How Smooth Is Your Engine Idle

[Jeff Balazs]

Well I wouldn't throw in the towel quite yet. It is possible that you may be able to get it to smooth out some more. A compression check is definitely in order.

 

What weight oil do you have in it? It would seem that at this time of year in your climate you would want something pretty light......10W30 or perhaps even a 5W? Just an idea that might have some effect on the way it runs.

Jeff

[55 Fargo]

Well I wouldn't throw in the towel quite yet. It is possible that you may be able to get it to smooth out some more. A compression check is definitely in order.

 

What weight oil do you have in it? It would seem that at this time of year in your climate you would want something pretty light......10W30 or perhaps even a 5W? Just an idea that might have some effect on the way it runs.

Jeff

Hi Jeff, will be doing a comp test soon.

I have 15 W 40 diesel oil, as my truck is in a heated insulated garage, and does not get driven in winter as a rule.

All in all, she is pretty good, I will not rule out any type of minor vacuum leaks too, you never know.....cheers

[Jeff Balazs]

If it were mine I think I would be inclined to try running some 5w 20 oil in it....at least for a short period of time .....to see if the lighter oil helped get the valves freed up etc... I feel like the oil you are running is better suited to a newer engine in much warmer climate.

Jeff

[55 Fargo]

If it were mine I think I would be inclined to try running some 5w 20 oil in it....at least for a short period of time .....to see if the lighter oil helped get the valves freed up etc... I feel like the oil you are running is better suited to a newer engine in much warmer climate.

Jeff

Hi Jeff, trust me, the warm weather driving season here is hot hot hot, but short, this engine did not like 10 W 30 in summer, it would be okay now, if used a lot, or even 5 w 30.

I have not replaced the dizzy cap or rotor, don't think it is the problem, as she runs really well, jut a bit of a rough idle. 

I wonder if the carb is having issues, in the idle circuit.

I could possibly try  the lighter oil first thing in the spring, and see what it may do loosen up the lifters, and maybe some MMO too.....thanx for your suggestions

[55 Fargo]

Okay just went outside to the shop, cap rotor points look great and new, i installed them within the last 2 years. 

I started the engine turned off the lights and had a look under hood, no stray current or sparks either.

It then dawned on me, listening to the exhaust,  a little poof-poof sounds like exhaust blowing as well as drawing. I really believe now it has a burnt or sticking valve or valves. I did the paper test at the tail pipe it failed.

I have a choice, rebuild, do a valve job, or live with it for now, or find another engine. 

[NiftyFifty]

Piles of 218's around, but getting tougher to get the 251/265's, I'd rebuild what you have. I do have a line on a 230 short in Winnnipeg that a friend dropped out of a 49 coupe.

[55 Fargo]

Piles of 218's around, but getting tougher to get the 251/265's, I'd rebuild what you have. I do have a line on a 230 short in Winnnipeg that a friend dropped out of a 49 coupe.

I have 3 -251 engines, 1 in the truck, and 2 on the floor.how about a 283 SBC...hehehe Probably will drive her like this for a while, lots of power, good oil pressure, and does not burn or leak oil much.

I could be wrong with my diagnosis, and possibly could be missing something, but the poof-poof in the exhaust is a dead give away, maybe do an in truck valve and ring job, and learn something.....

[55 Fargo]

1 other idea, going to try some "seafoam" snake oil tomorrow, see if it will help it run a little smoother....

[Frank Elder]

Don C. put some chevy valves [stainless?] in his 251 when he rebuilt it...I wonder what the advantage would be?

[NiftyFifty]

Why are you concerned with it now? We won't be in cruising weather for another 2 months at least, by then the crappy gas we have up here will be a big part of the problem. Tough to set everything properly until you can really be in operating temperatures and climate, and safely run the truck outside and mess with it. Setting it at -19 or 20 will show different results then +20.

[55 Fargo]

Why are you concerned with it now? We won't be in cruising weather for another 2 months at least, by then the crappy gas we have up here will be a big part of the problem. Tough to set everything properly until you can really be in operating temperatures and climate, and safely run the truck outside and mess with it. Setting it at -19 or 20 will show different results then +20.

Yes, I know, crappy gas, running Premium, but the winter blend might be part of the equation. BTW it's not -20 in the garage, it's 50f.

I like to get  some things done prior to spring, some guys have everything tucked away all winter, not me.

I do not see why the vacuum or a valve issue would be any different in warmer weather, can you please explain?

Here is a video of it running, do not think any tuning or tweaking will do anything now, firmly believe it's an exhaust  valve sticking or burnt.

I still have to verify this with a proper compression test.

