Time to rebuild?

[rich006]

1) Were there any signs the engine had gotten hot prior to your purchasing it.(new rad,thermo& gasket,recent flush tee, hoses etc)?

The car only had 6 miles on it since the previous title transfer. It sat in a garage for that 8 year period.

2) I have seen decent compression readings & piss poor leakdown readings, it doesn't automatically mean the rings are fine at all.
3) Does the engine stall immediately if You pull the PCV out of the valve cover, & is it difficult or impossible to restart like that?

Nope. If I pull the PCV valve out the idle drops slightly but quickly recovers. It starts the same with or without the PCV valve connected to the valve cover.

4) Did You in fact have a leaking fuel pump diaphragm, or was that a dart at the wall guess?

In hindsight it was probably not leaking.

5) How experienced is the tech doing this checking for You, esp. old school units.?

They do a lot of work on classic cars at this shop. The guy doing the check was youngish, but the owner is very experienced and told me he is SURE it's the rings.

6) Does this car have the catalyst on it?

No, I understand the catalytic converter was new for 1975 model year. Mine doesn't have it.

 

[AJ/FormS]

Another note: lately the idle has been really rough when cold, but fine when warm. Previously the idle was pretty smooth all the time. Today I repeated the vacuum check while the engine was not yet warm, and I noticed that the idle improved dramatically when I opened up the vacuum line from the intake manifold. Does this suggest that the choke is not coming off the way it should?

Probably it doesn't suggest that. but I suppose it might, Easy enough to prove; just pop the air filter house off an look.
What it suggests to me is that the carb is rich. There are many reasons for that, the choke being way down on the list.
Your vacuum results seem to indicate that the rings are fine.
Your vacuum break may not be sufficient.
I'd like to see a retest of the crankcase pressure, but with either.
A) the cooling fan disabled, and the PCV removed from the cover and the hole plugged, or
B) plug all openings into the crankcase and put a pressure gauge on the dipstick tube. Use a fuelpump pressure tester. Start her up and let her idle.If the pressure builds to 4 psi, shut her down.! There is indeed something wrong, probably with your rings.Or maybe just maybe, with a headgasket.
C) Remember back in post #12; the compression test showed a 5 psi drop on cylinders #1 and #2? You might want to repeat the compression test, having made sure the valves are all adjusted the same. I would do this retest inside at any comfortable room temperature, or if you have a block heater, still inside, plug it in. Let the car acclimate for at least 4 to 8 hours hours prior to the test, depending on the temp of it's prior environment.The purpose of this acclimation is to make sure the temp of the engine does not change during the test. The actual temp of the test is less important than that it remain unchanged. Your Italian tune-up may have changed things, as in cleaned out all the carbon.The valves may have been hung open on the previous test by that carbon. Or the rings in those two low ones may have been stuck. In any case test them all.It's not the absolute numbers that will tell the whole story, but rather the differences from hi to lo.

 

[rich006]

Your vacuum break may not be sufficient.

Sorry, I don't know what you mean by that.

A) the cooling fan disabled, and the PCV removed from the cover and the hole plugged, or

You mean remove the fan belt? How would that affect the crankcase? EDIT: Do you mean so that the fumes blowing out of the breather would be visible instead of being blown away by the fan?

I do plan to adjust the valves as soon as I get a chance. Then I'll redo the compression test. I think you're suggesting to do it cold just to make sure the temperature is the same for all of the cylinders? I believe last time I did it I rechecked 1 and 2 after finishing the others, just to see if anything changed as the block cooled in the interim. But I'm not positive I did that.

I've looked at the choke with the engine idling and air cleaner off, but I don't have a sense for how fully it should close and how quickly it should open at a given ambient temperature. Maybe I can post a video of it.

 

[pishta]

Cold choke should be called out in the rebuild kit, or one of SSD's links. Usually its called out using a feeler guage against the choke valve and side of venturi. When warm, the choke should be fully vertical. I must repeat that the valve lash needs to be adjusted as this effects many factors such as vacuum readings. And of course check your exhaust heat valve for freedom of movement. It should bounce against the spring when cold. Have you sprayed down your carb throat with carb cleaner during a fast idle? I had some air bleeds that were clogged and that messed up my off choke warm idle.

