ill probably mark wires/cap with silver sharpie for easy on/off. anything im forgetting?

rustyroger

You forgot to award yourself a pat on the back for getting it spot on.


Roger.