 

[Jeff Balazs]

You should expect a lower vacuum reading when the engine is cold and as the block gets up to it's true operating temperature it should give slightly higher readings. I think that is pretty typical......and I would expect to see a difference of 1/2" to 1 1/2" from cold to warm on an engine that is well worn in. I certainly see this with my truck every time it is run as I have a full time vacuum gauge in the cab. It isn't really a weather issue as much as it is changes in clearances as the engine warms up. I only brought up your climate as I believe it may have a big impact on oil selection.

 

My suggestion to run a lighter oil was made because I think you probably still have a lot of sludge deposits in places that may effect how well it runs. Again I am basing this on my own discoveries as I revived rather than rebuilt my engine. I have been more than a bit surprised by the amount of crud that has "washed" out of this engine as I continue with it. At first it was the cooling system that seemed to hide an extraordinary amount of stuff.......but now I know this is also true of the lubrication system as well. Of course none of this is of much help if it turns out you have a burnt valve.

 

Jeff

[Plymouthy Adams]

my engine is so smooth it picked up a dual over head cam v8 in the bar parking lot last weekend

[55 Fargo]

You should expect a lower vacuum reading when the engine is cold and as the block gets up to it's true operating temperature it should give slightly higher readings. I think that is pretty typical......and I would expect to see a difference of 1/2" to 1 1/2" from cold to warm on an engine that is well worn in. I certainly see this with my truck every time it is run as I have a full time vacuum gauge in the cab. It isn't really a weather issue as much as it is changes in clearances as the engine warms up. I only brought up your climate as I believe it may have a big impact on oil selection.

 

My suggestion to run a lighter oil was made because I think you probably still have a lot of sludge deposits in places that may effect how well it runs. Again I am basing this on my own discoveries as I revived rather than rebuilt my engine. I have been more than a bit surprised by the amount of crud that has "washed" out of this engine as I continue with it. At first it was the cooling system that seemed to hide an extraordinary amount of stuff.......but now I know this is also true of the lubrication system as well. Of course none of this is of much help if it turns out you have a burnt valve.

 

Jeff

Hi Jeff, that's a good idea, and will be trying out in early spring.

I bought a pan gasket, and will be dropping it soon and cleanin/inspection etc.

I have done the filter housing as well as the side cover area too.

My engine oil gets black quickly after an oil change, so dropping and cleaning the pan should help.

[55 Fargo]

Just ran a compression test, on warm engine the following are the results,

Cyl 1 100

cyl 2 95

cyl 3100

cyl 4 85

cyl 5 90

cyl 6 100

 

This isi a dry reading tried a wet reading on a low cyls, no change. Now I know the source of my slightly rough idle, lower compression in cyl 4 and 5. My conclusion, older engine with wear, and slightly leaking valves...

[NiftyFifty]

You can set the idle speed in the shop, but unless you can actually take multiple drives after each change to see which way your going, you could be idling fine, but running rough when driving, and driving on a day like today is going to give different results then July. I can set my Monaco to absolutely purr in the shop....drive it and then you start getting into mid range and hard acceleration issues. Your dealing now with engine issues, so corrections to smooth that out may now mean bad drivability

[55 Fargo]

You can set the idle speed in the shop, but unless you can actually take multiple drives after each change to see which way your going, you could be idling fine, but running rough when driving, and driving on a day like today is going to give different results then July. I can set my Monaco to absolutely purr in the shop....drive it and then you start getting into mid range and hard acceleration issues. Your dealing now with engine issues, so corrections to smooth that out may now mean bad drivability

I drove it 20 miles today, heck the road was super dry, speeds up to 100 kmh.

I also poured some Seafoam down the carb, didn't seem to do a whole lot, but it made me feel good.

I don't understand not going for a drive on dry winter days.

Go to the HAMB, a few guys in Winnipeg are driving old classic cars year round, they are of course there old car beaters, but still they are having a blast

[NiftyFifty]

Ya, no thanks....none of my vehicles will ever see a winters day again. There's still ice to get to the dry roads and I just don't need some idiot sliding into me, and or breaking down in the cold and waiting for a tow. I've gotna buddy who runs his 1950 Studebaker year round..but it also runs a GM 4.3L and is on newer frame and suspension and he doesn't care about some rust issues with it.