 

[AJ/FormS]

Comments in the quote;click to expand

Sorry, I don't know what you mean by that.The vacuum break is the amount that the choke pull-off pulls the choke off, right after start-up when the vacuum comes up. Pishta explains.
You mean remove the fan belt? How would that affect the crankcase? EDIT: Do you mean so that the fumes blowing out of the breather would be visible instead of being blown away by the fan? No.and yes,lol.The fan could be causing your paper to waffle all about like in the video. We need to eliminate that, so we can tell what's what. The PCV needs to be removed so that it is not affecting what we are seeing; and the hole where it came from needs to be plugged so that any blow by is all forced out the open breather hole. The engine will be fine running without the fan for the few minutes it takes to run the test. Just have it all set up ready to roll when you hit the key, then after the video is recorded, put it all back together.
I do plan to adjust the valves as soon as I get a chance. Then I'll redo the compression test. I think you're suggesting to do it cold just to make sure the temperature is the same for all of the cylinders?Yeah that's right.A seasoned pro can set your valves in a few minutes; a short enough time that the engine's temp will not change over the course of the procedure.Since I am jumping to the conclusion that you might not be a seasoned pro quite yet, my recommendation was just to rule that out.
I believe last time I did it I rechecked 1 and 2 after finishing the others, just to see if anything changed as the block cooled in the interim. But I'm not positive I did that.
I've looked at the choke with the engine idling and air cleaner off, but I don't have a sense for how fully it should close and how quickly it should open at a given ambient temperature. Maybe I can post a video of it.At this time of year, it should snap shut,all the way,snap! Then as soon as it starts, within a couple of seconds, the choke pull-off should draw the choke blade open about 1/8 to 3/16 inch. There is a spec for that, for a new engine, or one that is operating like a new one. For you, if the engine is running rough, within one minute of start-up, manipulate the choke blade and find the perfect opening, to smooth her out. Measure it. Then shut her off and readjust this airgap, which is called the vacuum-break, to your perfect gap, by bending the little loop in the choke pull-off connector link.You will need to apply vacuum to the pull-off to see the results of your activity. You can do this on the running engine(which is best) if you know what you are doing and can do it fast enough. You only have a half a minute or perhaps a minute to get it right, before the choke starts to open the blade and then times up! If you didn't get it, you will have to try again at a later time when the engine is again stone-cold.This is why the spec exists, cuz it can take you several times to get it right.The spec makes it faster, more probable, to get it right the first time.

 

[rich006]

I had time for one minute of troubleshooting on my way to work this morning. Quick recap: engine starts right up when cold, but soon bogs down at idle until fully warm. Today after backing out of the garage I popped the hood and pulled on the rod coming from the choke thermostat. Every time I pulled on it, the idle came up and smoothed out. When I released it, it bogged down again. The block temperature was probably 50, ambient temp was about 45, and the engine had been running a minute or so. I'm not sure if this points to the thermostat or the choke pulloff.

 

[Killer6]

I had time for one minute of troubleshooting on my way to work this morning. Quick recap: engine starts right up when cold, but soon bogs down at idle until fully warm. Today after backing out of the garage I popped the hood and pulled on the rod coming from the choke thermostat. Every time I pulled on it, the idle came up and smoothed out. When I released it, it bogged down again. The block temperature was probably 50, ambient temp was about 45, and the engine had been running a minute or so. I'm not sure if this points to the thermostat or the choke pulloff.

Sounds like pull-off isn't working, either there is no vacuum to it, the diaphragm is bad, the linkage is binding, or it is adjusted wrong.

 

[AJ/FormS]

I had time for one minute of troubleshooting on my way to work this morning. Quick recap: engine starts right up when cold, but soon bogs down at idle until fully warm. Today after backing out of the garage I popped the hood and pulled on the rod coming from the choke thermostat. Every time I pulled on it, the idle came up and smoothed out. When I released it, it bogged down again. The block temperature was probably 50, ambient temp was about 45, and the engine had been running a minute or so. I'm not sure if this points to the thermostat or the choke pulloff.

It's just a too-small vacuum break

 

[rich006]

I readjusted the valves yesterday to 0.010" intake, 0.020" exhaust with the engine warm and running. By the end of the adjustment the 0.011" and 0.022" feelers were a very tight fight and the 0.010" and 0.020" feelers would slide with some noticeable friction but not too much. I did see all of the rockers dribbling out oil. All of them needed tightening, mostly about 1/8 turn each. #6 exhaust was the one making the noise; it sure is nice to drive without hearing the valve noise all the time (although now I have to listen to my noisy/leaking power steering pump and an intermittent squeaky gurgle--is that the water pump?).

While the valve cover was off I cleaned out the baffles with a piece of coat hanger, a toothbrush and some paper towels. As Dan predicted, there wasn't nearly enough gunk in there to prevent airflow.

The warm idle is a little rough now, but I have yet to set the idle mixture carefully. There's now a pretty regular "lope" about 2.5 times per second idling in Drive (~150 lopes per minute: one every 4th engine revolution?). Next up: set idle mixture, redo compression test, check again for fumes blowing out crankcase breather.