[whtbaron]

Reading your comments about it running hot in the summer if you used lighter oil, and I'm wondering if this could be a timing issue with the advances. Memory is fuzzy, but it seems to me that I had the centrifugal advances jamb up in an IHC 6 and it ran really hot. Rev the engine with the timing light on and see if it's moving the advance off the mark with the vacuum plugged and unplugged. Running 10-30 in that motor really shouldn't be a problem. Those compression numbers really aren't horribly bad for a motor that old. If you've already run the seafoam through it I would pour engine oil down the carb until it stalls for a couple times and then head out for a good run down the highway. I'd also be a little suspicious of the new spark plug wires. I've picked up some of the new Chinese crap and they weren't worth bringing home. If there's no radio in the truck I'd be looking for some good old Mallory wire cores or something equivalent.

[55 Fargo]

Reading your comments about it running hot in the summer if you used lighter oil, and I'm wondering if this could be a timing issue with the advances. Memory is fuzzy, but it seems to me that I had the centrifugal advances jamb up in an IHC 6 and it ran really hot. Rev the engine with the timing light on and see if it's moving the advance off the mark with the vacuum plugged and unplugged. Running 10-30 in that motor really shouldn't be a problem. Those compression numbers really aren't horribly bad for a motor that old. If you've already run the seafoam through it I would pour engine oil down the carb until it stalls for a couple times and then head out for a good run down the highway. I'd also be a little suspicious of the new spark plug wires. I've picked up some of the new Chinese crap and they weren't worth bringing home. If there's no radio in the truck I'd be looking for some good old Mallory wire cores or something equivalent.

Hello, I never had any issues with overheating with this engine, but with 10 W 30 oil, she runs a little thin when really good and hot outside.

This engine has good oil pressure, 50-55 on the highway, and 30-35 the very lowest at idle in summer when the engine is good and hot. It does not use oil or leak much at all, even after 500 -1000 miles see very little change on the dip stick.

The wires, are a decent quality accel better tan the lower end chinese crap, thats for sure.

As you say, compression is not all that bad, this engine most likley had only 100-110 when frresh, with it's less than 7 to 1 compression ratio.

Yesterday ran a bit of Seafoam down the carb, not much a few ounces, did not  do all that much, drove her like I stole her after that for about 10 minutes, then did a compression test.

I do have vacuum advance on the distribuotr, and you can see it with a timing light. This engine has really decent puick up for what it is, not rough running that way, just a bit of a rough idle, not as smooth as I would like it, but she is old and paid her dues, so maybe I need to remember this.

I will be dropping the oil pan soon for inspection clean up and new gaskets.

I see your In Manitoba, in the Winnipeg area? Maybe should meet up to talk old Mopar some time....

[55 Fargo]

Ya, no thanks....none of my vehicles will ever see a winters day again. There's still ice to get to the dry roads and I just don't need some idiot sliding into me, and or breaking down in the cold and waiting for a tow. I've gotna buddy who runs his 1950 Studebaker year round..but it also runs a GM 4.3L and is on newer frame and suspension and he doesn't care about some rust issues with it.

I am not exactly driving on slushy salty roads, and wouldn't either.

I do drive on occasion a a frozen dry road, nothing at all splatters on the under side of the truck.

I do not like driving too much in a lot of rain though, so like to keep her dry.

I know Bamfordsgarage drives his 47 D25 all winter, it is an older unrestored car, and does not look any worse for it. He also drives the Model T in winter, and it is in really nice shape. I do not think He drives the Speedster in winter.

I really admire Chris and the miles and place this car has been, a real adventurer....

[Jeff Balazs]

I really don't think your climate is a major factor in getting this engine to run smoothly. The real indicator is the type of reading you were getting with the vacuum gauge. The needle should not fluctuate the way it does at steady idle. Period. That fluctuation indicates something is amiss in at least one cylinder. The only other thing that I know of that would give that sort of reading would be if you had a faulty PCV valve. Apparently you do not. Based on what all you have said it sounds likely that you either have a sticky valve or a burnt one. Since sticking valves are a fairly common item with these engines especially when they are not fresh....this would be my initial focus. You should do a compression check to help pinpoint the problem and make certain you have no vacuum leaks.

 

My suggestion about running a lighter oil was made as a possible way to help free up a sticking valve. Back in the day it was a fairly common practice to dilute motor oil with a quart or so of kerosene and run it for a short period to flush out sludge and particulate matter. The idea is that lighter lubricating oil tends to help carry away or flush this matter out of tight areas. You may or may not get the desired results by doing something like this. But if your engine runs as good as you have said I think there is a decent chance for this to work.