 

[BillGrissom]

Good you determined it is an O/F problem and the engine is sound. The first responses of "just rebuild the engine" would have set you off into la-la land and still wouldn't have fixed the problem. Once warmed up, the choke should be fully open. You should feel the choke spring pulling hard. In-between is what they try to design for and could never do near as well as electronic fuel injection. Your year has all kind of add-ons like an intake air heater and choke heater, all attempts to kludge the mechanical system into working acceptably.

The biggest thing to verify is that your "choke pull-off" works. Those are often damaged by spraying carb cleaner. To test, use a Mighty-Mite hand pump on the vacuum port and see if the rubber diaphragm holds vacuum. If you don't have one, push it in, block the port w/ your finger and see if it stays in. Of course, it will extend slightly until it builds vacuum. The theory is the choke should be tightly closed when cranking to give a rich mixture. The second the engine fires and speeds up, it should pop open slightly (manual shows a drill bit measurement), due to intake vacuum. If not, the engine will die from "too rich". Wish I had understood that decades ago when I kept fussing w/ the choke adjustment in my 1969 slant between summer and winter. I don't know if most mechanics then even understood how it was supposed to work.

 

[rich006]

I fixed the choke pull-off (break) with a new piece of vacuum hose. I did the "pull it and cover with finger" test. It held vacuum but wasn't getting the vacuum signal until I replaced the hose. Now it works as advertised.

However, I have yet to resolve the blowby issue. I should have some time to work on it this weekend.

 

[slantsixdan]

Good you determined it is an O/F problem and the engine is sound.

That has not yet been determined. There's still blowby to deal with, and this car's constant short-trip usage with the choke far too rich (no pull-off action) means there's still a fairly strong likelihood that a rebuild will be required.

I don't know if most mechanics then even understood how it was supposed to work.

The good ones did.

 

[rich006]

I set the idle mixture today. It was a little lean before, and seems to idle better now. Unfortunately there's still blowby as you can see in this video (I can't get the video embedded but the link should work).

View My Video

The paper stays down at idle, gets blown up at higher rpm, and gets sucked down on deceleration.

Tomorrow I hope I'll have time to redo the compression test, but I don't expect any different results.

 

[slantsixdan]

Sounds like it's running reasonably well. Still looks like a fair amount of blowby evident when you rev up the engine.

I don't think there's much of anything to be gained by a compression test do-over. A leakdown test done extra-carefully, with the engine warmed up, is a better diagnostic tool.

 

[AJ/FormS]

There now, that looks about normal for her age. And see how snappy she revs up?

 

[Killer6]

I fixed the choke pull-off (break) with a new piece of vacuum hose. I did the "pull it and cover with finger" test. It held vacuum but wasn't getting the vacuum signal until I replaced the hose. Now it works as advertised.

However, I have yet to resolve the blowby issue. I should have some time to work on it this weekend.

Cool deal, the fact that the engine stayed running & restarted w/the PCV out means the rings weren't toasted, maybe fuel-washed too many times. I have a 225 60ft. from where
I'm sitting that pumps 115-120psi & leak downs were abominable, the guy "just re-did the head", thing smoked like a freight train warm. If the rings are toasted & worn they can
act like a bad master cyl., if You stab it quick You've got a pedal, but gently pushed it goes right to the floor...no tension in them but "fluff" cranking quickly enough. On the intake
stroke it's the opposite, & the vacuum suffers, the crankcase & the intake are both filling the cyl...not good & it will stall immediately when You pull the PCV out of the VC.
Looks like You've got it running decent now, but as AJ said "for her age", the blow-by may improve if the over-fueling cold didn't do too much damage. Fact is, she's old & a
rebuild is probably the only way to eliminate that completely.

 

[BillGrissom]

I watched the video. Can't say I've ever done this test on a gas engine, but it is very common on my M-B diesels. Those owners would be very happy to see such minimal blow-by. Most diesel engines show puffing from the oil fill cap just at idle, but they also have 400 psig compression (new, <300 psig when old and getting hard to start on cold mornings). If you had the PCV valve disconnected in the video, then it is probably "as expected". The PCV system sucks up all those vapors, and the blow-by flow probably wouldn't overwhelm it. To feel confident in the engine, turn it over by hand. You can use a socket on the crank bolt (many slants need to add a bolt, same size as Hemi's) if tugging/pushing on the fan belt doesn't work. If you feel 3 strong "air springs" per rev resisting you, and each takes >5 sec to hiss down and let you proceed, your engine has excellent compression, and you can sleep well.

 

[rich006]

Since fixing the choke pull-off I've noticed that the engine still bogs down at idle shortly after a cold start--not as soon or as badly as it did before, but within about 30 seconds of starting it starts to feel what I would describe as over-choked or flooded. I might suspect the electric choke heater isn't working, but the ambient temperature has been too low for that system to kick in. So it's not the electric choke assist. Also, while this was happening I removed the air cleaner lid and pushed the choke plate open with my finger, thinking that would help. However, opening the choke had no effect (before I pushed it wide open, there was maybe 1/8" or 3/16" gap next to the plate).