 

As I mentioned before I revived rather than rebuilt my engine in this manner. I did remove the head and oil pan before I ran it. It had been rebuilt at some point and the cylinders were in very good shape. There was however quite a bit of sludge in the oil pan. I cleaned all this out as well as cleaning the valve inspection areas and replaced the timing chain too. I also cleaned and flushed the oil pressure relief valve and filter housing. When I first started running the engine the vacuum and compression readings I got were lower than they are now. I also had a funky PCV valve which I eliminated. At that point I had a minor fluctuation in vacuum at idle which went away slowly and is now as steady as a rock. I found a better PCV and have it working now with no detrimental effect on the vacuum readings. I am also running a 180 degree thermostat and a better breather. This was all done to help reduce or eliminate the formation of sludge in the system. Hey and guess what ? It all works........the engine runs very smoothly and the oil stays nice and clean now.

 

I honestly hope some of this helps you.

Jeff

[55 Fargo]

I really don't think your climate is a major factor in getting this engine to run smoothly. The real indicator is the type of reading you were getting with the vacuum gauge. The needle should not fluctuate the way it does at steady idle. Period. That fluctuation indicates something is amiss in at least one cylinder. The only other thing that I know of that would give that sort of reading would be if you had a faulty PCV valve. Apparently you do not. Based on what all you have said it sounds likely that you either have a sticky valve or a burnt one. Since sticking valves are a fairly common item with these engines especially when they are not fresh....this would be my initial focus. You should do a compression check to help pinpoint the problem and make certain you have no vacuum leaks.

 

My suggestion about running a lighter oil was made as a possible way to help free up a sticking valve. Back in the day it was a fairly common practice to dilute motor oil with a quart or so of kerosene and run it for a short period to flush out sludge and particulate matter. The idea is that lighter lubricating oil tends to help carry away or flush this matter out of tight areas. You may or may not get the desired results by doing something like this. But if your engine runs as good as you have said I think there is a decent chance for this to work.

 

As I mentioned before I revived rather than rebuilt my engine in this manner. I did remove the head and oil pan before I ran it. It had been rebuilt at some point and the cylinders were in very good shape. There was however quite a bit of sludge in the oil pan. I cleaned all this out as well as cleaning the valve inspection areas and replaced the timing chain too. I also cleaned and flushed the oil pressure relief valve and filter housing. When I first started running the engine the vacuum and compression readings I got were lower than they are now. I also had a funky PCV valve which I eliminated. At that point I had a minor fluctuation in vacuum at idle which went away slowly and is now as steady as a rock. I found a better PCV and have it working now with no detrimental effect on the vacuum readings. I am also running a 180 degree thermostat and a better breather. This was all done to help reduce or eliminate the formation of sludge in the system. Hey and guess what ? It all works........the engine runs very smoothly and the oil stays nice and clean now.

 

I honestly hope some of this helps you.

Jeff

Thanx Jeff, yes all very good suggestions, and I am like you in the beleif we are dealing with a sticky valve or 2.

I spoke to the owner of the vacuum gauge yesterdy, and he did tell me this gauge flutters a bit on all the tests he has recently done about 3 engines. So will try it on my healthy 3.3 l V6 Dodge and se what I get.

I did a compression test yesterday, did you see the results? Not bad a few a little low.....thanx again for being a part of this thread...

[Jeff Balazs]

No I missed that. Sometimes I think the go to the last unread comment feature here "sticks" a bit.

Ok so that is helpful. Explains why 18" is the best you can get right now. I believe my initial compression readings averaged around 105 /110 or so with #5 being the lowest and 10# low. It has come up some as it has run in and I have continued to flush and change the oil. All are within about 5# of each other now.

[55 Fargo]

No I missed that. Sometimes I think the go to the last unread comment feature here "sticks" a bit.

Ok so that is helpful. Explains why 18" is the best you can get right now. I believe my initial compression readings averaged around 105 /110 or so with #5 being the lowest and 10# low. It has come up some as it has run in and I have continued to flush and change the oil. All are within about 5# of each other now.

Not sure, possibly having 85 and 90 could result in a lower reading, but in reality 17-21 is consdiered a healthy engine, according to specs.

I am near 1000 ft above sea level, and not sure if barometeric pressure would have any effects, as we have high pressure this past number of days, hence the old arctic air flowing southward. The gauge? It's a NAPA Ultra Pro brand, made in China, might be another reason...

Your reading of 105-110, would certainly create a better vacuum draw than my 95 -100 psi range, at least that shoudl make sense, maybe not....

All info regarding a normal vacuum reading with needle vibrating a small amount  point to ignition issues, bad plug, bad wire cap, coil primary circuit. or High lift longer duration camshaft, which I do not have. Valve isses show themsleves in unsteady reading where needle moves 3-4 inches or more..

I am going to try another gauge, then if reading is still unsteady, will revisit my ignition circuit..

Edited March 1, 2015 by Fargos-Go-Far