I thought maybe my fast idle is adjusted too low, so I raised it a little, but that didn't seem to make much difference. (It's a little hard to tell because I couldn't check the results until the next day, which wasn't as cold.) Could it be the electric choke assist is heating when it shouldn't, and opening the choke too much too soon? Could it be a more basic problem with the idle circuit or the float bowl? I haven't looked at the carb yet. I could try rebuilding and swapping in the carb that was removed from the car just before I got it.

 

[BillGrissom]

1/8" open sounds about right, since that is how far the choke pull-off is supposed to pull it open. You can play with the choke's thermostat adjustment. There are rich (R) and lean (L) marks to tell you which way to rotate it. Don't fool with the idle mixture, since you want that correct when the engine warms up. If it doesn't stall or stutter before it warms up, you are doing about the best the system ever did. Chokes were always inexact, and why they kept kludging on additions to try to improve them. You will never get it as smooth as modern fuel injection, or even 1980's electronic carburetors. In the 1950's, the driver had a manual choke cable, and teaching most drivers how to adjust that as the engine warmed was difficult. My mom never quite understood what the choke or clutch did and was lucky to muddle through, often stalling at red lights, then saying, "Oh, I forgot I'm supposed to push in the left pedal when I stop".

 

[slantsixdan]

No, the '73-up factory (and factory-type replacement) chokes are not adjustable. There are no R or L marks, and there's nothing to rotate. If you want to be able to adjust the choke thermostat—which is very handy for dialling-in appropriate cold-start and warmup behaviour—then get a № 1234 Electric choke kit and drop it on. Take you about 20 minutes, and is a large improvement over the primitive and notoriously cold-blooded factory '73-up choke setup.

 

[rich006]

Bill, I already adjusted the idle mixture warm, and won't mess with it now. It idles pretty well warm, and I'm not sure what would be different cold other than the choke. The thing is it used to idle just fine cold, until recently. It didn't get worse after anything I did, just on its own.

Dan, thanks for the tip on the electric choke upgrade. (But I still don't think the choke assist is involved in this specific problem unless it's somehow heating when it shouldn't.)

Manual chokes were still around in the 70's. My 1971 Volvo had one. The setting was like this: you pull it out to start, push it halfway in when you pass the stoplight, and the rest of the way in as you're entering the highway.

 

[slantsixdan]

Dan, thanks for the tip on the electric choke upgrade. (But I still don't think the choke assist is involved in this specific problem unless it's somehow heating when it shouldn't.)

You may well be right, but the point is that the stock choke system tends to give cold-blooded behaviour like this what you describe, and they cannot be adjusted. The electric choke kit replaces that primitive system with fully electric modulation. That works better, and plus the adjustability means you can dial in the choke behaviour to get the cold (stomp the gas, turn the key, drive away) behaviour the good-running, well-adjusted '60s cars gave.

 

[Killer6]

I have a few things to note;
1) Is the choke thermostat the same unit between Holley 1920 & Carter BBS?
2) Is the new base gasket exactly the same thickness as the OE?
3) If the answer to either of the above is no, the choke calibration will be wrong.
4) When the choke is closed, the pull off(break) dictates the initial start-up idle & drive off quality. The timing of the choke opening beyond that is dependent on the thermo coil.
5) If the carb is raised or lowered, You have altered the timing/calibration, same if a different model engages the rod at a different level.
6) I had to make a gasket for My 3.9 Dak 'cause the kit didn't include the extra for the spacer, it was thicker, & pulls the choke open too soon. I have a sag during the warm up
cycle between cold start & roughly 80% fully warm.

 

[rich006]

I have the Holley 1945, and the gasket is about 1/4" or maybe 5/16" thick. I get what you're saying about the gasket affecting the choke operation. However...

Yesterday on cold start after work (ambient temp 55 degrees) I tried pushing the choke closed with my finger as well as open. Closing it made things worse. Opening it didn't make things better. I suspect the choke is working fine and either there's some non-choke-related problem or my expectations for smooth cold idle are too high. This morning I tightened the fast-idle screw another half-turn, and that may have improved things a bit.

 

[rich006]

I took the choke thermostat off the manifold, sprayed the coil with WD-40, and reinstalled it. The good news: on the next cold-start, the idle was so much higher that I backed the fast-idle screw way out. The bad news: apparently I backed out the screw too far, because now it's completely gone. Ugh.

So I'll probably get the electric choke conversion to replace my rusty choke coil (and a new fast-idle screw), but I'm sure the choke wasn't the only problem.